Rice is second only to maize among the world's most important cereal crops, with a global harvested area of approximately 158 million hectares and an annual production of more than 700 million tonnes as paddy rice. At this scale, rice production generates vast amounts of waste in the form of straw, husk, and bran. Because of high cellulose, lignin, and silica contents, rice biowaste (RB) can be used to produce rice biochar (RBC) and rice compost (RC). Furthermore, RB can be used as sorbents, soil conditioners, bricks/concrete blocks, flat steel products, and biofuels, all of which make significant contributions to meeting United Nations Sustainable Development Goals (UNSDGs). Although previous reviews have explored individual applications of rice feedstocks, inadequate attention has been paid to multifunctional values and potential multi-utilities. Here, we offer a comprehensive review of RBC and RC with respect to: (1) preparation and characterization; (2) applications as soil conditioners and organic fertilizers and their effects on soil-carbon sequestration; (3) remediation of toxic element–contaminated soils and water; (4) removal of colors, dyes, endocrine-disrupting chemicals, personal-care products, and residual pesticides from water; and (5) applications in the construction industry. Specifically, we describe the opportunities for the sustainable use of RBC and RC in the management of contaminated soils and water as well as the construction industry. Overall, this review is expected to lengthen the list of possible multifunctional applications of RBC and RC.

Sustainable applications of rice feedstock in agro-environmental and construction sectors: A global perspective

Owing to the sustainability, environmental friendliness, and structural diversity of biomass‐derived materials, extensive efforts have been devoted to use them as energy storage materials in high‐energy rechargeable batteries. A timely and comprehensive review from the structures to mechanisms will significantly widen this research field. Here, it starts with the operation mechanism of batteries, and it aims to summarize the latest advances for biomass‐derived carbon to achieve high‐energy battery materials, including activation carbon methods and the structural classification of biomass‐derived carbon materials from zero dimension, one dimension, two dimension, and three dimension. Each strategy starts with carefully selected examples and then moves to illustrate the underlying transport mechanism of electrons in the structure. In the end, challenges, strategies, and outlooks are pointed out for the future development of biomass‐derived carbon materials. Overall, this review will help researchers choose appropriate strategies to design biomass‐derived carbon materials, thereby promoting the application of biomass materials in battery design.

https://eprints.qut.edu.au/229602/8/Adv_Funct_Materials_2022_Sun_Biomass_u2010Derived_Carbon_for_High_u2010Performance_Batteries_From_Structure_to_Properties_1_.pdf

Biomass‐Derived Carbon for High‐Performance Batteries: From Structure to Properties

A comparative study of physical and chemical activation of rice straw derived biochar to enhance Zn+2 adsorption

Anaerobic digestion has been widely accepted for energy and resource recovery from biomass residues. However, the produced biogas from the process mainly composed of methane and carbon dioxide is lower in calorific content, which is a major drawback for its direct application as an energy fuel. Therefore, different biogas upgradation systems based on physical, chemical, and biological processes have been applied to either remove carbon dioxide and other gaseous constituents from the biogas or utilize carbon dioxide into methane. This review discusses the possible hydrogen-assisted pathways for converting carbon dioxide into methane in the presence of hydrogen and improving its proportion in the biogas composition during anaerobic digestion through in-situ biogas upgradation. Additionally, a co-production of hydrogen and methane in two-stage anaerobic digestion has been proposed for methane enrichment. Technical challenges, stabilization of process parameters, innovative modification and microbial pathways have been explored and discussed. The findings and prospects from this article could be an interesting state-of-the-art for optimizing process parameters during hydrogen-assisted pathways and its mainstream application on existing digestion systems.

Enhancing methane production in anaerobic digestion through hydrogen assisted pathways – A state-of-the-art review

Considering the global issue of vegetable wastes generation and its impact on the environment and resources, this study evaluated the conversion of four largely produced vegetable wastes (cauliflower, cabbage, banana peels and corn cob residues) into biochar. Each waste was tested individually and as a combined blend to assess feedstock influences on biochar properties. In addition, various pyrolysis temperatures ranging from 300 °C to 600 °C and two particle size fractions (less than 75 µm, 75–125 µm) were considered. Biochars were characterized for various properties that can influence the biochars’ effectiveness as a soil amendment. It was found that pyrolysis temperature was the most dominant factor on biochar properties, but that individual feedstocks produced biochars with different characteristics. The biochars had characteristics that varied as follows: pH 7.2–11.6, ECE 0.15–1.00 mS cm−1, CEC 17–cmolc kg−1 and ζ-potential − 0.24 to − 43 mV. Based on optimal values of these parameters from the literature, cauliflower and banana peels were determined to be the best feedstocks, though mixed vegetable waste also produced good characteristics. The optimum temperature for pyrolysis was around 400 °C, but differed slightly (300–500 °C) depending on the distinct feedstock. However, smaller particle size of biochar application was always optimal. Biochar yields were in the range of 20–30% at this temperature range, except for corn cobs which were higher. This study demonstrates that pyrolysis of dried vegetable wastes is a suitable waste valorization approach to produce biochar with good agricultural properties.

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Biochar from vegetable wastes: agro-environmental characterization

Biomass is a green energy source and is available in abundance. Biochar is a carbon-rich material derived from a wide range of biomass or organic waste through the thermochemical route. Biochar has received increasing attention because of its distinctive properties such as high carbon content, greater specific surface area, cation exchange capacity, nutrient retention capacity, and stable structure. This review paper extensively studies and reports the different pyrolysis processes, reactor types, the effect of process parameters on biochar yield, and its physicochemical properties, biochar activation methods, and applications. It also details the status of the research and development (R&D) progress in biochar production through conventional and advanced technologies. The study found that unlike many products (at R&D stage) biochar has high potential to scale up and has a direct impact on crop yield, water purification (for domestic and industrial application), alternative fuels (clean solid fuel for cookstove), air purification, catalyst, biogas production, purification, and storage. In addition, the paper lists the merits and challenges in the novel biochar applications like hydrogen storage, electrochemical capacitor, and fuel cell technology.

Abhijeet Anand

Papers

Production, activation, and applications of biochar in recent times

A comparative study of physical and chemical activation of rice straw derived biochar to enhance Zn+2 adsorption

Suitability of rice straw for biochar production through slow pyrolysis: Product characterization and thermodynamic analysis

Sustainable utilization of rice straw to mitigate climate change: A bioenergy approach

Copper(II) removal from aqua solution using rice straw derived biochar