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      A critical review on the biochar production techniques, characterization, stability and applications for circular bioeconomy

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          Highlights

          • Recent research on remediation of toxic pollutants by biochar has been summarized.

          • The production techniques of the biochar have been narrated.

          • Biochar properties, stability and its environmental issues have been analysed.

          • Applications of biochar in soil fertility and removing pollutants have been reported.

          • The major stumbling block in biochar production is cost of production.

          Abstract

          There is an upsurge enthusiasm for utilizing biochar produced from waste-biomass in different fields, to address the most important ecological issues. This review is focused on an overview of remediating harmful contaminants utilizing biochar. Production of biochar utilizing various systems has been discussed. Biochar has received the consideration of numerous analysts in building up their proficiency to remediate contaminants. Process parameters are fundamentally answerable for deciding the yield of biomass. Biochar derived from biomass is an exceptionally rich wellspring of carbon produced from biomass utilizing thermal combustion. Activating biochar is another particular region for the growing utilization of biochar for expelling specific contaminations. Closed-loop systems to produce biochar creates more opportunities. Decentralized biochar production techniques serve as an effective way of providing employment opportunities, managing wastes, increasing resource proficiency in circular bioeconomy. This paper also covers knowledge gaps and perspectives in the field of remediation of toxic pollutants using biochar.

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          Most cited references149

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          Biochar as a sorbent for contaminant management in soil and water: a review.

          Biochar is a stable carbon-rich by-product synthesized through pyrolysis/carbonization of plant- and animal-based biomass. An increasing interest in the beneficial application of biochar has opened up multidisciplinary areas for science and engineering. The potential biochar applications include carbon sequestration, soil fertility improvement, pollution remediation, and agricultural by-product/waste recycling. The key parameters controlling its properties include pyrolysis temperature, residence time, heat transfer rate, and feedstock type. The efficacy of biochar in contaminant management depends on its surface area, pore size distribution and ion-exchange capacity. Physical architecture and molecular composition of biochar could be critical for practical application to soil and water. Relatively high pyrolysis temperatures generally produce biochars that are effective in the sorption of organic contaminants by increasing surface area, microporosity, and hydrophobicity; whereas the biochars obtained at low temperatures are more suitable for removing inorganic/polar organic contaminants by oxygen-containing functional groups, electrostatic attraction, and precipitation. However, due to complexity of soil-water system in nature, the effectiveness of biochars on remediation of various organic/inorganic contaminants is still uncertain. In this review, a succinct overview of current biochar use as a sorbent for contaminant management in soil and water is summarized and discussed.
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            Review of fast pyrolysis of biomass and product upgrading

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              Mechanisms of metal sorption by biochars: Biochar characteristics and modifications.

              Biochar produced by thermal decomposition of biomass under oxygen-limited conditions has received increasing attention as a cost-effective sorbent to treat metal-contaminated waters. However, there is a lack of information on the roles of different sorption mechanisms for different metals and recent development of biochar modification to enhance metal sorption capacity, which is critical for biochar field application. This review summarizes the characteristics of biochar (e.g., surface area, porosity, pH, surface charge, functional groups, and mineral components) and main mechanisms governing sorption of As, Cr, Cd, Pb, and Hg by biochar. Biochar properties vary considerably with feedstock material and pyrolysis temperature, with high temperature producing biochars with higher surface area, porosity, pH, and mineral contents, but less functional groups. Different mechanisms dominate sorption of As (complexation and electrostatic interactions), Cr (electrostatic interactions, reduction, and complexation), Cd and Pb (complexation, cation exchange, and precipitation), and Hg (complexation and reduction). Besides sorption mechanisms, recent advance in modifying biochar by loading with minerals, reductants, organic functional groups, and nanoparticles, and activation with alkali solution to enhance metal sorption capacity is discussed. Future research needs for field application of biochar include competitive sorption mechanisms of co-existing metals, biochar reuse, and cost reduction of biochar production.
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                Author and article information

                Contributors
                Journal
                Biotechnol Rep (Amst)
                Biotechnol Rep (Amst)
                Biotechnology Reports
                Elsevier
                2215-017X
                21 November 2020
                December 2020
                21 November 2020
                : 28
                : e00570
                Affiliations
                [a ]Department of Chemical Engineering, Sri Sivasubramaniya Nadar College of Engineering, Kalavakkam, Chennai, 603 110, Tamil Nadu, India
                [b ]SSN-Centre for Radiation, Environmental Science and Technology (SSN-CREST), SSN College of Engineering, Chennai, 603110, Tamil Nadu, India
                [c ]Gujarat Pollution Control Board, Gandhinagar, 382010, Gujarat, India
                [d ]Department of Biotechnology, Rajalakshmi Engineering College, Chennai, 602105, India
                Author notes
                [* ]Corresponding author. drsvs18@ 123456gmail.com
                [** ]Corresponding author at: Department of Chemical Engineering, Sri Sivasubramaniya Nadar College of Engineering, Kalavakkam, Chennai, 603 110, Tamil Nadu, India. senthilchem8582@ 123456gmail.com
                Article
                S2215-017X(20)30002-3 e00570
                10.1016/j.btre.2020.e00570
                7718465
                33304842
                63024655-95fb-4950-bdc6-ab85e5613e28
                © 2020 Published by Elsevier B.V.

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

                History
                : 4 January 2020
                : 10 November 2020
                : 20 November 2020
                Categories
                Review

                biochar,production techniques,pollutants removal,carbon sequestration,circular bioeconomy

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