Biochar and its Composites: Fundamentals and Applications (Materials Horizons: From Nature to Nanomaterials) [1st ed. 2023] 9819952387, 9789819952380

Table of contents :
Preface
Contents
About the Editor
1 Introduction of Biochar: Sources, Composition, and Recent Updates
1 Introduction
2 Sources of Biochar
3 Composition of Biochar
4 Biochar Production
4.1 Pyrolysis
4.2 Hydrothermal Carbonization
4.3 Gasification
4.4 Torrefaction and Quick Carbonization
5 Properties of Biochar
5.1 Physical Properties
5.2 Chemical Properties
6 Applications of Biochar
7 Potentials of Biochar in India
8 Conclusion
References
2 Biochar in Catalysis and Biotransformation
1 Introduction
2 Characterization of Biochar
3 Properties of Biochar
3.1 Hydrogen Ion Strength (pH) of Biochar (BC)
3.2 Biochar Cation Exchange Capacity (CEC)
3.3 Stability of Biochar (BC)
4 Biochar in Catalysis
5 Classification of Biochar-Derived Solid Catalysts
5.1 Acid Catalysts
5.2 Alkali Catalysts
6 Biochar—A Favorable Catalyst
6.1 Biodiesel Production with Biochar-Derived Catalysts
6.2 Energy Storage
6.3 Remediation
6.4 Soil Amelioration
7 Biochar and Biotransformation
8 Bicohar in Bioremediation
9 Role of Biochar in Biotransformation—A Few Studies
9.1 Degradation of Roxarsone by Shewanella oneidensis MR-1
9.2 Glucose to L-Histidine Through Escherichia Coli Metabolism
9.3 Denitrification and Mitigation of N2O Production
9.4 Biotransformation of Phosphorous
9.5 Remediation of Chromium Toxicity by Biochar, Poultry Manure, and Sewage Sludge (Biosolids) in Rice Crop
9.6 Adsorption of Manganese and Its Biotransformation by Streptomyces Violarus Strain SBP1 Cell-Immobilized Biochar
9.7 Microbial Biotransformation of Arsenic in Paddy Soil After Straw-Biochar and Straw-Amendments
9.8 De-chlorination of Pentachlorophenol in a Microbial Consortium
9.9 Chemical and Microbial Transformation of Pentachlorophenol in Paddy Soil
10 Conclusion
11 Future Perspectives
References
3 Biochar: A Potent Adsorbent
1 Introduction
2 Effects of Properties of Biochar on Adsorption Performance
2.1 Surface Functional Groups
2.2 Specific Surface Area (SSA)
2.3 Pore Size Distribution and Pore Volume
2.4 The pH Value of Biochar
3 Biochar for Water Treatment
3.1 Adsorption of Organic Contaminants
3.2 Adsorption of Inorganic Contaminants
3.3 Microbial Contaminants Removal
4 Biochar for Air Treatment
4.1 Adsorption of Organic Contaminants
4.2 Adsorption of Inorganic Contaminants
5 Future Directions
6 Conclusion
References
4 Biochar in Carbon Sequestration
1 Introduction
2 Biochar
2.1 Biochar Production
2.2 Biochar Modification
3 Biochar for CO2 Sequestration
3.1 Wooden Biochar
3.2 Seeds/Kernel-Originated Biochar
3.3 Shell/Husk-Originated Biochar
4 Conclusions and Future Directions
References
5 Biochar for Management of Wastewater
1 Introduction
2 Modification of Biochar
2.1 Biochar Activation by Physical Methods
2.2 Biochars Chemical Activation Using Acidic and Alkaline Solutions
3 Biochar as an Adsorbent of Organic and Inorganic Pollutants
3.1 Organic Pollutants
3.2 Inorganic Pollutant Removal
4 Future Prospective and Outlook
5 Conclusion
References
6 Biochar for Climate Change Mitigation
1 Introduction
1.1 Carbon Capture and Climate Change
1.2 Biochar
1.3 Sustainable Development and Climate Change
1.4 Applying Biomass/Biochar for Development
2 Sustainability and Development Indexes
2.1 Human Development Index (HDI)
2.2 HDI Calculation
2.3 Sustainable Development
2.4 HDI: Progress and Improvement
2.5 Potential of Biochar to Bring PHDI Closer to HDI
3 Climate Change: International Security Paradigm
3.1 Climate Change and Global Warming
3.2 Consequences of Global Warming and Climate Changes
4 The Evolution of the Security Paradigm
4.1 Climate Change Mitigation: Global Efforts
5 Conclusions
References
7 Clay-Biochar Composites for the Agriculture Industry
1 Introduction
2 Document Search and the Co-occurrence-Keywords Analysis
3 Clay-Biochar Composites: Production Methods and Current Applications
4 Improvement in the Physico-Chemical Characteristics of Clay-Biochar Composites
5 Clay-Biochar Composite Applications for Agriculture Industry
5.1 Clay-Biochar Composite Application in Soil Remediation
5.2 Clay-Biochar Composite Application in the Removal of the Contaminant in Agricultural Wastewater
5.3 Clay-Biochar Composite Application as Fertilizer
6 Conclusion
References
8 New Trends in Biochar–Mineral Composites
1 Introduction
2 Nanoscale Influence in Composite Synthesis and Properties
3 Biotechnology and Interaction of Composites with Living Organisms
3.1 Interaction of Biochar with Rhizosphere in Natural Environments
4 Environmental Applications of Biochar–Mineral Composites
4.1 Inorganic Substance Remotion
4.2 Emerging Organic Substances Remotion
5 Conclusion
References
9 Magnetic Composites of Biochar and Its Applications
1 Introduction
2 Synthetic Methods of Magnetic Composites of Biochar
2.1 Impregnation-Pyrolysis
2.2 Co-precipitation
2.3 Hydrothermal Carbonization
3 Utilization of Magnetic Composite of Biochar for the Adsorption of Several EPs
3.1 Adsorption of Dye
3.2 Adsorption of Heavy Metals
3.3 Adsorption of EPs for Wastewater Treatment
4 Adsorption Mechanism
5 Conclusion and Future Perspectives
References
10 Biochar Composites for Environmental and Energy Applications
1 Introduction
2 Biochar Activation
2.1 Physical Activation
2.2 Chemical Activation
3 Biochar Composites
3.1 Clay-Biochar Composites
3.2 Metal-Biochar Composites
3.3 Carbonaceous Material-Biochar Composites
3.4 Microorganism–Biochar Composites
3.5 Summary of Biochar Composites
4 Environmental Application of Biochar Composites
4.1 Water and Wastewater Treatment
4.2 Soil Remediation
4.3 Catalyst and Activator
4.4 Supercapacitor
4.5 Fuel Cell
5 Future Directions
6 Conclusion
References

Citation preview

Materials Horizons: From Nature to Nanomaterials

Ashok Kumar Nadda   Editor

Biochar and its Composites Fundamentals and Applications

Materials Horizons: From Nature to Nanomaterials Series Editor Vijay Kumar Thakur, School of Aerospace, Transport and Manufacturing, Cranfield University, Cranfield, UK

Materials are an indispensable part of human civilization since the inception of life on earth. With the passage of time, innumerable new materials have been explored as well as developed and the search for new innovative materials continues briskly. Keeping in mind the immense perspectives of various classes of materials, this series aims at providing a comprehensive collection of works across the breadth of materials research at cutting-edge interface of materials science with physics, chemistry, biology and engineering. This series covers a galaxy of materials ranging from natural materials to nanomaterials. Some of the topics include but not limited to: biological materials, biomimetic materials, ceramics, composites, coatings, functional materials, glasses, inorganic materials, inorganic-organic hybrids, metals, membranes, magnetic materials, manufacturing of materials, nanomaterials, organic materials and pigments to name a few. The series provides most timely and comprehensive information on advanced synthesis, processing, characterization, manufacturing and applications in a broad range of interdisciplinary fields in science, engineering and technology. This series accepts both authored and edited works, including textbooks, monographs, reference works, and professional books. The books in this series will provide a deep insight into the state-of-art of Materials Horizons and serve students, academic, government and industrial scientists involved in all aspects of materials research. Review Process The proposal for each volume is reviewed by the following: 1. Responsible (in-house) editor 2. One external subject expert 3. One of the editorial board members. The chapters in each volume are individually reviewed single blind by expert reviewers and the volume editor.

Ashok Kumar Nadda Editor

Biochar and its Composites Fundamentals and Applications

Editor Ashok Kumar Nadda Department of Biotechnology and Bioinformatics Jaypee University of Information Technology Waknaghat, India

ISSN 2524-5384 ISSN 2524-5392 (electronic) Materials Horizons: From Nature to Nanomaterials ISBN 978-981-99-5238-0 ISBN 978-981-99-5239-7 (eBook) https://doi.org/10.1007/978-981-99-5239-7 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

In the past decade, several researchers are focusing on the production of biochar from a variety of raw materials and its applications in various fields. This carbon-based product has gained much interest due to its unique properties and its direct correlation with carbon sequestration and mitigation of greenhouse gases in atmosphere. The biomass from various sources of animals, plants, agriculture, and forestry can be converted by simple techniques of pyrolysis under oxygen-deficient conditions into biochar. The biochar particles can be amalgamated with various other materials such as magnetic particles and nanofibers and that can improve its properties. Usually, the synthesized biochar is a highly porous material that has high water and gas absorption properties. Thus, it can be utilized for the removal of various water pollutants, metal ions, soil pollutants, and dyes and to improve the texture of soil. Also, the porous nature makes it a suitable carrier for loading the fertilizers and their release in the soil. Biochar also works as a habitat for the growth and colonization of various soil-inhabiting microorganisms that are useful for the health of the soil. The current methods of biochar synthesis and its composites need upcycling of various types of biowaste and tuning their surface properties and durability. Therefore, it is quite important to upgrade the biochar manufacturing technologies following the demand for various applications in energy and environment. The contribution from various researchers, and renowned collaborators in the field of biochar and its composites, has made this book a suitable volume for its readers. The information provided in this book is worth of interest in the areas of water treatment and biotransformations along with the mitigation of climate change. The compiled chapters will provide as a suitable reference manuscript for the soil scientists, enviornmentalists, who are keen to get the most recent advancements in the area of energy and climate change. The book will serve as a unique reference for environmental science professionals pursuing their work in biomass treatment, bio-based products as well as environmental management. The first chapter describes the general introduction of biochar, and recent updates. The next three chapters highlight the role of biochar in catalysis, as adsorbant, and in carbon sequestration. Chaps. 5 and 6 detail the role of biochar in wastewater treatment and mitigation of climate change. Further to explore the application of v

vi

Preface

biochar composites in various fields, Chaps. 7–9 emphasize on the role of biochar composites in agriculture improvement and environment. The last chapters highlight the applications of biochar in energy and environment. Waknaghat, India

Ashok Kumar Nadda

Contents

1

Introduction of Biochar: Sources, Composition, and Recent Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J. Maniraj, M. Ramesh, S. Ganesh Kumar, and A. Felix Sahayaraj

1

2

Biochar in Catalysis and Biotransformation . . . . . . . . . . . . . . . . . . . . . K. Sobha, J. L. Jayanthi, G. Kavitha, and A. Ratnakumari

19

3

Biochar: A Potent Adsorbent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Khaled Zoroufchi Benis, Jafar Soltan, and Kerry N. McPhedran

49

4

Biochar in Carbon Sequestration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mohammad Shirzad, Mohsen Karimi, Alírio E. Rodrigues, and José A. C. Silva

73

5

Biochar for Management of Wastewater . . . . . . . . . . . . . . . . . . . . . . . . . 107 Ritu Painuli, Chetan Kumar, and Dinesh Kumar

6

Biochar for Climate Change Mitigation . . . . . . . . . . . . . . . . . . . . . . . . . 123 Ehsan Shahhoseini, Moslem Arefifard, and Mohsen Karimi

7

Clay-Biochar Composites for the Agriculture Industry . . . . . . . . . . . 145 Nurhani Aryana, Witta Kartika Restu, and Bayu Arief Pratama

8

New Trends in Biochar–Mineral Composites . . . . . . . . . . . . . . . . . . . . . 169 Javier Sartuqui, Noelia L. D’Elía, and Paula V. Messina

9

Magnetic Composites of Biochar and Its Applications . . . . . . . . . . . . 185 Abhinay Thakur and Ashish Kumar

10 Biochar Composites for Environmental and Energy Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Khaled Zoroufchi Benis, Kerry N. McPhedran, and Jafar Soltan

vii

About the Editor

Dr. Ashok Kumar Nadda is working as an Assistant Professor in the Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan, Himachal Pradesh, India. He holds extensive research and teaching experience of more than 10 years in the field of microbial biotechnology, with research expertise focusing on various issues pertaining to nano-biocatalysis, microbial enzymes, biomass, bioenergy and climate change. Dr. Nadda is teaching enzymology and enzyme technology, microbiology, environmental biotechnology, bioresources and industrial products to the bachelor, master and Ph.D. students. He holds international work experiences in South Korea, India, Malaysia and People’s Republic of China. He worked as a post-doctoral fellow in the State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China. He also worked as a brain pool researcher/ Assistant Professor at Konkuk University, Seoul, South Korea. Dr. Nadda has a keen interest in microbial enzymes, biocatalysis, CO2 conversion, biomass degradation, biofuel synthesis, and bioremediation. Dr. Nadda has published more than 200 scientific contributions in the form of research, review, books, book chapters and others at several platforms in various journals of international repute. The research output includes 140 research articles, 50 book chapters and 22 books. He has presented his research findings in more than 40 national/international conferences. He has attended more than 50 conferences/ workshops/colloquia/ seminars etc. in India and abroad. His research works have gained broad interest through his highly-cited research publications, book chapters, conference presentations, and invited lectures.

ix

Chapter 1

Introduction of Biochar: Sources, Composition, and Recent Updates J. Maniraj, M. Ramesh, S. Ganesh Kumar, and A. Felix Sahayaraj

1 Introduction In several studies biochar have been manufactured using plants and degradable materials from biowaste. Biochar is often used to improve the soil quality and suitable for agriculture. Biochar is manufactured using hydrothermal carbonization, pyrolysis, gasification, and flash carbonization, etc. [1]. Biochar comprises 70% carbon, and the remainder consists of nitrogen, oxygen, and hydrogen. Numerous researches carried out on biochar manufacturing and the chemical processes that increase the soil fertility [2–5]. The micropores in biochar have the remarkable property of terra preta soil (soil manufactured using biochar), which accompanies living organisms and leads to a higher yield in agricultural fields. This increases the production of crops, and the terra preta biochar soil adsorption behavior leads to holding the water content needed for agriculture. Land requires 10 L of water for agricultural purposes [6–8]. The biochar-developed soil required only 6 L of water in the same area. Furthermore, 40% of the water requirement is reduced, whereas soil fertility is increased. Biochar reduces soil acidity and pollution of the water table. The carbon pores in the biochar act as the filters that filter it, leading to the natural absorption of impurities in the water. Biochar is manufactured using paddy straw (natural fibers and crop waste), bio-compost, and charcoal too [9–11]. Degradation of the fibers, composts, and charcoal produced the biochar. Biochar is often used to store more carbon, which increases agriculture efficiency.

J. Maniraj · M. Ramesh (B) · A. F. Sahayaraj Department of Mechanical Engineering, KIT-Kalaignarkarunanidhi Institute of Technology, Coimbatore, Tamil Nadu, India e-mail: [email protected] S. G. Kumar Department of Mechanical Engineering, Sri Eshwar College of Engineering, Coimbatore, Tamil Nadu, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 A. K. Nadda (ed.), Biochar and its Composites, Materials Horizons: From Nature to Nanomaterials, https://doi.org/10.1007/978-981-99-5239-7_1

1

2

J. Maniraj et al.

Fig. 1 Overview of biochar and its applications

Crop wastes decompose slowly by partially burnt carbon, such as paddy straw and natural fibers. Heating of biomass with low oxygen content leads to the formation of biochar, which is said to be a pyrolysis process. Biochar is available for several years in the soil, which makes the soil more fertile. The partial burning in an environment of low oxygen content prevents the complete combustion of wood or biowaste. In the biochar manufacturing process, agricultural wastes, crops, and natural fibers are partially burned, and charcoal is manufactured, which stores the carbon content for agriculture. In addition to agriculture, biochar is also used in treating the wastewater and soil conditioning, and its application in various sectors is enlisted as follows [12–15]. An overview of biochar and its applications were shown in Fig. 1.

2 Sources of Biochar Different sources, such as manure, leaves, animal wastes, wood chips, industrial wastes, and animal wastes, manufacture biochar through two pyrolysis processes. The fast and slow pyrolysis processes yield a varied range of biochar productions. The process and various sources of biochar are shown in Fig. 2 [16].

1 Introduction of Biochar: Sources, Composition, and Recent Updates

3

Fig. 2 Sources and process of biochar [16]

3 Composition of Biochar The biochar is black, highly porous, lightweight, with approximately 70% carbon, and remains composed of nitrogen, oxygen, and hydrogen [17]. The chemical properties of biochar include aromatic carbon rings with various functional groups such as nitrogen, carbon, hydrogen, and sulfur [18]. Crystals of the graphite structure were observed at low temperatures. Morphological comparison of aged and fresh biochar was shown in Fig. 3. Other elements, including oxygen, hydrogen, and nitrogen, made up the remaining percentage. There are several methods that can be used to determine the composition of biochar, including proximate analysis, CHN analysis, and feedstock approaches. Proximate analysis, a thermo-gravimetric technique, has historically been regarded as the most fundamental method for establishing char quality [19]. Chars utilized as a fuel in boilers at chosen temperatures. For this application, char moisture and ash

Fig. 3 Comparison of fresh and aged biochar [18]

4

J. Maniraj et al.

constituents were those whose energy contents were unaffected. Excellent charcoal has a high proportion of fixed carbon, some volatiles to facilitate fire and little ash. CHN analysis is the second most popular technique and is essential for further characterization to measure the carbon, hydrogen, and nitrogen contents in biochar [20]. Using this technique, carbon dioxide (CO2 ), hydrogen (H2 ), and nitric oxide (NO) are produced when a biomass burned at extremely high temperatures with additional oxygen. The results of this analysis were presented as a percentage of the dry weight of the sample [21]. Additionally, sulfur and oxygen contents can be separately trapped and measured as part of the elemental analysis. From the analysis volume of carbon, nitrogen, oxygen, chlorine, and ash can be calculated. The method of measuring oxygen by difference is challenging because mineral oxides in the ash ontinue to decompose. The feedstock with pyrolysis process have a notable impact on the biochar composition [22]. For instance, biochar produced by slow pyrolysis contain over 90% carbon and small amount of other elements. In contrast, biochar produced by pyrolysis method which could contain only 35% carbon, a small amount of oxygen, and more than 60% ash because of the high percentage of silica of the feedstock and yield low carbon during the process [23, 24]. The majority of inorganic components do not volatilize at ordinary pyrolysis temperatures, and the constituents of the ash content of biochar are largely reliant on the minerals present in the feedstock. There are various methods for determining which components are present in biochar and in what proportions.

4 Biochar Production Biomass is being converted to biochar because of growing interest in its use in various applications. Thermochemical conversion is the most common technique used to prepare biochar [25]. The classification of thermochemical conversion techniques is shown in Fig. 1. To obtain maximum biochar yield, choosing an appropriate fabrication technique and operating factors (temperature and heating time) is crucial. These factors significantly influence the properties of the fabricated biochar. In addition, during biochar fabrication, the weight loss from biomass changes with respect to time and environmental conditions. While heating at 100 °C, water vapor in the biochar evaporated, and further heating tend to the degradation of cellulose, hemicellulose, and lignin contents in the biochar [26]. The combustion of carbonaceous waste is the final cause of weight loss. Various biochar production techniques were shown in Fig. 4.

1 Introduction of Biochar: Sources, Composition, and Recent Updates

5

Fig. 4 Biochar production techniques

4.1 Pyrolysis Pyrolysis is a frequently adopted technique to convert waste biomass into valuable biochar [27, 28]. In this process, organic compounds are thermally degraded without oxygen. This process involves various reaction mechanisms, such as depolymerization, fragmentation, and cross-linking, which are carried out on lignocellulosic components. The output is obtained in multiple states, such as biochar (solid) and bio-oil (liquid), whereas CO, CO2 , H2 , and syngas are the gaseous outputs. The biochar fabrication requires a variety of reactor designs, including agitated sandrotating kilns, wagon reactors, bubbling fluidized beds, and paddle kilns. The type of biomass and process variables like temperature and time affect, how biochar develops. Generally, as the temperature increases during production, the biochar is reduced, and gaseous product output is increased. Pyrolysis is further divided into two processes, fast and slow, based on various factors. Fast pyrolysis is thought to be a direct thermochemical method with a high heating rate that has great potential for converting solid biomass into biochar and bio-oil [29]. Meanwhile, the slow pyrolysis heating rate was low, with a longer residence time. Biomass consists of the following components: cellulose, hemicellulose, and lignin. In slow pyrolysis, cellulose decomposition at a low heating rate and long residence time produce biochar at a higher volume. Levoglucosan is produced by fast pyrolysis, which takes place at a higher temperature for a shorter time. Furthermore, Levoglucosan undergoes dehydration for producing the bio-oil and syngas. Additionally, this process yields solid product biochar. Hemicellulose degradation is similar to cellulose degradation. Depolymerization of the hemicellulose results in the formation of oligosaccharides. Various chemical reactions occur during pyrolysis to produce biochar, bio-oil, and syngas. The lignin decomposition mechanism is different from those of cellulose and hemicellulose. Free radicals are created when the lignin bonds break [30]. By absorbing protons from different species, these produces free radicals form degraded compounds. These free radicals are transferred to different molecules and initiate new chain reactions.

6

J. Maniraj et al.

4.2 Hydrothermal Carbonization Hydrothermal carbonization is another technique used to produce biochar at low processing temperatures (180–250 °C) [31]. This is a cost-effective way to produce biochar compared to pyrolysis. In this process, biomass was mixed with water and kept in a closed reactor. To increase stability, the temperature was gradually increased. The following items were created at various temperatures. Hydrothermal carbonization, which produces biochar below 260 °C, and hydrothermal liquefaction, which yields bio-oil between 260 and 420 °C, are terms used to describe the production of syngas at temperatures above 420 °C. The biochar (hydrochar) fabrication process involves condensation, polymerization, and intramolecular dehydration [32]. The conversion of lignin to hydrochar is a difficult process. Dealkylation and hydrolysis are the first steps in the degradation of lignin, which produces phenolic compounds. The final product, char, is formed by polymerization and cross-linking of the intermediates. The dissolved parts of lignin in the liquid phase are converted into hydrochar, which is similar to pyrolysis.

4.3 Gasification It is a thermo-chemical process that produces syngas and hydrocarbons from carbonaceous material. The gasification was performed at higher temperatures in the presence of oxygen [33]. The reaction temperature most significantly influence the syngas production. CO and H2 production increase with increasing temperature, but the production of CH4 , CO, and hydrocarbons decreased. Syngas is the major endproduct of this process, and char is to be a by-product with a minimum yield. The biomass moisture content was fully evaporated during this process, and no energy was recovered. When biomass has a huge moisture content, drying is done separately during the gasification process. The primary sources for the gasification process are the oxidation and combustion of the gasification agents. CO2 , CO, and water are produced in the gasifier as a result of the interaction between these agents and the combustible species.

4.4 Torrefaction and Quick Carbonization Torrefaction is a recently developed method for biochar preparation at a slow heating rate [34]. This process uses inert ambient air without oxygen at 300 °C. The oxygen, moisture, and CO2 available in the biomass are eliminated during various breakdown processes. Biomass parameters were modified during torrefaction. Torrefaction involves the following processes:

1 Introduction of Biochar: Sources, Composition, and Recent Updates

7

(a) Steam torrefaction: In this process, steam was used to treat biomass at a temperature (260 °C) for 10 min. (b) Wet torrefaction: This process occurs due to biomass being in contact with water in a temperature range of 180–260 °C for 5–240 min. (c) Oxidative torrefaction: This method involves treating biomass with oxidizing agents, such as gases used in combustion, to produce heat. This heat is employed to create the necessary temperature. Torrefaction is a form of incomplete pyrolysis that occurs under the following conditions: 200–330 °C, less than 40 min of residence time, less than 60 °C/min heating rate, and an absence of O2 . Heating, drying, torrefaction, and cooling are some processes that make up the dry torrefaction process [35]. There are two types of drying processes: pre-drying and post-drying. The biomass was heated through this process until the necessary temperature was maintained and the biomass moisture content evaporated. This process continued at 100 °C until all the biomass’s moisture evaporated. The water content get fully evaporated when the temperature was raised to 200 °C. A higher temperature causes bulk content to be lost. During this procedure, a stable temperature of 200 °C was attained. Room temperature is attained by allowing the temperature to cool after product production before it comes into contact with air. High pressure is used to ignite the flash fire on a tightly packed layer of biomass, which causes it to transform into solidand gas-phase products. The entire procedure was completed in less than 30 min at a temperature of 300–600 °C. With increasing pressure, the process slows down to where approximately 40% of the biomass is transformed into solid products. Flash carbonization is a technique that has rarely been utilized in the literature.

5 Properties of Biochar 5.1 Physical Properties 5.1.1

Particle Size

The particle size of the feedstock before pyrolysis was comparable to that of particle size of chars produced at low temperature [36]. The char steadily loses the volatile compounds throughout the pyrolysis process and becomes increasingly porous while maintaining its general size and shape. The incomplete feedstock combustion and creation of dust from rubbing the now-friable char particles during pyrolysis resulted in fine particles that were produced, such as those found at the bottom of charcoal kilns. The quick escape of volatiles is thought to produce fine at higher heating rates as particles fracture under the internal pressure created. Chars from these processes often have a very small particle size (1–100 µm) owing to the preprocess grinding of feedstock, which is typically performed to facilitate the heat transfer for quick gasification and pyrolysis [37]. The risk of problems arising from dust increases as

8

J. Maniraj et al.

the particle size decreases. The easiest way to quantifying the particle size is through a sieve down to approximately 50 µm. Techniques for counting laser particles may be useful for smaller particles. The low density of chars makes it challenging to apply settling techniques such as those used to categorize soil texture (char floats instead of sinking in water). Both bulk density, which accounts for structural and pore space volume, and particle density, also known as skeletal or true density, which solely accounts for the volume occupied by solid molecules, can be used to determine the density of the char. The bulk density can be calculated by incorporating a known quantity of sample mass into a known volume container. Because of the enormous impact of compaction on pore volumes, measurement standards usually incorporate specific guidelines for sample packing or settling. Biochar has a low bulk density of 0.2–0.5 g/cc, although this may change depending on the feedstock and manufacturing procedure. For instance, the contribution of the mineral material will result in much greater densities of chars from high-ash feedstocks or methods that produce low char carbon levels. A pycnometer was used to measure the particle density, higher than the bulk density for a particularly solid material because the pore volume was no longer be considered. The compaction did not affect the particle density. As carbon condenses into dense, aromatic ring structures at high pyrolysis temperatures, the biochar particle density typically ranges between 1.6 and 1.8 g/cc. The particle densities of some high-temperature chars may even be close to that of solid graphite (2.25 g/cc) [38]. Particle density increases with ash content, much like bulk density, and for high-ash chars can exceed 2.0 g/cc.

5.1.2

Pore Size

Based on pore size, biochar has one of three types of porosity. Material scientists categorize pores into micropores, mesopores, and macropores based on their internal dimensions, which are 2, 2–50, and >200 nm, respectively [39, 40]. Each range of pore sizes influences the characteristics of the sample. The majority of the surface area of activated carbon (AC) is contributed by micropores (2 nm), which are essential for adsorption applications. Biochar macropores impact soil hydrology and microbiological habitats when used in soil applications. The easier it is for water, roots, and fungal hyphae to pass through the particle with greater the number of pores. Pores offer protection to micro-organisms from larger predatory organisms. Due to plant structure maintenance, biochar frequently has specific pore size distributions and arrangements. Numerous approaches have been used to measure the pore distribution in solid materials [41]. Micropore analysis with CO2 and N2 are examples of this technique used for chars. Mercury porosimetry is another technique that determines the size of a pore depending on the force needed to pore. Macro and mesopore measurements are frequently performed using mercury porosimetry. Mercury porosimetry has the drawback of simultaneously measuring both the internal and external pores [42]. When given as a single sample attribute, porosity is the ratio between the total pore volume to the total sample volume.

1 Introduction of Biochar: Sources, Composition, and Recent Updates

9

Fig. 5 Key parameters affecting the efficiency of a typical biochar

5.1.3

Surface Area

The amount of interaction of biochar and the soil environment is highly influenced by the surface area of the biochar; the higher the surface area, the more chemical interactions per gram of biochar are possible [43]. The method for calculating the surface area, which is useful for soil applications, has been a topic of debate. The measurement of the gas sorption isotherm was the most systematic analysis. Surface area measurements can vary depending on the isotherm temperature and gas used for analysis. The surface area of the AC is typically measured using the Brunauer– Emmett–Teller (BET) N2 gas physisorption method at 77 °K over the normal pressure range. The BET surface areas for lower-temperature biochar are about 1 m2 /g, which is slightly greater than that of lingo-cellulosic biomass since the majority of pores are macropores. Long residence duration, higher temperatures, and activation techniques, such as steam heating, all lead to high BET surface areas, which encourage the growth of micropores in the carbon. Depending on the feedstock and pyrolysis technique, some biochar can have surface areas of 100 or even 1000 m2 / g, potentially making them appropriate for AC applications. However, the maximum achievable surface area was reached because the surface area was lost as the micropore structure finally transformed into macropores. The parameters considered in the manufacturing of biochar and the key parameters that determine the performance of biochar are shown in Fig. 5.

5.2 Chemical Properties 5.2.1

Heating Value

The high heating value (HHV) of the char, which increases with the energy it contains, influences whether it is used as charcoal or biochar [44]. Bomb calorimetry, which assumes that all combustion products are allowed to cool to 26 °C, is used to

10

J. Maniraj et al.

calculate the amount of energy that can be produced from the char by burning. A different approach to figuring out the energy content using the lower heating value examines the energy of burning. Generally, the HHV increases as the carbon and H2 contents increase and decreases respectively and the moisture, oxygen and ash contents increase. The HHV of chars also differs because feedstock and technique considerably impact the char composition. Char co-products from the processes have substantially lower HHVs than low-ash slow pyrolysis chars, which can have HHVs of around 35 MJ/kg.

5.2.2

Carbon Fraction

The majority of the chemical characteristics of biochar are relevant to “carbon fraction” ideas called aromaticity and functionality [45]. Aromaticity is the measure of how much carbon in char participates in aromatic bonding. Because lignin (aromatic rings) and sugar polymers have only aliphatic carbons, lignocellulosic feedstocks have limited aromaticity. During the pyrolysis process, oxygen and hydrogen were destroyed, allowing the excess carbons to form new bonds. The structures get increasingly “orderly” as the temperature rises, generating ever larger sheets of interlinked aromatic rings. At the greatest temperatures, the organization of these sheets changes from chaotic to aligned, stacked sheets that resemble graphite. The value of aromatic condensation in biochar is assumed to be connected to environmental noncompliance because carbons in dense, aromatic structures are more resistant and few microorganisms have enzymes that can break down such bonds. Aromatic molecules are more stable because they have many bonds where electrons are shared. By “spreading out” electrons across the molecule, these molecules are able to reside in lower energy states than non-aromatic compounds. Electrons can be efficiently shared by graphite and some other highly condensed chars, and they can even conduct electricity. The majority of techniques for determining the degree of aromatic condensation in char are comparable to those for determining surface functionality. The two other ways being researched are electrical conductance/resistivity and particle density. Numerous chemical inter-relations between biochar and the environment are influenced by the surface chemistry of the biochar [46]. In lignocellulosic feedstocks, -OH groups, COOH, and short alkyl groups, like methyl groups, are the most common surface functional groups. This form of surface chemistry typically results in feedstocks that are polar, hydrophilic, or mildly reactive. The chars created by pyrolysis have very different surface chemistry. After the majority of functional groups have volatilized off, aromatic carbon surfaces are still present. The surfaces were nonpolar, decreased, and hydrophobic (carbon was in the CO oxidation state). As these surfaces are exposed to air over time, carbon oxidation causes the surface to become polar once more. There is a production of new functional groups with oxygen, such as hydroxyl, carbonyl, and carboxylic acids [47]. These functional groups are essential for the interactions between biochar and soil. First, depending on the pH, these functional groups can take or donate protons (H+) due to their varying charges. At higher pH

1 Introduction of Biochar: Sources, Composition, and Recent Updates

11

values, some hydroxyls (-OH) and carboxylic acids (−COOH) acquire a negative charge. Under low pH, these similar groups can take up protons. When using high-ash alkaline chars, the feedstock’s ash percentage can counteract the effects of the carbon fraction on the pH. Secondly, positively charged cations can be drawn to negatively charged surface functional groups, significantly raising soil CEC. The hydrophobic and hydrophilic portions of the biochar surface allow for the adsorption of polar and nonpolar organic molecules from the environment. For instance, when char absorbs organic molecules or contaminants from the environment, this adsorptive potential might be useful. A pesticide may, on the down side, adhere to these surfaces and lose some of its potency. To find out more about the potential chemical interactions of biochar, various aspects of its surface functioning might be investigated. It is important to keep in mind that in all of these processes, especially at initially, the surfaces of the biochar alter with contact to the environment [48]. Fresh char that has just been removed from the pyrolizer has surface properties that are very different from biochar that has been buried for many years or left out in the open for a number of weeks.

5.2.3

pH

When choosing the right char for a particular application, it is crucial to understand how biochar impacts pH because soil pH has a significant impact on a variety of physical, chemical, and biological characteristics [49]. Another method for figuring out the acidity of char is titration. By titrating the char with progressively stronger bases, this method determined the kinds of acidic functional groups that were present. Acids of different potencies can be used to make comparable measurements of char alkalinity. For high-ash content of chars, which might act as liming agents in soils, the general ability of biochar to neutralize acids is especially important. The pH of the biochar varies from 4.6 to 9.3. Biochar is often used to reduce the soil’s acidity, directly increasing soil pH, making it suitable for agricultural use [50]. Biochar is produced at 300–400 °C. The properties and behavior of fresh and aged biochar vary with the carbon content. The SEM images show the surface smoothness of aged biochar and fresh biochar. A reduction in oxygen content and an increase in carbon content were observed in aged biochar. The physical properties of a typical biochar include its surface area, particle size, grinding ability, bulk density, and particle density [51].

6 Applications of Biochar Biochar is used in various sectors such as the food industry, wastewater treatment, building sector, energy production, soil conditioner support for catalyst development, cosmic industries, and metallurgy etc. [52]. It is used as a natural filter in wastewater treatment. The micropores in the biochar led to water filtration, leading to purification.

12

J. Maniraj et al.

Biochar is often used for the removal of pesticides, volatile compounds, contaminants, chlorine, etc. The removal of volatile organic compounds is done using the biochar by carbon adsorption technique. Numerous studies have been conducted on biochar filtration of organic compounds. Active biochar filters are the most effective filters for volatile compounds, odors, etc., and have proven that the presence of hydroxyl and carboxyl ions acts as cation exchangers. The classical structure of graphite connects neighboring atoms with carbon atoms, increasing the absorption property of biochar [53–55]. Due to its low thermal conductivity, biochar is often used in the building sector. Biochar restricts heat transfer through the walls. Hence, it is used as an insulator for fences. The biochar was mixed with cement mortar and lime at a 1:1 ratio for wall insulation. This leads to an excellent breathing property of the walls that maintains a relative humidity of 45–70% in summer and winter. This, in turn, prevents the user from respiratory disorders, allergies, etc. Biochar was used as a soil conditioner. It enhances soil quality and increases the water-absorbing capacity owing to its porous nature. Thus, this reduces the cost and frequency of irrigation. The water consumption of agricultural fields is reduced, resulting in a reduction in water evaporation. In addition, biochar has a liming effect, which leads to increased alkalinity to maintain the pH value of the acidic soil. In metallurgy industries, biochar significantly improves leach and pulp carbon. Mining companies use biochar to reduce carbon content. AC is used in floating circuits, and powdered carbon is used as a modifier. Molybdenum, zinc, and copper are examples of the application of biochar in the mining industry. In 2010, the Japan Consulting Institute suggested that biochar be produced in the place of coke and coal. Palm shell biochar has been proven to be the best alternative fuel for furnaces [56–58]. The biochar process completely replaces environmental pollution caused by heavy metals such as mercury, arsenic, and selenium. The ash residue is free from hazardous waste and reduces pollution. The application of biochar in the food industry in the form of AC is used in sugarcane refining, purification of liquid sugar, manufacturing of beverages, fruit juices, star-based food products, biochemical food products, natural glycerin, food oils, lactose, and flavoring [59]. Biochar is used in energy production, the most cost-effective way of producing electrical energy, and it acts as a substitute for coal. Syngas is produced as a coproduct, whereas biochar is used as an alternative fuel to diesel and petrol in internal combustion engines. Syngas and bio-oil are substitutes for gasoline and biodiesel oils. The energy density of syngas oil is higher than that of biochar; hence, it acts as a promising energy storage material used for burning to produce electricity and is used in gasoline engines [60]. Biochar oils have a high vapor content, leading to the corrosion of steel surfaces.

1 Introduction of Biochar: Sources, Composition, and Recent Updates

13

7 Potentials of Biochar in India In India, most work is concentrated in the agricultural industry. Improvement in soil fertility leads to farm production efficiency. The global demand for biochar has been analyzed and is based on the production of biochar in India [61]. It has increased considerably in past decades. 80% of India’s biochar is used to improve soil fertility in agricultural lands. An average of 376.11 megatons of carbon dioxide equivalent carbon in the soil could help India reduce emissions from 41 to 61% of farming fields. Since biochar has the potential in food, mining, agricultural, water treatments, and soil conditioning, the biochar potential is more and is needed for multiple industries to manufacture the commercial products. Agriculture is India’s backbone. Hence, the biochar will definitely help the manufacturers for mass production of goods to increase the country’s economy. Biochar is applied to sandy desert soil for low water consumption to cultivate crops [62]. Researchers have demonstrated a 16% increase in the efficiency of crop production in sandy desert soils. Nitrogen is a crucial component of plant growth and reproduction. The presence of nitrogen in biochar helps plant reproduction and growth. Among the manufacturing processes for biochar, pyrolysis is an efficient process often used to manufacture biochar. During pyrolysis, the biomass is heated and partially burnt without oxygen. During pyrolysis, biomass generates power and syngas. Biomass is stored and dried initially in dedicated biomass storage equipment. The dried biomass was transferred to the pyrolysis reactor through a conveyor or bucket feeder. The biomass was allowed to flow into the pyrolysis reactor, where hot and dried air flowed into the biomass chamber before entering the reactor. Hot airflow reduces the moisture content, which allows it to burn efficiently during pyrolysis. Biomass, such as husks, natural fibers, wood pieces, and animal waste, is fed to the pyrolysis reactor. The moisture content accumulated depended on the biomass process material. The upper part of the reactor was maintained at a high temperature to reduce the moisture content of the biomass. After the biomass process material dehumidifies, the degasification process is carried out in the process chamber at 300–400 °C to remove volatile components such as carbon monoxide, carbon dioxide, and nitrogen. After degasification in the reactor, the biomass was treated at a high temperature for carbonization. In this phase, the disappearance of the fiber structure and its transformation into carbon leads to biomass production, which improves the grindability and porosity of the biomass material. After the carbonization process, the process material (biomass) weight was reduced, allowing suitable transportation from one place to another [63]. After the carbonization reaction, the biomass material had a calorific value of 29–31 MJ/kg of biochar. The biochar produced was allowed to cool in the cooling chamber using cross-flow heat exchangers at ambient temperature after the carbonization reaction.

14

J. Maniraj et al.

8 Conclusion Biochar is a gift of nature that supports agriculture, metallurgical fields, food, mining, etc. Due to the broad scope of biochar, its suitability is higher, and its manufacturing potential is high in India due to the agricultural backbone of the nation. From the research, the following statements are concluded. • The porosity of the biochar was high, which reduced the irrigation frequency. The suitability of biochar for desert sandy soils was high. • High carbon content increases the plant growth and acts as a filter for organic impurities and volatile compounds. • Porosity in nature leads to water treatment plants’ application and increases plants’ adsorption effect.

References 1. He M, Xu Z, Hou D, Gao B, Cao X, Ok YS, Rinklebe J, Bolan NS, Tsang DC (2022) Wastederived biochar for water pollution control and sustainable development. Nat Rev Earth Environ 3(7):444–460 2. Bolan N, Hoang SA, Beiyuan J, Gupta S, Hou D, Karakoti A, Joseph S, Jung S, Kim KH, Kirkham MB, Kua HW (2022) Multifunctional applications of biochar beyond carbon storage. Int Mater Rev 67(2):150–200 3. Liu Z, Xu Z, Xu L, Buyong F, Chay TC, Li Z, Cai Y, Hu B, Zhu Y, Wang X (2022) Modified biochar: synthesis and mechanism for removal of environmental heavy metals. Carbon Res 1(1):1–21 4. Foong SY, Chan YH, Chin BLF, Lock SSM, Yee CY, Yiin CL, Peng W, Lam SS (2022) Production of biochar from rice straw and its application for wastewater remediation—an overview. Bioresour Technol 127588 5. Al-Rumaihi A, Shahbaz M, Mckay G, Mackey H, Al-Ansari T (2022) A review of pyrolysis technologies and feedstock: a blending approach for plastic and biomass towards optimum biochar yield. Renew Sustain Energy Rev 167:112715 6. Kamali M, Sweygers N, Al-Salem S, Appels L, Aminabhavi TM, Dewil R (2022) Biochar for soil applications-sustainability aspects, challenges and future prospects. Chem Eng J 428:131189 7. Adeniyi AG, Abdulkareem SA, Iwuozor KO, Ogunniyi S, Abdulkareem MT, Emenike EC, Sagboye PA (2022) Effect of salt impregnation on the properties of orange albedo biochar. Clean Chem Eng 3:100059 8. Hoang AT, Goldfarb JL, Foley AM, Lichtfouse E, Kumar M, Xiao L, Ahmed SF, Said Z, Luque R, Bui VG, Nguyen XP (2022) Production of biochar from crop residues and its application for anaerobic digestion. Bioresour Technol 127970 9. Ling L, Luo Y, Jiang B, Lv J, Meng C, Liao Y, Reid BJ, Ding F, Lu Z, Kuzyakov Y, Xu J (2022) Biochar induces mineralization of soil recalcitrant components by activation of biochar responsive bacteria groups. Soil Biol Biochem 172:108778 10. Khan AA, Gul J, Naqvi SR, Ali I, Farooq W, Liaqat R, AlMohamadi H, Štˇepanec L, Juchelková D (2022) Recent progress in microalgae-derived biochar for the treatment of textile industry wastewater. Chemosphere 135565 11. Luo Z, Yao B, Yang X, Wang L, Xu Z, Yan X, Tian L, Zhou H, Zhou Y (2022) Novel insights into the adsorption of organic contaminants by biochar: a review. Chemosphere 287:132113

1 Introduction of Biochar: Sources, Composition, and Recent Updates

15

12. Xie Y, Wang L, Li H, Westholm LJ, Carvalho L, Thorin E, Yu Z, Yu X, Skreiberg Ø (2022) A critical review on production, modification and utilization of biochar. J Anal Appl Pyrol 161:105405 13. Qin F, Zhang C, Zeng G, Huang D, Tan X, Duan A (2022) Lignocellulosic biomass carbonization for biochar production and characterization of biochar reactivity. Renew Sustain Energy Rev 157:112056 14. Anand A, Pathak S, Kumar V, Kaushal P (2022) Biochar production from crop residues, its characterization and utilization for electricity generation in India. J Clean Prod 368:133074 15. Zheng X, Xu W, Dong J, Yang T, Shangguan Z, Qu J, Li X, Tan X (2022) The effects of biochar and its applications in the microbial remediation of contaminated soil: a review. J Hazard Mater 129557 16. Chen WH, Hoang AT, Nižeti´c S, Pandey A, Cheng CK, Luque R, Ong HC, Thomas S, Nguyen XP (2022) Biomass-derived biochar: from production to application in removing heavy metalcontaminated water. Process Saf Environ Prot 160:704–733 17. Gopi R, Mahendran B, Nisha M, Nithya K, Mahesh P (2021) Biochar and its scope in nutrient, pest and disease management in sugarcane. Biot Res Today 3(7):627–630 18. Yang X, Wan Y, Zheng Y, He F, Yu Z, Huang J, Gao B (2019) Surface functional groups of carbon-based adsorbents and their roles in the removal of heavy metals from aqueous solutions: a critical review. Chem Eng J 366:608–621 19. Tripathi M, Sahu JN, Ganesan P (2016) Effect of process parameters on production of biochar from biomass waste through pyrolysis: a review. Renew Sustain Energy Rev 55:467–481 20. Enders A, Hanley K, Whitman T, Joseph S, Lehmann J (2012) Characterization of biochars to evaluate recalcitrance and agronomic performance. Biores Technol 114:644–653 21. Kumar RP, Muthukrishnan M, Sahayaraj AF (2022) Experimental investigation on jute/snake grass/kenaf fiber reinforced novel hybrid composites with annona reticulata seed filler addition. Mater Res Express 9(9):095304 22. Yang X, Ng W, Wong BSE, Baeg GH, Wang CH, Ok YS (2019) Characterization and ecotoxicological investigation of biochar produced via slow pyrolysis: effect of feedstock composition and pyrolysis conditions. J Hazard Mater 365:178–185 23. Wang K, Brown RC, Homsy S, Martinez L, Sidhu SS (2013) Fast pyrolysis of microalgae remnants in a fluidized bed reactor for bio-oil and biochar production. Biores Technol 127:494– 499 24. Manickam T, Iyyadurai J, Jaganathan M, Babuchellam A, Mayakrishnan M, Arockiasamy FS (2022) Effect of stacking sequence on mechanical, water absorption, and biodegradable properties of novel hybrid composites for structural applications. Int Polym Proc. https://doi. org/10.1515/ipp-2022-4274 25. Li DC, Jiang H (2017) The thermochemical conversion of non-lignocellulosic biomass to form biochar: a review on characterizations and mechanism elucidation. Biores Technol 246:57–68 26. Brown R (2012) Biochar production technology. In: Biochar for environmental management. CRC Press, pp 159–178 27. Yadav K, Jagadevan S (2019) Influence of process parameters on synthesis of biochar by pyrolysis of biomass: an alternative source of energy. In: Recent advances in pyrolysis. IntechOpen 28. Arockiasamy FS (2022) Experimental investigation on the effect of fiber volume fraction of sponge gourd outer skin fiber reinforced epoxy composites. Polym Compos 43(10):6932–6942 29. Brigagão GV, Araújo ODQF, de Medeiros JL, Mikulcic H, Duic N (2019) A technoeconomic analysis of thermochemical pathways for corncob-to-energy: fast pyrolysis to bio-oil, gasification to methanol and combustion to electricity. Fuel Process Technol 193:102–113 30. Yang H, Yan R, Chen H, Zheng C, Lee DH, Liang DT (2006) In-depth investigation of biomass pyrolysis based on three major components: hemicellulose, cellulose and lignin. Energy Fuels 20(1):388–393 31. Volpe R, Volpe M, Fiori L, Messineo A (2016) Upgrading of olive tree trimmings residue as biofuel by hydrothermal carbonization and torrefaction: a comparative study. Chem Eng Trans 50:13–18

16

J. Maniraj et al.

32. Reza MT, Uddin MH, Lynam JG, Hoekman SK, Coronella CJ (2014) Hydrothermal carbonization of loblolly pine: reaction chemistry and water balance. Biomass Convers Biorefinery 4(4):311–321 33. Gomaa MR, Mustafa RJ, Al-Dmour N (2020) Solar thermochemical conversion of carbonaceous materials into syngas by co-gasification. J Clean Prod 248:119185 34. Huang YF, Cheng PH, Chiueh PT, Lo SL (2017) Leucaena biochar produced by microwave torrefaction: fuel properties and energy efficiency. Appl Energy 204:1018–1025 35. Sá LC, Loureiro LM, Nunes LJ, Mendes AM (2020) Torrefaction as a pretreatment technology for chlorine elimination from biomass: a case study using eucalyptus globulus Labill. Resources 9(5):54 36. Shen J, Wang XS, Garcia-Perez M, Mourant D, Rhodes MJ, Li CZ (2009) Effects of particle size on the fast pyrolysis of oil mallee woody biomass. Fuel 88(10):1810–1817 37. Han YM, Cao JJ, Lee SC, Ho KF, An ZS (2010) Different characteristics of char and soot in the atmosphere and their ratio as an indicator for source identification in Xi’an, China. Atmos Chem Phys 10(2):595–607 38. Krishnamoorthy V, Pisupati SV (2019) Effect of temperature, pressure, feed particle size, and feed particle density on structural characteristics and reactivity of chars generated during gasification of Pittsburgh No.8 coal in a high-pressure, high-temperature flow reactor. Energies 12(24):4773. https://doi.org/10.3390/en12244773 39. Huang S, Ding Y, Li Y, Han X, Xing B, Wang S (2021) Nitrogen and sulfur co-doped hierarchical porous biochar derived from the pyrolysis of mantis shrimp shell for supercapacitor electrodes. Energy Fuels 35(2):1557–1566 40. Jenish I, Sahayaraj AF, Appadurai M, Irudaya Raj EF, Suresh P (2022) Sea sand abrasive wear of red mud micro particle reinforced cissus quadrangularis stem fiber/epoxy composite. J Nat Fibers 1–16 41. Sun H, Hockaday WC, Masiello CA, Zygourakis K (2012) Multiple controls on the chemical and physical structure of biochars. Ind Eng Chem Res 51(9):3587–3597 42. Schimmelpfennig S, Glaser B (2012) One step forward toward characterization: some important material properties to distinguish biochars. J Environ Qual 41(4):1001–1013 43. Akhil D, Lakshmi D, Kartik A, Vo DVN, Arun J, Gopinath KP (2021) Production, characterization, activation and environmental applications of engineered biochar: a review. Environ Chem Lett 19(3):2261–2297 44. Demirbas A, Pehlivan E, Altun T (2006) Potential evolution of Turkish agricultural residues as bio-gas, bio-char and bio-oil sources. Int J Hydrogen Energy 31(5):613–620 45. Lin Y, Munroe P, Joseph S, Henderson R, Ziolkowski A (2012) Water extractable organic carbon in untreated and chemical treated biochars. Chemosphere 87(2):151–157 46. Lonappan L, Rouissi T, Brar SK, Verma M, Surampalli RY (2018) An insight into the adsorption of diclofenac on different biochars: mechanisms, surface chemistry, and thermodynamics. Biores Technol 249:386–394 47. Lee D, Hong SH, Paek KH, Ju WT (2005) Adsorbability enhancement of activated carbon by dielectric barrier discharge plasma treatment. Surf Coat Technol 200(7):2277–2282 48. Jenish I, Sahayaraj AF, Suresh V, Appadurai M, Irudaya Raj EF, Nasif O, Kumaravel AK (2022) Analysis of the hybrid of mudar/snake grass fiber-reinforced epoxy with nano-silica filler composite for structural application. Adv Mater Sci Eng 49. Kookana RS, Sarmah AK, Van Zwieten L, Krull E, Singh B (2011) Biochar application to soil: agronomic and environmental benefits and unintended consequences. Adv Agron 112:103–143 50. Kannan P, Paramasivan M, Marimuthu S, Swaminathan C, Bose J (2021) Applying both biochar and phosphobacteria enhances Vigna mungo L. growth and yield in acid soils by increasing soil pH, moisture content, microbial growth and P availability. Agric, Ecosyst Environ 308:107258 51. Kang Z, Jia X, Zhang Y, Kang X, Ge M, Liu D, Wang C, He Z (2022) A review on application of biochar in the removal of pharmaceutical pollutants through adsorption and persulfate-based AOPs. Sustainability 14(16):10128 52. Maroušek J, Vochozka M, Plachý J, Žák J (2017) Glory and misery of biochar. Clean Technol Environ Policy 19(2):311–317

1 Introduction of Biochar: Sources, Composition, and Recent Updates

17

53. Huang P, Zhang P, Wang C, Tang J, Sun H (2022) Enhancement of persulfate activation by Fe-biochar composites: synergism of Fe and N-doped biochar. Appl Catal B 303:120926 54. Amalina F, Abd Razak AS, Krishnan S, Sulaiman H, Zularisam AW, Nasrullah M (2022) Biochar production techniques utilizing biomass waste-derived materials and environmental applications–a review. J Hazard Mater Adv 100134 55. Patel AK, Katiyar R, Chen CW, Singhania RR, Awasthi MK, Bhatia S, Bhaskar T, Dong CD (2022) Antibiotic bioremediation by new generation biochar: recent updates. Biores Technol 358:127384 56. Cimirro NF, Lima EC, Cunha MR, Thue PS, Grimm A, dos Reis GS, Rabiee N, Saeb MR, Keivanimehr F, Habibzadeh S (2022) Removal of diphenols using pine biochar. Kinetics, equilibrium, thermodynamics, and mechanism of uptake. J Mol Liq 364:119979 57. Zhu H, Guo A, Wang S, Long Y, Fan G, Yu X (2022) Efficient tetracycline degradation via peroxymonosulfate activation by magnetic Co/N co-doped biochar: emphasizing the important role of biochar graphitization. Chem Eng J 450:138428 58. Qin F, Li J, Zhang C, Zeng G, Huang D, Tan X, Qin D, Tan H (2022) Biochar in the 21st century: a data-driven visualization of collaboration, frontier identification, and future trend. Sci Total Environ 818:151774 59. Eggleston G, Lima I (2015) Sustainability issues and opportunities in the sugar and sugarbioproduct industries. Sustainability 7(9):12209–12235 60. Guo M, Song W, Buhain J (2015) Bioenergy and biofuels: History, status, and perspective. Renew Sustain Energy Rev 42:712–725 61. Anand A, Kumar V, Kaushal P (2022) Biochar and its twin benefits: Crop residue management and climate change mitigation in India. Renew Sustain Energy Rev 156:111959 62. Peng Y, Zhang B, Guan CY, Jiang X, Tan J, Li X (2022) Identifying biotic and abiotic processes of reversing biochar-induced soil phosphorus leaching through biochar modification with MgAl layered (hydr) oxides. Sci Total Environ 843:157037 63. Ji M, Wang X, Usman M, Liu F, Dan Y, Zhou L, Campanaro S, Luo G, Sang W (2022) Effects of different feedstocks-based biochar on soil remediation: a review. Environ Pollut 294:118655

Chapter 2

Biochar in Catalysis and Biotransformation K. Sobha , J. L. Jayanthi , G. Kavitha , and A. Ratnakumari

1 Introduction Biochar, a high-carbon solid, is produced by the thermal decomposition of feedstocks like crop waste, livestock manure, and cellulose-rich materials under low oxygen conditions [1]. Rapid industrialization, urbanization, and population growth result in the generation of massive amounts of organic waste, which include agro-, industrial, sea-, forestry-, domestic-, or municipal-solid waste (MSW), and animal manure. Along with these, the global energy requirement is also increasing. The preparation and utilization of biochar to improve soil fertility is followed since ancient times by agriculturists across the globe. Biochar is most commonly made by smoldering agricultural waste in pits or trenches [2]. Organic wastes, the major fraction of solid biomass, can be turned into biochar. The physico-chemical characteristics like the high surface area to volume, porosity/voidity, organic reactive groups, ion exchange ability, and stable strength make it suitable for various ecological applications. Process parameters, viz. temperature, biomass nature, persistence/residence time, temperature rise per unit time (heating rate), and pressure decide the yield of biochar [3]. The major components of all biochar are carbon and minerals, but the ultimate composition and characteristics are determined by the biomass type, reaction conditions, and reactor types used for the carbonization. The activated carbon from coal approximately contains 80–95% carbon, while biochar contains 45–60 wt% carbon and carbon black have the highest, about 98% [4]. The physical and chemical characteristics of biochar produced vary with temperatures employed for processing. The lightweight black deposit, called ‘Biochar’ (BC), contains inorganic elements like K, Na, Ca, Mg, and Fe in small quantities [5]. The amount and composition of inorganics will vary greatly depending on the chemical build-up of raw biomass [6].

K. Sobha (B) · J. L. Jayanthi · G. Kavitha · A. Ratnakumari Department of Chemical Engineering, RVR and JC College of Engineering (A), Guntur, Andhra Pradesh 522019, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 A. K. Nadda (ed.), Biochar and its Composites, Materials Horizons: From Nature to Nanomaterials, https://doi.org/10.1007/978-981-99-5239-7_2

19

20

K. Sobha et al.

Functionalization of biochar, using its surface functional groups, facilitates the manufacture of biochar-supported metal-catalysts [7]. Kitano et al. [8] investigated cellulose hydrolysis by a 2D carbon allotrope, viz. graphene sheets containing SO3 H, −COOH, and phenolic −OH groups, functioning like solid-catalytic agents. The sulfonated carbon is reported to be better at hydrolyzing cello-hexose than sulfonic acid (SO3 H)-bearing resins. The carbon material contains fatty acid (−COOH) and phenolic-hydroxyl (-OH) groups as sites for the adsorption of ligands. Research reports suggest that biochar-based solid-acid catalysts with a combination of these functional groups show good efficiency for hydrolyzing cellulose and 1,4-glucan. Biochar adsorbs toxic heavy metals and contaminants, and its sorption efficiency is directly related to its physicochemical attributes, augmented by treatment with acid/ alkali/oxidizing chemical substances [9–11]. The advantages of biochar include its eco-friendliness, ease of preparation, reusability, cost-effectiveness, and ability to convert waste into repurposed products [12, 13]. An essential property of biochar is its porosity, along with the availability of numerous surface functional groups. Due to this feature, it can immobilize diverse chemical pollutants present in the soil and thereby decrease their bioavailability and toxicity. Biochar and the electroactive bacteria present in the habitat can exchange electrons [14, 15] and thus mediate oxidation–reduction reactions [16]. In addition, biochar serves as a nutrient substrate for electroactive bacteria [14] and plants. Biochar has immense potential to sequester soil pollutants in agricultural fields. Several varieties of crop refuge like the straw of cereals, viz. paddy and wheat [17, 18], wood scrap [19], sugar-beet tailings [20], and maize cob [21], are utilized for producing BC. Plant refuges (e.g. rice husk, wood bark, sugar beet tailings, skeletons of fruit-free bunches, pinewood, and woodchips) and animal-derived organic wastes (e.g. human, cattle, and poultry manure) are the common feedstocks for biochar production. The raw materials and the production methods influence the heavy metals, viz. Cu, Zn, Ni, Pb, Cr, Mn, and several organic pollutants, viz. perfluoro-octane-sulfonic acid (PFOS), polycyclic-aromatic hydrocarbons (PAH), perfluoro-octanoic acid (PFOA), phenols/dioxins/furans (PCDD/F), and organic acids [22]. Furthermore, BC produced from animal discards has a specific pore characteristic (generally, on the lower side) due to the ash and other inorganic compositions of the feedstock, as compared to BC generated from plants at the same process (pyrolysis) conditions and retention time [23, 24]. Biochar applications include soil fertility enhancement, increased seed germination rate, improved growth rate of plants, enhanced pathogen deprivation of soil, adsorption of toxicants, reduction of greenhouse gas emissions [25, 26], wastewater treatment [27], energy production [28], and catalysis [29, 30]. Besides, biochar serves as an energy fuel and carbon sink. Magnetic biochars (MBCs), with their high adsorption capacity and total recovery due to magnetic properties, have fascinated researchers across the globe toward their development from diverse biomass feedstocks. Magnetic biochar/c-Fe2 O3 is prepared by keeping the biomass submerged in a solution of FeCl3 for 2 h followed by keeping it at 80 °C for 2 h in ambient

2 Biochar in Catalysis and Biotransformation

21

environmental conditions and then, pyrolyzed in a furnace at 600 °C for 1 h in N2 enriched ambience. When compared to conventional BC, the adsorption capacity of MBC increases 3–4fold [31–34]. In terse, the first and foremost benefit is the simplicity of the BC production and economic feasibility because of the possibly uninterrupted supply of biomass feedstocks and evolved techniques. Second, the physical and chemical properties can be designed as per the requirement of the application [35]. Third, biochar can also aid catalysis because of its inherent structure, availability of inorganic species, surface charges, etc. [36].

2 Characterization of Biochar The methods employed in characterization give valuable information about the structure/topology of the material, constituent functional groups, and elemental composition, and thereby help in the determination of functional characteristics. Structural and molecular characterization is done by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray diffraction (XRD), Nuclear Magnetic Resonance (NMR), and Raman spectroscopy methods. Of these, scanning electron microscopy is used to identify biochar morphology; functional/reactive groups through Fourier transform infrared, nuclear magnetic resonance, and Raman spectroscopy; and surface elements are identified through scanning electron microscopy and energy dispersive X-ray analyses. Physical properties like pH, electrical conductivity, and chemical properties (surface area/expanse, particle size distribution, bulk density, and pore dimensions) are determined by Brunauer–Emmett–Teller (BET) analysis.

3 Properties of Biochar Biochar’s ‘void fraction’ and ‘expanse’ are two factors that influence its metal sorption capacity. Depending on the pyrolysis temperature, pore sizes of biochar range from micro (50 nm) through nano (500 °C, has a low CEC due to aromatization and loss of binding groups [39], while biochar formed at a lower temperature has a high CEC and can hold cations like ammonium [42].

3.3 Stability of Biochar (BC) The stability of biochar depends on its source material characteristics and the pyrolysis temperatures; enhanced pyrolysis produces sturdier biochar [43]. Such stable biochar is ideal for long-term soil amendments like nutrient retention [44], carbon sequestration, and pesticide-remediation of contaminated soils.

4 Biochar in Catalysis Salient features of biochar that contribute to its catalytic activity include its unique chemistry and measurable, maneuverable surface functional groups that could be employed for functionalization. This offers effective support for diverse chemical processes, including the upgradation of biomass, its hydrolysis, dehydration, pyrolysis, gasification, and bio-oil generation. With increasing efforts to explore renewable energy sources in sufficient quantities, the production of biofuels like biodiesel with the use of carbon-based catalysts has emerged. It was reported by Konwar et al. [45] that biodiesel production can be enhanced with the use of biochar as a catalyst. However, biomass-derived biochar has inherent limitations with respect to its catalytic and/or catalytic support activity, in terms of low surface area, porosity, and a lesser number of functional moieties. Therefore, activation and functionalization processes are pre-requisites for tapping the highest catalytic potential of the biochar produced from different types of feedstock material. As aforementioned, the activation process results in an increased number of active sites and high loading and mass transfer capacities that are crucial to catalysis and increase the yield of the desired

2 Biochar in Catalysis and Biotransformation

23

products. The steps involved in the activation or functionalization needed to override the innate limitations in terms of low surface area, porosity, and a lesser number of functional moieties, are outlined in the flowchart (Fig. 1).

Fig. 1 An overview of biochar activation/functionalization and major applications

24

K. Sobha et al.

The regulated stream of water vapor, CO2 , or both at a temperature of 700 °C causes the separation of ‘C’ from C–H2 O and/or C–CO2 by erosion, and with the result, the surface carbons get stripped off, the biochar matrix gets opened up, and the specific surface area gets significantly enhanced. In general, the extent of activation is influenced by the biomass type and its microstructure, the activating gas, and the reaction conditions. However, the general outcome of the reported experimental studies suggests a dramatic enhancement in the porosity and surface area of the biochar material. In general, the porosity and the surface area increase with the increase in temperature up to 1000 °C, but a further rise in temperature decreases the surface area due to the collapse of the pore walls, leading to the formation of a graphite-like structure in the biochar matrix. Dehkhoda et al. [46] reported more than twofold higher electrosorption capacitance at 675 °C as compared to 1000 °C. In general, the biochar produced at temperatures below 400 °C demonstrates a low pH, a small surface area, and low electrical conductivity [47], and from researchers’ reports, it can be inferred that the properties of biochar are closely related to the charring temperature range of 100–600 °C and, in turn, related to the functional groups [47, 48]. It is important to note the following with respect to the functional groups and the transition in the charring temperatures: 1. 1D-NMR spectra demonstrate a two-phase characteristic; the transition temperature for charring occurs at 300 °C. 2. Aliphatic O-alkylated carbons (HCOH) were predominant at 73 ppm, and these were replaced by fused-ring aromatic structures (128 ppm). 3. For biochars produced at temperatures below 300 °C, the NMR bands overlapped in the region of 50–100 ppm, while for temperatures above 300 °C, the overlapping region was between 100 and 150 ppm [49, 50]. 4. Further, for wood char, treatment at 300 °C produced lignin and celluloseenriched residues, with carbohydrates being totally lost at 350 °C, and at 450 °C, the aromatic structures completely replaced those of lignocellulose. From the synchronous and asynchronous maps of 2D C13 NMR correlation spectra, it can be inferred that the biochar production from plant-derived polymers is by dealkylation, dihydroxylation/dehydrogenation, and aromatization, as the intensity of aliphatic O-alkylated (73 ppm) and fused-ring aromatic structure (128 ppm) changed with the increasing charring temperature. The order identified from asynchronous maps is from 73–105 ppm (cleavage of aliphatic O-alkylated groups and aromatic O–C–O carbons) to 128 ppm (generation of fused-ring aromatic structures). Further, research studies suggest the determination of the properties of biochar, viz. pH and electrical conductivity (EC), as negatively correlated to O-alkylated groups and positively correlated to fused aromatic ring structures. Two major steps are involved in converting the produced biochar into an efficient catalyst: one is the physical and/or chemical modification, followed by surface functionalization through acidification, amination, oxidation, and metal impregnation; the second is better activation of the biochar by providing higher temperatures, which in turn results in better yields (Table 1). The raw biomass, or biochar, is treated

2 Biochar in Catalysis and Biotransformation

25

Table 1 Yields of biochar from different bio-resources with the values of surface area and void/ pore characteristics Expanse/surface area (m2 /g)

Void/pore characteristics Volume (cm3 /g

Size (nm)

Maize residue

5.5

0.0142

Palm shell

570.85

0.260

Feedstock

Yield

References

17.3

90% @300 °C

Lee et al. [29]

3.6

80% @550 °C

Yek et al. [53], Chen et al. [54] Lee et al. [29]

Pine cone

375

0.0289

2.9

43% @380 °C

Rice husk

24

0.0189

4.8

58% @350 °C

Japanese wood

371

0.0177

2.9

56.4% @380 °C

Mixed wood

1.3

0.0019

10.6

53.9% @380 °C

Table 2 Feedstocks for biochar and derived catalysts with their generation methods Feedstock/raw material

Generation (production) method Biochar (BC)

Biochar-derived catalyst

Banana

Carbonization (Combustion)

Moisture-loaded Alkali (wet impregnation)

Jitjamnong [55]

Corn stover

Hydrolysis

Sulfonation

Acid

Sihan et al. [56]

Switch grass

Hydrolysis

Sulfonation

Acid

Sihan et al. [56]

Woody biomass

Fast pyrolysis

Chemical activation

Alkali

Cao et al. [4]

Kitchen waste

Slow pyrolysis

Physical activation

Alkali

Lishan Niu et al. [57]

Pamelo peel, Palm kernel with shell

Carbonization (Combustion)

Moisture loaded Alkali (wet impregnation) Calcination

Solid catalyst

References

Zhao et al. [58]

with metal salts of FeCl3 , FeCl2 , and MgCl2 to form metal oxide–biochar composites by raising the pH. Magnesium is considered a suitable cation for metal impregnation due to its role in the chlorophyll formation of plants. Avocado seed biochar was impregnated with iron or magnesium oxide by post-pyrolysis and used for the removal of phosphate [51]. By impregnation method and pyrolysis [52], using sugarcane as feedstock and Fe/Mn, metals are impregnated, and the adsorption of ozone was 122 and 116.2 mg/g by Fe- and Mn-impregnated catalytic biochar, respectively.

5 Classification of Biochar-Derived Solid Catalysts The biochar-based catalysts are solid and classified into two types: acid and alkali catalysts.

26

K. Sobha et al.

5.1 Acid Catalysts When carbon-rich biochar is acid-treated, particularly with an acid reagent containing sulfur, a solid-acid biochar catalyst is formed. Sulfonation is the main process for making biochar into a solid-acid catalyst, which has many applications such as the production of biofuels, energy conversion, as electrodes, heavy metal removal from industrial effluents, helping to prevent contamination of soil and water, etc. Ageratina sp. and Quercus sp. biochars are converted to solid-acid biochars by sulfonating with concentrated sulfuric acid, chlorosulfonic acid, and p-toluenesulfonic acid. The biochar was treated with a solid-to-acid ratio of 1:20 for concentrated sulfuric acid and chlorosulfonic acid and 53.52 g of p-toluene sulfonic acid, which contain equivalent mole numbers of sulfonic acid, using hydrothermal, simple heating, ambient temperature, and CHCl3 -assisted treatments. Chlorosulfonic acid, concentrated sulfuric acid, and p-toluenesulfonic acid show acidification efficiency in increasing order under hydrothermal treatment [59]. The reagents commonly utilized for the sulfonation of biomass and/or biomass-derived biochar include concentrated sulfuric acid, oleum, gaseous sulfur trioxide, chlorosulfonic acid, sulfamic acid, sulfosalicylic acid, and p-toluene sulfonic acid [60–62]. Direct sulfonation of incompletely carbonized organic matter produced amorphous carbon with SO3 H, COOH, and OH groups that demonstrated exceptional, insoluble bronsted acid activity for various acid-catalyzed reactions (e.g. cellobiose hydrolysis). These acid catalysts showed higher reactivity and efficacy for crystalline cellulose, glucose, and cellobiose hydrolyses than with niobic acid, H-mordenite, and resins like Amberlyst-15 and Nafion NR50 [8, 63, 64]. Sihan et al. [56] used solid biochar-derived acid catalysts for the hydrolysis of biomass. A sulfonating rice husk char with concentrated H2 SO4 was prepared as a catalyst for the esterification of oleic acid and methanol conversion [65]. Cheng et al. [36] prepared a solid-acid catalyst with the biochar of a partially carbonized peanut shell by sulfonation, while Joyleene et al. [66] made a heterogeneous biocharderived catalyst via KOH activation and fuming H2 SO4 sulfonation. They found that the transesterification yield of canola oil was 44.2% at 150 °C and 1.52 MPa with this catalyst (Table 2).

5.2 Alkali Catalysts An alkali-based BC catalyst is prepared by impregnating alkali chemicals into biochar at high temperatures [67]. The biochar surface chemistry and porosity properties can be altered by impregnating with alkali metals. Anthonysamy et al. [68] modified the biochar with four different alkali chemicals, viz. Potassium hydroxide, Potassium bicarbonate, Sodium Hydroxide, and Sodium bicarbonate, by varying their mass ratio from 1:1 to 3:1 parts, respectively (alkali chemical/biochar) for adsorption of nitric oxide (NO). The KOH-impregnated biochar demonstrated 62.0 and 63.0 mg/g adsorption capacity for an impregnation ratio of 1:1 and 3:1 respectively, and it shows

2 Biochar in Catalysis and Biotransformation

27

maximum NO uptake (87.0 mg/g) for 2:1 impregnation ratio at an optimum temperature of 600 °C. A porous carbon melaleuca bark alkali biochar, synthesized with KOH at a temperature of 1023 °K, had a high expanse of 3170 m2 g−1 , a large void volume of 0.86 cm3 g −1 , and numerous surface oxygen groups, and presumably these factors contributed to its high H2 storage capacity (4.08 wt% at 77 °K and 1 MPa) [69]. Anthonysamy et al. [70] studied the BC catalyst (derived from biomass)-driven oxidation of NO to NO2 , at ambient temperature. Lignocellulosic waste derived from rubber seed shell (RSS) was converted to biochar for NO capture. The NO adsorption capacity of pristine biochar was low, about 17.61 mg/g at 30 °C. Hence, Cerium (Ce) was impregnated into the biochar surface; this 3 wt% Ce-loaded biochar demonstrated the NO adsorption of 75.59 mg/g at the same adsorption conditions.

6 Biochar—A Favorable Catalyst Biochar can be a good heterogeneous catalyst and/or catalyst support by virtue of its intrinsic properties [55]. It has a good thermally, mechanically, and chemically stable, hierarchical structure that originates from biomass. As a supporter of catalysts for carbon-rich nanoparticles, biochar provides more active sites to undergo catalytic degradation reactions [71]. Metal-supported biochar catalysts promote the performance of bio-refineries and electrochemical industries [4]. The incorporation or fixing of copper (Cu), cadmium (Cd), and lead (Pb) into biochar pores results in less metal escape into the aqueous phase [4, 72, 73]. The following are some of the distinctive characteristics of biochar: (i) Heterogeneity: The reaction mixture can be segregated from other reactants. (ii) Bifunctionality: Both esterification and transesterification could be effected; (iii) Recyclability: Easy desorption of the adsorbate confers recyclability. (iv) Porosity: Different pore types, viz. cavities, channels, or interstices, present in biochar could be altered or introduced during pyrolysis to serve as microbial carriers. (v) Non-graphi¸table: do not form crystals when heated to high temperatures [74]. There are many applications of biochar as a catalyst [73] in many different fields (Fig. 1), like transesterification [56], biodiesel and syngas production [66], electrochemical industries [75], agriculture, environment (degrading organic contaminants) [57], energy [67], tar removal, wastewater treatment [76, 77], and production of chemicals [78]. Due to the presence of inorganic elements including Fe and K, biochar is catalytically active in cracking tar [79]. Biochar-based catalysts are, in a nutshell, economical, environmentally friendly, easy to synthesize, and recyclable when compared with other solid-based catalysts.

28

K. Sobha et al.

6.1 Biodiesel Production with Biochar-Derived Catalysts Xiong et al. [30] studied the catalytic use or support of biochar for different highimpact applications, including the production of methyl esters, commonly called biodiesel. Biodiesel produced from plant sources like cotton stalks, waste wood chips, pine chips, palm kernels, vegetable oils, etc. is a potential alternative to petrochemical diesel. From the literature, sulfonated biochar could be identified as an efficient catalyst for biomass hydrolysis and subsequent biodiesel production. However, for viable practical application of biochar catalysts for biodiesel generation [80, 81], the strength of biochar catalysts must be ensured and remove the need for Ca or S removal by post-treatment methods. Biochar is used as a catalyst in the production of biodiesel from the esterification of free unsaturated fats or the transesterification of vegetable oils with alcohol (Fig. 1). Biodiesel production using heterogeneous (solid) catalysts offers a number of advantages, such as lower corrosion risk, easy separation, and being eco-friendly and reusable. For biodiesel production, CaO or biochar or K2 CO3 or KOH-functionalized biochar can be used as catalysts. A conventional solid catalyst is CaO for the transesterification of oils from their respective feedstocks. The advantages of CaO-based catalysts are that they are highly basic in nature, so they require mild conditions and are easy to prepare from natural resources with little or no cost. Calcium carbonate from palm kernel shell biochar (PKSB) is an excellent source material for producing a CaO-based catalyst by gasification [82]. The time required for the catalyst for the transesterification of sunflower oil to their corresponding fatty acid methyl esters (FAMEs) and glycerol is 4 h. The optimum reaction conditions calculated from the kinetic model are a 3% catalyst amount based on the oil mass, a 65 °C temperature, and a methanol-to-oil molar ratio of 9:1. The PKSB catalyst can be reused for three consecutive runs without any modification. Weldeslase et al. [83] prepared Zn–Cao nanocatalyst from the calcinated limestone and 5% Zn by wet impregnation process for large-scale production of biodiesel. The size of Zn-doped lime-based CaO nanoclays is 12.51 nm. The process of biodiesel production from waste cooking oil and CaO nanocatalyst was optimized using the box-Behnken design of response surface methodology, and the optimized parameters are a methanol-to-oil molar ratio of 14:1, or 5% weight, catalyst loading rate at 57.5 °C temperature, and 120 min time obtained 96.5% highest biodiesel conversion. By box-Behnken design of response surface methodology, the production of biodiesel from allamanda seed oil (ASO) was optimized by Abdullahi et al. [84] using a KOH-modified metakaolin catalyst. With the optimized conditions of reaction temperature (52.5 °C), time (180 min), catalyst concentration (0.5% wt), and methanol/ASO molar ratio (5:1), a maximum yield of 90.14% biodiesel was obtained, which met the fuel standard specifications of ASTM D-6751 and EN 14,214. Alsaiari et al. [85] reported that with CaO nanoparticles synthesized at 950 °C from eggshells and used as a catalyst with date seed oil as the feedstock, 85% biodiesel yield was obtained. The other optimum conditions are 4 wt.% catalyst loading, a 1:12 oil–ethanol ratio, and a 75 °C temperature, and the

2 Biochar in Catalysis and Biotransformation

29

characteristics of the formed ethyl esters were consistent with the ASTM D-6571 and EN 14,214 specifications.

6.2 Energy Storage In electrical and electronic devices like lithium-ion batteries and super capacitors, energy storage is required, which mainly depends on the type of electrode material (Fig. 1). Carbon nanotubes, activated carbon, and graphene are generally used electrodes that have a high surface area and porosity, providing active sites for the oxidation process. The use of carbon materials as electrodes is limited due to their high cost; the alternative is biochar, which possesses all the required characteristics of an electrode at a lower cost. In microbial fuel cells and super capacitors, biochar acts as an electrode [86]. Super capacitors have a high power density, good stability, and a swift capacity to charge and discharge. The biochar prepared from the Syzygium cumini (Jamun) seeds by acid pretreatment and CO2 activation [87] is used in the preparation of symmetric super capacitor devices. For the de-ashing of biochar, acid pretreatment was performed, and the CO2 activation of raw biochar at 900 °C for 1 h showed a higher surface area than that of acid-treated biochar. Both biochars are fabricated in a super capacitor device to test the capacitance. Acid-treated biochar exhibited a specific capacitance of 33.5 F/g, while activated biochar had a supercapacitance of 42.3 F/g at a 0.1 A/g current density comparable to commercial activated carbon. The fabricated coin cell super capacitor had an energy density and power of 19.8 Wh/kg and 2096.5 W/kg, respectively. Recent advancements in biochar-based catalyst applications have enabled the identification of their potential as novel electrode materials for super capacitors. Their high electrical conductivity and porosity confer on them the capacity to function as electrodes [88]. The functionalized surfaces with bound nitrogen groups are preferably used as electrical terminals (anode/cathode) for super capacitors. Super capacitors, made of carbon materials, are used as energy storage devices. Since BC is a carbon-rich solid material with a high surface-to-volume ratio and voidity, it serves as a good energy storage device, which in turn can help some developed countries back up their excess energy generation.

6.3 Remediation There has been a positive correlation between metal uptake and BC-based catalysts. Adsorption capacity depends on the active sites available on the catalyst’s surface. So, the selection of biochar should be made based on the type of heavy metal to be treated or the source of water pollution. By changing the temperatures for biochar production and the type of feedstock, activated biochar suitable for the desired heavy metal removal can be developed. Since biochar is economically feasible, environmentally

30

K. Sobha et al.

friendly, and can be manufactured with ease, it has a remarkable potential in the heavy metal seclusion from wastewater [54]. Biochar contains high levels of oxygen, functional groups, and minerals, all contributing to the efficient removal of Cr (III) and Cd (II) [89]. Using fish scales as a precursor [90], self-doped biochar composites with MgO-loaded N and P were produced through an impregnation method that demonstrated good adsorption of Cu, Pb, and Cd in soils.

6.3.1

Remediation of Organic and Inorganic Pollutants

Organic Pollutants The biochar acts as a catalyst for the removal of organic and inorganic pollutants (Fig. 1). The addition of biochar to the soil adsorbs agricultural organic pollutants such as insecticides, pesticides, fungicides, herbicides, viz. atrazine, simazine, and carbofuran, and others; antibiotics and drugs such as acetaminophen, tetracyclin, sulfamethazine, tylosine, and ibuprofen; and industrial chemicals such as polycyclic aromatic hydrocarbons (PAH). The size and functional groups present on the surface of the biochar influence its capacity to remediate pollutants. The smaller the particle size, the higher the surface area and capacity of remediation. The interaction between biochar and pesticides is due to the presence of phenolic and carboxylic functional groups on the biochar surface. The type of biomass, temperature, pH, and ratio of pollutant to biochar are the major factors that influence the biochar–pollutant interaction. The main mechanisms involved in remediation are physi-sorption (electrostatic attraction and repulsion, pore diffusion, hydrophobicity, and H-bonding), chemisorption (electrophilic interaction) (Fig. 2), and other mechanisms such as chemical transformation, partitioning, and biodegradation [91]. The biochar from agricultural waste and zero-valent iron composite was used for the removal of tetracycline [92], and the removal efficiency was 275 mg/g.

Inorganic Pollutants Biochar produced at low temperatures possesses many functional groups that are helpful in the adsorption process. Its porous structure and high organic carbon content help in the removal of inorganic pollutants, mainly heavy metals like copper, zinc, cadmium, lead, nickel, and mercury, by ion-exchange mechanisms. Copper, chromium, and lead metals have a strong affinity for OH and COOH groups, and their removal depends on the type of biomass, pH, biochar dosage, and porosity. An increase in pH decreases the zeta potential and cation exchange capacity. At pH 6–7, the removal of heavy metals was by an ion-exchange mechanism, and at higher pH 7–9, the removal was by complexation and electrostatic attraction. Chromium removal was found to be maximal at pH 2, whereas lead removal was high at pH 2 and 5.

2 Biochar in Catalysis and Biotransformation

31

Fig. 2 Biochar particle and its diverse non-covalent interactions with the ligands (adapted from Ahmad et al. [93] with a few modifications)

6.4 Soil Amelioration The addition of biochar to the soil enhances the porosity, surface area, oxygen uptake, water holding, and adsorption capacity of the soil (Fig. 1). Increased porosity of the soil maintains the moisture and aeration that are useful in colonizing the bacteria and fungi and increases the absorption of nutrients from the soil [94]. The surface of the biochar, consisting of carboxylic, phenolic, amino, and hydroxyl groups, can interact with the hydrogen ions in the soil and increase the soil pH, whereas carbonate, bicarbonate, and silicate neutralize the soil pH by interacting with hydrogen ions in the soil. The addition of biochar to the soil increases soil fertility, cation exchange capacity, and microbial activity, and reduces greenhouse gas emissions. The presence of Ca, K, N, and P in biochar adds nutrients to the soil. Nanoparticles prepared from biochar of pinewood and rice straw at 20 mg/L showed the mobilization of positively polar (trimethoprim and ciprofloxacin) and nonpolar contaminants (naphthalene and pyrene) while inhibiting the transport of sulfamethoxazole and bisphenol A, which

32

K. Sobha et al.

are negatively charged and neutral hydrophilic compounds [95]. The addition of wood, sunflower, and rice husk biochar to soil increased the adsorption capacity of Cu, Zn, and Pb by more than 77%, which is due to the presence of hydroxyl, phenolic, and ester functional groups on its surface [96]. Zn adsorption increased to 11–21%, while Cu and Pb adsorption increased by 9–19%.

7 Biochar and Biotransformation As has been stated earlier, the carbon-enriched solid product obtained by the thermal treatment of bio-organic material in a low-O2 atmosphere is called ‘biochar’ [97]. There are a myriad variety of organic materials available as discards in nature that are good enough to be used as raw materials for biochar synthesis. Although large-scale synthesis of biochar by established preparatory methodologies appears to be simple and straightforward, there are a number of challenges in preparing suitable biochar precursors intended for specific purposes. Findings from recent research indicate ‘biochar’ as a suitable medium for the growth of plants and microorganisms [98]. Segregation of inorganic and organic compounds from the source by sorption and cation exchange capability to support microbial growth [99], soil pH conditioning, and providing hormone analogues for plant growth are some of the notable functions of biochar. Since biochar is generated from plant or animal waste and/or microbes, it contains several important nutrients of biological significance. Some of the important literature related to the role of biochar is presented in Table 3. Biotransformation, a biological process in which organic compounds are modified into reversible products, is a natural and essential phenomenon in nature. The biochemical reactions are catalyzed by biocatalysts called ‘enzymes’ synthesized by microbial, plant, and animal cells. Microbes, which include bacteria, archaea, and fungi, are ubiquitous in nature and have tremendous catabolic capacities for minimizing environmental chemical impurities by converting them to less reactive compounds and completing mineralization [102, 103]. Microbial transformation is the prime degeneration process in environmental transformations when compared to photolysis or abiotic redox reactions [104]. Increasing chemical contaminants in the ecosystems adversely affect the biota and the environment. Table 3 A few constituents of biochar and their role in paddy cultivation S. No.

Substance in biochar

1

2-Acetyl-5-methyl furan Hormone analog for rice seedling growth

Yang et al. [100]

2

14 candidate drugs

Cold tolerance of rice seedlings

Yuan et al. [15]

3

Mineral, nitrogen, and sulfur content

Microbial growth

Lehmann [101], Yang [98]

Biological significance

References

2 Biochar in Catalysis and Biotransformation

33

For optimized microbial transformation, the system designer needs to consider the cause–effect relationship between contaminant removal and the microbes’ catabolic pathways, including the level of enzymes and the conditions required for biotransformation. A number of factors influence the rate at which a given contaminant is removed and the type of yielding product. Some of them are the existing concentration of the contaminant, the microbial community’s capability and composition, e− —donors or acceptors, and the availability of substrates [105, 106]. Different bio-physico-chemical factors, viz. redox potentials, ambient temperatures, atmospheric moisture, nutriment availability, hazard exposures, and microbial continuance time, influence the biotransformation. For each contaminant type, the range of biotransformation is determined by its chemical structure and ability to interact with enzymes.

8 Bicohar in Bioremediation Biotransformation is a ‘remediation’ method for both contaminated soil and water. Biochar in the soil increase the rate of bioremediation process as it provide natural habitat for the growth of microbes. If the treatment of the contaminated site is effected at its location, then it is termed ‘in situ’ biotransformation. In opposition to this type, ex situ biotransformation requires excavation of contaminated soil or pumping of groundwater to a separate treatment location before it can be treated. ‘On-site’ or in situ biotransformation has the advantages of being less expensive, achieving complete contaminant removal, having lower equipment and operating costs, posing a lower risk to workers, creating less dust, and treating a large area of soil at a time. The disadvantages are that they are slow to process, can be difficult to manage, and work best in permeable soil. The advantages of ex situ biotransformation are that it is fast, easier to monitor, and can be used to treat a broad spectrum of contaminants and soil types. However, the disadvantages are that they require excavation and treatment of contaminated soil before and after biotransformation.

9 Role of Biochar in Biotransformation—A Few Studies 9.1 Degradation of Roxarsone by Shewanella oneidensis MR-1 Roxarsone (3-nitro-4-hydroxyphenylarsine) is a feed additive that controls intestinal parasites and improves meat pigmentation [107, 108]. Although the current use of roxarsone in the poultry industry is banned in several countries, its earlier extensive use created the problem of bio-accumulation along the food chains in the food web [7, 109]. In an animal body, roxarsone is decomposed and excreted in its unmodified

34

K. Sobha et al.

form along with animal waste [110]. Due to its aqueous dissolution, roxarsone easily finds its way into the surface of groundwater and soil [108, 109]. Roxarsone undergoes oxidation–reduction and methylation–demethylation [111–114] via a variety of physical, chemical, and biological reactions, yielding an array of arsenic compounds. Natural organic matter (NOM)-mediated microbial redox reactions, in the cyclic flow of carbon and redox-active compounds, are important. Biochar was prepared using dried wheat straw powder by heating in a stainless steel reactor for 2 h at three different temperatures (300, 500, and 600 °C) in a muffle furnace under anoxic conditions. Roxarsone degradation by MR-1 was evaluated with and without BC for 68 h. Roxarsone was almost completely degraded, and the decreasing order of degradation rates was 600 BC biotic to only MR-1 through 500 BC biotic and 300 BC biotic. Decomposition rates were elevated by 9.79%, 6.84%, and 3.23% respectively, with the addition of 600 BCC, 500 BCC, and 300 BCC. The addition of biochar causes an apparent increase in the biomass of microorganisms. The combination of biochar with MR-1 when used for oxidation–reduction [115], the biochar produced at 400– 600 °C showed the optimal capability for electron ‘to and fro’ transfer and vice versa for biochar produced at low temperatures. MR-1 growth adapted itself to the high temperature because biochar provides nutrients and habitat for microorganisms.

9.2 Glucose to L-Histidine Through Escherichia Coli Metabolism Since the composition of biochar is complex, it is difficult to establish the significance of each of its constituents and map the same to a particular biological function. Hence, Yang et al. [116] performed molecular docking studies with the compounds in biochar as ligands against the receptor proteins of the L-histidine synthetic pathway. The carbon compounds present in biochar were extracted by both polar and nonpolar solvents and analyzed by Yang et al. [116] using GC–MS, employing 1 μl ml−1 IPA (diluted at 1 μg ml−1 in methylene chloride) as an aromatic hydrocarbon-certified standard for reference. Out of the nine functional groups identified to contribute to different biological functions, >C = O, −COOH, and –OH were the predominant ones in the biochar extraction solution. Based on GC–MS results, the molecular structures of carbon compounds were constructed by GaussView and subjected to docking against the 1H3D receptor molecule downloaded from the RCSB protein database. From the docking results, the inducer molecules for the biosynthesis of L-histidine were identified. This study inferred the ‘switching on’ of his G gene expression by different biochar treatments, and consequent promotion of L-histidine biosynthesis in E. coli. Among the four biochar concentrations in percent tested (viz. 1, 3, 5, and 7), a low biochar treatment of 3% was found beneficial for the biosynthesis of L-histidine because of the highest amounts of different bioactive ingredients at that concentration. The sum of the three major compounds, viz. eugenol, salicyl alcohol,

2 Biochar in Catalysis and Biotransformation

35

and cyclopentane, 1, 2, and 3-trimethyl, was reported to function like a hormone analogue in stimulating his G gene expression.

9.3 Denitrification and Mitigation of N2 O Production Denitrification is an important activity that facilitates the survival of essential and beneficial microbes in the soil that aid plant growth through their metabolites and soil enrichment. Microbes that grow in oxygen-deficient soils are endowed with the ability to convert toxic soluble nitrates (NO3 − ) to nitrites (NO2 − ), N2 O (GHG causing environmental pollution and global warming), and finally N2 in order to obtain the oxygen required for their metabolism [117, 118]. Nitrous oxide (N2 O), a potential greenhouse gas, is produced and consumed in the soil by a network of processes, including abiotic redox and biotic nitrification/denitrification and/or nitrifier denitrification [119–121] reactions. Incomplete denitrification is one of the leading causes of N2 O emissions in agricultural soils. In this context, it has been found that the addition of biochar to the soil will amend and enrich the soil biota, and augment crop production without the release of potential greenhouse gases like N2 O. Biochar, as an established electron shuttle and conductive material, is believed to mediate extracellular electron transfer and influence microbial metabolism. However, many soil bacteria that effect denitrification (such as the electricigenic, humic, Fe– Mn, and others) do not exhibit extracellular respiration. Recently, an interesting study on the mitigation of N2 O emission from bacterial denitrification through the distribution of reducing power among the enzymes of the denitrification cascade via modulation of carbon metabolism was reported [122]. The denitrification response of the model soil bacterium (Paracoccus denitrificans) to biochar addition was analyzed by ‘proteomic’ and ‘metabolomic’ data, and reported a positive correlation between the efficiency of biochar and its pyrolytic production temperatures of 300–500 °C, and dosages between 0.1 and 1% [122]. Further, the study revealed that the sources of biochar tested, namely corn (CS) and wheat straw, did not contribute to the biochar’s efficiency. According to the study, the ‘stimulant nature’ of CS biochar built at 500 °C was purely due to the gross particles, and not the dissolvable compounds released in the process. It was proposed that the bulk CS-500 particles adsorb to the cell’s extracellular metabolites and direct the reactions of the cell’s carbon metabolic pathway. A major part of the reducing power generated through oxidative metabolism and growth assimilation is utilized for nitrogen reduction, and this could be corroborated with the upregulation of the proteinaceous-enzyme expression and activity of nitrite-, NO-, and N2 O-reductase. This was evident from the maximum electron-sharing among the denitrifying enzymes and reduction of N2 O accumulation by 98%. Consequently, the growth kinetics of P. denitrificans increased, implicating biochar in denitrification and N2 O mitigation reactions. Bacteria depend on the energy supplied by the reduction reactions of nitrogen oxide species for their growth and assimilation. But when the biochar adsorbs to

36

K. Sobha et al.

the extracellular metabolites of the bacterial cell, like in P. denitrificans, the cell depends on the reactions of oxidative metabolism for the supply of needed energy, and in the process accumulate PHA (polyhydroxyalkanoate) as a carbon/energy and/ or reducing power storage molecule [122– 124]. As stated earlier, in biochar-enriched soils containing denitrifying bacteria with genome-based PHA storage ability, the high N2 O-reduction potential of denitrifying bacteria would be explained through the adsorptive potential of biochar for extracellular metabolites. As this may not be the only mechanism, further investigations to unravel the mechanism in denitrifiers without the capability of PHA storage are imperative.

9.4 Biotransformation of Phosphorous Enhanced biological phosphorus removal (EBPR) bio-solid, turned into BC, is a potential phosphorus (P) fertilizer. Pseudomonas putida, a soil microorganism, regulates the ‘P’ turnover in soil. Biochar was produced at two different temperatures, viz. 400 and 700 °C; of the two, biochar produced at 700 °C (E700) released molecules that were readily absorbed by the microbe P. putida and are not the same with the biochar produced at 400 °C (E400); this could presumably be induced by the low pH [125] and the role of microbial organic acids in complexation [126]. E400 has a detrimental affect on intracellular poly-P formation in P. putida due to free-radicalinduced oxidative stress. This in turn affects the bacterial survival and their interaction with the surroundings. Besides ‘P’, a number of heavy metals [127, 128] and harmful organic constituents of biochar [129, 130] passively enter the soil and cause contamination. This was evident from the study by Khan et al. [127] which demonstrated a rise in soil levels of Cu, Zn, and Cd when treated with bio-solid-derived biochar. Additionally, the free radicals (FR) [131–134] adhered to some biochar can induce cytotoxicity and inhibit seed germination and plant growth.

9.5 Remediation of Chromium Toxicity by Biochar, Poultry Manure, and Sewage Sludge (Biosolids) in Rice Crop Agronomic plants suffer from chromium concentrations of 0.5–5 mg ml−1 in nutrient solutions and 5–100 mg kg−1 in soil. Biochar as well as poultry manure and biosolids/sewage sludge augment the activity of microbes. The mechanism involved in the remediation of chromium by the microbes is that the microbes act as electron donors and reduce the toxic Cr6 + to non-toxic Cr3 + and further lower the oxygen level of the soil, creating reducing conditions. High chromium concentrations in soil are toxic to rice [135]. Chromium is shown to have a direct effect on rice grain and rice straw yield as well. The lowest rice grain yield value of 23.37 g pot−1 was found in the treatment at Cr50, with the yield lowered by 13% in comparison with the control

2 Biochar in Catalysis and Biotransformation

37

(26.7 g pot−1 ). The greatest direct effect on rice straw yield was observed at Cr50 (28.20 g pot−1 ). Out of the three materials tested, viz. biochar, poultry manure, and sewage sludge, a significantly higher rice grain yield of 31.73 g pot−1 was achieved upon treatment at Cr0+ biochar, while the minimum yield recorded was at Cr50 (23.80 g pot−1 ) without amendment.

9.6 Adsorption of Manganese and Its Biotransformation by Streptomyces Violarus Strain SBP1 Cell-Immobilized Biochar Manganese levels in potable water were set at 0.05 mg L−1 (ppm) by the Water Act for safe drinking. Above the normal level, manganese tends to damage the central nervous system and cause Parkinson’s-like symptoms. Natural biochar, i.e. carbonized wood waste, is obtained from the wood vinegar industry through the pyrolytic process. Both raw biochar and H2 O2 -modified biochar were subjected to immobilization with a manganese-oxidizing potent bacterial strain, Streptomyces violarus strain SBP1. Modified biochar showed a significantly higher adsorption capacity of 1.15 mg g−1 in opposition to the adsorption capacity of unmodified biochar which was 0.77 mg g−1 , and a removal efficiency of 78%—all attributed to the presence of a higher proportion of functional groups with oxygen. Pseudosecond-order and Langmuir models are the best fit for Mn adsorption studied with native and modified biochars. A synergistic combination of biochar and biological oxidation by SBP1, in which biochar adsorbs the dissolved manganese (Mn2+ ) while the microbial cells oxidize the dissolved manganese to particulate Mn3+ and/or Mn4+ , contributes to the removal of manganese. The results of X-ray Fluorescence Spectroscopy (XRF) and X-ray Absorption Near Edge Structure (XANES) confirmed the dispersal of microbial cells and their adhesion to deeper layers [136] resulting in manganese adsorption and bio-oxidation. These findings suggest the potential application of cell-immobilized biochar as a bio-filtration medium.

9.7 Microbial Biotransformation of Arsenic in Paddy Soil After Straw-Biochar and Straw-Amendments Arsenic (As) biogeochemical cycling in the soil-rice system is remarkably altered by the application of straw biochar, and straw to paddy soil. High-throughput sequencing of microbial 16S rRNA gene showed that both straw biochar and straw enrich iron-reducing bacteria, while methanogens were enriched by the straw amendment [137]. It is proposed that arsenate [As(V)] reduction is mediated by arsAgene containing iron-reducing bacteria (e.g. Geobacter and Shewanella) in biochar and arsC-containing Gamma-proteobacteria in straw amendments. Methylated As

38

K. Sobha et al.

concentration is regulated by methanogens and sulfate-reducing bacteria (SRB) in the soil-rice system, by virtue of the arsM gene. Arsenic (As) biotransformation microbes (ABMs) are demonstrated to have stronger interactions in the rhizosphere zone as compared to bulk soil by the network analysis. Arsenite [As(III)] methylators carrying arsM gene [138] showed a stronger co-occurrence pattern with arsC-gene containing As(V) reducers than with arsA-containing As(V) reducers.

9.8 De-chlorination of Pentachlorophenol in a Microbial Consortium Biochar, generated from raw materials like rice husk, bamboo, caragana, and garbage by pyrolysis at 500 °C for 4 h under an N2 flow of 1.5 L min−1 , was studied for its effect on the reductive de-chlorination of pentachlorophenol (PCP). Pentachlorophenol (a halogenated aromatic compound), popularly used as a wood preservative, insecticide, and anti-mold agent, is toxic to the liver and kidneys. Microbial anaerobic de-chlorination occurs in soils and sediments. In recent years, biochar has been investigated as a solid-phase electron shuttle to support redox transformations by microbes. Capacities for the transfer of electrons were found to be within the range of 61.63–155.83 mol g−1 , and stable electron transfer was found to be mediated only by caragana-derived biochar. Electrochemical analyses using a potentiostat revealed the electrical conductivity of caragana biochar to be of the highest value of 2.22 × 106 S cm−1 . Hence, its electron transfer was enabled at its maximum, resulting in the greatest promotion of reductive de-chlorination activity, while those of the other biochar were around 1500 S cm−1 only. However, the cyclic voltammetry suggested no obvious redox peaks for the biochar, and FTIR analysis revealed that all biochar possessed similar structural and functional classes of reactive chemical groups [72], and, therefore, the enhancement of PCP de-chlorination was not attributed to the redox reaction.

9.9 Chemical and Microbial Transformation of Pentachlorophenol in Paddy Soil Rapeseed straw was processed to generate biochar for the transformation of pentachlorophenol in paddy soil. The biochar promoted de-chlorination of PCP by reduction and acted as an electron mediator between the soil organic compounds and the bacteria, which in turn enhanced the growth and metabolism of bacteria. Biochar improved the sorption and transformation of PCP and the generation of Fe (II) in soils amended with rapeseed-straw biochar that was HCl-extractable. From the findings of Tong et al. [139], it could be inferred that the PCP de-chlorination rates obtained were higher with higher dosages of biochar.

2 Biochar in Catalysis and Biotransformation

39

10 Conclusion The versatile biochar characteristics, like its porous structure, labile calcium, high pH, and electrochemical properties, greatly influence the microbial communities present in the soil. India plays a pivotal role in the agricultural domain. Agricultural residues of different crops can be converted to produce biochar of different physicochemical properties, which can be used in various fields as catalysts or catalytic support. The production of renewable chemicals and advanced transportation fuels from wastederived sugars through a low-temperature process results in a good hybrid solid catalyst with tunable acid/base character. However, the stability of biochar is important, which can be improved by pyrolysis under certain temperatures for different feedstocks. Biochar as a catalyst has emerging applications in various fields, which include biofuel production, syngas production, heavy metal removal, wastewater treatment in different sectors (agriculture, industrial, and domestic wastewaters), composting, electrochemical and microbial fuel cells for energy storage, environmental applications, etc. Biochar can be tailored to meet specific needs by modifying its surface morphology and functional groups. Therefore, conventional chemical catalysts can be replaced by biochar-based catalysts. Furthermore, biochar could be employed in several significant biotransformation reactions and effect the synthesis of desirable compounds, convert toxic metabolites, or alleviate their production.

11 Future Perspectives Although the advantages of green catalysts like biochar appear to outweigh the disadvantages, the development of these catalysts is still in its infancy. So, there is a need to explore novel techniques that can facilitate the industrial-scale production, activation, and functionalization of biochar for its improved catalytic performance. Researchers are concentrating on the modifications that may be made to biochar-based and nanomaterials for their application in domains like catalysis for the production of specific, selective, qualitative, and quantitative products for efficient industrial operations and environmental safety. Future research should focus on the temperature and reaction time of the production processes so that it could become a ‘single-pot’ synthesis with easy activation and functionalization methods to achieve high-quality and reusable catalysts. These catalysts would then make biotransformations simpler and more effective, leading to the generation of value-added products for human use. Acknowledgements The authors express their sincere gratitude to the principal and management of RVR and JC College of Engineering (A) for their encouragement and moral support.

40

K. Sobha et al.

References 1. Tomczyk A, Sokolowska Z, Boguta P (2020) Biochar physicochemical properties: pyrolysis temperature and feedstock kind effects. Rev Environ Sci Biotechnol 19:191–215. https://doi. org/10.1007/s11157-020-09523-3 2. Solomon D, Lehmann J, Thies J, Schäfer T, Liang B, Kinyangi J, Neves E, Petersen J, Luizão F, Skjemstad J (2007) Molecular signature and sources of biochemical recalcitrance of organic C in Amazonian Dark Earths. GeochimCosmochimActa 71:2285–2298. https://doi.org/10. 1016/j.gca.2007.02.014 3. Sharma A, Pareek V, Zhang D (2015) Biomass pyrolysis—a review of modelling, process parameters and catalytic studies. Renew Sust Energ Rev 50:1081–1096 4. Xuefei C, Shaoni S, Runcang S (2017) Application of biochar—based catalysts in biomass upgrading: a review. RCS Adv 7:48793–48805 5. Luo L, Xu C, Chen Z, Zhang S (2015) Properties of biomass—derived biochars: combined effects of operating conditions and biomass types. Bioresour Technol 192:83–89 6. Zhao L, Cao X, Masek O, Zimmerman A (2013) Heterogeneity of biochar properties as a function of feedstock sources and production temperatures. J Hazard Mater 1:256–257 7. Wang S, Shan R, Gu J, Zhang J, Zhang Y, Yuan H, Chen Y, Luo B (2020) Reactivity and deactivation mechanisms of toluene reforming over waste peat char supported Fe/Ni/Ca catalyst. Fuel 271:117517 8. Masaaki K, Yamaguchi D, Suganuma S, Nakajima K, Kato H, Hayashi S, Hara M (2009) Adsorption-enhanced hydrolysis of β-1, 4-glucan on graphenebased amorphous carbon bearing SO3H, COOH, and OH groups. Langmuir 25:5068–5075 9. Jothirani R, Senthil Kumar P, Saravanan A, Narayan AS, Dutta A (2016) Ultrasonic modified corn pith for the sequestration of dye from aqueous solution. J Ind Eng Chem 39:162–175 10. Senthil Kumar P, Ramalingam S, Abhinaya RV, Thiruvengadaravi KV, Baskaralingam P, Sivanesan S (2011) Lead(II) adsorption onto sulphuric acid treated cashew nut shell. Sep Sci Technol 46:2436–2449 11. Suganya S, Senthil Kumar P, Saravanan A, SundarRajan P, Ravikumar C (2017) Computation of adsorption parameters for the removal of dye from wastewater by microwave assisted sawdust: theoretical and experimental analysis. Environ Toxicol Pharmacol 50:45–57 12. Gayathri R, Gopinath KP, Kumar PS (2021) Adsorptive separation of toxic metals from aquatic environment using agro waste biochar: application in electroplating industrial wastewater. Chemosphere 262:128031 13. Hemavathy RV, Kumar PS, Kanmani K, Jahnavi N (2020) Adsorptive separation of Cu(II) ions from aqueous medium using thermally/chemically treated Cassia fistula based biochar. J Clean Prod 249:119390 14. Prevoteau A, Ronsse F, Cid I, Boeckx P, Rabaey K (2016) The electron donating capacity of biochar is dramatically underestimated. Sci Rep 6:32870. https://doi.org/10.1038/srep32870 15. Yuan Y, Bolan N, Prévoteau A, Vithanage M, Biswas JK, Ok YS et al (2017) Applications of biochar in redox-mediated reactions. Bioresour Technol 246:271–281. https://doi.org/10. 1016/j.biortech.2017.06.154 16. Saquing JM, Yu YH, Chiu PC (2016) Wood-derived black carbon (biochar) as a microbial electron 479 donor and acceptor. Environ Sci Technol Lett 3:62–66. https://doi.org/10.1021/ acs.estlett.5b00354 17. Luo L, Wang G, Shi G, Zhang M, Zhang J, He J, Xiao Y, Tian D, Zhang Y, Deng S, Zhou W, Lan T, Deng O (2019) The characterization of biochars derived from rice straw and swine manure, and their potential and risk in N and P removal from water. J Environ Manag 245:1–7 18. Qian TT, Wu P, Qin Q-P, Huang Y-N, Wang Y-J, Zhou D-M (2019) Screening of wheat straw biochars for the remediation of soils polluted with Zn (II) and Cd (II). J Hazard Mater 362:311–317 19. Yargicoglu EN, Sadasivam BY, Reddy KR, Spokas K (2015) Physical and chemical characterization of waste wood derived biochars. Waste Manage 36:256–268

2 Biochar in Catalysis and Biotransformation

41

20. Yao Y, Gao B, Inyang M, Zimmerman AR, Cao XD, Pullammanappallil P, Yang LY (2011) Biochar derived from anaerobically digested sugar beet tailings: characterization and phosphate removal potential. Bioresour Technol 102:6273–6278 21. Duan X-L, Yuan C-G, Jing T-T, Yuan X-D (2019) Removal of elemental mercury using large surface area micro-porous corn cob activated carbon by zinc chloride activation. Fuel 239:830–840 22. Al-Wabel MI, Al-Omran A, El-NaggarAH NM, Usman ARA (2013) Pyrolysis temperature induced changes in characteristics and chemical composition of biochar produced from conocarpus wastes. BioresourTechnol 131:374–379 23. Ok YS, Chang SX, Gao B, Chung H-J (2015) SMART biochar technology—a shifting paradigm towards advanced materials and healthcare research. Environ Technol Innov 4:206–209 24. Singh BP, Cowie AL, Smernik RJ (2012) Biochar carbon stability in a clayey soil as a function of feedstock and pyrolysis temperature. Environ Sci Technol 46:11770–11778 25. Awasthi MK, Wang M, Chen H, Wang Q, Zhao J, Ren X, Li D-S, Awasthi SK, Shen F, Li R, Zhang Z (2017) Heterogeneity of biochar amendment to improve the carbon and nitrogen sequestration through reduce the greenhouse gases emissions during sewage sludge composting. Bioresour Technol 224:428–438 26. Matovic D, Duic N, Guzovic Z (2011) Biochar as a viable carbon sequestration option: global and Canadian perspective. Energy 36:2011–2016 27. Wang B, Wang Z, Jiang Y, Tan G, Xu N, Xu Y (2017) Enhanced power generation and wastewater treatment in sustainable biochar electrodes based bioelectrochemical system. Bioresour Technol 241:841–848 28. Shen Y (2015) Chars as carbonaceous adsorbents/catalysts for tar elimination during biomass pyrolysis or gasification. Renew Sust Energ 43:281–295 29. Lee J, Jung JM, Oh JI, Ok YS, Lee SR, Kwon EE (2017) Evaluating the effectiveness of various biochars as porous media for biodiesel synthesis via pseudo-catalytic transesterification. Biores Technol 231:59–64 30. Xiong X, Yu IKM, Cao L, Tsang DCW, Zhang S, Ok YS (2017) A review of biochar-based catalysts for chemical synthesis, biofuel production, and pollution control. Bioresour Technol 246:254–270 31. Thines KR, Abdullah EC, Mubarak NM, Ruthiraan M (2017) Synthesis of magnetic biochar from agricultural waste biomass to enhancing route for waste water and polymer application: a review. Renew Sustain Energy Rev 67:257–276. https://doi.org/10.1016/J.RSER.2016.09.057 32. Zhang M, Gao B, Varnoosfaderani S, Hebard A, Yao Y, Inyang M (2013) Preparation and characterization of a novel magnetic biochar for arsenic removal. Bioresour Technol 130:457– 462. https://doi.org/10.1016/J.BIORT ECH.2012.11.132 33. Peng X, Luan Z, Di Z, Zhang Z, Zhu C (2005) Carbon nanotubes iron oxides magnetic composites as adsorbent for removal of Pb(II) and Cu(II) from water. Carbon N. Y. 43:880– 883. https://doi.org/10.1016/j.carbon.2004.11.009 34. Mubarak NM, Alicia RF, Abdullah EC, Sahu JN, Haslija ABA, Tan J (2013) Statistical optimization and kinetic studies on removal of Zn2 + using functionalized carbon nanotubes and magnetic biochar. J Environ Chem Eng 1:486–495. https://doi.org/10.1016/J.JECE.2013. 06.011 35. Windeatt JH, Ross AB, Williams PT, Forster PM, Nahil MA, Singh S (2014) Characteristics of biochars from crop residues: potential for carbon sequestration and soil amendment. J Environ Manage 146:189–197 36. Cheng F, Li X (2018) Preparation and application of biochar-based catalysts for biofuel production. Catalysts 346. https://doi.org/10.3390/catal8090346 37. Bruun S, Clauson-Kaas S, Bobulska L, Thomsen IK (2013) Carbon dioxide emissions from biochar in soil: role of clay, microorganisms and carbonates. Eur J Soil Sci 65:52–59 38. Schulze M, Mumme J, Funke A, Kern J (2016) Effects of selected process conditions on the stability of hydrochar in low-carbon sandy soil. Geoderma 267:137–145

42

K. Sobha et al.

39. Rasse DP, Budai A, O’Toole A, Ma X, Rumpel C, Abiven S (2017) Persistence in soil of Miscanthus biochar in laboratory and field conditions. PLoS ONE 12(9):e0184383. https:// doi.org/10.1371/journal.pone.0184383 40. Rahman MT, Guo ZC, Zhang ZB, Zhou H, Peng XH (2018) Wetting and drying cycles improving aggregation and associated C stabilization differently after straw orbiochar incorporated into a vertisol. Soil Tillage Res 175:28–36 41. Naisse C, Girardin C, Lefevre R, Pozzi A, Maas R, Stark A, Rumpel C (2015) Effect of physical weathering on the carbon sequestration potential of biochar and hydrochars in soil. GCB Bioenergy 7:488–496 42. Leng L, Xiong Q, Yang L, Li H, Zhou Y, Zhang W, Jiang S, Li H, Huang H (2020) An overview on engineering the surface area and porosity of biochar. Sci Total Environ. https:// doi.org/10.1016/j.scitotenv.2020.144204 43. Smith JL, Collins HP, Bailey VL (2010) The effect of young biochar on soil respiration. Soil Biol Biochem 42:2345–2347 44. Dai Z, Xiong X, Zhu H, Xu H, Leng P, Li J, Tang C, Xu J (2021) Association of biochar properties with changes in soil bacterial, fungal and fauna communities and nutrient cycling processes. Biochar 3:239–254 45. Konwar LJ, Boro J, Deka D (2014) Review on latest developments in biodiesel production using carbon-based catalysts. Renew Sustain Energy Rev 29(C):546–564 46. Dehkhoda AM, EllisN GE (2014) Electrosorption on activated biochar: effect of thermochemical activation treatment on the electric double layer capacitance. J Appl Electrochem 44:141–157 47. Lehmann J (2007) A handful of carbon. Nature 447:143–144 48. Manya JJ (2012) Pyrolysis for biochar purposes: a review to establish current knowledge gaps and research needs. Environ Sci Technol 46:7939–7954 49. Cao XY, Pignatello JJ, Li Y, Lattao C, Chappell MA et al (2012) Characterization of wood chars produced at different temperatures using advanced 13 C solid-state NMR spectroscopic techniques. Energy Fuels 26:5983–5991 50. Zhang GC, Zhang Q, Sun K, Liu XT, Zheng WJ et al (2011) Sorption of simazine to corn straw biochars prepared at different pyrolytic temperatures. Enviorn Pollut 159:2594–2601 51. Kang J, Parsons J, Gunukula S, Tran DT (2022) Iron and magnesium impregnation of avocado seed biochar for aqueous phosphate removal. Clean Technol 4:690–702. https://doi.org/10. 3390/cleantechnol4030042 52. Verdida RA, Caparanga AR, Chang CT (2023) Facile synthesis of metal-impregnated sugarcane-derived catalytic biochar for ozone removal at ambient temperature. Catalysts 13(2):388. https://doi.org/10.3390/catal13020388 53. Yek PNY, Liew RK, Osman MS, Lee CL, Chuah JH, Park YK, Lam SS (2019) Microwave steam activation, an innovative pyrolysis approach to convert waste palm shell into highly microporous activated carbon. J Environ Manage 15(236):245–253. https://doi.org/10.1016/ j.jenvman.2019.01.010. Epub 2019 Feb 5 PMID: 30735943 54. Chen WH, Hoang AT, Nižeti´c S, Pandey A, Cheng CK, Luque R, Ong HC, Thomas S, Nguyen XP (2022) Biomass-derived biochar: From production to application in removing heavy metal-contaminated water. Process Saf Environ Prot 160:704–733 55. Jitjamnong J, Thunyaratchatanon C, Luengnaruemitchai A, Kongrit N, Kasetsomboon N, Sopajarn A, Chuaykarn N, Khantikulanon N (2021) Response surface optimization of biodiesel synthesis over a novel biochar-based heterogeneous catalyst from cultivated (Musa sapientum) banana peel. Biomass Convers Biorefinery 11:2795–2811 56. Li S, Gu Z, Bjornson BE, Muthukumarappan A (2013) Biochar based solid acid catalyst hydrolyze biomass. J Environ Chem Eng 1:1174–1181 57. Niu L, Hu Y, Hu H, qian Zhang, Wu Y, Giwa AS, Huang S (2022) Kitchen-waste-derived biochar modified nanocomposites with improved photocatalytic performances for degrading organic contaminants. Environ Res 214:114068 58. Zhao C, Lv P, Lingmei Y, Xing S, Wen L, Wang Z (2018) Biodiesel synthesis over biocharbased catalyst from biomass waste pomelo peel. Energy Convers Manage 160:477–485

2 Biochar in Catalysis and Biotransformation

43

59. Xie Q, Yang X, Xu K, Chen Z, Sarkar B, Dou X (2020) Conversion of biochar to sulfonated solid acid catalysts for spiramycin hydrolysis: Insights into the sulfonation process. Environ Res 188 60. Aro T, Fatehi P (2017) Production and application of lignosulfonates and sulfonated lignin. Chemsuschem 10:1861–1877 61. Chen G, Fang B (2011) Preparation of solid acid catalyst from glucose-starch mixture for biodiesel production. Bioresour Technol 102(3):2635–2640. https://doi.org/10.1016/j.bio rtech.2010.10.099. Epub 2010 Oct 25 PMID: 21067915 62. Zhang H, Lin K, Wang H, Gan J (2010) Effect of Pinusradiata derivedbiochars on soil sorption and desorption of phenanthrene. Environ Pollut 158(9):2821–2825 63. Fukuhara K, Nakajima K, Kitano M, Kato H, Hayashi S, Hara M (2011) Structure and catalysis of cellulose-derived amorphous carbon bearing SO3H groups. Chemsuschem 4:778–784 64. Suganuma S, Nakajima K, Kitano M, Yamaguchi D, Kato H, Hayashi S (2008) Hara M (2008) hydrolysis of cellulose by amorphous carbon bearing SO 3H, COOH, and OH groups. J Am Chem Soc 130(38):12787–12793. https://doi.org/10.1021/ja803983h 65. Li M, Chen D, Zhu X (2013). Preparation of solid acid catalyst from rice husk char and its catalytic performance in esterification. Chin J Catal 34(9):1674–1682. https://doi.org/10. 1016/S1872-2067(12)60634-2 66. Yu JT, Dehkhoda AM, Ellis N (2011) Development of biochar-based catalyst for transesterification of canola oil. Energy Fuels 25:337–344. https://doi.org/10.1021/ef100977d 67. Passe-Coutrin N, Jeanne-Rose V, Ouensanga A (2005) Textural analysis for better correlation of the char yield of pyrolysed lignocellulosic materials. Fuel 84:2131–2134. 10.1016/j 68. AnthonysamySI LP, Mohammadi M, Mohamed AR (2022) Alkali—modified biochar as a sustainable adsorbent for the low-temperature uptake of nitric oxide. Int J Environ Sci Technol 19:7127–7140 69. Zhang F, Ma H, Chen J, Li GD, Zhang Y, Chen JS (2008) Preparation and gas storage of high surface area microporous carbon derived from biomass source cornstalks. Bioresour Technol 99:4803–4808 70. Anthonysamy SI, Lahijani P, Mohammadi M, Mohamed AR (2020) Low temperature adsorption of nitric acid on cerium impregnated biomass-derived biochar. Korean J Chem Eng 37:130–140 71. Akpasi SO, Anekwe IMA, Adedeji J, Kiambi SL (2022) Biochar development as a catalyst and its application. Book Chapter, Intechopen. https://doi.org/10.5772/intechopen.105439 72. Zhang C, Zhang N, Xiao Z, Li Z, Zhang D (2019) Characterization of biochars derived from different materials and their effects on microbial dechlorination of pentachlorophenol in a consortium. RSC Adv 9:917 73. Sanroman MA, Lee DJ, Khanal S, Ok YS (2017) Special issue on biochar: production, characterization and applications—beyond soil applications. Bioresour Technol 1:246 74. Dehkhoda AM, Ellis N (2013) Biochar based Catalyst for simultaneous reactions of esterification and transesterification. Catal Today 207:86–92 75. Rahman MZ, Edvinsson T, Kwong P (2020). Biochar for electrochemical applications. Current opinion in green and sustainable chemistry 23:25–30 76. Al-Rahbi AS, Williams PT (2017) Hydrogen-rich syngas production and tar removal from biomass gasification using sacrificial tyre pyrolysis char. Appl Energy 190:501–509. https :// doi.org/https://doi.org/10.1016/J.APENE RGY.2016.12.099. 77. Enaime G, Baçaoui A, Yaacoubi A, Lübken M (2020) Biochar for wastewater treatment— conversion technologies and applications. Appl Sci 10: 3492. https://doi.org/10.3390/app101 03492 78. Gomez-Eyles JL, Sizmur T, Collins CD, Hodson ME (2011) Effects of biochar and the earthworm Eiseniafetida on the bioavailability of polycyclic aromatic hydrocarbons and potentially toxic elements. Environ Pollut 159:616–622 79. MaximeHervy SB, Weiss-Hortala E, Chesnaud A, Gerente C, Villot A, Minh DP, Thorel A, Le Coq L, Nzihou A (2017) Multi-scale characterisation of chars mineral species for tar cracking. Fuel 189:88–97

44

K. Sobha et al.

80. Ormsby R, Kastner JR, Miller J (2012) Hemicellulose hydrolysis using solid acid catalysts generated from biochar. Catal Today 190:89–97 81. Zhang XG, Wilson K, Lee AF (2016) Heterogeneously catalyzed hydrothermal processing of C5−C6 Sugars. Chem Rev 116:12328−12368 82. Kostic MD, Bazargan A, Stamenkovic OS, Veljkovic VB, McKay G (2016) Optimization and kinetics of sunflower oil methanolysis catalyzed by calcium oxide-based catalyst derived from palm kernel shell biochar. Fuel 163:304–313. https://doi.org/10.1016/j.fuel.2015.09.042 83. Weldeslase MG, Benti NE, Desta MA, Mekonnen YS (2023) Maximizing biodiesel production from waste cooking oil with lime-based zinc-doped CaO using response surface methodology. Sci Rep 13:4430. https://doi.org/10.1038/s41598-023-30961-w 84. Abdullahi K, Ojonugwa SS, Yusuff AS, Umaru M, Mohammed IA, Olutoye MA, Aberuagba F (2023) Optimization of biodiesel production from allamanda seed oil using design of experiment. Fuel Commun 14:100081. https://doi.org/10.1016/j.jfueco.2022.100081 85. Alsaiari RA, Musa EM, Alqahtani H, Rizk MA (2023) Biodiesel production from date seed oil via CaO-derived catalyst from waste eggshell. Biofuels. https://doi.org/10.1080/17597269. 2023.2172769 86. Rhodes AH, Carlin A, Semple KT (2008) Impact of black carbon in the extraction and mineralization of phenanthrene in soil. Environ Sci Technol 42:740–745 87. Rawat S, Jinlin L, Ambalkar AA, Hotha S, Muto A, Bhaskar T (2023) Syzygiumcumini seed biochar for fabrication of supercapacitor: role of inorganic content/ash. J Energy Storage 60:106598. https://doi.org/10.1016/j.est.2022.106598 88. Ramos R, Abdelkader-Fernández VK, Matos R, Peixoto AF, Fernandes DM (2022) Metal— supported biochar catalysts for sustainable biorefinery, electrocatalysis, and energy storage applications: a review. Catalysts 12:207 89. Qian L, Zhang W, Yan J, Han L, Gao W, Liu R, Chen M (2016) Effective removal of heavy metal by biochar colloids under different pyrolysis temperatures. Bioresour Technol 206:217– 224 90. Qi X, Yin H, Zhu M, Yu X, Shao P, Dang Z (2022) MgO-loaded nitrogen and phosphorus selfdoped biochar: high-efficient adsorption of aquatic Cu2+, Cd2+qnd Pb2+ and its remediation efficiency on heavy metal contaminated soil. Chemosphere 294:133733 91. Xiong W, Zeng Z, Li X, Zeng G, Xiao R, Yang Z, Xu H, Chen H, Cao J, Zhou C, Qin L (2019) Ni-doped MIL-53(Fe) nanoparticles for optimized doxycycline removal by using response surface methodology from aqueous solution. Chemosphere 232(2019):186–194 92. Wang G, Zong S, Ma H, Wan B, Tian Q (2023) Removal efficiency and performance optimization of organic pollutants in wastewater using new biochar composites. Catalysts 13:184. https://doi.org/10.3390/catal13010184 93. Ahmad M, Rajapaksha AU, Lim JE, Zhang M, Bolan N, Mohan D, Vithanage M, Lee SS, Ok YS (2014) Biochar as a sorbent for contaminant management in soil and water: a review. Chemosphere 99:19–33. https://doi.org/10.1016/j.chemosphere.2013.10.071 94. Chan KY, Van Zwieten L, Meszaros I, Downie A, Joseph S (2007) Agronomic values of green waste biochar as a soil amendment. Soil Res 45:629 95. Ma P, Qi Z, Wu X, Ji R, Chen W (2023) Biochar nanoparticles-mediated transport of organic contaminants in porous media: dependency on contaminant properties and effects of biochar aging. Carbon Res. 2:4 96. Burachevskaya M, Minkina T, Bauer T, Lobzenko I, Fedorenko A, Mazarji M, Sushkova S, Mandzhieva S, Nazarenko A, Butova V, Wong MH, Rajput VD (2023). Fabrication of biochar derived from different types of feedstocks as an efficient adsorbent for soil heavy metal removal. Sci Rep13. https://doi.org/10.1038/s41598-023-27638-9 97. Meng J (2013) Biochar in China: status quo of research and trend of industrial development. J Shenyang Agric Univ Soc Sci Ed 15:1–5 98. Yang E, Jun M, Haijun H, Wenfu C (2015) Chemical composition and potential bioactivity of volatile from fast pyrolysis of rice husk. J Anal Appl Pyrolysis 112:394–400. https://doi. org/10.1016/j.jaap.2015.02.021

2 Biochar in Catalysis and Biotransformation

45

99. Hong N, Cheng Q, Goonetilleke A, Bandala ER, Liu A (2020) Assessing the effect of surface hydrophobicity/hydrophilicity on pollutantleaching potential of biochar in water treatment. J Ind Eng Chem 89:222–232. https://doi.org/10.1016/j.jiec.2020.05.017 100. Yang E, Meng J, Hu H, Cheng D, Zhu C, Chen W (2019) Effectsof organic molecules from biochar-extracted liquor on the growth of riceseedlings. Ecotoxicol Environ Saf 170:338–345. https://doi.org/10.1016/j.ecoenv.2018.11.108 101. Lehmann J (2009) Biochar for environmental management: science and technology. Earthscan, Sterling, VA 102. De Lorenzo V (2008) Systems biology approaches to bioremediation. Curr Opin Biotechnol 19(6):579–589 103. Ufarte L, Laville E, Duquesne S, Potocki-Veronese G (2015) Metagenomics for the discovery of pollutant degrading enzymes. Biotechnol Adv 33(8):1845–1854 104. Fenner K, Canonica S, Wackett LP, Elsner M (2013) Evaluating pesticide degradation in the environment: blind spots and emerging opportunities. Science 341(6147):752–758 105. Meckenstock RU, Elsner M, Griebler C, Lueders T, Stumpp C, Aamand J, Agathos SN, Albrechtsen H-J, Bastiaens L, Bjerg PL, Boon N, Dejonghe W, Huang WE, Schmidt SI, Smolders E, Sorensen SR, Springael D, van Breukelen BM (2015) Biodegradation: updating the concepts of control for microbial cleanup in contaminated aquifers. Environ Sci Technol 49(12):7073–7081 106. Poursat BAJ, van Spanning RJM, de Voogt P, Parsons JR (2019) Implications of microbial adaptation for the assessment of environmental persistence of chemicals. Crit Rev Environ Sci Technol 49(23):2220–2255 107. Nachman KE, Baron PA, Raber G, Francesconi KA, Navas-Acien A, Love DC (2013) Roxarsone, inorganic arsenic, and other arsenic species in chicken: a U.S.-based market basket sample. Environ Health Perspect 121:818–824. https://doi.org/10.1289/ehp.1206245 108. Silbergeld EK, Nachman K (2008) The environmental and public health risks associated with arsenical use in animal feeds. Ann N Y Acad Sci 1140:346–357. https://doi.org/10.1196/ann als.1454.049 109. Huang K, Peng H, Gao F, Liu QQ, Lu X, Shen Q et al (2019) Biotransformation of arseniccontaining roxarsone by an aerobic soil bacterium Enterobacter sp. CZ-1. Environ Pollut 247:482–487. https://doi.org/10.1016/j.envpol.2019.01.076 110. Makris KC, Quazi S, Punamiya P, Sarkar D, Datta R (2008) Fate of arsenic in swine waste from concentrated animal feeding operations. J Environ Qual 37:1626–1633. https://doi.org/ 10.2134/jeq2007.0479 111. Chen G, Ke Z, Liang T, Liu L, Wang G (2016) Shewanellaoneidensis MR-induced Fe(III) reduction facilitates roxarsone transformation. PLoS ONE 11:e0154017. https://doi.org/10. 1371/journal.pone.0154017 112. Garbarino JR, Bednar AJ, Rutherford DW, Beyer RS, Wershaw RL (2003) Environmental fate of roxarsone in poultry litter. I. degradation of roxarsone during composting. Environ Sci Technol 37:1509–1514. https://doi.org/10.1021/es026219q 113. Han J-C, Zhang F, Cheng L, Mu Y, Liu D-F, Li W-W et al (2017) Rapid release of arsenite from roxarsonebioreduction by exoelectrogenic bacteria. Environ SciTechnol Lett 4:350–355. https://doi.org/10.1021/acs.estlett.7b00227 114. Oyewumi O, Schreiber M (2017) Using column experiments to examine transport of as and other trace elements released from poultry litter: implications for trace element mobility in agricultural watersheds. Environ Pollut 227:223–233. https://doi.org/10.1016/j.envpol.2017. 04.063 115. Wengang L, Fang C, Rong Z, Cuihong C (2022) Biochar-Mediated Degradation of Roxarsone by Shewanellaoneidensis MR-1. Front Microbiol 13:846228. https://doi.org/10.3389/fmicb. 2022.846228 116. Yang E, Meng J, Cal H, Li C, Liu S, Sun L, Liu Y (2021) Effect of biochar on the production of L-Histidine from glucose through Escherichia coli metabolism. Front Bioeng Biotechnol. https://doi.org/10.3389/fbioe.2020.605096

46

K. Sobha et al.

117. Torres MJ, Simon J, Rowley G, Bedmar EJ, Richardson DJ, Gates AJ, Delgado MJ (2016) Nitrous Oxide metabolism in nitrate-reducing bacteria: physiology and regulatory mechanisms. Adv Microb Physiol 68:353–432. https://doi.org/10.1016/bs.ampbs.2016. 02.007 118. Gaimster H, Alston M, Richardson DJ, Gates AJ, Rowley G (2018) Transcriptional and environmental control of bacterial denitrification and N2O emissions. FEMS Microbiol Lett 365(5). https://doi.org/10.1093/femsle/fnx277 119. Butterbach-Bahl K, Baggs EM, Dannenmann M, Kiese R, Zechmeister-Boltenstern S (2013) Nitrous oxide emissions from soils: how well do we understand the processes and their controls? Philos Trans R Soc B 368:20130122 120. Zhu X, Burger M, Doane TA, Horwath WR (2013) Ammonia oxidation pathways and nitrifier denitrification are significant sources of N2 O and NO under low oxygen availability. Proc Natl Acad Sci USA 110:6328–6333 121. Sgouridis F, Ullah S (2015) Relative magnitude and controls of in situ N2 and N2O fluxes due to denitrification in natural and semi-natural terrestrial ecosystems using 15N tracers. Environ Sci Technol 49:14110–14119 122. Zhang Y, Zhang Z, Chen Y (2021) Biochar mitigates N2 O emission of microbial denitrification through modulating carbon metabolism and allocation of reducing power. Environ Sci Technol 55(12):8068-8078. https://doi.org/10.1021/acs.est.1c01976 123. Kourmentza C, Placido J, Venetsaneas N, Burniol-Figols A, Varrone C, Gavala HN, Reis MA (2017) Recent advances and challenges towards sustainable polyhydroxyalkanoate (PHA) production Bioengineering 4:55 124. Nehra K, Chhabra N, Sidhu PK, Lathwal P, Rana J (2017) Molecular identification and characterization of Poly-βhydroxybutyrate (PHB) producing bacteria isolated from contaminated soils. Asian J Microbiol Biotechnol Environ Sci 17:281–290 125. He H, Qian T-T, Liu W-J, Jiang H, Yu H-Q (2014) Biological and chemical phosphorus solubilization from pyrolytical biochar in aqueous solution. Chemosphere 113:175e181 126. Efthymiou A, Grønlund M, Müller-Steover DS, Jakobsen I (2018) Augmentation of the phosphorus fertilizer value of biochar by inoculation of wheat with selected Penicillium strains. Soil BiolBiochem 116:139e147 127. Khan S, Chao C, Waqas M, Arp HPH, Zhu YG (2013). Sewage sludge biochar influence upon rice (Oryza sativa L) yield, metal bioaccumulation and greenhouse gas emissions from acidic paddy soil. Environ Sci Technol 47(15):8624e8632 128. Zielinska A, Oleszczuk P (2015) The conversion of sewage sludge into biochar reduces polycyclic aromatic hydrocarbon content and ecotoxicity but increases trace metal content. Biomass Bioenergy 75:235e244 129. Smith CR, Buzan EM, Lee JW (2012) Potential impact of biochar water extractable substances on environmental sustainability. ACS Sustain Chem Eng 1(1):118e126 130. Wang Y-Y, Jing X-R, Li L-L, Liu W-J, Tong Z-H, Jiang H (2016) Biotoxicity evaluations of three typical biochars using a simulated system of fast pyrolyticbiochar extracts on organisms of three kingdoms. ACS Sustain ChemEng 5(1):481e488 131. ZhengYulin BW, Wester AE, Chen J, He F, Chen H, Gao B (2019) Reclaiming phosphorus from secondary treated municipal waste water with engineered biochar. Chem Eng J 362:460–468 132. Liao S, Pan B, Li H, Zhang D, Xing B (2014). Detecting free radicals in biochars and determining their ability to inhibit the germination and growth of corn, wheat and rice seedlings. Environ Sci Technol 48(15):8581–8587 133. Lieke T, Zhang X, Steinberg CEW, Pan B (2018). Overlooked risks of biochars: persistent free radicals trigger neurotoxicity in Caenorhabditis elegans. Environ Sci Technol 52(14):7981– 7987 134. Liu Y, Dai Q, Jin X, Dong X, Peng J, Wu M, Liang N, Pan B, Xing B (2018). Negative impacts of biochars on urease activity: high pH, heavy metals, polycyclic aromatic hydrocarbons, or free radicals? Environ Sci Technol 52(21):12740–12747 135. Behera JK, Sharma PK, Behera T, Krishna KR, Arvind V (2020) Remediation of chromium toxicity by biochar, poultry manure and sewage sludge in rice (Oryza sativa) crop. Int J CurrMicrobiol App Sci 9(03):2294–2306. https://doi.org/10.20546/ijcmas.2020.903.260

2 Biochar in Catalysis and Biotransformation

47

136. Youngwilai A, Kidkhunthod P, Jearanaikoon N et al (2020) Simultaneous manganese adsorption and biotransformation by Streptomyces violarus strain SBP1 cell-immobilized biochar. Sci Total Environ 713:136708. https://doi.org/10.1016/j.scitotenv.2020.136708. PMID: 32019044 137. Yang YP, Zhang HM, Yuan HY, Duan GL, Jin DC, Zhao FJ, Zhu YG (2018) Microbe mediated arsenic release from iron minerals and arsenic methylation in rhizosphere controls arsenic fate in soil-rice system after straw incorporation. Environ Pollut 236:598–608. ISSN 0269-7491. https://doi.org/10.1016/j.envpol.2018.01.099 138. Yang YP, Tang XJ, Zhang HM, Cheng WD, Duan GL, Zhu YG (2020) The characterization of arsenic biotransformation microbes in paddy soil after straw biochar and straw amendments. J Hazard Mater 391:122200. https://doi.org/10.1016/j.jhazmat.2020.122200. Epub 2020. 139. Tong H, Hu M, Li FB, Liu CS, Chen MJ (2014) Biochar enhances the microbial and chemical transformation of pentachlorophenol in paddy soil. Soil Biol Biochem 70:142–150 140. Wang G, Han N, Liu L, Ke ZC, Li BG, Chen GW (2020) Molecular density regulating electron transfer efficiency of S. oneidensis MR-1 mediated roxarsone biotransformation. Environ Pollut 262:114370. https://doi.org/10.1016/j.envpol.2020.114370

Chapter 3

Biochar: A Potent Adsorbent Khaled Zoroufchi Benis , Jafar Soltan, and Kerry N. McPhedran

1 Introduction Adsorption is a process in which components (atoms, ions, or molecules) of a gaseous or liquid phase are accumulated on the surface of the adsorbent. Adsorbates refer to the accumulated components, while the adsorbent refers to the solid phase that accumulates the adsorbates. Adsorption is often characterized as a physisorption or chemisorption process, depending on the nature and intensity of bonding among the adsorbents and the adsorbates. In physical adsorption (physisorption), the adsorbent and adsorbate interactions are mainly controlled by weak electrostatic interactions, such as dipole–dipole interactions and Van der Waals forces. In comparison, chemical adsorption (chemisorption) entails strong bonds between the adsorbate and the adsorbent [1]. Of these two processes, chemisorption interactions are stronger than physisorption interactions. Generally, adsorption consists of three steps (Fig. 1): (1) adsorbate transfers from the bulk medium to the outer adsorbent surface; (2) adsorbate diffuses into the adsorbent pores; and (3) adsorbate is adsorbed onto the adsorbent’s active sites (physisorption or chemisorption) [2]. Therefore, an effective adsorbent should have features that reduce the time required to complete these steps. Effective commercial adsorbents possess both a highly porous structure and a large surface area, however, are typically high cost. Other qualities of excellent materials for adsorption are low cost, K. Zoroufchi Benis · J. Soltan (B) Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, Canada e-mail: [email protected] K. N. McPhedran Department of Civil, Geological and Environmental Engineering, University of Saskatchewan, Saskatoon, SK, Canada K. Zoroufchi Benis · J. Soltan · K. N. McPhedran Global Institute for Water Security, University of Saskatchewan, Saskatoon, SK, Canada © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 A. K. Nadda (ed.), Biochar and its Composites, Materials Horizons: From Nature to Nanomaterials, https://doi.org/10.1007/978-981-99-5239-7_3

49

50

K. Zoroufchi Benis et al.

Fig. 1 Schematic of the mass transfer phenomena in adsorption process

sufficient structural and mechanical properties to withstand attrition and mechanical forces due to fluid flow in a fixed-bed adsorption process, high adsorption capacities and high adsorption rates, and regeneration capabilities [3]. Adsorption techniques are widely used in numerous fields, such as pollution control, chromatography, purification or separation of gas and liquid mixtures, organic solvent drying, gas masks, gas deodorization, etc. [4, 5]. Synthetic, natural, and semi-synthetic adsorbents are the three major categories of adsorbents. Synthetic adsorbents are manufactured materials with a high adsorption capacity that are often more expensive than other adsorbents. Natural adsorbents are natural materials like agricultural residues and minerals that usually suffer from low adsorption capacity. Semi-synthetic adsorbents are comprised of natural materials that have been chemically or physically modified to produce a highly porous surface [6]. Considering the high cost of synthetic adsorbents and the low adsorption capacity of natural adsorbents, semi-synthetic adsorbents are cheaper than synthetic adsorbents while having sufficient adsorbent capacities. Different types of natural biomaterials, such as wood residues, wastewater sludges, and agriculture residues, are widely available, inexpensive, and sustainable for use in adsorption processes [7]. However, low adsorption capacities, coloration problems, and possible release of soluble organic compounds into the treated water are their inherent disadvantages that may hinder their use as adsorbents [1]. However, the production of semi-synthetic adsorbents from biomaterials can overcome these drawbacks and allow them to be widely employed in adsorption processes. The three types of treatment processes for producing biomaterial-based semi-synthetic adsorbents documented in the literature are chemical treatments using acids and alkaline solutions, composites, and biochars. Chemical treatment improves the adsorption capacity, surface area, and porosity of biomaterials by removing soluble organic

3 Biochar: A Potent Adsorbent

51

compounds, oxidizing the surface to create oxygen-containing functional groups, altering or adding functional groups, and eliminating coloration problems [8–10]. The surface of biomaterials, either untreated or chemically treated, is modified by the deposition of activating agents (e.g., metal oxides) to create composites [1]. Biochar is a carbon-rich solid that is produced through the thermochemical degradation of biomaterials in an oxygen-depleted condition. Biochar has most of the desirable characteristics of an effective adsorbent including a high specific surface area (SSA) and porous structure and a large number of diverse functional groups [11]. With a porous structure comparable to activated carbon, biochar is a popular and very efficient adsorbent worldwide for treating various contaminants in air and water [12, 13]. Biochar is cheaper to produce and requires less energy than activated carbon which is usually produced at high temperatures. The environmental and economic benefits of biochar make it an attractive material for use in environmental remediation [14]. Pristine biochar can be used directly in adsorption processes, however, it can also be employed as a precursor to produce biochar composites or activated biochar. Physical and chemical activation using steam, acids, and base improve the porosity, SSA, and functionality of biochar. Biochar composites, on the other hand, are created by utilizing activated or pristine biochar as support for embedding new materials and functional groups such as metals, and organic compounds to adsorb the target contaminants [10, 15]. In this chapter, emphasis has been placed on the application of pristine and activated biochar in the adsorption process and mechanisms involved in contaminants removal. Adsorption performance is influenced by biochar characteristics, contaminant concentration and characteristics, operating conditions, adsorbent dosage, temperature, contact time, solution pH, and the presence of interfering species. The current chapter first overviews the effects of biochar characteristics on adsorption performance (Sect. 2), and then provides a framework for understanding the capability of biochar to be used to remove inorganic and organic chemicals from water (Sect. 3) and air (Sect. 4). Finally, future research directions for using biochar as an adsorbent are discussed (Sect. 5).

2 Effects of Properties of Biochar on Adsorption Performance The mechanisms underlying adsorption may be better understood by examining the connections between the characteristics of biochar and its adsorption capabilities. This section outlines the major parameters, including surface functional groups, SSA, pore volume and pore size distribution, and pH of biochar that significantly impact its absorption capacity. Figure 2 illustrates the porous structure of biochar containing various functional groups.

52

K. Zoroufchi Benis et al.

Fig. 2 Schematic of a porous biochar and its surface functional groups

2.1 Surface Functional Groups Adsorption of contaminants by biochar occurs through various mechanisms such as ionic exchange, surface complexation, surface precipitation, electrostatic attraction, hydrogen bonding, and π-π electron donor–acceptor interactions. These mechanisms are driven by a wide variety of functional groups on the biochar surface, such as minerals and hydroxyl, carbonyl, carboxyl, and amino groups [16, 17]. The distribution and types of surface functional groups of biochar depend on the feedstock (biomass) composition and the applied pyrolysis and activation process conditions. Several technologies can be utilized to investigate these functional groups [18], such as Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure spectroscopy (XAFS). In general, hydroxyl functional groups serve as electron donors, whereas carboxyl functional groups are electron withdrawing. Oxygen-containing functional groups may increase the cation exchange capability and polarity of biochar, hence boosting the removal of hydrophilic volatile organic compounds [19]. Additionally, more oxygen-containing functional groups improve the adsorption capacity of biochar toward organic compounds, partly due to π-π interactions between electron donorreceptors (i.e., C–C bonds of biochar with the aromatic rings of an organic compound). Moreover, oxygen-containing functional groups can enhance the adsorption of contaminants through complexation between adsorbate and biochar and hydrogen bonding [20, 21]. In addition, the inclusion of sulfur or phosphorus atoms

3 Biochar: A Potent Adsorbent

53

in the surface functional groups can raise the positive charge density of nearby carbon sites and enhance the hydrogen bonding interactions. On the other hand, nitrogen atoms can act as either electron donors or acceptors depending on their location at different sites [22]. The minerals on the biochar surface enhance the co-precipitation and complexation of heavy metal ions. Biochar has a higher cation exchange capacity due to the abundance of negatively charged surface functional groups [15, 23]. Additionally, biochar’s electrostatic attraction towards positively charged heavy metal ions is enhanced by its negatively charged functional groups.

2.2 Specific Surface Area (SSA) Specific surface area (SSA) and porosity are significant factors in the assessment of the adsorption capacity of biochars. The majority of research indicates a linear relationship between SSA and adsorption capacity [17, 24, 25], however, some literature has also indicated no correlations between adsorption capacity and the biochar’s SSA [26]. Typically, improving the SSA of biochar using chemical or physical activation is viewed as a viable technique for enhancing its adsorption capacity [27, 28] Specifically, physical activation produces a microporous structure and larger SSA. For example, raising the pyrolysis temperature can expedite the formation of porosity [29] by conversion of unstable components (e.g., cellulose, lignin, and hemicellulose) and opening up the pore channels, forming more porous structures, and creating new active sites [30]. However, it has been observed [10, 31], that increasing pyrolysis temperatures reduces the oxygenated functional groups that result in decreasing the surface charge negativity, which may reduce the adsorption of positively charged ions. Chemical activation has been utilized extensively to improve the SSA of biochar. For example, the SSA can be greatly increased by impregnating biomaterial with chemical activators before pyrolysis. Some of the common activators are H2 SO4 , H3 PO4 , NaOH, and KOH [32], however, the SSA of biochar may change depending on the type of activator used. In addition, the biomaterial/activator ratio and impregnation time have been shown to substantially affect the SSA of the activated biochar [33]. Thus, the amount of activator and the activation process should be optimized to obtain the desired SSA.

2.3 Pore Size Distribution and Pore Volume Pore size is the average pore diameter of an adsorbent. The International Union of Pure and Applied Chemistry (IUPAC) classifies pore sizes as macropores (>50 nm), mesopores (2–50 nm), and micropores (