Risk Evaluation of Pyrolyzed Biochar from Multiple Wastes

Abstract

This paper aims at demonstrating the significance of biochar risk evaluation and reviewing risk evaluation from the aspects of pyrolysis process, feedstock, and sources of hazards in biochar and their potential effects and the methods used in risk evaluation. Feedstock properties and the resultant biochar produced at different pyrolysis process influence their chemical, physical, and structural properties, which are vital in understanding the functionality of biochar. Biochar use has been linked to some risks in soil application such as biochar being toxic, facilitating GHGs emission, suppression of the effectiveness of pesticides, and effects on soil microbes. These potential risks originate from feedstock, contaminated feedstock, and pyrolysis conditions that favor the creation of characteristics and functional groups of this nature. These toxic compounds formed pose a threat to human health through the food chain. Determination of toxicity levels is a first step in the risk management of toxic biochar. Various sorption methods of biochar utilized low-cost adsorbents, engineered surface functional groups, and nZVI modified biochars. The mechanisms of organic compound removal was through sorption, enhanced sorption, modified biochar, postpyrolysis thermal air oxidation and that of PFRs degradation was through activation, photoactive functional groups, magnetization, and hydrothermal synthesis. Emissions of GHGs in soils amended with biochar emanated through physical and biotic mediated mechanisms. BCNs have a significance in reducing the health quotient indices for PTEs risk contamination by suppressing cancer risk arising from consumption of contaminated food. The degree of environmental risk assessment of HM pollution in biomass and biochars has been determined by using potential ecological risk index and RAC while organic contaminant degradation by EPFRs was considered when assessing the environmental roles of biochar in regulating the fate of contaminants removal. The magnitude of technologies’ net benefit must be considered in relation to the associated risks.

Recent advancements in the use of biochar for cementitious applications: A review

“…Such chem i cal sta bil ity can pos si bly be achieved through the ad di tion of biochars into ce men ti tious ma te ri als for var i ous con struc tion ap pli ca tions. The chem i cal sta bil ity of biochar de pends heav ily on the sta bil ity of fixed car bon as well as the ex is tence and vol ume of groups of oxy gen within the chem i cal com posi tion [ 90 ]. Some find ings have pro posed that bet ter chem i cal sta bility of biochar is ac com plished when fast py rol y sis at a tem per a ture of 800 °C is used.…”

Biochar physicochemical properties: pyrolysis temperature and feedstock kind effects

“…In contrast, slow pyrolysis tends to yield higher proportions of biochars because of slow heating rates and longer residence times (Daful and Chandraratne 2018). Furthermore, the pyrolysis of biomass may contribute to the formation of phytotoxic and potentially carcinogenic compounds under some conditions (type of feedstock, pollution in feedstock, and pyrolysis parameters) (Ndriangu et al 2019). Some of the heavy metals are transformed into less toxic forms, pathogens are eliminated as the result of the pyrolysis process (Paz-Ferreiro et al 2018), but nitrogen and sulphur are lost during pyrolysis (Maguire and Agblevor 2010).…”

A Mini Review of Biochar Synthesis, Characterization, and Related Standardization and Legislation

“…Therefore, the standardization of biochar prior to applications is significant as their performance can be generalized and predicted [64,75]. To date, the biochar standards have been established by the International Biochar Initiative (IBI-BS), European Biochar Foundation (European Biochar Certificate, EBC); as well as the British Biochar Foundation (Biochar Quality Mandate, BQM) [76][77][78]. Referring to Verheijen et al [9], the common objectives of these certifications are to provide the quality and safety indicator for biochar utilization as a soil amendment agent, to promote the biochar's industrial growth and commercialization, as well as for future legislative or regulations.…”