Recent Trends in Composting Technology 9789391029067

Table of contents :
front cover
Title page
Copyright
Preface
Contents
Chapter 1: Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India
Chapter 2: Composting: Exploitation of Microbial Metabolic Diversity Therein
Chapter 3: Soil Enrichment with Polyphenols Rich Composting
Chapter 4: Composting Technology in Sugar and Agro-Based Industry: Solution for High BOD Waste and Its Plausible Environmental Impacts
Chapter 5: Value Addition in Compost
Chapter 6: Nanomaterials as Fertilizers: Types, Advantages and Concerns
Chapter 7: Waste Processing and Disposal
Chapter 8: Prospects of Vermicomposting
Chapter 9: Vermicomposting: A New Vista for Livelihood Generation and Environmental Management (Case Studies from South West Bengal, India)
Chapter 10: Story of the Unsung Heroes: Exploring the Factors Affecting Composting
Chapter 11: An Overview of Biocomposting
Chapter 12: Role of Fungi in Composting
Chapter 13: Fish Solid Waste Composting: An Alternative Approach for Production of Organic Fertilizer
Chapter 14: The Technology behind Composting: Economic Aspects in Agriculture
Index
back page

Citation preview

TM

RECENT TRENDS IN

COMPOSTING

Bikas Ranjan Pati Santi M. Mandal

Bikas Ranjan Pati Santi M. Mandal

978-93-89583-59-5

Distributed by: 9 789389 583595 TM

TM

RECENT TRENDS IN

COMPOSTING

Bikas Ranjan Pati Santi M. Mandal

Bikas Ranjan Pati Santi M. Mandal

978-93-89583-59-5

Distributed by: 9 789389 583595 TM

Recent Trends in Composting Technology

Bikas Ranjan Pati

Professor Vidyasagar University West Bengal

Santi M. Mandal

Central Research Facility Indian Institute of Technology Kharagpur Kharagpur (WB), India

Recent Trends in Composting Technology Authors: Bikas Ranjan Pati Published by I.K. International Pvt. Ltd. 4435, 36/7, Ansari Rd, Daryaganj, New Delhi, Delhi 110002 ISBN: 978-93-91029-06-7 EISBN: 978-93-91029-07-4 ©Copyright 2021 I.K. International Pvt. Ltd., New Delhi-110002. This book may not be duplicated in any way without the express written consent of the publisher, except in the form of brief excerpts or quotations for the purposes of review. The information contained herein is for the personal use of the reader and may not be incorporated in any commercial programs, other books, databases, or any kind of software without written consent of the publisher. Making copies of this book or any portion for any purpose other than your own is a violation of copyright laws. Limits of Liability/disclaimer of Warranty: The author and publisher have used their best efforts in preparing this book. The author make no representation or warranties with respect to the accuracy or completeness of the contents of this book, and specifically disclaim any implied warranties of merchantability or fitness of any particular purpose. There are no warranties which extend beyond the descriptions contained in this paragraph. No warranty may be created or extended by sales representatives or written sales materials. The accuracy and completeness of the information provided herein and the opinions stated herein are not guaranteed or warranted to produce any particulars results, and the advice and strategies contained herein may not be suitable for every individual. Neither Dreamtech Press nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Trademarks: All brand names and product names used in this book are trademarks, registered trademarks, or trade names of their respective holders. Dreamtech Press is not associated with any product or vendor mentioned in this book. Edition: 2021 Printed at: Rekha Printers

Preface The natural decomposition process of organic material into humus-like plant growth promoting substances is called compost. Composting has been practised for thousands of years, when ancient Akkadian Empire in the Mesopotamian Valley recommended the use of clay tablets in agriculture. The Bible and Talmud both evidenced not only the use of rotten manure straw but also notable writers such as William Shakespeare and Sir Francis Bacon mentioned the use of compost. The process is simple but improved with huge demand by the advancement and acceleration of technology. Modern compost is rich with balanced plant nutrients that are involved in a methodical multi-step composting process by altering environmental factors. Compost improves the quality of almost any soil, and for this reason it is most often considered a soil conditioner. Research shows that soil treated with compost tends to produce plants with fewer pest problems and higher productivity. In India to enhance agricultural yield, farmers have to spend more money for buying pesticides, herbicides and chemical fertilizers for eradication of weeds. Thus, increase in production cost of agriculture results in higher debt on farmers. We can minimize cost of production, increase output per hectare by using organic manures like compost, green manure, dry leaf manure prepared from weed biomass. Composting provides a way of reducing the amount of waste to be disposed of while simultaneously converting it into a product that is useful for gardening, landscaping, or house plants. This book is designed to introduce the updated concept and developed technologies in composting manure preparation. It strongly provides the basic knowledge on composting technology and their large scale management. It also describes a variety of composting types and their beneficial role for both farmers and the ecosystem. This book also provides adequate new insights to students, teachers, other professionals and NGO’s interested to open new entrepreneurship on compost manure preparation or to enrich the subject of knowledge in composting process. The context of this book is highly relevant to the students of Environmental Studies, Microbiology, Biotechnology, Botany, Zoology, Plant Protection, Agriculture and Agronomy. The book has been divided into fourteen chapters that balance the composting enrichment process with value addition, top to bottom composting process from raw

vi Preface materials to municipal waste, and their uses in different parts of India. Role of microbial diversity in multistep composting process has been well described. A chapter on recent updates on nanofertilizers and their future concerns is also there. We would like to thank all the scientists, authors and publishers whose works and texts have been sources of enlightenment, inspiration and guidance in presenting this book. Bikas Ranjan Pati Santi M. Mandal

Contents Preface

v

1. Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India 1 Lahar Jyoti Bordoloi, Samarendra Hazarika, Dibyendu Chatterjee and Dibyendu Sarkar 2. Composting: Exploitation of Microbial Metabolic Diversity Therein Ekramul Islam, Mriganka Munshi Karmakar and Kiron Bhakat

25

3. Soil Enrichment with Polyphenols Rich Composting Munmun Mallik Ghosh, Samiran S. Gauri, Santi M. Mandal and Bikas R. Pati

50

4. Composting Technology in Sugar and Agro-Based Industry: Solution for High BOD Waste and Its Plausible Environmental Impacts Debarati Paul and Kalyan K. Bandyopadhyay 5. Value Addition in Compost Niharendu Saha, Sunanda Biswas, Sudeshna Mondal, Dipankar Dey and Subhadip Dasgupta

69 91

6. Nanomaterials as Fertilizers: Types, Advantages and Concerns 110 Renuka Saraf, Shweta Chaudhary, Nidhi Kanwar Shekhawat and Dipjyoti Chakraborty 7. Waste Processing and Disposal Almitra H. Patel

129

8. Prospects of Vermicomposting Partha S. Das, Santi M. Mandal and Bikas R. Pati

139

9. Vermicomposting: A New Vista for Livelihood Generation and Environmental Management (Case Studies from South West Bengal, India) 147 Susanta Kumar Chakraborty 10. Story of the Unsung Heroes: Exploring the Factors Affecting Composting Raktim Bhattacharya and Rabindranath Bhattacharyya

162

viii Contents 11. An Overview of Biocomposting Anusaya Mallick, A. C. Samal and S. C. Santra

183

12. Role of Fungi in Composting Kishalay Paria, Smritikana Pyne, Santi M. Mandal and Bikas R. Pati

213

13. Fish Solid Waste Composting: An Alternative Approach for Production of Organic Fertilizer S. Pati, S. K. Nayak, S. Maity, S. Mohapatra and D. P. Samantaray 14. The Technology behind Composting: Economic Aspects in Agriculture Sunayana Saha, Rabindranath Bhattacharyya and Abhijit Dey Index

229 238 257

CHAPTER

1

Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India

Lahar Jyoti Bordoloi 1, Samarendra Hazarika 2, Dibyendu Chatterjee 3 and Dibyendu Sarkar 4* 1

ICAR Research Complex for North Eastern Hill Region, Medziphema, Nagaland, India 2 ICAR Research Complex for NEH Region, Umiam, Meghalaya, India 3 ICAR-National Rice Research Institute, Cuttack, Odisha, India 4 Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, West Bengal, India *E-mail: [email protected]

ABSTRACT The complex, diverse, risk-prone and resource-poor nature, a hallmark of agricultural production systems of northeast India, warrants clinical implementation of a viable nutrient management strategy for sustenance of the system. Nutrient enriched compost, or more precisely phosphosulpho-nitro (PSN) compost, prepared by adopting a well thought out waste recycling protocol exclusively using locally available organic matter (crop residue, weed biomass, animal dung) along with nominal quantities of mineral additives might be a potent tool for implementation of that strategy. One such protocol for production of phospho-sulpho-nitro compost was developed and successfully standardised in the Division of Natural Resources Management, ICAR Research Complex for NEH Region, Umiam, Meghalaya, India and ICAR Research Complex for NEH Region, Medziphema, Nagaland, India. Altogether, four different types of PSN compost were produced by varying the types of animal manure slurry. Phospho-sulpho-nitro compost prepared by using poultry manure slurry, pig manure slurry and cow dung slurry were found superior to that prepared by using plain soil slurry in terms of nutrient supplying potential and chemical properties. Overall, PSN compost applied at 2.5 t ha–1 was estimated to supply up to 73 kg N, 123 kg P, 46 kg K and 16 kgS ha–1. As experimented in different parts of Meghalaya and Nagaland, inclusion of PSN compost as an integral component of integrated nutrient management module was found to be highly effective in increasing productivity of a wide array of crops, viz., paddy, maize, soybean, groundnut, ginger, turmeric and seasonal vegetables. Continuous application of PSN compost also brought about gradual improvement in soil quality. A number of application methodologies, viz., broadcasting, placement in pit, pot mixture, mulching, spraying as compost tea, etc., were also highlighted. Besides the multiple benefits of PSN compost application in terms

2 Recent Trends in Composting Technology of crop productivity and soil health improvement, commercial production of the compost was estimated to have a benefit-cost ratio of 1.8:1 to 2.0:1. Keywords: Phospho-sulpho-nitro Compost, Substrate, Nutrient, Mineral Additive, Animal Manure, Residue Recycling, Crop Productivity.

1.1 INTRODUCTION Sir Albert Howard, often referred to as the father of modern organic agriculture (Howard, 1943), worked in India from 1905 until 1934. He combined his scientific knowledge with the observations of the farmers on composting methods to develop a new method of composting, which is known as the Indore method. Thereafter, several new methods of composting were developed by the Indian workers. Bangalore method of composting started gaining popularity, which were followed by introduction of rapid composting modules such as Barkley rapid composting (1953), Windrow method, Beccari process (1971), Indore process of USA (1976), etc. However, a void always existed for a method that is rapid although not highly mechanised and still produces superior quality compost. In this regard, PSN compost, product of a newly developed enriched composting methodology, has been found to suit the bill perfectly. Under rigorous trial in the Indian Institute of Soil Science, Bhopal and the ICAR Research Complex for NEH Region, Meghalaya, India, this method has shown tremendous potential to cater to the needs of quality plant nutrient supplement and soil conditioners in nutrient starved farmlands of our country. The prevalent agricultural land use patterns in the hill and mountain ecosystem of northeastern (NE) region of India is complex, diverse and risk prone. The productivity of crops in this region is low due to increased soil erosion, deficiencies/toxicities of nutrients and low biological activity in acidic soil and frequent moisture stress (Baishya and Sarkar, 2015). Crop productivity can be increased by using chemical fertilisers and amendments, but these are too expensive for poor farmers and are not easily accessible in this region. Moreover, heavy rainfall and successive surface runoff due to sloppy land are the reasons for using inefficient festilizers. On the other hand, indiscriminate use of chemical fertilisers may cause pollution in lower valley lands. To restore soil fertility for sustained crop production in the region, an attractive alternative is to produce good-quality compost using waste materials from farm and household. Other than livestock manure, crop residues and weed biomass (5–20 tha–1) in both cropped and non-cropped areas of NE region serve as the raw materials for production of compost. The consumption of plant nutrients in the region is very low (Table 1.1), which indicates a deficit of plant nutrient supply.

Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India

3

Table 1.1 : Consumption of plant nutrients in northeast India (2013-14). States

Plant Nutrients (kg ha–1) N

P

K

Total

0.00

0.00

0.00

0.00

151.26

41.70

80.08

273.04

Manipur

8.27

1.37

1.16

10.80

Meghalaya

3.51

1.04

0.27

4.82

Mizoram

2.94

0.23

0.29

3.46

Arunachal Pradesh Assam

Nagaland

1.07

0.70

0.34

2.11

Tripura

10.66

7.89

4.35

22.90

Sikkim

0.00

0.00

0.00

0.00

177.71

52.93

86.49

317.13

Total Source: Anonymous, 2015

Replenishment of the nutrient deficiency using chemical fertilisers alone is not sufficient because of their low use efficiency. A viable option is to use quality compost alone or in combination with chemical fertilisers. Application of organic manure in nutrient starved soil enables farmers to increase agricultural productivity through maintaining soil quality, which is evidenced by reduced soil erosion and loss of nutrients in the runoff and increased fertiliser use efficiency (Baishya & Sarkar, 2015). Use of organic manure in the form of farmyard manure (FYM), poultry manure, and pig manure has long been practised in the region, but inferior quality of these manures hardly meets the crop demands for nutrients. Therefore, there is a necessity to develop technology for preparation of quality compost that suits the resource poor farmer of the region. Since the availability of crop residues and weed biomass is plenty in the NE hill region, their utilisation for production of quality compost hold promise (Chatterjee et al., 2016).

1.1.1 Why Composting? Composting is an attractive proposition to turn on farm waste materials into farm resources. In fact, the newly emerged global consciousness recognised the sustainable nutrient management through composting as a technology.

1.1.2 Composting Process Composting can be defined as the decomposition of organic matter by a mixed population of microorganisms in a warm, moist and aerobic and/or anaerobic environment. Composting invariably depends on an interaction between the organic waste (substrate), microorganisms, moisture and oxygen as the driving force of the process (Bordoloi et al., 2015). Under natural conditions, the decomposition of organic material of varied origin occurs at its own pace at the surface of the ground with the prevailing ambient temperature and

4 Recent Trends in Composting Technology mostly under aerobic environment. The natural decomposition of organic wastes can be accelerated by putting the materials into heaps to conserve part of the heat of decomposition so that the temperature of the mass rises ensuring a faster reaction rate (Gajalakshmi & Abbasi, 2008; Mengistu et al., 2017). Oxygen demand for composting is met and more stable products like humic compounds are formed at the end with liberation of carbon dioxide and water. Under natural conditions, the organic materials have a set of colonisers, which are an indigenous and mixed population of microorganisms derived from the surrounding environment (i.e., water or soil). The natural colonisers carry out the process of decomposition at a slow pace; but when the moisture content of the substrate is brought to a suitable level and the mass is aerated, the activity of the microorganisms speeds up. While decomposing the substrate, part of the energy is used by the microorganisms for their metabolic processes, while the remaining is given off as heat. The end product of decomposition is compost, which is made up of more resistant residues of the substrate, breakdown products, dead and some living microorganisms combined with products developed from further chemical reaction amongst these materials. Hence, composting can be technically termed as biochemical accomplishment of waste recycling.

1.1.3 Benefits of Composting ‡ Excellent technology of recycling organic wastes (i.e., crop residue, weed biomass, kitchen wastes, etc.). ‡ Matured compost contains good quantity of organic matter as well as nutrients. ‡ Maintains environmental health by recycling organic wastes. ‡ Application of compost increases availability of nutrients and water holding capacity of soils, and improves soil structure. ‡ Application of compost improves biological activity in soil. ‡ Compost provides supplemental amount of slow-release nutrients. ‡ Compost helps to maintain soil pH (acidity/alkalinity). ‡ Compost helps to protect plants from drought and freezing. ‡ Compost moderates soil temperature and controls weeds when used as mulch. ‡ Some composts have the ability to suppress fungal diseases. ‡ Compost reduces the need for commercial soil conditioners and fertilisers.

1.2 COMPOSTING METHODS The concept of waste recycling through the process of composting is centuries old. Only the scale and complexities of the process have gone up manifolds with passage of time. In a broader sense, all the existing (and still evolving) practices of composting can be grouped into two methodological categories, viz., ‘traditional’ and ‘rapid’ (Fig. 1.1).

Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India

5

Fig. 1.1: Methods of composting (Bordoloi et al., 2015).

Traditional methods adopt an approach of anaerobic decomposition, or aerobic decomposition based on passive aeration through measures like little and infrequent turnings or static aeration provisions like perforated poles/pipes. These are time taking processes involving several months (Misra et al., 2016). On the other hand, rapid methods involve application of treatments like shredding and frequent turning, use of mineral nitrogen, phosphorus and sulphur compounds, use of effective microorganisms, worms, cellulolytic organisms, forced aeration with or without mechanical turnings, etc., to expedite the aerobic decomposition process and bring down the composting period (Bordoloi et al., 2015). Fortifying the substrate with mineral nutrients to obtain nutritionally superior compost is another point of focus. It produces superior quality compost.

6 Recent Trends in Composting Technology

1.3 RAW MATERIALS FOR COMPOSTING AVAILABLE IN NORTHEAST INDIA One of the prerequisites for composting technology to thrive successfully is the availability of raw materials, technically known as ‘substrates’. Mainly, substrates can be obtained from two sources: ‡ Biomass generated in arable and non-arable areas, viz., crop residues, weed biomass, etc. ‡ Livestock wastes, viz., dung, urine, bedding litter, etc.

1.3.1 Crop Residue The potential availability of residues of major crops in NE India has been estimated (Table 1.2). These residues are a reservoir of nutrients if used properly. The quantum of nutrient supply from these crop residues will be substantial if tapped properly (Table 1.3). Total NPK supply from crop residues can thus be projected at 9860, 2120 and 35490 tonnes, respectively, which corresponds to 2.47 kg N, 0.53 kg P2O5 and 8.87 kg K2O per hectare. Table 1.2 : Availability of major crop residues (‘000 t year–1) in northeast India. State

Rice

Maize

Pulses

Oilseeds

Total

Arunachal Pradesh

214.0

116.0

8.8

30.6

369.7

Assam

5615.6

34.1

107.1

230.1

5986.9

Manipur

583.8

30.4

8.1

2.0

624.3

Meghalaya

249.2

57.8

4.9

7.9

319.8

Mizoram

183.6

38.3

2.5

16.4

240.7

Nagaland

310.4

69.6

20.9

32.9

433.9

Tripura

889.4

4.2

8.8

11.0

913.4

Total

8047.0

350.3

166.7

332.1

8896.1

Source: Bujarbaruah (2004).

1.3.2 Weed Biomass The climatic conditions of NE region favour profuse growth of diverse weed species both in cropped and non-cropped areas. The biomass production of weeds roughly ranges from 5 to 20 tha–1 depending upon the weed species, seasons and growing conditions (Rajkhowa et al., 2005). Table 1.3 : Production (106 t) and supply (103 t) of nutrients from crop residues in northeast India. Crop residue

Total production

Potentially available * 4.00

Potential nutrients

Probable nutrients**

N

P2O5

K2O

N

P2O5

K2O

Rice

8.00

14.4

0.32

28.4

8.64

0.19

17.04

Maize

0.35

0.18

0.76

2.82

29.7

0.46

1.7

17.82

Pulses

0.17

0.09

0.65

0.16

0.48

0.39

0.10

0.29

Oilseeds

0.33

0.17

0.61

0.22

0.56

0.37

0.13

0.34

*50% of total produce; ** Assuming 40% loss of potential nutrients Source: Datta (2007)

Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India

7

The weed biomass varied widely in nutrient contents and offers multiple options for fitting them in any composting methodology. The potential weed species of NE region as substrate for composting are given in Plate 1. The nutrient contents of common weed species of NE India are presented in Table 1.4. Table 1.4 : Nutrient contents (%) of some common weed species available in northeast India. Weed species Nitrogen

Phosphorus

Potassium

Eupatorium odoratum

3.42

0.16

0.97

Eichhornia crassipes

2.94

0.94

0.16

Ipomoea sp.

2.12

0.45

0.46

Ambrosia artemisiifolia

3.14

0.17

0.82

Lantana camara

2.48

0.11

1.33

Mikania micrantha

2.98

0.22

1.79

Azolla caroliniana

2.32

0.59

2.82

1.3.3 Animal Manure Different categories of livestock waste, viz., dung, urine, bedding litter, slaughterhouse wastes, etc., constitute an extremely important section of substrates for any composting methodology. The potential availability of livestock dung in NE India is given in Table 1.5. Besides being nutrient rich (Table 1.6), they also provide the seat for initialising the activities of the decomposing microorganisms. The decomposed mixture of dung, litter, urine and leftover materials from roughage or fodder fed to cattle (N, P, K contents of 0.93, 0.25 and 0.91% respectively) is an excellent substrate for compost making. Table 1.5 : Potential availability of dung of different categories of livestock. Livestock

Dung Production Per Animal Per Year (Tonnes /Year)*

Livestock Population in Northeast India (‘000 Numbers) **

Potential Dung Production Per Year (‘000t)

Range

Average

Cattle

0.4-1.8

1.10

11030

12133

Buffalo

0.8-1.9

1.35

840

1134

Pigs

0.2-0.3

0.25

3816

954

Sheep

0.1-0.2

0.15

227

34.05

Goats

0.1-0.2

0.15

4366

654.9

Poultry (100 birds)

0.14

0.14

36462

51.05

Source: *Kumaresan et al. (2006), **17th Livestock census by Deptt. of Animal Husbandry (2003).

8 Recent Trends in Composting Technology

Lantana camera

Stakis terpeta indica

Spilanthes acmella

Alternanthera philoxeroides

Ageratum conyzoides

Galinsoga parviflora

Solanum khasianum

Eupatorium spp.

Bidens pilosa

Ambrosia artemisiifolia

Plate 1: Potential weed species available for composting (Photo courtesy: Dr. Rajesh Kumar, Division of NRM, ICAR Research Complex for NEH Region, Umiam, Meghalaya, India). Table 1.6 : Average nutrient content (%) in the dung of different livestock. Livestock dung Cattle Pig Sheep and goat manure Poultry manure (fresh) Duck manure Source: Kumaresan et al. (2006).

Nitrogen 0.15 0.60 0.65

Phosphorus 0.01 0.50 0.50

Potassium 0.05 0.20 0.03

0.76

0.63

0.22

0.91

0.38

0.36

Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India

9

1.4 RECYCLING OF CROP RESIDUE AND WEED BIOMASS INTO COMPOST The protocol for production of enriched compost utilizing weed biomass and crop residues has been developed by the Division of Soil Science, ICAR Research Complex for NEH Region, Umiam, Meghalaya. An estimate shows that the research farm of the division generates approximately 2.1 t of dry weed biomass from 1.6 ha of land area (approx. 5.3 t on fresh weight basis) during four months of peak monsoon activity from June to September. Major fraction of these weeds feed on the nutrients applied to the Kharif crops and converting the weed biomass into compost provides ample scope for recycling the nutrients.

1.5 METHODOLOGY The protocol was developed (Fig. 1.2) using different combinations of locally available substrates, nutrient sources and practices.

Fig. 1.2: Protocol used for preparing phospho-sulpho-nitro compost.

10 Recent Trends in Composting Technology The objective behind this protocol was to produce nutritionally superior compost within shortest possible time through: ‡ XVHRIEHVWFRPELQDWLRQRIVXEVWUDWHVDYDLODEOH ‡ XVHRIORFDOO\DYDLODEOHRUJDQLFQXWULHQWVRXUFHVDQG ‡ MXGLFLRXVXVHRIPLQHUDODGGLWLYHV

1.5.1 Ingredients 1.5.1.1 Substrates Two types of organic substrates were used: (a) crop residue, e.g., paddy straw and maize, groundnut and soybean stalks, and (b) weed biomass e.g., Ambrossiaartimisifolia, Eupatorium spp., Ageratum conyzoides, Lantana camara, etc.

1.5.1.2 Slurry The slurry consisted of cow dung/ poultry excreta/pig dung, soil and well rotten compost in 1:1:0.5 ratio (Das et al., 2010a). Slurry prepared from 100 litres of water containing 35 kg of fresh cow dung/poultry excreta (one month old) /pig dung (one month old), 35 kg dry soil and 17 kg of well rotten compost is enough for a single pit of 3 m (L) × 2 m (B) × 1 m (D) dimension. Before making slurry, poultry excreta and pig dung are dried under shade, debris removed and lumps broken. Slurry is used as a source of microbial inoculum and for supplementing nutrients to the compost (Plate 2). Importance of slurry in composting ‡ Provides moisture to the dry substrates. ‡ Ensures uniform distribution and mixing of the mineral additives to each layer of the substrate. ‡ Provides the seat for initialization of microbial activity inside the compost pit.

Plate 2: Preparation of slurry.

1.5.1.3 Mineral Additives External addition of nutrients such as N, P and S in nominal quantities to the substrate hastens the process of composting and improves the quality of compost. Urea, rock phosphate and elemental sulphur are added as mineral additive.

Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India

11

Importance of mineral additives Urea: ‡ Serves as a source of N. It narrows down the C:N ratio of the substrate thereby facilitating its rapid decomposition. ‡ Provides a labile source of N for microbes at the initial stages of decomposition. ‡ Boosts the nutritional status of the final product, i.e., compost. Rock phosphate: ‡ Cheap source for enriching the compost with P. ‡ Serves as a P supplement to the decomposer microbes. ‡ Plays a key role to control the rate of decomposition. Time for composting reported to be inversely proportional to the rate of addition of rock phosphate. ‡ The organic acids released from dung/excreta subjected to microbial decomposition causes rapid release of water soluble and citrate soluble P from rock phosphate making them usable by the decomposers. ‡ The status of water and citrate soluble P of the compost is improved manifold. ‡ Helps to obtain an ideal nutrient source for the P deficient acidic soils of NE India. Elemental sulphur: Hastening of the composting process due to addition of elemental S has not been established. However, enhancement of nutritive value of compost has been of great importance especially in sulphur deficient soils.

1.6 PROTOCOL 1.6.1 Pre-composting Treatment for Substrate 1.6.1.1 Shredding The dry and hard substrates (weed biomass and crop residues) are chopped using a sharp knife. Although the recommended substrate size for rapid composting is as low as 2.5 cm, however about 10 cm size was maintained to reduce the cost of labour (Plate 3). Why Shredding? Reduction in substrate particle size increases the surface area for microbial activity and thus hastens the process of decomposition.

1.6.1.2 Mixing The natural dry crop residues and weed biomass are mixed with green and succulent ones in equal proportions.

12 Recent Trends in Composting Technology Why to mix dry and green substrates? Carbon (C) to nitrogen (N) ratio of the substrate should be around 30:1. Mixing of dry and green substrates in equal proportion helps to bring down the C:N ratio to the desired range.

Plate 3: Shredding of dry crop residue and weed biomass.

1.6.2 Pit making and Filling with Substrate 1.6.2.1 Digging The pit method of composting was followed. Pits of 3 m × 2 m × 1 m dimensions were dug in a location of the farm which is free from water stagnation. With this dimension, each pit can accommodate approximately 300 kg mixed substrate. The sides and the bottom of the pit should be made free from cracks and crevices (Plate 4).

Plate 4: The compost pit.

Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India

13

1.6.2.2 Plastering of Pit Before filling the pit with substrates, the inner sides and bottom of the pit are plastered using the slurry. Plastering with slurry creates a nearly impervious layer that checks seepage loss of nutrients and prevents entry of water from outside. The slurry at the bottom of pit provides an ideal seat for microbial activity (Plate 5).

Plate 5: Plastering of pit interiors with slurry of manure and soil.

1.6.2.3 Pit Filling The most critical part of the composting process is proper filling of the pit with layers of substrate, slurry and mineral additives. It is a multi-step process involving the following activities in sequence. Step I: Placing the substrates in layers Approximately 20 cm thick layer of the substrate is placed uniformly on the pit bottom. Care should be taken to avoid too much compaction of the substrate while layering (Plate 6).

Plate 6: Layering of substrate inside the pit.

Step II: Sprinkling and mixing of slurry After placing each layer of the substrate, the slurry (cattle dung/poultry droppings/pig dung+ soil + well rotten compost + water) is sprinkled over each of the layers in sufficient quantity to ensure a coating of the whole substrate with slurry. The slurry acts as a sticker that helps the mineral additives to adhere on the substrate (Plate 7).

14 Recent Trends in Composting Technology

Plate 7: Sprinkling of slurry over substrate layers.

Step III: Application of mineral additives Immediately after sprinkling of slurry, mineral additives are applied to the substrate layer. As per the protocol, N was applied at 0.5% as urea; P2O5 at 1.5% as rock phosphate and S at 0.5% as elemental S. After adding mineral additives, another new layer of substrate is placed in the similar fashion (Plate 8). a

b

c

d

Plate 8: Application of mineral additives (a) urea, (b) rock phosphate, (c) elemental sulphur and (d) their mixing with the substrate.

Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India

15

Step IV: Steps I to III are repeated in similar fashion till the pit gets filled up with substrate and reaches a height of 1 ft above the ground level. The materials inside the pit are moistened with water sufficiently (70% moisture content). Step V: Plastering of pit top After filling the pit, a dome shape is given to the substrates remaining above the ground level. The pit top is then plastered with a thick layer of the slurry. Care should be taken to maintain proper consistency of the slurry so that cracks do not develop on drying (Plate 9). b

a

c

Plate 9: (a) Dome shape of substrate, (b) plastering of pit top with slurry, and (c) a completely sealed compost pit.

Importance of plastering of pit top ‡ To help gain temperature rapidly inside the pit. ‡ To act as a semi-impervious layer restricting entry of excess water from outside. ‡ To check entry of flies, etc. ‡ To ensure diffusion of oxygen to the underlying substrates in a controlled manner. Step VI: Turning the substrate After plastering the pit top, the compost pit is kept as such for 20 days. After 20 days, the materials inside the pit are turned manually. The moisture content of the partially decomposed substrate inside the pit is to be checked and water is added, if necessary, to maintain moisture level of nearly 70%. The pit top should be covered again with slurry. Same process needs to be repeated at an interval of 20 days till the completion of composting (till 100–105 days, approximate time of completion of the composting process).

16 Recent Trends in Composting Technology Importance of turning ‡ Frequent turning of substrate is vital for rapid composting. ‡ Turning ensures uniform distribution of temperature throughout the compost pile facilitating production of a homogenous end product. ‡ Turning also helps maintain moisture uniformly throughout the compost pile. ‡ Overheating of huge compost piles can be avoided through regular turning of the substrates. ‡ Turning also facilitates proper aeration, which is required for uninterrupted decomposition at a faster rate. Step VII: Completion of decomposition The completion of the composting process is marked by a number of indicators, both physical and chemical. These indicators are known as compost maturity and stability indices. As it is not possible for the farmers to evaluate the chemical indices, they have to rely on the physical indicators (Plate 10). Physical indicators to judge the maturity of compost ‡ No more reduction in volume. ‡ Conversion of the substrates to a dark brown to black coloured mass. ‡ Absence of the pleasant smell, giving way to a soil like musty odour. ‡ Little or no presence of substrate recognizable in original form. ‡ Complete cooling down of the compost pile. No more heating upon wetting. ‡ Production of mass is friable and brittle when dry.

Plate 10: Matured compost ready for harvesting.

Step VIII: Harvesting of matured compost Once composting is complete, the end product is collected from the pit. Proper care must be taken to avoid scraping of the pit-bottom-soil along with compost as presence of foreign materials like soil deteriorates the quality of the compost (Plate 11).

Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India

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Plate 11: Harvesting of matured compost.

Step IX: Post-harvest processing After collection from the pit, compost is spread under a shade to remove excess moisture and unwanted materials like, stone, pebbles, plastics, metals, etc. (Plate 12).

Plate 12: Drying, sorting and sieving of compost.

The final product should contain 35–50% moisture. Dry compost is sieved using 1 inch mesh to obtain a uniform size. The processed compost is then stored in a cool and dry place for future use. Moisture content in compost ‡ The ideal moisture content in finally processed compost is between 35–50%. ‡ Compost, if excessively wet (beyond 60% moisture) is heavy, forms lumps and is difficult to handle. ‡ Compost, if too dry (less than 30% moisture) is dusty and irritating to work with. ‡ Too dry compost also takes unduly longer time for decomposition and release of nutrients when applied to a relatively dry soil.

18 Recent Trends in Composting Technology

1.7 NUTRITIVE VALUE OF COMPOST Using the protocol, PSN enriched composts are prepared from the mixture of crop residue and weed biomass. Three different types of slurry using cattle dung, poultry droppings and pig dung as one of the components are used. The substrate composition (crop residues + weed biomass) and the ratio of different ingredients in slurry remain same as mentioned in the protocol. The comparative advantage of using animal excreta in slurry preparation was evaluated against a slurry having soil and compost but without animal excreta (i.e., control). Mineral fortification was done following the standard protocol. The nutrient composition and other important properties of the composts are presented in Table 1.7 and Table 1.8. Table 1.7 : Nutritional variability of different enriched composts. Types of Compost

pH

C (%)

N (%)

C: N

P (%)

K (%)

S (%)

PSN-CDS

7.2

26.2

2.5

10.48

4.4

1.3

0.74

PSN-PIMS

7.1

29.8

2.8

10.64

4.6

1.6

0.68

PSN-POMS

6.8

27.6

2.9

9.52

4.9

1.8

0.63

PSN-PSS

6.8

38.8

1.9

20.42

4.1

1.1

0.65

FP

6.6

42.7

0.8

53.38

0.3

0.4

0.21

PSN-CDS, PSN-PIMS, PSN-POMS and PSN-PSS represent phospho-sulfo-nitro enriched compost prepared using slurry containing cow dung, pig dung, poultry litter devoid of animal excreta, respectively; FP represents ordinary compost (farmer’s practice) Table 1.8 : Potential supply of plant nutrients through composts under variable rates of application. Plant Nutrients (kg ha-1)

Types of Compost and Application Rate (t ha–1) PSN-CDS

PSN-PIMS

PSN-POMS

PSN-PSS

FP

2.5*

5.0**

2.5

5.0

2.5

5.0

2.5

5.0

2.5

5.0

Nitrogen

62.5

125.0

70.0

140.0

72.5

145.0

47.5

95.0

20.0

40.0

Phosphorus

110.0

220.0

115.0

230.0

122.5

245.0

102.5

205.0

7.5

15.0

Potassium

32.5

65.0

40.0

80.0

45.5

91.0

27.5

55.0

10.0

20.0

Sulphur

18.5

37.0

17.0

34.0

15.8

31.5

16.3

32.5

5.3

10.6

1.8 USE OF PSN COMPOST The rates and methods of compost application vary depending on compost quality, soil condition, type of crop, and purpose of its use. Some common applications of PSN compost are listed below: ‡ Broadcasting: Compost is broadcasted at least 10 days prior to sowing or planting of field crops. Immediately after broadcasting, it is mixed thoroughly with the soil.

Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India

19

Experiments conducted at Divisional Research Farm of Soil Science Division, Umiam, Meghalaya showed that broadcasting of PSN enriched compost 2.5 and 5.0 tha-1 significantly improved the crop yield and soil quality. ‡ Placement in pit: Compost is applied in pits during planting of crops like ginger, turmeric, potato tubers, seedlings of vegetables such as cabbage, cauliflower, knolkhol, etc. PSN compost can be applied 250–300 g per pit to obtain a good harvest (Plate 13). b

a

Plate 13: Pit soil mixed with PSN compost (a) and growth of vegetable (b).

‡ Compost as pot mixture: An ideal pot mixture for flowers and vegetables can be prepared by mixing PSN compost, sand and garden soil in a ratio of 1:1:1. Transferring seedlings along with pot mixture to the field helps avoid stress to the seedlings besides other benefits (Plate 14).

a

b

Plate 14: Vegetable seedlings raised using compost as pot mixture (a) and transferring of seedlings to field along with the mixture (b).

‡ Compost as mulch: Compost can be applied as mulching material. Compost mulch conserves moisture, improves water balance and soil structures, controls weeds, minimizes fluctuations of soil temperature, increases soil fertility and reduces water erosion of soil (Bhardwaj, 2013). Three to four inches of thick layer compost can be applied as mulch on the soil surface without incorporation (Plate 15).

20 Recent Trends in Composting Technology

Plate 15: Compost mulching for onion.

‡ Use of compost tea: Compost tea is the water extract of compost (Plate 16). It is rich in micronutrients, humic acids and growth promoting substances. It can be sprayed to crops as growth booster. Spraying compost tea is an excellent way to nourish indoor or outdoor potted plants (Martin, 2015; Islam et al., 2016). It can be prepared following a few easy steps (Martin, 2015): Step 1: Fill a cloth bag with finished compost. Step 2: Place the bag in a bucket of water. Step 3: Let it sit for an hour. Step 4: Remove the bag after one hour. Step 5: Collect the resulting liquid, the “compost tea”. Step 6: Empty the contents of the bag into the garden or farm and use as compost mulch or soil amendment.

Plate 16: Preparation of compost tea.

Enriched Compost: A Boon for Nutrient Starved Agriculture in Northeast India

21

‡ Top dressing: Mostly used for maintenance of grasses in lawns. Top dressing with DɌWRôLQFKOD\HURIZHOOGHFRPSRVHGFRPSRVWLVDGYRFDWHGDWOHDVWWZLFHD\HDU Care should be taken to continue with the routine watering of the lawn as excessively dry condition prevents decomposition of compost.

1.9 CROP PRODUCTIVITY WITH PSN COMPOST Broadcasting of PSN enriched compost at 2.5 or 5.0 t ha–1 has significantly improved the yield of various crops. The use of PSN compost as a component of integrated nutrient management packages has shown great potential in improving soil health and crop productivity. High yield (7 tha–1) of lowland paddy was recorded when PSN compost was applied 5 tha–1 along with 50% recommended dose of fertilisers. Application of inorganic fertiliser at 50% of recommended dose along with PSN compost at 2.5 tha–1 and furrow applied lime at 300 kgha-1 has been found to enhance productivity of upland cereals by 67%, that of spices by 51% and that of pulses and oil seeds by 49%. Besides improving crop yield, PSN compost also improved soil fertility significantly. Continuous addition of PSN compost at 2.5 tha–1 for five years resulted in build-up of available P in acid soil. A rise in soil pH from 4.8 to 5.5 and beyond was also recorded with continuous addition of PSN compost at 5.0 t ha–1 for 3 year.

1.10 ECONOMICS The economics involved in production and use of PSN compost was evaluated (Table 1.9). The economic analysis was done considering: ‡ Standard size of the pit: 3 m (length) × 2 m (breadth) × 1 m (depth) ‡ Total amount of substrate accommodated in one pit: 330 kg ‡ PSN compost to be generated from one pit: 110 kg (considering 30% recovery) ‡ State approved rate of improved compost: Rs. 30 kg–1 Table 1.9 : Economics involved in production and use of PSN compost. Cost Items A. Labour charge 1. Pit making (3 m × 2 m × 1 m size) 2. Substrate collection (3.3 quintals) 3. Substrate chopping and mixing 4. Slurry making and pit filling 5. Substrate turning and watering (7 times during the whole composting period) 6. Harvesting, drying, sieving and packaging

Rate (Rs. Per Unit Item)

Amount (Rs.)

1 man-day at Rs. 200 1 man-day at Rs. 200 ôPDQGD\DW5V ôPDQGD\DW5V 3 men-day altogether at Rs. 200

200.00 200.00 100.00 100.00 600.00

1 man-day at Rs. 200

200.00 Contd...

22 Recent Trends in Composting Technology Cost Items B. Material cost 1. Urea (3 kg) 2. Rock phosphate (17 kg) 3. Sulphur powder (1.5 kg) 4. Cow dung/poultry manure/pig manure (35 kg) 5. Polythene bags for packaging (5 kg capacity)

Rate (Rs. Per Unit Item)

Rs. 11.0 per kg Rs. 7.0 per kg Rs. 160.0 per kg Rs. 1.0 per kg 20 number at Rs. 3.0

Total cost (C) Benefits (B) Approved rate of the compost

Amount (Rs.) 33.00 119.00 240.00 35.00 60.00 1827.00

Rs. 30.0 per kg

Benefit-cost ratio * The benefit-cost ratio increases to 2.03: 1 from 2nd year onwards due to elimination of the cost of pit making.

3,300.00 1.81:1*

1.11 EPILOGUE Improper nutrient management has been a major bottleneck in the agricultural production systems prevalent in the NE region of India. The inherent characteristics, viz., complex, diverse and resource poor nature of the system has called for a viable management strategy to be devised and implemented for sustenance of productivity at an optimum level. The strategy in question needs to be a unique amalgamation of locally available resources and technical knowhow seamlessly blended with synthetic inputs and improved technology as well. The objective behind genesis of PSN compost was to counter the menace of poor use efficiency of applied nutrients. Researchers in the Division of Natural Resource Management, ICAR Research Complex for NEH Region, Umiam, Meghalaya, India took up rigorous field trials as well as laboratory analysis for developing a viable production as well as application methodology of PSN compost which was followed by its successful demonstration among the farmers in East Khasi Hills of Meghalaya, India. Now, it has been established that PSN compost provides plant nutrients in a form moderately embedded in a carbon matrix of decomposed organic matter, thereby imparting it with a nature of labile-cum-slow release nutrient source. Thus, the PSN compost bears tremendous potential as an ideal nutrient source in NE region soils marred with constraints in relation to very poor nutrient use efficiency owing to lighter texture causing severe leaching, rampant surface runoff and erosion. The nominal use of synthetic fertilisers in preparation of this enriched compost is another feature of this technology which can address the poor availability of synthetic nutrient sources in the region.

REFERENCES 1. Anonymous (2015). “Agricultural statistics at a glance 2014”.Directorate of Economics and Statistics, Department of Agriculture and Cooperation, Ministry of Agriculture, Government of India. 1st Edition, Oxford University Press, New Delhi (India). p. 452.

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2. Baishya, L.K. & Sarkar, D. (2015). “Land–soil resources of north eastern region of India: constraints and management options”. In: Rajkhowa, D.J. et al (eds), Integrated Soil and Water Resource Management for Livelihood and Environmental Security. ICAR Research Complex for NEH Region, Umiam, Meghalaya, India. pp. 20-33. 3. Bhardwaj, R.L. (2013). “Effect of mulching on crop production under rainfed condition - A review”. Agricultural Reviews. 34: 188-197. 4. Bordoloi, L.J., Hazarika, S., Deka, B.C., Kumar, M., Verma B.C. & Chatterjee, D. (2015). “Nutrient enriched compost”. ICAR Research Complex for NEH Region, Nagaland Centre, Jharnapani, Medziphema(India). p. 34. 5. Bujarbaruah, K.M. (2004). “Organic farming: Opportunities and challenges in north eastern region of India”. In: Souvenir (Nature 2004), International Conference on Organic Food, 14-17 February, 2004. pp. 13-24. 6. Chatterjee, D., Kuotsu, R., Kikon, Z.J., Sarkar, D., Ao, M., Ray, S.K., Bera, T. & Deka, B.C. (2016). “Characterization of vermicomposts prepared from agricultural solid wastes in north eastern hill region of Nagaland, India”. Proceedings of the National Academy of Sciences, India, Section B Biological Sciences. 86: 823-833. 7. Das, A., Baiswar, P., Patel, D.P., Munda, G.C., Ghosh, P.K., Ngachan, S.V., Panwar, A.S. & Chandra, S. (2010a). “Composts quality prepared from locally available plant biomass and their effect on rice productivity under organic production system”. Journal of Sustainable Agriculture. 34: 1-17. 8. Datta, M. (2007). “Management of soil health for sustainable organic food production in north east India”. In: Munda, G.C. et al. (eds). Advances in Organic Farming Technology in India. ICAR Research Complex for NEH Region, Umiam, Meghalaya (India). pp. 205-217. 9. Gajalakshmi, S. & Abbasi, S.A. (2008). “Solid waste management by composting: State of the art”. Critical Reviews in Environmental Science and Technology. 38: 311-400. 10. Howard, A. (1943). “An Agricultural Testament”. Oxford: The Oxford University Press. 11. Islam, M.K., Yaseen, T., Traversa, A., Kheder, M.B., Brunetti, G. & Cocozza, C. (2016). “Effects of the main extraction parameters on chemical and microbial characteristics of compost tea”. Waste Management. 52: 62-68. 12. Kumaresan, A., Pathak, K.A., Bujarbaruah, K.M., Das, A. & Vinod, K. (2006). “Integrated livestock-fishculture in Mizoram”. Technical Bulletin. ICAR Research Complex for NEH Region, Umiam, Meghalaya (India). 13. Martin, C.C.S. (2015). “Enhancing soil suppressiveness using compost and compost Tea”. In: Organic Amendments and Soil Suppressiveness in Plant Disease Management. Springer International Publishing. pp. 25-49.

24 Recent Trends in Composting Technology 14. Mengistu, T., Gebrekidan, H., Kibret, K., Woldetsadik, K., Shimelis, B. & Yadav, H. (2017). “Comparative effectiveness of different composting methods on the stabilization, maturation and sanitization of municipal organic solid wastes and dried faecal sludge mixtures”. Environmental Systems Research. 6: 5. 15. Misra, R.V., Roy, R.N. & Hiraoka, H. (2016). “On-farm composting methods”. Rome, Italy: UN-FAO. 16. Rajkhowa, D.J., Gogoi, A.K. & Yaduraju, N.T. (2005). “Weed utilization for vermicomposting”. Technical Bulletin No. 6. NRC for Weed Science, Jabalpur (India).

CHAPTER

2

Composting: Exploitation of Microbial Metabolic Diversity Therein Ekramul Islam *, Mriganka Munshi Karmakar and Kiron Bhakat Department of Microbiology, University of Kalyani, Kalyani-741235, Nadia, West Bengal, India *E-mail: [email protected]

ABSTRACT Composting, a natural process of biodegradation and nutrient recycling, occurs in the environment. It is a slow and gradual decomposting process in which biological components like microorganisms, nematodes, worms, protozoa, and variety of insects participate along with abiotic factors like pH, temperature, humidity, salinity, and nutrient concentration. Quality of composting depends on the following attributes: (i) Succession of the dominating microbial taxa, (ii) different functional groups of microorganisms, and (iii) total microbial activity during the composting. This review demonstrates a complete overview of all the composting processes in various sectors which exploited huge microbial metabolic repertoire by taking into concern the microbial abundance, species diversity and function as well as abiotic factors during successful composting.

2.1 INTRODUCTION Composting is the complex process of breakdown or degradation of complex solid organic structure or larger molecule to stable and humidified simpler molecule by aerobic microbial metabolic process yielding a suitable product that can be added to the soil. Microbial metabolic process lies into the heart of the composting process to degrade plant or animal parts with the release of energy in the form of heat. The major concerns that are linked to ultimate outcome of the composting process include: (1) Requirement of favourable growth and activity of several microorganisms, since composting is a biological process. Hence, studies are being carried out to achieve maximum microbial activity and reduction of composting time. Microbial single activity in the composting process could be enhanced by monitoring external conditions such as moisture level, pH, etc. It has been observed that the optimum conditions of microbial growth and activity in the composting process are largely influenced by the nature of organic substances in the composting material (Cozzolino et al., 2016). (2) Aerobic process requires aeration. Aeration depends

26 Recent Trends in Composting Technology on porosity of composting materials. Air filled space in the composting matrix ensure oxygen supply to the microorganisms. (3) Composting depends on a certain thermal regime and basically a thermophilic process. Increased microbial metabolic activity leads to oxidation of organic matter with the generation of heat, creating self-heating conditions and water evaporation. Hence, from the start to end during composting process composting material passes through different thermal phases: (i) a mesophilic phase: growth and proliferation of the microbe takes place in this phase, (ii) a thermophilic phase: characterized by high growth of thermophilic organisms with high biodegradation, and the inhibition of heat labile organisms, (iii) cooling, stabilization and maturation phase: mesophilic microbial growth and the humification of the compost (Ryckeboer et al., 2003). Although composting process reflects a unique microbial system, it is very tedious to monitor optimum condition of the thermal phases. Hence, achieving thermophilic temperatures by balancing aeration, moisture, porosity and biodegradable organic matter content is not often a simple task. (4) Compost amendments in soil: the most important aspect is that compost should be added in soil without any deterioration of soil system. It should not only provide nutrients to plants like mineral fertilizers, but also prevent soil erosion, increase carbon sequestration, save water and most importantly improve soil microbiology for enhancement of soil health. Various microbial activities during composting are summarized in Fig. 2.1.

Fig. 2.1: Different microbial activities during composting.

2.2 PURPOSES OF COMPOSTING There are several purposes of composting; all could be grouped into two: (i) reduction of volume and hazards of wastes, and (ii) recycling of organic materials. Composting is not only considered a viable means of waste disposal but also creates provision of restoration of soil fertility. Composts are widely used for promoting long-term productivity of agro ecosystem. Being an old practice for the biological conversion of organic waste material to a humus-like substance composting can improve physical, chemical and biological

Composting: Exploitation of Microbial Metabolic Diversity Therein 27

characteristics of the soil. This process utilizes a plethora of fungal and bacterial species like actinomycetes, and helps to convert a low value material into a higher valuable product. This process is widely accepted as it diminishes odour, reduces overall size of the waste and elevates the nutritive value of the waste. Organic wastes resulting from agricultural fields, wood processing industry, and food processing plants, municipal sewage and other wastes, various industrial wastes can be successfully decomposed by utilizing a wide range of biological agents in an eco-friendly way (Fig. 2.2).

Fig. 2.2: Microbial aided composting exploited in different sectors.

2.3 COMPOSTING: THE ‘-OMICS’ APPROACH In the search of useful and important microbial genes, we always go for cultured microbes, but recent studies showed that only a small amount of microbial species present in the environment are cultivable in laboratory conditions. Therefore, culture independent approaches are considered to check all the genetic information of uncultivable microbes in a designated natural habitat. Metagenome, a term conceived by Hendelsman, isolated and analysed the metagenome of a soil sample, containing the structural and functional genetic information of every organism present in the sample. These kind of genomic samples are known as environmental DNA or eDNA. One drawback of the genomic approach to study the diversity of microorganisms in a given sample is that it can’t differentiate between the metabolically active and inactive ones, as not all the microbes function at the same time in a habitat. Here, transcriptomics comes to the rescue. Just like genome, transcriptome refers to all the RNA present in a specific sample, and we can deduct from the analysis of RNA samples, which are facilitating at that time. Likewise, proteomics confers to all the proteins functioning at that time and it can provide us with a clear picture of the protein profiles of a specific sample (Kim et al., 2010).

28 Recent Trends in Composting Technology Metagenomics has attracted many investigators, who aspire to not only nourish our wisdom on protein sequence space in nature but also to search for and isolate various novel enzymes with potentially advantageous applications (Sulaiman et al., 2012). The microbial community in compost is composed of a myriad of microbes and the inherent microbes of compost produce several enzymes such as cellulase, amidohydrolase, glucosylhydrolase, invertase, alkaline phosphatase, aminopeptidase, lipase, protease, etc. The compost heaps contains plethora of microbial species, thus, these habitats are believed as one of the most extraordinary bioreactors for renewable bio-salvation (Wang et al., 2016). However, to date, only a limited amount of research work is done about the community genomic analysis of compost, even if it is a highly complex and efficient bioprocessing platform for waste material and simultaneously recycling the same. Very little explanation is available to understand and analyze how the microbial population present in the compost simultaneously degrades the solid waste and uses the end products together in high temperature (Wang et al., 2016). Recent works on the structural and functional genomic analysis of a large number of environmental specimens generated sufficient data that contains information about the gastrointestinal tract of termite (Warnecke et al., 2007), earthworms (Navarro-Fernández et al., 2011), bovine rumen (Brulc et al., 2009), dynamically fermenting platform communities and soil from pastureland (Delmont et al., 2012; Hollister et al., 2012). Pang et al. (2009) identified cellulase genes from compost soils and characterized a novel endogluconase which has broad application in industries like detergent, textile, brewing, animal feed, etc. Kim et al. (2010) isolated nine positive esterase clones from a metagenomic library of completely fermented compost and distinguished a novel family VIII alkaline esterase. Sulaiman et al. (2012), using metagenomic approach, isolated a novel cutinase homolog from leaf-branch compost that has polyethylene terephthalate degrading activity. Cutinase is an eseterolytic/lipolytic enzyme that breaks down cutin, a chief constituent of plant cuticle, and other water soluble esters and insoluble triglycerides. Lately it has drawn much attention for its ability to decompose aliphatic and aromatic polyesters, like polyethylene terephthalate, also known as PET, which is a synthetic aromatic polyester derived from terephthalic acid (TPA), and ethylene glycol. Kang et al. (2011) isolated a novel family VII esterase from compost metagenomic library which is stable up to 60°C and can degrade polyester polyurethane and specifically produce (S)-ketoprofen, which is a non-steroidal anti-inflammatory drug (NSAID) from (R/S)ketoprofen ethyl ester. Verma et al. (2013) characterized a novel alkali stable and thermostable xylanase encoding gene (Mxyl) by cloning, and expression study of a compost soil metagenome. This enzyme is of high demand in paper industry for paper pulp bleaching and for producing xylooligosaccharides by breaking down xylan component of agro-residues. Uchiyama et al. (2013) isolated and characterized a novel E-glucosidase with very high transglycosylation activity from compost microbial metagenome. These kind of enzymes are of high interest because of their cellulolytic

Composting: Exploitation of Microbial Metabolic Diversity Therein 29

activity and their ability to convert cellobiose into glucose. Martins et al. (2013) showed us that the tropical composting operation habitat of São Paulo Zoo Park is dominated by the members of Lactobacillus genus. He further indicated that the biomass degradation is fully done by the enzymes produced by bacteria, mainly by the representatives of the Clostridiales and Actinomycetales orders. Allgaier et al. (2010) metagenomically analyzed glycoside hydrolases from a switchgrass compost habitat by using green waste compost inoculum in a bioreactor simulating thermophillic compost conditions. Xing et al. (2012) applied metagenomic techniques for mining enzymes for biofuel synthesis from microbial communities using feedstock. López-López et al. (2014) used metagenomic approaches to isolate lipases and esterase with high industrial value from hot springs, composts, soil and marine environment. Lämmle et al. (2007) used metagenome expression cloning for the isolation and identification of novel enzymes with different hydrolytic activities like lipase/esterase, phosphatase, protease, amylase and pigment production. Sun et al. (2015) did cloning, expression study of thermostable xylanase gene from metagenomic DNA from cow dung compost habitat for the enzymatic conversion of xylooligosaccharides from corncob. Wang et al. (2016) enriched microbial consortia by metagenomic analysis and shed lights to lignocelluloses degradation by Actinobacteria. These works suggest that metagenomic techniques could provide us with a bird’s eye view of the operation of environmental microbial communities related with compost.

2.4 COMPOSTING OF AGRICULTURAL WASTES Huge quantities of crop residues are generated every year and constitute a rich but underutilized source of renewable biomass in agriculture. The management of this waste material should be carried out in an easy manageable way. Half the quantity of agro wastes produced, find its way to be used as animal feed, roofing material, fuel, packing material, etc., while the other half disposed of by burning them simply in the field which might cause several other environmental problems like air pollution, soil erosion (Walia et al., 1999). Using microbial communities under high temperature, composting is exploited to manage agricultural waste successfully (Tuomela et al., 2000; Bernal et al., 2009). Composting has gained importance in agriculture as a useful means for disposal of organic wastes like that of sugarcane trash, paddy straw and several other agricultural wastes. Previous study on maize straw based on integrated meta-omics has shown to provide an excellent substrate used as natural composts (Zhang et al., 2015b). The second largest biomass feedstock in the world produced is wheat straw, which is a common resource of agricultural waste (Talebnia et al., 2010). Plant residues of agricultural waste contain mainly lingocellulosic material. High content of lignin may limit the enzymatic and microbial degradation of the cellulose content in paddy straw. Microorganisms that degrade cellulose can speed up the biodegradation of crop residues such as leaves, straw, trash, etc. These cellulolytic cultures have been used for composting of plant residues (Gaur, 1999). Microbial ability to

30 Recent Trends in Composting Technology decompose these organic matters depends highly on their enzymes which are needed for degradation of the substrates containing cellulose, hemicelluloses and lignin. The synergistic action of different group of microorganisms provides degradation of complex organic compounds down to smaller molecules, which can be further utilized by microbial cells (Golueke, 1991). Bacteria, fungi and also invertebrates like earthworms play a crucial role during composting. Hundreds of fungal species are found to be able of degrading lignocellulosic materials. Under appropriate conditions, cellulolytic bacteria are capable to degrade cellulose but their capability of lignin degradation is found to be limited (Ball et al., 1989). Aerobic mesophiles like Cytophaga and Cellulomonas are found to be capable of breaking down cellulose. Several mesophilic aerobic as well as anaerobic Bacillus sp. like, B. subtilis, B. brevis, B. polymyxa, B. pumilus, B. licheniformis, B. firmus, B. megaterium, B. circulans, and B. cereus are known which can readily degrade cellulose and hemicellulose (Strom, 1985). Actinomycetes are found to solubilise cellulose and are also able to modify the lignin structure extensively. Recently, a study on Streptomyces sp. has suggested that it can delignify paddy straw content (Saritha et al., 2012). Thermophilic fungal consortium of A. nidulans, Scytalidium thermophilum and Humicola sp. are noticed to be highly effective in degrading soybean trash and paddy straw mixtures actively during the summer months (Kumar et al., 2008). Using mixed cultures of microorganisms can enhance the rate of lignocellulose degradation greatly rather than using fungi, bacteria and actinomycetes singly in composting processes, as their synergistic activity can utilize the various intermediate degradation products (Kanotra & Mathur et al., 1994). Using mixed populations or microbial consortium is thus required to enhance the degradation processes of these complex agro wastes (Frontera et al., 2002).

2.5 MUNICIPAL WASTE COMPOSTING Municipal solid waste (MSW) generally consists of yard and kitchen waste. As a part of biorecycling of these wastes, many municipalities adopted landfill composting as efficient and eco-friendly approach (Otten, 2001; Wolkowski, 2003). Composting MSW lessens the quantity of the waste, exterminates pathogens that may be there, reduces germination of weeds in agricultural farms, and eliminates malodorous composites (Jakobsen, 1995). With growing interest in organic agriculture, the generation of organic-grade MSW compost for agricultural use is also achieving fame because of its benevolent effect on biological, physical, and chemical soil factors (Iglesias-Jimenez & Alvarez, 1993). Soil microbial ecology is nowadays being more used to determine soil quality, as the microbial population of soil is more susceptible to any kind of changes in soil parameters including soil nutrients, moisture content, particle aggregation status and others. Application of MSW compost to soils dramatically improves the microbial biomass carbon and respiration level of the concerned soil, which is a key parameter to measure soil metabolic activity (Bhattacharyya et al., 2003). In a field trial that lasted for several years,

Composting: Exploitation of Microbial Metabolic Diversity Therein 31

it has been proven that several supplementations of compost end products amplified the microbial biomass carbon of the concerned soil and this effect stayed strong for about 8 years after application (Garcia-Gil et al., 2000). A different evaluation of soil microbiological strength is the soil enzyme activity related to the conversion of the major nutritious materials (Crecchio et al., 2004). The activity of enzymes commonly found in soils like protease, alkaline phosphomonoesterase, deaminase, phosphodiesterase, urease and arylsulphatase, increased to a higher degree after the employment of compost end products (Perucci, 1990). The temperature increase in the compost habitat occurs when inhabiting microbes proliferate in the compost heap and elevate the temperature up to 45 to 70°C. This elevation in temperature is equally important for proper composting as it inhibits the growth and survival of potential pathogenic microorganisms like faecal Salmonella, Staphylococci, Streptococci, Shigella and most distinctively Escherichia coli, as they cannot withstand the elevated temperature. The viable count of these foretold pathogens reduced to a great degree when the heap temperature reaches 55°C and beyond, during the composting process (Hassen et al., 2001).

2.6 MANAGEMENT OF INDUSTRIAL WASTES THROUGH BIOLOGICAL MEANS Rapid growth in industrialization and population has led to increase in the amount of solid waste matter being produced every year. Industrial wastes removal through bioremediation is a challenging task because there is no technology available which may serve sustainably in complete removal of these pollutants from the location. Ultimately, the diverse groups of microorganisms already existing in the nature may present a solution for the bioremediation of toxic industrial waste materials (Okpokwasili, 2007). As there are vast differences found in processing mechanisms among the different industries, wastes should be separated and characterized carefully and the right solution to biodegrade them should be found.

2.6.1 Fruit and Vegetable Industry Fruits and vegetables are an important part of food industry because it is an increasing market rising day-by-day. But, however, as a consequence of rapid marketing and growth, the generation of waste residues is also increasing. The solid wastes produced from fruit and vegetable industries can be treated with composting or land farming with prior removal of water and adjusting the pH in order to provide the best niche for microbial growth. Many varieties of bulking agents can be added like straw, paper, mature compost, etc., in order to improve the microbial action on such wastes as well as it even helps in excess water drainage (Thassitou & Arvanitoyannis, 2001). The waste water generated from fruit and vegetable processes contains various water soluble organic compounds and sometimes also large amounts of suspended solids hence increasing the biological oxygen demand and become highly reactive when come in contact with microorganisms.

32 Recent Trends in Composting Technology

2.6.2 Meat and Poultry Industry The solid residues and waste water produced by the meat and poultry industry varies from place to place due to adaptation of varied methods of processing and quality monitoring. Generally, for liquid water wastes the organic matter content can be degraded by microbes using anaerobic condition without any previous supplementation of nutrients. The wastes generated from poultry and meat industry mainly contain fat, oil and grease-like substances. High amount of ammonia gas is produced from these industries because of the breakdown of proteinaceous wastes into amino acid and ammonia, which is harmful. The volatilization of ammonia can be reduced by immobilising the ammonium ions with co-composting poultry manure with carbon-rich organic waste materials (Mahimairaja et al., 1994) and then further adsorption of ammonia and/or ammonium ions using adsorbents such as zeolites and peat (Witter & Kirchmann, 1989).

2.6.3 Beverage Industry Processing of beverages occurs via various crucial steps and each of them produces various kinds of contaminants that pollute the environment if released in untreated condition. The wastes produced from such industries are also rich in high levels of BOD content. Such wastes from the fermentation industries are hard to treat as they contain high organic load in the waste flow as the waste contains tannins, phenols and organic acids. Also the amount of organic load of the waste from distilleries depends according to the starting raw material used. A residue called vinasse which is always produced from these industries needs a precise and long time biological treatment before release in order to reduce the organic load of the waste (Thassitou & Arvanitoyannis, 2001).

2.6.4 Dairy Industry Dairy industries contribute mainly to water as well as soil pollution all over the world. Dairy waste is normally high in organic matter mainly composed of fatty acids, protein material, sugars, etc., and largely varies on the kind of industry and the final product produced. There occurs a great range of quality and quantity in such industry, thus many types of both anaerobic and aerobic processes are needed to treat the wastewater of the dairy industry. Activated sludge process is also used for partial denitrification and removal of phosphorous.

2.7 COMPOSTING OF ANIMAL WASTE Animal wastes contain many nutrients such as nitrogen, potassium, phosphorus and various other minerals. Raw animal wastes are often offensive, dirty and also may contain many unwanted pathogens, parasites, etc. Vast amounts of biodegradable wastes are generated by livestock industry, which must be managed tactfully using appropriate disposal practices in order to avoid a negative impact on the environment (Burton & Turner, 2003). In order to overcome such offensive odour, resolve the difficulties, and

Composting: Exploitation of Microbial Metabolic Diversity Therein 33

inactivate the pathogens, parasites present in them. Stabilization of the organic constituents of animal waste product is essential to produce a uniform organic material suitable for further application. This technique can be harnessed not only to eliminate or reduce the risk of spreading of pathogens, parasites and weed seeds associated with manure application. It also leads to the production of a final stabilized product which can be used to advance and preserve quality and fertility of the soil (Larney & Hao, 2007). Animal manures have high fertilizer content, and nowadays their composting is found to be an alternative of recycling the manures in farms without enough agricultural land for their direct use as a fertilizer. Microorganisms play a vital role in the decomposition of organic manures (Ryckeboer et al., 2003). Bacteria are found to predominate early in composting, fungi are present during all the process but mostly predominate when the water level is below 35% and are not active at temperatures above 60ºC, whereas actinomycetes are found during stabilization and curing, and together with fungi they are able to degrade the resistant polymers.

2.8 MICROBIAL ROLE IN CONTAMINATED SITES TREATED BY COMPOSTING Various pollutants entering the soil are pesticides, chlorophenols, petroleum, polyaromatic hydrocarbons (PAHs), and related products and also heavy metals. Microbial mediated composting is gaining importance day-by-day for its cost effectiveness and environment friendliness. It is becoming a promising technology for the bioremediation of soil wastes and has also gained advantage over the physical and chemical strategies. The success or failure of composting/compost remediation strategy depends on a number of factors, most of which pollutant bioavailability or biodegradibility are the most important. Diverse strategies are employed for bioremediation of the soil contaminants which involve direct composting, addition of compost, bioaugmentation, introduction of bulking agents and application of surfactant. Often the researchers opt for a single strategy or a mixture of such methods to achieve the successful end.

2.8.1 Bioremediation Application of Organic Pollutants Degradation In recent years, microbial mediated cleaning of the contaminated sites of pollutants has gained interest. A large number of microorganisms play an active role in bioremediation of organic pollutants like petroleum, PAHs, other related hydrocarbon products and pesticides from contaminated sources.

2.8.1.1 Composting of PHAs using Microbes PHAs are made up of fused benzene rings which are recalcitrant in the soil because of the unique physical property they possess (Zhang et al., 2006). This class of organic compounds accumulates in environment mainly due to combustion of fossil fuels and is potentially harmful to human health due to their mutagenic and carcinogenic nature (Sayara et al., 2011; Ortega-Calvo et al., 2013). To facilitate degradation of these pollutants, various

34 Recent Trends in Composting Technology surfactants-like products are included into the soil which greatly increase their bioavailability (Cheng et al., 2008). The compounds which contain more benzene rings were less available to microbes than those with fewer number of rings. Microbial diversity is greatly increased with the addition of vermicompost in sites that are contaminated with PAHs (Di Gennaro et al., 2009). It is also noticed that the addition of vermicompost mainly enhances the metabolic activities of microbial community by inducing biodegradable indicator gene expression in the native microbes as well as supplementing new PAH-degrading microbe. A large number of Pseudomonas strains isolated from soil and aquifers are found to be capable of degrading PAHs (Kiyohara et al., 1992; Pathak et al., 2008). With the significant community shifts, highest PAH removal rate was observed in compost dominated by yeasts and Bacilli. (Covino et al., 2016).

2.8.1.2 Biodegradation of Petroleum and Related Products Various organometallic constituents, along with complex mixture of hydrocarbons and other organic compounds, together make up the oil (Butler & Mason, 1997). It is made up of hundreds or thousands of aliphatic, aromatic as well as branched hydrocarbons, which are normally harmful to the living organisms (ATSDR, 1995). Unexpected petroleum spills could persist in the soil for long and pose various environmental threats. The currently used physical and chemical treatments for degradation of petroleum products are quite effective, but they lag far behind the technology of eco-friendly biocomposting. By exploiting the natural populations of microorganisms petroleum and other hydrocarbon pollutants are eliminated from the environment. Environmental parameters which effect the degradation of hydrocarbons by microbes, elucidating the metabolic pathways involves genetic approach of how these hydrocarbons are dissimilated with the aid of microorganisms and the effects caused by hydrocarbon contamination on the communities of microbes have also been an intense area of interest. Biodegradation of petroleum has been reported to get enhanced mostly in the presence of bacterial consortium rather than monospecies activities (Ghazali et al., 2004). Mixed bacterial consortium has reported to have decreased the crude oil content from 78 to 52%, with an increase in the oil concentration from 1 to 10% (Rahman et al., 2003). Indigenous bacteria present in the soil help in the microbial remediation of hydrocarbon contaminated sites. Oily sludge contains a wide range of target constituents that are capable of easy degradation by these organisms. Typical bacterial groups found to degrade hydrocarbons belong to Pseudomonas sp., Marinobacter sp., Microbulbifer sp., Sphingomonas sp., Alcanivorax sp., Micrococcus sp., Cellulomonas sp., Dietzia sp., and Gordonia sp. (Brito et al., 2006). Chaillan et al. (2004) have reported some species of molds belonging to the genera of Aspergillus sp., Penicillium sp., Neosartorya sp., Paecilomyces sp., Graphium sp., Fusarium sp., Talaromyces sp., and the yeasts like Yarrowia sp., Candida sp. and Pichia sp., are capable of degrading hydrocarbons. Aerobic metabolism requires the presence of oxygenase enzymes that incorporate molecular oxygen into the reduced substrate. On the other hand, aliphatic hydrocarbons help further breakdown of initially produced alcohols that

Composting: Exploitation of Microbial Metabolic Diversity Therein 35

get sequentially oxidised to carboxylic acids via dehydrogenase enzymes which further XQGHUJRǃR[LGDWLRQ,QFDVHRIDURPDWLFK\GURFDUERQVWKHULQJVWUXFWXUHJHWVK\GUR[\ODWHG with the help of mono- or dioxygenase enzymes, and then the ring gets cleaved and further degraded after diol formation (Cerniglia, 1984). Anoxic condition prevails during anaerobic metabolism of hydrocarbons, carried out by sulphate reducing bacteria and other anaerobes like methanogens use variety of electron acceptors as the oxidant (Ward & Brock, 1978; Aeckersberg et al., 1991).

2.8.1.3 Biodegradation of Pesticides Pesticides are applied worldwide to agricultural fields annually for the control of pests. But most of the pesticides remain unused and ultimately sink into the ecosystem affecting soil property both biochemically and microbially. Their persistence in the environment and the tendency to bioaccumulate threatens non-target organisms, mainly humans. The major classes of pesticides generally grouped under the classes of chlorophenoxy acids, organochlorines, organophosphates, carbamates and s-triazines. Different research groups have developed a variety of biological strategies for the assessment of pesticide by biodegradation, bioattenuation, biostimulation, bioaugmentation, phytoremediation and several other composting techniques for detoxification, treatment and remediation of pesticide contaminated sites (Fogarty & Tuovinen, 1991; Häggblom, 1992; Alexander, 2000). The limiting conditions which prevail in the soil environment and also in the nature of pesticides, most of the pesticide undergoes only partial degradation which leads to the accumulation of metabolites in the soil system. Bioremediation is advantageous as different microbes and some plants are used for detoxification of these environmental threats. Most microbial species which are able to degrade pesticides belong to genera Pseudomonas, Flavobacterium, Burkholderia, Arthrobacter, Azotobacter, Bacillus, Klebsiella, Pandoraea and Mycobacterium. Pseudomonas sp. and Klebsiella pneumonia, both have hydrolytic enzymes, that are capable of breaking down s-triazine containing herbicides, namely, atrazine. Pseudomonas and Alcaligenes sp. utilize the enzymes like oxygenase, hydroxylases, hydrolases and isomerases to degrade toxic herbicide like 2, 4-D (Mulbry & Kearney, 1991). Thus enzymes also take part in the degradation of pesticide compounds and detoxify various polluting substances (Rao et al., 2010). Phytoremediation of pesticides is a comparatively less disturbing process and also has better public acceptance. The most important feature regarding phytoremediation is the selection of plants that are effective accumulators and can readily uptake the target contaminants from the soil (Emiko et al., 2009). Behrens et al. (2007) studied genetically modified plants like Arabidopsis thaliana, tomato, tobacco and soybean plants which have been extensively used for potential pesticide phytoremediation. Corn plants have been found to express aryloxyalkanoate dioxygenase enzymes (TfdA) and have been patented for the successful degradation of 2,4-D and pyridyloxyacetate herbicides (Scott et al., 2010). Some natural biodegradable compounds like exogenous poly amines are shown to

36 Recent Trends in Composting Technology absorb more pollutants than untreated plants, and are also reported to tolerate 500 times higher concentration of pollutants than those from untreated plants (Maheshwari et al., 2014).

2.8.2 Biorestoration of Inorganic Substances (Heavy Metals) Contaminated Sites Soil and aquatic environments are being constantly polluted with the release of heavy metals such as cadmium, copper, lead, nickel, zinc, etc., through various human activities which leads to altered biogeochemical cycling. In order to survive in heavy metal polluted habitats, microorganisms have developed strategies on their own. These organisms developed and adopted by themselves different mechanisms such as biosorption, bioaccumulation, biotransformation and biomineralization, and they harness such strategies for detoxification of heavy metals either ex situ or in situ (Vargas-García et al., 2012). Heavy metals are actively (bioaccumulation) and/or passively (adsorption) uptaken by microorganisms. The cell wall of microbes, mainly structured with polysaccharides, lipids and proteins, as well as functional groups like carboxylate, hydroxyl, amino and phosphate are capable of binding heavy metal ions. Among the various remediation methods driven by microbes, the biosorption process seems to be more practicable for the application at large scale because the microbes require further nutrient supplements for uptake of heavy metals actively, which further increases their biological oxygen demand or chemical oxygen demand inside the waste. Among fungi Penicillium, Aspergillus and Rhizopus have been extensively explored and are found potential for heavy metal removal from aqueous solutions (Volesky & Holan, 1995; Huang & Huang, 1996). In 2010, Xiao et al., in one of their works have reported efficient biosorbents from endophytes, which act as a hyperaccumulator, and are become more suitable than the traditional method of obtaining biosorbents. New approaches are harnessed such as the designer plant approach and their modification of rhizospheric environment to carry out bioremediation in a much cheaper and safer way.

2.8.2.1 Bioremediation by Adsorption The binding sites for heavy metal adsorption are present at the cellular structure of microbes. The binding of metals to these cellular structures is metabolic energy independent. The various reactive species on bacterial cell wall show significant effects on the acid-base properties and metal adsorption (Guiné et al., 2006). Extracellular polymeric substances (EPSs) can combine with complex heavy metals via various mechanisms, including proton exchange and micro-precipitation of metals (Comte et al., 2008; Fang et al., 2010).

2.8.2.2 Bioremediation by Biosorption and Biotransformation Affinity of a biosorbent towards sorbate (metal ions) is achieved through the biosorption process, and is continued until equilibrium is established between the two components (Das et al., 2008). For example, organism like Saccharomyces cerevisiae acts as a biosorbent

Composting: Exploitation of Microbial Metabolic Diversity Therein 37

and facilitates the removal of Zn (II) and Cd (II) through the ion exchange mechanism (Chen & Wang, 2007; Talos et al., 2009). Another promising sorbent, Cunninghamella elegans has been reported to remove heavy metals released by textile wastewater (Tigini et al., 2010). Many fungi have been reported to be capable of transforming heavy metals into less toxic forms and thus considered potential biocatalysts (Pinedo-Rivilla et al., 2009). Klebsiella oxytoca, Stachybotrys sp., Phlebia sp., Allescheriella sp., Pleurotus pulmonarius, Botryosphaeria rhodina are found to have potential metal binding capacity (D’Annibale et al., 2007). Fungal species like Hymenoscyphus ericae, Neocosmospora vasinfecta and Verticillium terrestre were reported to be able to biotransform toxic mercury Hg (II) state to a nontoxic state (Kelly et al., 2006). Microorganisms are capable of using heavy metals and other trace elements as terminal electron acceptors and reduce them further through detoxification mechanism, for the removal of metals from the contaminated environmental sites. Microorganisms employ redox reactions to derive energy for detoxification of toxic heavy metals and also utilize both enzymatic and non-enzymatic processes.

2.8.2.3 Bioremediation Process using Genetically Modified Microorganisms Genetically designed bacterium has the advantage to resist adverse stressful situations and can be used as a potent bioremediator under various complex environmental conditions. Deinococcus geothermalis has been reported to reduce mercury (Hg) at high temperatures by the expression of mer operon from E. coli, coded for Hg2+ reduction (Brim et al., 2003). Modifications have been made on Pseudomonas strain with the pMR68 plasmid carrying novel genes (mer) which has made that strain resistant to mercury (Sone et al., 2013).

2.8.2.4 Remediation of Heavy Metals using Plants (Phytoremediation) Plants along with associated microorganisms are capable of either partial or complete remediation of heavy metal contaminants from sludge, soil, sediments, wastewater and ground water. The process of phytoremediation harnesses variety of plants and also exploits physical characteristics of plants to carry out the remediation of contaminated sites. Recently this technique is hugely exploited for heavy metal remediation from polluted soils (Martinez et al., 2006). Heavy metals get immobilized by plants through sorption by the roots, precipitation and formation of a complex or reduction in metal valence taking place in the rhizosphere region (Penny et al., 2010). Also, plants absorbed several heavy metals and get them converted into volatile forms which get subsequently released into the atmosphere by the process called phytovolatilization. This process is capable of removing some volatile heavy metals like mercury and selenium from polluted soils (Karami & Shamsuddin, 2010).

2.9 COMPOSTING: PROS & CONS Advancements in the composting techniques opened a new road for waste management and applications of white biotechnology. Composting of the end products of our day-to-

38 Recent Trends in Composting Technology day activities and various industrial processes not only helped us to control the waste produced, but also assisted us in several other ways. But, as all the good things come with consequences, there are some adverse effects of composting as well, which we will have to keep in mind while practising it in the long run.

2.9.1 Prospect Waste management: The effect of composting in waste management in enormous. Dayby-day, the daily production of waste materials from household, municipal areas, agricultural fields, industrial processes are increasing exponentially. To cope up with the huge loads of wastes produced, composting approach comes in handy as it breaks down the wastes by various biochemical and enzymatic techniques mediated by microbes like bacteria and fungi. Different kinds of wastes like animal manure (cow and swine, poultry litter), municipal solid wastes, sewage sludge, food wastes, various industrial wastes like tannery, refinery, agricultural wastes like straws, corncobs, green and wood waste can be composted prior to disposing of to landfills or environment, as it doesn’t only reduce the toxic effects of the wastes, but also reduce the whole amount of waste being disposed of. Fertilizer production: Composting is a green approach that can be well executed for the betterment of mankind. Composting of several types of wastes like cow and swine manure, poultry litter, food and agricultural wastes generate end products that can be easily used as fertilizer in agricultural fields. Amendment of soil with compost is benevolent for the soil as it improves soil quality, helps in the aeration of the soil due to high porosity, increases availability of plant nutrients, and stimulates microbiological activity of the soil to a high degree. Cozzolino et al. (2016) showed that the application of compost to maize field soil provided higher amount of total N and P to the plants than the control. The addition of compost influenced the growth and colonization of arbuscular mycorrhizal fungi in the maize roots. This study also showed that the compost of different maturation stages have different effects on plant growth, microbial community and soil quality. Organic amendment: Organic matter has quintessential role on soil quality, notably when the growth of plant is concerned. One of the most important roles of organic matter amendment in soil as compost is the increase in the microbiological activity in the applied area. The well examined effects of organic matter addition in soil are: (1) compost end products slowly release the nutrients present therein (95% nitrogen in organic state), (2) it binds readily to the inorganic and organic contents of the soil, it may be contaminants present in the soil or nutritive materials, (3) because of its high organic content, it drastically elevates the water holding capacity of the soil, (4) it helps in forming soil particle agglomerates, due to which aeration and water penetration in the soil increases, and (5) due to the microbial activity in the soil, it can sequestrate carbon in the soil, which is not available for decomposition for a prolonged time, but not permanently. So, addition of compost in soil mitigates greenhouse gas (GHG) emission, since it sinks down some CO2

Composting: Exploitation of Microbial Metabolic Diversity Therein 39

produced by fossil fuel combustion. That is, the augmentation of only the end products of composts, rich in organic materials, changes the physicochemical properties of the soil. Plant disease inhibition: Different plant diseases are generally known to be caused by different genus of fungi, capable of producing spores, rather than the infection of bacteria. Many research works have been conducted to shed lights on the capability of compost end products as inhibitors of plant diseases of different crops, because the use of fungicides to control plant pathogens can be regulated or absolutely discontinued with the application of compost end products in the field. The effect of compost on plant pathogens can be generic or particular and they work by certain distinct mechanisms, which are: (1) competition for nutrient and space between nonpathogenic and pathogenic microbes (bacteria, fungi, or actinomycetes) present in the compost as well as soil. The competition generally favours the indigenous microbes of compost and leads to the abolishment of pathogens. One of the key factors of this competition is the fight for iron, the increased number of siderophore producers in soil after the augmentation of compost results in the reduced amount of iron in the soil, which inhibits the growth and colonization of several plant pathogens, (2) several compost microbes like Pseudomonas and Bacillus are established antibiotic producers which work as biocontrol agents for plant pathogens, (3) in another scenario, compost microbes directly attack the plant pathogens resulting in lysis or death of pathogens, and (4) systemic acquired resistance (SAR), in which pathogen triggers a local defence signalling system in plants and the plant responds by producing generally salicylic acid and other various pathogenesis related various proteins, and induced systematic resistance (ISR), which can result from pathogens, different chemical components or benevolent compost microbes. Generic suppression means a large number of microbial species are accountable for the inhibition of pathogenic organisms. In total contrast with generic suppression, in case of specific suppression, for the suppression or subsequent annihilation, a limited number of microbes can be accounted for.

2.9.2 Constraints Ammonia production: Manure composts are one of the major sources of air and water pollution because of the estimated 117,000 tonnes of ammonia produced from beef and dairy industries (DEFRA, 2002). Emission of ammonia is pretty high within the first few days of compost process as the indigenous bacterial proliferation in the compost pile increases the temperature to a significant level. Most of the ammonia released from the compost heap is within the first 30 days, given that the compost heap is not turned, mixed or forked, which accelerates ammonia formation within the pile. Rainfall reduces ammonia emission as it decelerates compost process, but it can result in the leaching of several water-borne pollutants, that can contaminate groundwater and freshwater streams or ponds, when drainage happens. Once again ammonia production elevates when the compost heap is broken before application to concerned lands (Smith et al., 2002). Greenhouse gas emission: CO2 is a well known greenhouse gas and is generated while aerobic respiration, but when in contrast with fossil fuel combustion generated CO2 is

40 Recent Trends in Composting Technology considered. CO2 resulting from degradation of plant bodies does not really assist much to the greenhouse effect and global warming as it has already been removed beforehand from the environment by photosynthesis. N2O is the product of microbial denitrification process, which is an anaerobic process, and a very little amount is produced by nitrification. CH4 is emitted from anaerobic metabolism when CO2 is reduced by microbes. The addition of N2O and CH4 leads to the intensification of greenhouse gases in the atmosphere (Hellman et al., 1997). The production of CH4 from compost heaps can be used in our advancements if the whole composting process is done under anaerobic conditions and the CH4 produced is stored to be used later as necessary source of energy. Anaerobic conditions in compost heaps can result in a total mess as composting is an aerobic process and its success depends on the supply of O2 to the decomposing microorganisms resting in the pile. So, it can be concluded that a well maintained and heavily aerated compost plant should not be of considerable benefaction to the release of greenhouse gases, whereas ill maintained compost heap can result in high CH4 and N2O fluxes. Compost leaching: Many research works and studies disclosed that the leachate resulting from green and non-green feedstock composts may consist of organic compounds, different nutrients, which may increase the BOD and COD levels of water and cause eutrophication of stagnant waters, pathogens and/or metals which may cause serious contamination of water (ODEQ, 2001). The amount of waste water disposal must be reduced and proper treatment before wastewater discharge should be administered to protect valuable natural water sources. Toxic elements: Feedstock wastes taken for biodegradation by composting means sometimes contains large concentrations of hazardous elements naming zinc, cadmium, nickel, chromium, mercury, lead, copper and others, for which threshold values have been calculated and taken into account in many countries, depending on the concentration ranges in sewage sludge samples. Organic material: The waste materials discharged for composting may contain a large number and concentration of organic contaminants, like industrial contaminants, pharmaceutical drugs or pesticides, and end products of these contaminants in the compost heap largely depend on their nature and complexity. The more durable ones of various organic materials will still remain in the compost heap even after severe microbiological actions and elevated temperature, due to their recalcitrant nature and time taken for breakdown, e.g., diazinon, a pesticide, which has a durability in soil of about 3 months was not present in compost, but pentachlorophenol that normally abide in soil for about five years is found to be in the compost (Deportes et al., 1995). Fate of a specific pesticide in composting process may engage fractional decomposition to transitional metabolites, humification, volatilization, and adsorption, depending on the compound, composting practices and the indigenous microbial population in the compost habitat. The ample distribution of carbon sources on the compost also help in the

Composting: Exploitation of Microbial Metabolic Diversity Therein 41

decomposition of xenobiotics or through co-metabolism. Wastes generated from meat, poultry and dairy industries and animal litters from firms or sewages usually contain notable concentrations of therapeutic agents (compounds used to cure and prevent diseases). These agents act similar to pesticides and leftover remains in the end products even after complete composting, and are generally ignored (Jjemba, 2002). Incomplete metabolized therapeutic drugs are expelled into the environment with urine and faecal matter and together with leftover livestock feed, they go into the waste materials, and they may even withstand the harsh composting process and remain in the end product. Organic compounds are also produced in compost process itself, like methyl esters and fatty acids are produced by microbes during metabolism, but as the concentrations are pretty low, they are not considered hazardous (Gonzales-Vila et al., 1982). One of the key concerns of compost is the foul odour that is due to compounds like methyl mercaptan that contains sulphur, which results from the disintegration of amino acid methionine (Catton, 1983). Human pathogens: Recent studies have disclosed that the catering and food wastes may contain pathogens like E. coli 0157, Newcastle disease, Campylobacters, Salmonellas, exotic pig viruses, transmissible spongiform encephalopathy, and various parasites (Gale, 2002). Kitchen waste and table waste containing meaty products, oil, grease and various dairy products may contain pathogens (ODEQ, 2001). Compost process can be exceptionally efficient in annihilation of pathogenic microorganisms (Epstein, 1997). The key method of pathogen obliteration in composting is the consequence of elevated temperatures (80°C) over an extended period of time. A lot of countries have schemes which necessitate, either by legislative principles or from controlled plans, the compost matter to be increased up to a least temperature level for a minimum amount of time. On top of that, the composting scheme engages substantial alterations in the biochemical properties of the material intended to be composted. Antagonistic outcomes and degradation of the mesophilic microbes results in the inhibition and annihilation of pathogenic ones and also reduce their chance of recolonization in the compost heap. Bioaerosols: Inhalation of bioaerosols resulting from dust of organic materials can easily invade our lungs and cause severe respiratory diseases in humans through infection. The major ailments resulting from bioaerosol inhalation are inflammation, allergy and respiratory tract infection. Bioaerosols that are of huge concern and related to composting are spores from fungus Aspergillus fumigates, endotoxins, which are heat stable, phospholipid-polysaccharides-protein complex macromolecules, and organic dust. Plant pathogens: Gale, (2002) reported that a few nematodes, some specific plant pathogenic fungi produce tough, heat resistant, resting spores and a number of plant pathogenic viruses may endure the complex composting procedure. Five of the plant pathogens were recognized as significant: Pepino mosaic virus, Potato spindle tuber viroid, Sclerotium cepivorum (white rot of onions), Polymyxa betae (vector of beet necrotic yellow vein virus which causes Rhizomania), and Plasmodiophora brassicae (club root).

42 Recent Trends in Composting Technology

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C H A P T E R

3 Soil Enrichment with Polyphenols Rich Composting

Munmun Mallik Ghosh 1, Samiran S. Gauri 2, Santi M. Mandal 3 and Bikas R. Pati 2,* Department of Zoology, Vidyasagar University, Midnapore-721102, WB, India Department of Microbiology, Vidyasagar University, Midnapore-721102, WB, India 3 Central Research Facility, Indian Institute of Technology Kharagpur, Kharagpur-721302, WB, India *E-mail: [email protected] 1

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ABSTRACT Phenolic acids are the second most abundant organic constituents cycled in soil. They play an important role in organic matter decomposition, polymerize and condense phenols into humic substances. Heterotrophic microorganisms use them as a source of carbon, and serve as soil antioxidant. In India, all tea shops and tea industries always throw away lots of waste tea, daily, as leftover. Nowadays, the waste tea may have been mixed with manure during composting and finally applied to cultivated areas which may give immense importance to soil. The advantages and limitations of tea waste polyphenol rich composting manure application in soil has been described in detail in the current perspective.

3.1 INTRODUCTION More than a century after its momentous discovery, urea gained popularity as an artificial source of nitrogen for plants. And after the onset of synthetic fertilizer dependent agriculture, it took a little more than half a century to degrade many of the world’s most productive soils. The reasons for ineffectiveness of synthetic fertilizers in supplementing soil nitrogen depletion are: first, since most of the nitrogen absorbed by the non-leguminous crops is usually obtained from the soil organic reserves, non-judicious agricultural practices, including improper crop rotation, results in a decrease of soil nitrogen supply. Second, mineral nitrogen, particularly in the ammoniacal fertilizers stimulates microbial carbon decomposition that promotes the loss of crop residues and also indigenous organic matter, the major reservoir of soil nitrogen. Third, sometimes temporary increase in cereal yields due to higher nitrogen releasing rates from synthetic fertilizers leads to dire consequences resulting in further decline in soil productivity which, in turn, increases the need for synthetic fertilization cumulatively, creating food insecurity and

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environmental degradation (Khan, Mulvaney, Ellsworth & Boast (2007, 2009; Johnston, 1986). Fourth, in most parts of the world, environmental pollution caused due to synthetic fertilizer dependent agriculture is a major concern. The low uptake efficiency of synthetic fertilizer not only affects the economics adversely but the ecology also. Higher solubility of nitrates leads to their increased runoff, causing rise in aquatic nitrate concentrations and the growing occurrence of hypoxic dead zones in the coastal waters around the world in the last half century (Diaz & Rosenberg, 2008). Leaching of nitrates in the soil leads to increased nitrate levels in groundwater which if more than 10 ppm, can lead to child birth with blue baby syndrome (Savino et al., 2002). Fifth, the synthetic fertilizers also lead to increase in greenhouse gases like carbon dioxide and nitrous oxide in the atmosphere contributing to global warming. And lastly, excessive use of these fertilizers has a detrimental influence on phyto-nutritional quality of crops and reduced antioxidant levels in food (Arancon, et al., 2004; Toor et al., 2006). Thus, the prevailing system of agriculture does not provide the means to intensify food production without degrading the soil, water and air resources, even compromising with the quality of production. So we should look forward to depend more on the sustainable age-old agricultural practices that advocate the use of composts and manures for rejuvenating the major nitrogen reserves of the soil. Soil, the fundamental natural resource on sustainable agriculture and economic development, retains its fertility only through various agro inputs. Knowledge about the changes of soil nutrient status, phytochemical status, soil enzymes, morphological growth, etc., is the key to understand soil fertility management. Soil, the natural media for plant growth is made of four basic components such as organic matter, minerals, air and water. Soil minerals constitute around 45% of the total volume, air and water around 25% each and organic matter from 2–5%, organic constituents of soil is comprised of 10–20% carbohydrates, 20% nitrogen containing material, 10–20% aliphatic acids and alkanes, and 40–60% aromatic compounds. The biogeochemical transformations of minerals like N, S, Fe and C have profound impact on vegetation and soil health. The major constituents of soil aromatic compounds are phenolics and their derivatives (Whitehead, et al., 1983). The term “phenolic” or “polyphenol” can be precisely defined as a substance which has an aromatic ring bearing one (phenol) or more (polyphenol) hydroxyl substituent, including functional derivatives (esters, methyl ethers, glycosides, etc.). An interaction between soil physicochemical properties and biotic factors is essential for healthy plant growth. The surface soil that supports vegetation is very prone to erosion and degradation. Detrimental farming practices that lead to decline in soil fertility includes burning crop residues, leaving vast stretches of open cultivable land free from any vegetation, unprotected from the sun and wind, excessive or insufficient use of fertilizers and improper crop rotation. Protection of this thin layer of soil is fundamental to the existence of our race. On the other hand, soil fertility can be enhanced through mulching, the process in which soil surface is covered with a layer of organic material. Mulches prevent soil from

52 Recent Trends in Composting Technology damage because they improve soil and its water retention capacity by increasing infiltration rates and also stimulating growth of soil biota. They also reduce the destructive effect of raindrop impact on soil aggregates and thus soil erosion. Soil surface damage and erosion can be prevented through intercropping also. Other organic wastes undergoing decomposition with the help of soil microbes are also involved in many beneficial roles to maintain soil fertility. These types of fertilizers which are made from rotting plant and vegetable wastes are known as composts. Composts and manures have been used in agriculture as a significant source of organic matter and for mulching as well. The plant and vegetable wastes are broken down by microbes, especially bacteria, fungi, etc., and decomposed into compost, while manure is animal excreta used directly for fertilization. To increase crop productivity, soil fertility and soil structure, soil microbial population and activity and improved moisture holding capacity (Arancon et al., 2004), composts have been used through centuries. For building soil organic matter and recycling of soil nutrients as a part of sustainable agriculture composting is the key technology. Other benefits of composting include flexible manure management, increased odour control, weed control and reduced pollutants and diseases (Rynk, 1992). Crop productivity may be increased by adding some beneficial microorganisms into the soil, particularly those species that fix nitrogen, enhance nutrition, phosphorus availability, dissolved minerals and increase mineralization of soil organic matter. The widely used strains of nitrogen fixing bacterium are Rhizobium, Azotobacter, Azospirillum and mycorrhiza fungi which enhance plant phosphorus nutrition. A diverse class of compounds originating from plants and microbes interactions is phenolic acids and their derivatives. These phytochemicals are commonly found in plant decomposition products. They are universally distributed in plants and are important precursors of humic substances in soils and serve as intermediate products of natural polymers containing aromatic rings, like lignins and tannins. Phenolics from root and seed exudates, leaf leachates, decaying plant matter, play multiple roles in soil formation and pedogenesis, directly influencing the organic matter dynamics as well as recycling of mineral elements present in soil (Seneviratne & Jayasinghearachchi, 2003). Through phenolics such as chlorogenic acid, green leaves and decomposing litter can influence rhizosphere nitrogen. By forming organic metallic complexes, phenolic exudates have been reported to have increased the availability of micro- and macronutrients (Micales, 1997).

3.2 SOURCES OF PHENOLIC ACIDS IN SOIL The major source of phenolics in soil is lingocellulosic material of plant cell wall (Buchanan Gruissem & Jones, 2015), whereas the free phenolics in soil solutions come from leachates of leaves and litter, root exudates, release of bound forms of microbial metabolism (Blum, Shafer & Lehman, 1999). Plants acquire metabolic flexibility that is essential for anticipating and overcoming biotic and abiotic stress, through production of an extremely diverse

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group of low molecular secondary metabolites (Dixon, 2001). Such low molecular weight metabolites are generally derived from fatty acid, alkaloid, isopropanoid, phenylpropanoid, and metabolism pathways. Phenolic compounds are generally synthesized from either the shikimic acid pathway or the malonate acetate pathway or both (Buchanan, Gruissem & Jones 2015). A majority of the phenolic compounds in plants, fungi, and bacteria is synthesized involving the shikimic acid pathway using simple carbohydrate precursors derived from glycolysis and the pentose phosphate pathway derived through aromatic amino acids, phenylalanine and tryptophan (Mandal, Chakraborty & Dey, 2010). In fungi and bacteria, phenolic acids are synthesized through malonic acid pathway, whereas in higher plants this pathway is of less significance. Flavonoids are the largest single group of phenolic C15 compounds composed of two phenolic rings connected by a three carbon unit biosynthetically derived from p-coumaroyl CoA and malonyl CoA, derived from shikimate and acetate respectively (Mann, 1978). In plants phenolic compounds are utilized in defense to pathogen attack, for pigmentation, aroma, growth and reproduction. Several classes of phenolics have been categorized on the basis of their basic skeleton: C6 (simple phenol, benzoquinones), C6-C1 (phenolic acid), C6-C2 (acetophenone, phenyl acetic acid), C6-C3 (hydroxycinnamic acids, coumarins, phenylpropanes, chromones), C6-C4 (naphthoquinones), C6-C1-C6 (xanthones), C6-C2-C6 (stilbenes, anthraquinones), C6-C3-C6 (flavonoids, isoflavonoids), (C6-C3)2 (lignans, neolignans), (C6-C3-C6)2 (biflavonoids), (C6-C3)n (lignins), (C6)n (catechol melanins), (C6-C3-C6)n (condensed tannins). The phenolic acids found in plant cell walls and lignins have a unique chemical structure of C6-C3 (phenylpropanoid type) whereas those of microbial origin are of C6-C1 (phenyl-methyl type). The most common phenolic compounds present in soil environment are 4-hydroxybenzoate and ferulic, p-coumaric, vanillic, cinnamic, tannic and syringic acids as plant roots exudate. Another way of phenol pollution is associated with pulp mills, coal mines, refineries, wood preservation plants, and various chemical industries, as well as their discharged waste waters (van Schie & Young, 1998). The discharge of Olive Mill Wastewater (OMW) from olive oil production industry has become a major environmental problem in last few years. Typical OMW composition was reported having 4–16% organic compounds where the majority of organic fraction contains phenolic compounds which is further divided into low-molecular weight (caffeic acid, tyrosol, hydroxytyrosol, p-coumaric acid, ferulic acid, syringic acid, protocatechuic acid etc.) and high molecular weight compounds (tannins, anthocyanins, etc.) Different source of phenolic acids in soil and their accumulation are summarized in Fig. 3.1.

3.3 EFFECT OF PHENOLICS IN SOIL POPULATION Phenolic compounds and derivatives are the natural aromatic compounds present everywhere in the environment as common organic pollutants. Phenolic acids are the most abundant organic constituent cycled in soil, next to cellulose and can account for 20–30% of biological carbon cycling in the biosphere (Buchanan, Gruissem & Jones, 2015). Chemicals such as dyes, explosives, pesticides and drugs are manufactured using polyphenols. During paper manufacturing, polyphenols are used in the bleaching process.

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Fig. 3.1: Schematic diagram represents different sources of phenolic acids in soil.

In the soil, phenols undergo several transformations (Hättenschwiler & Vitousek, 2000) : 1) soil microbes polymerize and condense them into recalcitrant humic substances, thus acting as important constituent of soil organic matter. In soil, phenol derivatives form complexes with complexes with different peptides, amino acids, polysaccharides, and other organic substances forming stable soil organic matter. 2) Heterotrophic microorganisms use them as a source of carbon and thus degrade them into minerals. 3) Phenolic acid forms chelate complexes with aluminium or iron and thus gets absorbed into soil minerals. 4) When phenolic acids remain in dissolved form, they get leached by percolating water, and finally leave the ecosystem as part of dissolved organic carbon. In plants phenolic compounds can act as protective agents, inhibitors, natural animal toxicants and pesticides against invading organisms, i.e., herbivores, nematodes, phytophagous insects, and fungal and bacterial pathogens. Certain phenolics are responsible for the scent and pigmentation that can attract symbiotic microbes, as well as pollinators and animals that disperse fruits (Bhattacharya, Sood & Citovsky, 2010). On the other hand, the high amount of soil phenolic acids can affect soil nutrient dynamics adversely by forming complexes with proteins and delaying organic matter decomposition and mineralization (Hättenschwiler & Vitousek, 2000). Thus, they can decrease the available inorganic nitrogen for plant uptake in soil, as well as change the nutrient dynamics of the soil. Consequently, they can inhibit seed germination, seedling growth, or early plant growth in soil (Krogmeier & Bremner, 1989). The phenolic derivatives like benzoic and cinnamic acids, coumarins, flavonoids, isoflavonoids, tannins have well reported allelopathic characteristics (Callaway & Aschehoug, 2000).

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3.4 ADVANTAGES OF PHENOLIC ACIDS IN PLANTS 3.4.1 Role in Plant Nutrition Microorganisms present in soil are various strains of bacteria, protozoa, actinomycetes, and fungi. They proliferate within soil media and are found in compost as well. In productive soils their activity based on the presence of organic matter, is essential for growth of healthy plants. They play an important role in organic matter decomposition that lead to humus formation and nutrient availability (Figure 3.2). They polymerize and condense phenols into humic substances. Heterotrophic microorganisms use them as a source of carbon. Several soil bacteria play a role in decaying plant residues and oxidizing aromatic compounds and as an outcome of this decomposition process, simple phenolic compounds such as hydroxyl and methoxy benzoic acid and cinnamic acids are commonly formed (Whitehead, Dibb & Hartley, 1983). In limited environments, some diazotrophs may use phenolic acid as alternative carbon sources. Microorganisms such as mycorrhizal fungi and rhizobial bacteria that live on and near the roots, promote root activity by working symbiotically with plant roots, assisting them in extracting nutrients from soil. These microbes scavenge nutrients for the plants; in turn plants provide them carbon in the form of sugars and proteins. This symbiotic association benefits the beneficial organisms and the plant, but not the pathogens that attack the plant. By forming organic metal complexes, phenol exudates have been reported to have increased the availability of micro- and macronutrients to plants (Micales, 1997).

3.4.2 Role in Disease Control and Plant Defense The level and type of organic matter and microorganisms present in soils influence the growth of earthworms, which, increase water infiltration and aeration of soil, and suppress plant diseases. Increased population of certain microorganisms may suppress specific diseases such as Pythium and fusarium as well as nematodes (Vallance, Déniel, Floch, Guérin-Dubrana, Blancard & Rey, 2011). The composting process can be optimized to increase the population of these beneficial microorganisms. Few best known illustrations of protective role of phenolics are: In onion, water soluble phenolics, procatechuic acid and catechol diffuse out from the dead cell layers, aid against infection of Colletotrichum circinans, by inhibiting germination of spore and penetration of hyphae by the pathogen. 8-hydroxyquinolone, a strong antibacterial and antifungal phenolic allelochemical isolated from knapweed, kills pathogenic microbes such as Xanthomonas campestris, Rhizoctonia solani, Phytophthora infestans, Aspergillus niger, Fusarium oxysporum (Vivanco, Bais, Stermitz, Thelen & Callaway, 2004), etc. A broad spectrum of antimicrobial compounds is activated in plants in response to microbial attack. The activated defense response is expressed at the site of the attack as well as at a distance to the site of primary infection and further protects the plant from spread of infection. A network of interconnecting signal transduction pathways, signaling molecules which are mainly phenolic acids regulates this induced resistance in plants.

56 Recent Trends in Composting Technology Generally roots, seeds, or decomposed residues release phenolic compounds that can act against soil-borne pathogens and root feeding insects (Ndakidmi & Dakora, 2003). Roots must be a rich source of specific natural products that are the key molecules contributing to the competitiveness of invasive plant species and have a significant effect on plant and soil-borne microorganisms (Inderjit & Duke, 2003; Bais, Weir, Perry, Gilroy & Vivanco, 2006). Several studies have shown that release and accumulation of phenolic compounds in soil from the plants provide defense against soil-borne pathogens, nematodes and phytophagous insects (Dakora, 1995; Dakora & Phillips, 1996). The structure activity relationships between phenolic compounds and their substrates are diverse and play important role in plant microbe interaction. Both simple and complex phenols such as isoflavonoids, glyceolin, cajanin, coumesterol, medicarpin, rotenone, phaseolin, phaseolinin, flavonoids, act as phytoalexins, phytoanticipins and nematocides against soil-borne pathogens and phytophagous insects (Ndakidemi & Dakora, 2003; Dakora & Phillips, 1996). Several phenolics possess high antifungal activity as well (Nicholson, Hammerschmidt, 1992; Sarma & Singh, 2003). Hence, phenolics can be used as an alternative to chemical control to pathogens on agricultural crops (Dakora & Phillips, 1996). At the challenge sites, phenolic compounds accumulate, followed by localized production of reactive oxygen species driving cell wall crosslinking, thus reinforcing cell wall, displaying antimicrobial activity and defense signaling (Field, Jordán & Osbourn, 2006). The quality and quantity of flavonoids present in the rhizosphere is influenced by the microflora that modifies the root exudation patterns as well as catabolism of exudates. Attenuation of phenolic acid signaling in microbes may have several ecological consequences in plant-microbe interactions (Shaw, Morris & Hooker, 2006).

3.4.3 Role in Symbiosis Phenolic compounds play an important role in plant-microbe interaction or symbiosis. In the initiation of legume-rhizobia symbiosis and also in the establishment of arbuscular mycorrhizal symbiosis, they act as signaling molecules. Diverse classes of polyphenolic compounds including flavonoids, hydroxybenzoic and hydroxycinnamic acids are involved as signaling molecules in plant microbe interactions. In roots of leguminous plants, a variety of phenolic compounds regulate nod gene expression by the symbiont (Rhizobium), thus a variety of phenolic compounds secreted from roots of leguminous plants such as flavonols and flavanones in Vicia faba (Bekkara, Jay, Viricel & Rome, 1998), isoflavonoids in soybean (Lameta & Jay, 1987) and vanillin in peanuts, modify the legume rhizobial symbiosis. Also during expression of various symbiotic plasmid encoded nod genes, the host root secretes phenolic compounds that act as signaling molecules. In legumes, during seed germination and seedling growth phenolic acids are released rapidly from emerging roots (Bekkara, Jay, Viricel & Rome, 1998; Staman, Blum, Louws & Robertson, 2001). These phenolic acids accumulate in the soil and in response to these acids, Rhizobium community in the rhizosphere undergoes changes that provide a

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competitive advantage for nodulation to selective rhizobial strains. Generally, rhizobials utilize phenolic acids as carbon source. In Arachis hypogeae, roots and root nodules are involved in Rhizobial defense and nodule morphogenesis through a range of soluble and conjugated phenolic acids (Chakraborty & Mandal, 2008). In root nodules of Vigna mungo, endogenous phenolic acids stimulate the efficacy of IAA production by its symbiont (Rhizobium sp.) and regulate the morphogenesis (Mandal & Mandal, Das, Pati & Ghosh, 2009). Phenolic compounds modify the legume rhizobial symbiosis by strongly regulating nod gene expression of the symbiont (Li, Wang, Ruan, Pan, & Jiang, 2010). After induction of nod genes, the rhizobium releases signal molecules by that control root nodule organogenesis. Nod D activator proteins regulate the expression of these genes. In response to the phenolic signals Rhizobium releases lipochito oligosaccharide Nod factors as signal molecules that control root nodule organogenesis, cause morphological changes in root hairs, resulting in formation of infection thread, development of nodule and finally nitrogen fixation. Flavonoids act as activators of transcription and bind to rhizobial nod genes, while the products of these genes, in turn, activate transcription of other nod genes (Redmond, Batley, Djordjevic, Innes, Kuempel & Rolfe, 1986) and alter nodule organogenesis.

3.4.4 Pest Control Plants naturally protect themselves against pest animals, i.e., herbivores, nematodes, phytophagous insects, and fungal and bacterial pathogens with the help of phenolic compounds that can act as protective agents, inhibitors, natural animal toxicants and pesticides against the invading organisms. Examples are: 1) Toxic secondary metabolites produced by toxic Rhizobacteria protect the roots from herbivory. Hydrogen cyanide producing rhizobacteria residing in the roots of leguminous plants reduces root grazing by termites in vitro (Devi, Seth, Kothamasi & Kothamasi, 2007). 2) Volatile phenolic compounds in plant resins may attack the plant. 3) Phenolics act as chemical defense against herbivores in the kelp species Alaria marginata (Steinbery, 1984).

3.4.5 Metal Chelation One of the most important physicochemical properties of humic substances is their capacity to bind ions. Humic substance contains large number of reactive functional groups including carboxylic, phenolic, alcoholic and enolic hydroxyl groups, various carbonyl groups, N-, S-, and P- containing functional groups. The total amount of acidic functional groups, the overall chemical structures, steric hindrance, aromaticity, degree of humification, etc., determine the metal ion binding ability of humic substances. Interaction of metal ions with humic substances affects their involvement in mobility and transport, fixation and accumulation, chemical reactivity and bioavailability in soils (Tipping, 2002). Several metal ions such as Mg2+, Ca2+, Fe2+, and Fe3+, form a complex with humic substances through electrovalent – covalent coordination bindings that involve phenolic OH, carboxylate or HSO3 groups of humic acids (Baham, Ball & Sposito, 1978).

58 Recent Trends in Composting Technology Thus humic acids increase soil’s cation exchange capacity and its ability to store nutrients by chelation, being safely held in soil without getting leached by rain or irrigation. These cations are nutrients that are made available to plants. Compost, comprised mainly of humic substances, binds heavy metals and other contaminants, not only reducing their leachability but absorption by plants also. Soil organic matter with a molecular weight of 1 kDa or more has been found to reduce the concentration of free heavy metal ions such as Cu2+, thus reducing their availability and toxicity (Haghighi & Teixeira da Silva, 2016). Clay minerals bind to phenolic acids such as salicylic and coumaric acids and procatechuic acids by forming chelate complexes with metals [Li, Wang, Ruan, Pan & Jiang, 2010]. Phenolic exudates from roots form organic metal complexes and thus reported to have increased the availability of micro- and macronutrients for the plants (Micales, 1997). Therefore, by amending the native soil with compost, sites contaminated with various pollutants may often be cleansed. The same binding effect allows compost to be used as a filter media for storm water treatment and has been shown to have minimized leaching of pesticides in soil systems (Faucett, Jordan, Risse, Cabrera, Coleman & West, 2005).

3.4.6 Humic Substances and Soil Organic Matter Humification is the process in which organic materials in soils become stabilized. The process involves the breakdown of plant and animal residues into products, such as sugars, amino compounds, and quinones that again recombine through polymerization to form humic substances. During degradation of organic matter, one of the important roles played by free radicals is the breakdown of lignin, a polyphenolic compound. Lignin polymerization is very essential in the degradation process that involves specialized lignin degrading fungi and enzymatic hydrolysis by hydroxyl and other free radicals producing quinones (Hammel, Kapich, Jansen & Ryan, 2002). Stable organic free radicals containing semiquinone moiety are found in humic substances (Senesi, 1990), the concentration of this free radical being positively correlated to the degree of humification (Fig. 3.2). In order to obtain these stable semiquinone radicals, reactive free radicals must be scavenged thereby terminating the oxidative chain reaction. The antioxidants and scavenging compounds are assumed to be phenolics that act as scavengers, thus degrading the soil organic matter till their desired level is attained, preventing the soil organic matter from further degradation, thus forming recalcitrant SOM pool. In soil, phenolics generally occur as free, reversibly bound and bound forms. In rhizospheric soils, flooded with vegetable waste waters, free phenolic compounds may accumulate, directly affecting plant growth through their accumulation, availability and cycling of soil nutrients (Li, Wang, Ruan, Pan & Jiang, 2010). Phenolics are absorbed by clay minerals by forming chelate complexes with metals. Such phenolics are salicylic and o-coumaric acids, procatechuic and caffeic acids. Phenolics also form complexes with different peptides, amino acids, polysaccharides, and other organic substances forming stable organic matter.

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Lignin Attack by microorganisms Phenolic aldehydes and acids Further utilization by microorganisms and oxidation to carbon dioxide

Cellulose and other lignin substances

Utilization by microorganisms Polyphenols Phenoxidase enzymes Quinones

Amino compounds Humic acids

Amino compounds Fuivic acids

Fig. 3.2: The polyphenol theory of humus formation (Stevenson, 1982).

3.4.7 Increase Soil Antioxidants Antioxidant content of soil plays a significant role in the soil organic matter dynamics. Highly reactive, and potentially damaging, free radicals are always generated in our oxygen-rich environment, including biological systems. To provide protection against these free radicals, biological systems produce a wide range of antioxidant molecules, namely, the vitamins. Also, plant and animal remains that are naturally and regularly being added to soils contain tannins, which are stable polyphenolic compounds with known antioxidant properties. These antioxidants act upon the free radicals and get transformed into unreactive stable free radicals and this stops the destructive chain reaction of free radical formation. We get stable semiquinone free radicals in humic substances, the concentration of which increases as humification progresses. These semiquinone species are most likely to be derived from the reaction of phenolic compounds with reactive radicals. Thus, establishing the role of phenolics as antioxidants as they scavenge the reactive free radicals and terminating the oxidative chain reaction responsible for soil organic matter degradation. Hence, it is the soil phenolic content that controls the rate of breakdown of organic matter and provides a chemical mechanism for their recalcitrance (Rimmer & Smith, 2009). Again, in vermicompost treated plants, total phenolics and flavonoids content have been found to be 38% and 39% higher respectively, than those of synthetically fertilized soils indicating that greater amount of antioxidants are present in vermicompost treated plants than in chemically fertilized soils assuming that the antioxidants present in soil are transferred to the vegetation grown in it (Atiyeh, Edwards, Subler & Metzger, 2000; Omar, Hassan, Yusoff, Abdullah, Wahab & Sinniah, 2012).

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3.5 DISADVANTAGES OF PHENOLIC ACIDS IN PLANTS Phenolic compounds play important roles in the interaction between species and in shaping of communities. They are the pivotal compounds involved in the phenomenon in which one plant (or microorganism) affects the growth of another plant (or microorganism) directly or indirectly, positively or adversely through the release of chemicals in its vicinity, called allelopathy. These phenolics called allelochemicals isolated from different plants includes chlorogenic acid, procatechuic acid, gallic acid, caffeic acid, 3,5-dinitrobenzoic acids, p-hydroxy benzoic acids, 4-vinylphenol anisic acids, gentisic acids, 8-hydroxyquinoline, vanillic acids, catechin, etc. (Vivanco et al., 2004; Chou & Leu, 1992; Batish et al., 2009). Screening of these compounds for allelopathic effects has confirmed their harmful effects not only on agricultural crops but in the ecosystem in general (Mahall & Callaway, 1992). Phenolic acids reduce soil pH and change other soil characteristics (Whitehead et al., 1981) and inhibit plants from absorbing nutrients from the soil. Phenolics form complexes with proteins and delay organic matter decomposition and mineralization (Hättenschwiler, & Vitousek, 2000). Accumulation of these allelochemicals affects the soil microbial population (Blum, 2000). Reduction in root nodule formation as well as nitrogen fixation has been found to be involved with higher concentration of gallic acid and tannic acids in soil (Whitehead, Dibb & Hartley, 1981). Green leaves and decomposing litter exude chlorogenic acid that can influence rhizospheric nitrogen. Tannins reduce the rate of decomposition and nitrogen mineralization. Major groups of polyphenols are involved in the inhibition of mineral ion uptake by plants (Yu & Matsui, 1997). A deeper investigation into the mode of action at the cellular level reveals that phenolic compounds permeate the cell through the membrane and inhibit cell division, increase thickness of cortical cells, reduce cellular activity and the amount of Golgi bodies and damage other organelles. They reduce chlorophyll content, rate of photosynthesis, respiration, leaf transpiration, stomatal conduction and intercellular carbon dioxide concentration. They increase cell membrane permeability that leads to spilling of cell contents and increase lipid peroxidation. This results in inhibition of plant root elongation and ultimately growth (Li et al., 1993). At the molecular level, phenolics function by changing hormone as well as enzyme activities (He & Lin, 2000). Polyphenols including benzoic acids affected IAA and Gibberellin decomposition. Aqueous extract of Oryza sativa reduced IAA level by increasing IAA oxidase activity (Zeng et al., 2001). Pyrus communis, salicylic acid inhibited ethylene synthase (Leslie & Romani, 1988). Phenolics have damaging effect on DNA and RNA also. They can inhibit protein synthesis, amino acid transport, activities of phosphorylases and ATPases. Tannic acid can inhibit activities of peroxidase, catalase and cellulase. Ferulic acid reduced activities of hydrolase, maltase, phosphorylase, proteases and phenylalanine ammonialyase (Devi & Prasad, 1992).

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Phenolic allelochemicals released by invading plant species help them in their survival in the new environment (Callaway & Aschehoug, 2000; Ridenour & Callaway, 2001). Sometimes weeds exhibit allelopathic effect on crop plants. Inhibition of bacterial, rhizobial and fungal growth has been reported (Whitehead et al., 1981). Their presence and accumulation above the threshold concentration inhibits pre-emergence seed germination, post-germination, growth and plant functions (Whitehead, 1964). The root length and fresh weight of maize seedlings have been found to have been significantly reduced by ferulic acid (Dumas et al., 2003). In Schrenk spruce forest, the accumulation of phytotoxic substances including tannins, indoles and other phenolic compounds in the rhizosphere, due to leaching from senescent leaves, contributes to the regeneration problems, i.e., germination of seeds and growth of seedling in the same species (Li et al., 2010).

3.6 INFLUENCE OF PHENOLIC ACIDS ON VEGETATION IN COMPOST MANURE Different varieties of organic fertilizers taken from different sources and their interactions influence the phytochemical content of the plant products in a significant way. Phenolic compounds have important contributions to the sensory elements such as colour and flavour of fruits and vegetables that enhance their nutritional and commercial properties. When treated with vermicompost, the phenolic and flavonoid contents of the agricultural products have been found to be significantly higher compared to the mineral fertilizers and another variety of compost (empty fruit bunch compost). In vermicompost treated plants, total phenolics and flavonoid content have been found to be 39% and 38% higher respectively, than those of synthetically fertilized plants. Fertilization is considered to be an important factor influencing the phytonutritional quality of crops. Excessive fertilization has a detrimental influence, not only on the phytonutritional quality of the crops resulting in the reduction of antioxidant levels, but also on the environment, causing pollution. Increasing synthetic nitrogen fertilization has been found to decrease ascorbic acid concentration in several fruits and vegetables (Lee & Kader, 2000). On the other hand, organic fertilizers enhance the antioxidant contents in plants (Dumas et al., 2003). Nutritional quality, in terms of macronutrients, vitamins and minerals, of organically and conventionally grown plants have been compared by several authors, a few of them are: V. Worthington (2001) found that organically produced fruits and vegetables contain vitamin C, iron, magnesium and phosphorus in higher levels and nitrates and some heavy metals in lesser amount. Asami et al. (2003) found that higher amount of phenolics in organically grown marrionberries than in conventionally grown ones. Olson et al. (2006) reported higher levels of antioxidants, total phenolic acids, including ellagic acids and flavonol. Souse et al. (2005) reported that cabbages from organic farm had higher phenolic contents. Aminifard et al. (2013) determined the effect of compost on antioxidant compounds and fruit quality of sweet pepper, Capsicum annuum. Their result showed that compost has a strong influence on the quality of fruits and antioxidant compounds of pepper plants under field conditions. Change in fruit

62 Recent Trends in Composting Technology quality factors including pH, total soluble solids, titratable acidity, ascorbic acid content and fruit firmness were observed. The highest values of fruit quality factors were obtained using 15 tonnes of compost per hectare. Traditionally, composts and manures are being utilized in agriculture as a significant source of organic matter. Composts made from feed stock contain higher level of nutrients and organic matters (Maynard, 1995; Ozores-Hampton, 1998). In addition to imparting higher nutritional benefits, other utilities of compost are: i) composts hinder growth of pathogen, ii) composts can be used as mulch, iii) composts suppress growth of weeds, iv) composts are used as transplant media (Ozores-Hampton, 1998; Roe, 1998), v) compost reduces pollutants and diseases. Besides all these benefits composts change the physical and chemical characteristics of soil and increase beneficial microorganisms in the soil (Chung et al., 1988) that make nutrient availability and uptake by plant easier. Wang & Lin et al., 2003 has shown that strawberry plants grown with composts as soil supplement had significantly higher free radical inhibiting activity. When strawberry plants were grown in full strength fertilizer, with 50% soil plus 50% compost, they yielded fruits with highest level of phenolics. This indicates that strawberry fruits grown with compost had high scavenging activity for chemically generated active oxygen species, fertilizer strength affect strawberry plant growth (Wang & Liu, 2002) and highest antioxidant capacity is obtained at optimal conditions for plant growth (Woese et al., 1997). Composts and fertilizers significantly enhanced strawberry plant growth, plant dry weight, fruit yield, fruit size, fruit flavonoid content, fruit quality, leaf nitrate reductase activity and chlorophyll content. In addition to this, Wang & Lin, 2002 have also shown that strawberry plant cultivated in compost had significantly increased contents of N, K, organic acids like malic and citric acids, sugars like fructose, glucose, and total soluble solids and titratable acidity in fruits.

3.7 COMPOST MANURE FROM WASTE TEA LEAVES Tea is the most popular of all beverages used worldwide. After brewing, the remaining leaves offer a good source of composting and make people aware of the need and do their part to save the environment, using organic fertilizers. The loose or bagged tea swells in the pot, or strainer, making it moist and therefore more suitable to break down. It can be dumped in a garden or pot compost pile after use. Loose tea can be dumped as it is but for bagged tea, the bag needs to be cut open and the contents emptied into the pile. The bag can be composted as long as it’s made of biodegradable materials: paper, silk, or muslin; otherwise, it has to be thrown away. Tea powder is not only a great source of biodegradable garbage but it can make a good source of compost as well. In the rapidly degrading environment, where improper soil management cannot cope up with the grain demand of the ever increasing population, use of compost is the need of the time and beneficial to improve organic matter status of the soil. Analyzing the physicochemical parameters of the compost using waste tea

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powder which is generally thrown away is quite encouraging. The compost prepared by using waste tea powder has increased concentration of essential nutrients needed for plant growth and development as compared to the regular soil. Levels of essential nutrients like chloride, sulphate, total phosphorus, available phosphorus, organic matter, calcium and magnesium have been found to be higher in tea-compost. By using this compost, the plants grow very rapidly and there is increment in the leaf area, leaf density, height, and germination period and germination frequency of the plant. The use of this compost also reduces environmental pollution and also gives better yield of crops. Physicochemical properties like pH, conductivity, sulphate, chloride, total phosphorus, available phosphorus, calcium, magnesium, organic matter and silica were significantly improved resulting in enhanced Tagetes spp., Cicer arietinum and Vigna radiata yields in sodic soil. The morphological features of the plants have also been studied in response to compost to find the efficiency of the compost as a good fertilizer. Leaf length, leaf density, germination rate and height of the moong, chickpeas and marigold have been found to be enhanced. The period of germination has been decreased after application of compost (Schultze, 1998).

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66 Recent Trends in Composting Technology 38. Li, Z-H, Wang, Q., Ruan, X., Pan, C-D & Jiang, D-A. (2010). “Phenolics and plant allelopathy”. Molecules. 15: 8933. 39. Mahall, B.E. & Callaway, R.M. (1992). “Root communication mechanisms and intracommunity distributions of two mojave desert shrubs”. Ecology. 73: 2145-2151. 40. Mandal, S.M., Chakraborty, D. & Dey, S. (2010). “Phenolic acids act as signaling molecules in plant-microbe symbioses”. Plant Signaling & Behavior. 5: 359-368. 41. Mandal, S.M., Mandal, M., Das, A.K., Pati, B.R. & Ghosh, A.K. (2009). “Stimulation of indoleacetic acid production in a rhizobium isolate of vigna mungo by root nodule phenolic acids”. Archives of Microbiology. 191: 395-395. 42. Mann, J. (1978). “Secondary metabolism”. Oxford [England]: Clarendon Press. 43. Maynard, A.A. (1995). “Cumulative effect of annual additions of MSW compost on the yield of field-grown tomatoes”. Compost Science & Utilization. 3: 47-54. 44. Micales, J.A. (1997). “Localization and induction of oxalate decarboxylase in the brown-rot wood decay fungus postia placenta”. International Biodeterioration & Biodegradation. 39: 125-132. 45. Mulvaney, R.L., Khan, S.A. & Ellsworth, T.R. (2009). “Synthetic nitrogen fertilizers deplete soil nitrogen: A global dilemma for sustainable cereal production”. J. Environ. Qual. 38: 2295-314. 46. Minakshi Gurav, S.S. (2013). Preparation of organic compost using waste tea powder. In: National Conference on Biodiversity : Status and Challenges in Conservation - ‘FAVEO’ 2013. 47. Ndakidemi, P.A. & Dakora, F.D. (2003). “Legume seed flavonoids and nitrogenous metabolites as signals and protectants in early seedling development”. Functional Plant Biology. 30: 729-745. 48. Nicholson, A.R.L. & Hämmerschmidt, R. (1992). “Phenolic compounds and their role in disease resistance”. Annual Review of Phytopathology. 30: 369-389. 49. Olsson, M.E., Andersson, C.S., Oredsson, S., Berglund, R.H. & Gustavsson, K-E (2006). “Antioxidant levels and inhibition of cancer cell proliferation in vitro by extracts from organically and conventionally cultivated strawberries”. Journal of Agricultural and Food Chemistry. 54: 1248-1255. 50. Omar, N.F., Hassan, S.A., Yusoff, U.K., Abdullah, N.A.P., Wahab, P.E.M. & Sinniah, U.R. (2012). “Phenolics, flavonoids, antioxidant activity and cyanogenic glycosides of organic and mineral-base fertilized cassava tubers”. Molecules. 17: 2378. 51. Ozores-Hampton, M. (1998). “Compost as an alternative weed control method : Municipal waste compost production and utilization for horticultural crops”. American Society for Horticultural Science, Alexandria, VA, ETATS-UNIS. 52. Redmond, J.W., Batley, M., Djordjevic, M.A., Innes, R.W., Kuempel, P.L. & Rolfe, B.G. (1986). “Flavones induce expression of nodulation genes in rhizobium”. Nature. 323: 632-635.

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53. Ridenour, W.M. & Callaway, R.M. (2001). “The relative importance of allelopathy in interference: The effects of an invasive weed on a native bunchgrass”. Oecologia. 126: 444-450. 54. Rimmer, D.L. & Smith, A.M. (2009). “Antioxidants in soil organic matter and in associated plant materials”. European Journal of Soil Science. 60: 170-175. 55. Roe, N.E. (1998). “Compost utilization for vegetable and fruit crops”. HortScience: A publication of the American Society for Horticultural Science (USA). 56. Rynk, R. (1992). “On-farm composting handbook”. Natural Resource, Agriculture, and Engineering Service (NRAES), Ithaca (New York). 57. Sarma, B. & Singh, U. (2003). “Ferulic acid prevents infection by sclerotium rolfsii in cicer arietinum”. World J Microbiol Biotechnol. 19: 123-127. 58. Savino, F., Maccario, S., Migliore, G., Oggero, R. & Silvestro, L. (2002). “Blue baby syndrome”. J. Pediatr. Gastroenterol. Nutr. 34: 573. 59. Schultze, M., & Kondorosi, A. (1998). “Regulation of symbiotic root nodule development”. Annual Review of Genetics. 32: 33-57. 60. Senesi, N. (1990). Application of electron spin resonance (esr) spectroscopy in soil chemistry. In: Advances in Soil Science. B.A. Stewart (Ed.). New York: Springer. p. 77-130. 61. Seneviratne, G. & Jayasinghearachchi, H.S. (2003). “Phenolic acids: Possible agents of modifying nitrogen-fixing symbiosis through rhizobial alteration”. Plant and Soil. 252: 385-395. 62. Shaw, L.J., Morris, P. & Hooker, J.E. (2006). “Perception and modification of plant flavonoid signals by rhizosphere microorganisms”. Environmental Microbiology. 8: 1867-1880. 63. Staman, K., Blum, U., Louws, F. & Robertson, D. (2001). “Can simultaneous inhibition of seedling growth and stimulation of rhizosphere bacterial populations provide evidence for phytotoxin transfer from plant residues in the bulk soil to the rhizosphere of sensitive species?” Journal of Chemical Ecology. 27: 807-829. 64. Steinberg, P.D. (1984). “Algal chemical defense against herbivores: Allocation of phenolic compounds in the kelp. Science. 223: 405-407. 65. Tipping, E. (2002). “Cation binding by humic substances”. New York: Cambridge University Press. 66. Toor, R.K., Savage, G.P. & Heeb, A. (2006). “Influence of different types of fertilisers on the major antioxidant components of tomatoes”. Journal of Food Composition and Analysis. 19: 20-27. 67. Vallance, J., Déniel, F., Floch, G.L., Guérin-Dubrana, L., Blancard, D. & Rey, P. (2011). Pathogenic and beneficial microorganisms in soilless cultures. In: Sustainable Agriculture. Volume 2. E. Lichtfouse, et al. (Eds.). Springer Netherlands: Dordrecht. p. 711-726.

68 Recent Trends in Composting Technology 68. van Schie, P.M. & Young, L.Y. (1998). “Isolation and characterization of phenoldegrading denitrifying bacteria”. Applied and Environmental Microbiology. 64: 2432-2438. 69. Vivanco, J.M., Bais, H.P., Stermitz, F.R., Thelen, G.C. & Callaway, R.M. (2004). “Biogeographical variation in community response to root allelochemistry: Novel weapons and exotic invasion”. Ecology Letters. 7: 285-292. 70. Wang, S.Y. & Lin, H-S. (2003). “Compost as a soil supplement increases the level of antioxidant compounds and oxygen radical absorbance capacity in strawberries”. Journal of Agricultural and Food Chemistry. 51: 6844-6850. 71. Wang, S.Y. & Lin, S-S. (2002). “Composts as soil supplement enhanced plant growth and fruit quality of strawberry”. Journal of Plant Nutrition. 25: 2243-2259. 72. Whitehead, D.C. (1964). “Identification of p-hydroxybenzoic, vanillic, p-coumaric and ferulic acids in soils”. Nature. 202: 417-418. 73. Whitehead, D.C., Dibb, H. & Hartley, R.D. (1981). “Extractant pH and the release of phenolic compounds from soils, plant roots and leaf litter”. Soil Biology and Biochemistry. 13: 343-348. 74. Whitehead, D.C., Dibb, H. & Hartley, R.D. (1983). “Bound phenolic compounds in water extracts of soils, plant roots and leaf litter”. Soil Biology and Biochemistry. 15: 133-136. 75. Woese, K., Lange, D., Boess, C. & Bögl, K.W. (1997). “A comparison of organically and conventionally grown foods—results of a review of the relevant literature”. Journal of the Science of Food and Agriculture. 74: 281-293. 76. Worthington, V. (2001). “Nutritional quality of organic versus conventional fruits, vegetables, and grains”. The Journal of Alternative & Complementary Medicine. 7: 161-173. 77. Yu, J.Q. & Matsui, Y. (1997). “Effects of root exudates of cucumber (cucumis sativus) and allelochemicals on ion uptake by cucumber seedlings”. Journal of Chemical Ecology. 23: 817-827. 78. Zeng, R.S., Luo, S.M., Shi, Y.H., Shi, M.B. & Tu, C.Y. (2001). “Physiological and biochemical mechanism of allelopathy of secalonic acid on higher plants: Allelopathy in natural and managed ecosystems”. American Society of Agronomy, Madison.

CHAPTER

4

Composting Technology in Sugar and Agro-Based Industry: Solution for High BOD Waste and Its Plausible Environmental Impacts Debarati Paul * and Kalyan K. Bandyopadhyay Amity Institute of Biotechnology, Amity University, Noida, Sec 125, Uttar Pradesh *E-mail: [email protected]

ABSTRACT The biological process of composting, various process control parameters and technologies being used for composting have been discussed in this chapter. The highlight of the chapter is the derivation of total production of compost and its projected commercial value using distillery spentwash and municipal waste. The other important features of this chapter are the discussions on the uses and quality of compost obtained from various sources and the environmental effects of composting as a sustainable technology.

4.1 INTRODUCTION Composting is a biological process by which biodegradable wastes and organic matter are decomposed into humus via microorganisms and invertebrates. The process of degradation is natural, but may be accelerated by controlled circumstances and thereby it is used as a technology for waste treatment. Composting can be anaerobic, which means without the presence of oxygen. It can also be aerobic, which suggests the presence of air or oxygen. This includes even vermicomposting, where earthworms are used to digest the waste. In India, Municipal Solid Waste (Management and Handling) Rules, 2000 (MSWR) is implied, however, MSWR is of major concern to urban local bodies (ULBs) across the country. MSWR prescribes specific standards for composting as well as for compost as indicated in the “Information manual on pollution abatement and cleaner technologies” issued by CPCB (Central Pollution Control Board), in 2003. This process can be carried out locally at smaller scale through compost pits and heaps and at the central level, through composting plants. A brief outline of the biological process, important process control parameters and technologies being used for composting and quality criteria for the compost thus formed have been discussed in this chapter.

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4.2 BIO-WASTE AND ITS CATEGORIES The definition of bio-waste mentioned in Waste Framework Directive is: “biodegradable garden and park waste, food and kitchen waste from households, restaurants, caterers and retail premises and comparable waste from food processing plants”. It categorises waste depending on the following properties (JRC Scientific and Policy Reports, 2013): ‡ Nature or process of origin: garden/park waste, or food waste, or kitchen waste ‡ Properties of the waste: biodegradability ‡ Origin or industrial sector of origin: households, or restaurants, or catering, or retail premises, or food processing industry. Important waste categories containing bio-waste are ‡ Animal and vegetable wastes (excluding animal waste of food preparation and products; and excluding animal faeces, urine and manure) ‡ Animal waste of food preparation and products ‡ Animal faeces, urine and manure ‡ Household and similar wastes ‡ Mixed and undifferentiated materials. ‡ Common sludges (excluding dredging spoils) Composting yields manure and organic wastes have great potential as manure and as soil conditioner. However, the significance can be further improvised using following three methods: (a) increasing nutrients in a form available for cultivated plants; (b) enhancing rates of mineralization in soil; and (c) developing an improvised technology for composting. In rural areas of India, mostly agricultural refuse and dung generated from animal husbandary is used as domestic fuel for cooking (Mishra et al., 1999). As a result, all waste material including wastewater, loaded with high organic content and inorganics, viz., nitrogen, potash, phosphorous, trace elements, has been successfully converted to value added organic manure by adopting scientific composting procedures.

4.2.1 Generation of Industrial Bio-waste The waste treatment sector generates mainly ‘secondary’ waste, i.e., waste generated in a process that is known as a waste treatment operation (Table 4.1). It includes residual materials originating from recovery and disposal operations, such as incineration and composting residues. As indicated by the definition of waste, sewage treatment waste (i.e., sewage sludge) is considered ‘primary’ waste. A study by OECD (Organisation for Economic Co-operation and Development) in Flanders (Belgium) showed that waste treatment sector is by far the largest generator of industrial waste with a total of 9.478 K tonnes in 2005, or 12.863 K tonnes in 2006. The retail sector generated between 448 and 311 tonnes in 2005 and 2006, whereas, supermarkets, produced between 135 and 140 K tonnes. The food sector including fish, potatoes, juices, vegetables, fruits, oils and fats,

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dairy, tea, tobacco and fodder, was identified as the third largest generator of industrial waste, with a quantity of 1.477 K tonnes in 2006. In Lithuania, the alcoholic beverage industry generated about 323 K tonnes of biodegradable waste. Brewers generated 40-45 K tonnes of saladin or malt filtration waste, 8-8.5 K tonnes of liquid barm and 400-500 tonnes of malt cleaning waste. In India, the population is about 1,311,050,527 which is 115 times more than that of Belgium and waste generation follows a similar suite. As per the estimates of CPCB, annually around 7.66 million Metric Ton (MT) of hazardous waste is generated from 40,000 industries in the country, of which landfillable waste is 3.39 million MT (44.26%), incinerable waste is 0.65 million MT (8.50%) and recyclable hazardous type is 3.61 million MT (47.13%) (CPCB, 2010). The rate of municipal waste generation in India in 2011 was 127458.1 T/day. If this is divided by the then urban population we will get the per capita waste generation rate that is about 0.356 kg/day. The amount of waste generated per capita is now estimated to increase annually at the rate of 1- 1.33% (Pappu et al., 2007). Waste generation is expected to increase from 48 million tonnes to 300 million by 2047 (490 gm per capita to 945 gm per capita) in India. Even if the projection is not accurate, it is a warning! (CPCB, 2003, Information manual on pollution abatement and cleaner technologies). India has an estimated potential of producing about 4.3 million tonnes of compost each year from MSW (municipal sewage waste), which would reduce the existing gap between availability and requirement of organic manure in Indian soils (as shown below). According to a recent data from MNRE (Ministry of New and Renewable Energy, India), there is a potential of about 1300 MW alone from industrial wastes. Industries Sugar Mills

Prominent Wastes Generated Sugar bagasses

Treatment Option Combustion and Gasification

Pressmud

Composting

Sugar molasses

Fermentation

Quantity of Waste Generated Above 9 million tonnes/ year

Fermentative Yeast biomass Biomethanation Slaughterhouse

Tissues, Blood, Carcass, Animal excreta, etc

Biomethanation

0.5–7 tonnes/day

Paper Mills

Pulp

Biomethanation

30,000 tonnes/year

Paper shavings

Combustion

Wood wastes and Paper boards

Combustion and gasification

Dairy Plants

Whey and Milk cream

Biomethanation

Tanneries

Hide/skin of animals

Acid treatments 850 kg solid waste/1000 and biomethanation kg raw material

50–60 million litres/day

Vegetable and fruit processing units

Pulp wastes

Biomethanation

4.5 million tonnes /year

72 Recent Trends in Composting Technology Non-hazardous industrial wastes being different in terms of chemical and physical composition, moisture content, calorific values, etc. demand distinct treatment options which are broadly classified above. Adapted from weblink of EAI “Industrial wastes in India”. (http://www.eai.in/ref/ae/wte/typ/clas/india_industrial_wastes.html) Table 4.1: Various treatment options for non-hazardous industrial waste.

Total production of compost and its projected commercial value using distillery spentwash and municipal waste per annum in India. Case I: Distillery spentwash having 5% total solid (TS) Basis : 310 distilleries having installed capacity 32 u 105 KL rectified spirit per year : Assuming operating capacity 70% of installed capacity : Total production per year = 224 u 105 KL : Spentwash generation @10 KL /KL of Rectified spirit : Total spentwash generation = 224 u 106 KL As per CPCB norm 250 m3 spentwash having 5% TS would produce 50 MT compost having 30% moisture. Therefore, 224 u 106 KL spentwash would yield: 44800000 MT Revenue: Assuming selling cost of compost @ Rs 2000 per MT Net likely revenue: Rs 44800000 u 2000 = Rs 896 u 108 = Rs 8960 crore Case II: Municipal waste Basics : Municipal waste generation in India (2011) as per CPCB: 127458 MT/day : Total generation per year: 127458 u 365 = 46522170 MT : Assuming 30% of waste solid is compost : Total compost generation: 13956651 MT/year Net likely Revenue : Rs 13956651 u 2000 : Rs 27913302000 : Rs 2791.3 crore Total expected revenue from two sources: A + B: Rs 11751 crore Distilleries are allied to the sugar industry as they supply the basic raw material, molasses for alcohol production. Mostly Indian distilleries use molasses as the basic raw material, though other feedstock such as grain, malt and grapes are also used. At present there are about 319 distilleries in India with an installed capacity of 3.25 billion L of alcohol (Uppal, 2004). Potable alcohol constitutes nearly half (46%) of the production, among the major end products of the distilleries. Every 100 tonnes of sugarcane crushed on an average gives 10 T of sugar, 4.5 T of molasses, 33 T of bagasse and 2.5 T of pressmud. One tonne of molasses can produce around 225 L of alcohol. The sugar industry generates about 7.5 million tonnes of molasses, 45 million tonnes of bagasse, 5 million tonnes of pressmud and 40 million m3 of spentwash (Kumar, 2003; Uppal, 2004).

Composting Technology in Sugar and Agro-Based Industry: Solution for High BOD... 73

Tertiary treatment

Secondary treatment

Primary treatment

In case of sugar industries, distillery effluent (spentwash) contributes significantly for commercial composting. The biological oxygen demand (BOD) of the effluent is 90,000– 120000 mg/L (CPCB, 2002; Kumar et al., 2003), but initially appears relatively clean, however, after stagnating for about 5–7 days, it turns black and emits foul odour due to H2S gas formation. A general strategy followed for effluent treatment has been shown in Fig. 4.1. Untreated effluent Grit removal Anaerobic digestors

Biogas to Boiler

Lamella clarifier Trickling filters (3 stage) Lamella clarifier Open pucca lagoons (for natural evaporation of effluent) Polishing pond/Dilution with fresh water Treated effluent for Bio-composting

Fig 4.1: A flowchart on effluent treatment strategies followed in Indian distilleries to get zero discharge.

Industrial bio-waste management systems must be developed according to the following priorities (report on assessment of the options to improve the management of bio-waste in the European Union): ‡ waste treatment combined with energy generation and preservation of nutrients; ‡ waste treatment without energy generation but with the preservation of nutrients; and ‡ waste treatment by incineration and energy production.

4.2.2 Possible Technological Solutions ‡ Anaerobic digestion of food waste together with meat industry waste, producing biogas and generating power and heat. ‡ Collection of kitchen waste by separating it as source and anaerobic digestion of kitchen waste along with waste treatment sludge at sludge digestion plants (existing or future) in the near future. This would improve the organic load of anaerobic (methane) tanks – there would be no necessity to construct new ones.

74 Recent Trends in Composting Technology ‡ MBT (mechanical biological treatment) has proven to be another useful technique and should be installed in certain regions in the coming years. After a pre-treatment process of mechanical sieving and sorting, the biodegradable part of waste shall be anaerobically digested in methane tanks, with further composting of the obtained digestate. The part with high calorific value sorted by the mechanical sorting sieving process will be used as refuse delivered fuel (RDF) in specific co-incineration power plants. ‡ Compost Technology: Composting emerges as the most widely applicable process for handling diverse wastes in recycling wastes. Organic wastes are composted in an appropriate manner depending on their physicochemical nature to abate resulting environmental consequences of direct application to land and to satisfy the demand of organic manure for intensive agriculture. A wide variety of organic residues from plant, animal and industrial wastes may be composted for creating a stable eco-friendly manure (Haug, 1993). Thus, composting may be redefined as a way of waste ‘stabilization’ under appropriate conditions of moisture and aeration (Lasaridi & Steniford, 1998; Mondini et al., 2003). It produces thermophilic temperatures, and eliminates the pathogens associated with accumulation of organic substrates and salts. Thermophilic temperatures are attained by using highly concentrated aqueous solutions (Miller, 1992) under special provision for aeration (Raviv, 2005).

4.3 BIOCHEMICAL PROCEDURES FOR COMPOSTING In the technique of composting, microorganisms break down organic matter and produce carbon dioxide, water, heat and humus, the relatively stable end product. There is not only one type of microorganisms responsible for the decomposing process, but an ecosystem of different organisms (Manderson, 2009; http://www.eolss.net/). Composting is an aerobic process and consequently the aerobic microorganisms are dominant. However, there are always some pockets in any compost heap where the oxygen is depleted that harbour some anaerobes. Bacteria, fungi and actinomycetes account for decomposition and increase in temperature. These microbes are eaten by small animals, such as invertebrates and worms. The animals thereby mix the material, break larger particles into smaller ones and transform the material into more digestible form for the microbes.

4.3.1 Various Composting Methods There are several methods employed for composting depending on the type of waste and the nutritional load in it. Out of them few methods namely, in-vessel composting, hot composting and windrow composting are favourably used for treating industrial wastes. The other methods are used for treating agricultural, kitchen and/or garden wastes.

Composting Technology in Sugar and Agro-Based Industry: Solution for High BOD... 75

4.3.1.1 Sheet Composting/Mulching Sheet composting, also called lasagna composting and sheet mulching, may be a practical method to add organic matter back into the soil. Thin layers of organic material (i.e. compost ingredients) are spread on top of the soil surface and needs carbon, nitrogen, oxygen and water in appropriate amount to mineralise organic materials into a good growing medium. This technique may be used on a large scale, or small scale in the backyard, especially in cold composting method. Some also consider this technique to be “composting in place”. Spreading green manure is another means of sheet composting and serves as an excellent means to convert grass to vegetable beds, create new or enlarged perennial borders, improve soil composition and soil structure and recycle organic material. Sheet composting is slow and has minimal heat reaction from the microbes to hasten the process. Sheet compost beds usually take 6 months or longer to sufficiently decompose to be suitable for planting. A bed is “finished” and ready for planting when the layers have decomposed such that the original materials are not recognizable and looks and smells like fresh earth. In the lasagna garden, a 2–3 inch layer of compost or garden soil on top of the newly formed bed is sifted and then planted. (http://extension.oregonstate.edu/lane/sites/default/files/documents/lc731sheetmulch may2015_0.pdf).

4.3.1.2 In-vessel Composting In-vessel composting is becoming increasingly popular with large-scale compost producers. Composting is carried out in an enclosed containment system (often a cylindrical container). The equipment involved is typically quite expensive, thereby limiting its usage for large–scale or industrial operations; smaller vessels are often expensive. Numerous benefits of in-vessel composting include increased processing speed, year-round composting, and a highly controlled environment. There are several types of in-vessel composting reactors: vertical plug-flow, horizontal plug-flow, and agitated bin. The primary difference lies in the aeration systems and loading/unloading system. In vertical plug-flow systems, the biosolids and bulking agent mixture is introduced into the top of the reactor vessel and compost is discharged out from the bottom via horizontally rotating port. Air is introduced either from the bottom or through lances hanging from the top of the reactor. In horizontal plug-flow systems, the compost and bulking agent mixture is loaded into one end of the reactor and compost is discharged from the other end. Air is introduced via slots located in the reactor’s floor. The agitated-bed reactors are typically open topped from where biosolids and bulking agent mixture is loaded. Composting mass is agitated using a mechanical device periodically and air is introduced through the floor in the horizontal reactors. Agitated bed reactors can be operated in either plug flow or batch mode. In batch operations, the vessel is loaded with biosolids and bulking agent, processing takes place, and the vessel is emptied.

76 Recent Trends in Composting Technology

4.3.1.3 Biodynamic Composting This composting process dissembles the nutrients of one plant and reforms them into a material that another green plant can absorb and be benefitted. Biodynamic compost preparations regulate the breakdown and reform process of the waste and enhance the compost. Biodynamic composting evolved out of a complete system of farming developed by Rudolph Steiner (Austrian philosopher). Biodynamic composting is very particular about the shape of the compost pile, the layering pattern, and the materials used. Special plant-based preparations are made in a very specific manner by highly trained individuals. These preparations are said to produce a miraculous compost that is far superior than other techniques (Petherick, 2013). By regular application the two biodynamic field sprays BD500 and BD501 provided a medium for the growth and maintenance of soil fertility. Biodynamic techniques can be practised in small and big gardens apart from the agriculture fields. (http://demeter-usa.org/downloads/Demeter-Science-Biodynamic-Farming-%26Compost.pdf)

4.3.1.4 Anaerobic Composting Anaerobic composting involves biological breakdown of waste or organic materials by anaerobic organisms. In this system, majority of the carbon contained within the starting material is released as methane (http://www.fao.org/docrep/007/y5104e/y5104e05. htm). The process results in very strong odours and only a small amount of heat is generated. Therefore decomposition takes much longer and doesn’t attain adequate temperatures that can restrict or terminate plant pathogens, weed and seeds. External or artificial heat is normally provided for mitigation. Benefits of anaerobic composting include producing compost (in small scale) to produce more humus per unit of starting material than most other composting methods.

4.3.1.5 Trench Composting Trench composting involves digging holes in the soil and burying raw compost ingredients. Time consumed for this method is more than when using other composting techniques. However, it is good for composting materials that attract rodents such as meat, dairy, breads, and processed foods especially, pet waste. Trenching is a great a way of depositing nutrients in the soil near the root zones. (http://www.mvcc.vic.gov.au/~/media/Files/Environment/Environment2/My%20 Smart%20Gardens/Trench%20composting.pdf)

4.3.1.6 Bokashi Composting Bokashi in Japanese means fermented organic matter; bokashi composting therefore, describes the preparation of compost using fermentation. Compost material is inoculated with a starter culture of mostly anaerobic effective microbes (EM), and placed inside a

Composting Technology in Sugar and Agro-Based Industry: Solution for High BOD... 77

sealed container. Unlike other composting techniques, this method can speedily produce rich humus in about eight weeks! (http://www.timetorecycle.com/reduce/composting.asp)

4.3.1.7 Black Soldier Fly Composting Black soldier fly composting uses larvae of the fly species, Hermetia illucens, to digest or compost organic waste (e.g., animal manure). The larvae of black soldier fly voraciously consume large amounts of organic waste and enter into a pupae stage that are then harvested and used to feed reptiles, turtles, fish, chickens, pigs, and other livestock. Composting with black soldier flies is a relatively new technology, however, it is quite challenging. The technique claims the following: “black soldier fly larvae will revolutionize the way humans recycle their organic wastes.” (http://www.edthatmatters.com/composing-using-black-soldier-flies-bsf-and-theireffect-on-earth-worm-bins/)

4.3.1.8 Windrow Composting Aerated or turned windrow composting is suited for large volumes of waste that is generated by entire communities and collected by local governments, and high volume food-processing businesses (e.g., restaurants, cafeterias, packing plants). This type of composting involves forming organic waste into rows of long piles called “windrows” and aerating them periodically by either manually or mechanically turning the piles. The ideal pile height is between 4-8 feet with a width of 14 to 16 feet. The pile is large enough to generate enough heat and maintain temperatures, however, it is small enough to allow oxygen flow to the windrow’s core, that remains anaerobic. Large volumes of diverse wastes such as yard trimmings, grease, liquids, and animal byproducts (such as fish and poultry wastes) can be composted through this method. It may be a desirable proposition for local governments to make this product available to residents for a low or no cost. (file:///C:/Users/user/Downloads/Composting%20Guide_0908.pdf).

4.3.1.9 Hot Composting Hot composting is also called dynamic composting and is typically the method used in commercial operations. Some backyard gardeners also choose to use hot composting, however, it usually involves a lot of labour. The only lucrative proposition for this increased labour is rapid completion of the entire process. Higher temperatures may suit the nutrient quality of the compost. The HotRot equipment (Organic solutions, NZ) is designed to compost large amounts of putrescible waste for municipalities, waste processing companies and other organic waste producers such as food processors and breweries. It is also ideal for organic waste composting at zoos, universities, resorts and remote site organic waste disposal, e.g., mining, oil and gas projects. (http://www.compostjunkie.com/composting-techniques.html)

78 Recent Trends in Composting Technology

4.4 WINDROW COMPOSTING IN INDUSTRY: TECHNIQUES AND TECHNOLOGY Although outdoor composting in aerated windrows is suitable for green waste (possibly mixed with source-separated kitchen waste) it is less suitable for wastes as abattoir wastes, human and animal excreta or wastes very rich in protein, i.e., dairy wastes, due to emission of odour, and for hygienic reasons. For more problematic wastes, stricter process parameters are followed and enclosed composting is recommended. Aeration is either forced aeration in a static pile or by mechanical turning. Turning maintains self- ventilation in the heap, but with some technologies water can be added simultaneously (Fig. 4.2).

Fig 4.2: Management of windrows. Adapted from report of BCM (Commercial plant of Biocomposting Unit).

Land requirement for a composting per KL alcohol production = 4.5 ha Equipment required for composting in large scale include: (i) Tractor or trolleys for transportation of pressmud (industry waste) from storage site to composting area (ii) Homogenizing machine equipped with auto spraying system (iii) Turning machinery or Front end loaders (discussed below) (iv) Sieve machine (v) Sewing machine in case compost has to be bagged.

Composting Technology in Sugar and Agro-Based Industry: Solution for High BOD... 79

Aeration ( prime requirement for windrows composting) involves mechanical turning, via the following methods: ‡ Turning by front end loaders or other earthmoving equipment. ‡ Special windrow turners, self-powered or pulled by tractors, that straddle along the windrow, and turn the compost without moving the position of the heap. ‡ Using side cutting turners that turn the windrow by slicing layers from the side and rebuilding the heap in a new place. ‡ Tumble the waste in a rotating conditioner drum before putting it in windrows. The advantages and disadvantages with each technology have been compared in Table 4.2. Table 4.2: Advantages and disadvantages with different types of turning equipment. Front end loaders

Straddle turners

Side cutting turners

Advantages

Inexpensive machinery may be used

No limitations in Good mixing and windrow size; breakdown of material; space efficient space efficient if self powered

Disadvantages

Slight mechanical mixing and breakdown of material; insufficient aeration; requires abundant space; no watering

Limitations in size of windrows; Requires lot of space if tractor pulled

Relatively high capital costs; only large scale

Rotating conditioner drum Shortens the time needed in windrows

High capital costs post treatment with turning necessary

Source: Ekelund & Nystrom (2007)

Manual turning can be done in small-scale composts. Vermicomposting is another option where worms structure the material so that no additional turning is needed. Vermicomposting is different from conventional composting in several ways (see Chapters 8 and 9). While choosing a particular technology it should be noted that a proper mechanical mixing and turning is beneficial to the process as it breaks down bigger pieces, distributes the temperature evenly, and uncovers new areas to biological activity. Choice of equipment is also governed by the size of windrows; small windrows are more sensitive to weather conditions, and require more water and continued management.

4.5 USE AND QUALITY OF END PRODUCT Compost is a valuable product used for gardening and landscaping. The quality of compost differs depending on the waste being treated, nutrient content and the technology used. High temperatures, high pH and frequent turning decreases the nitrogen content

80 Recent Trends in Composting Technology since it is released as ammonia gas during the composting process. Quality of compost to be used depends on the use and the status of the soil nutrient-wise. In South Africa, compost marketed as a fertilizer is registered as a Group 2 fertilizer at the Department of Agriculture. To be granted a registration, a chemical analysis of the nutrient content of the compost is required. There is, however, no specification for acceptable levels of potential harmful substances in the compost. The parameters presented in Tables 3 and 4 should be viewed as a primary requirement of what should be specified. Organic matter content: The organic matter content is a measure of carbon-based materials in the compost. Contamination with dust and gravel lowers this figure. High quality compost usually has a minimum of 50 per cent organic content based on dry weight, low quality has only 20 per cent. Moisture content: Low moisture content expedites spreading and prevents moulding and bad odour. Moisture should be about 25 per cent or less. Inert material content: The content of (glass, plastic and particulate metal) affects the appearance of compost and has direct impact on marketability. So contamination should be low. Nutrient content: This parameter should be high. The most commonly required nutrients are phosphorus, potassium and sulphur. In general, nutrients found in compost are organically bound in the beginning and are released slowly as the compost decomposes in the soil. Salinity: Salinity (soluble salt content) is expressed as electrical conductivity (dS/m). Soluble nutrients, particularly potassium, calcium and nitrogen, mostly account for salinity; sodium is an undesirable soluble salt. pH: pH between 5 and 8 is acceptable. Metal content: Levels of lead, chrome, mercury, cadmium, copper, nickel, and zinc should be specified. Trace amounts of a few metals are essential for the plants; although at higher concentrations they are toxic. The level of stability and maturity should be specified as stable and mature compost has a low level of biological activity. Immature compost can contain naturally occurring substances that are poisonous to plants, (phytotoxins). Applying immature compost can cause immobilization of available nitrogen resulting in decreased levels of plant available nitrogen. Many proposed tests for maturity exist, but none is both simple and sufficient. Often the drops in temperature of compost, possibly together with cress germination tests indicate if there is phytotoxins in the compost. Mature compost has a dark brown to black colour and a soil-like or musty odour. There should be little or no recognizable grass or leaves. The compost should also be low in weeds and pathogens.

Composting Technology in Sugar and Agro-Based Industry: Solution for High BOD... 81 Table 4.3: Desired characteristics of the compost obtained by the various composting methods (Sherman, 2000). Characteristics

Reasonable Range

Preferred Range

Carbon to nitrogen (C:N) ratio

20:1–40:1

25:1–30:1

Moisture content

40–65%

50–60%

Oxygen content

>6%

~16–18.5%

pH

5.5–9.0

6.5–8.5