Production, activation, and applications of biochar in recent times

Abstract

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.

Activated biochars derived from wood biomass liquefaction residues for effective removal of hazardous hexavalent chromium from aquatic environments

“…The aim of the second step—CO 2 activation at 850°C was to develop a microporous structure which—as we anticipated—will play a crucial role in the adsorption experiments. Generally, the treatment's conditions were selected to be typical for biomass pyrolysis (oxygen‐free environment, temperature range of 300–500°C) and activation (CO 2 flow, temperature range of 700–900°C; Reza et al, 2020; Sakhiya et al, 2020). The physical processes and chemical reactions that occur during pyrolysis are complex and depend both, on the source of the biomass and the processing parameters.…”

Biochar remediation of soil: linking biochar production with function in heavy metal contaminated soils

“…Biochar's preparation condition also influence its physicochemical properties, which indirectly also control its HM immobilisation effects (Wang et al 2021). The production parameters that were found to control these biochar properties include, pyrolysis temperature, heating rates, vapour residence time, biomass type and particle size (Sakhiya et al 2020). Hence, recent biochar research directed at HM remediation highlights routes to improvement and modification of biochar's HM absorption efficacy through altering its production processes (Wang et al 2019).…”

“…Gas purging of biochar (another physical modification process) with CO 2 at high temperature was found to increase biochar surface area and pore volume relative to unmodified ones (Xiong et al 2013). Chemical modification, in general, is a heat treatment process (450-900 °C) of biochar with chemical activating reagents (Sakhiya et al 2020). Studies show that chemical modification creates opportunities for biochar to chemically react with HMs more efficiently through (1) increased surface area and sorption sites; (2) more conducive surface to electrostatic attraction, surface complexation, and/or precipitation, and (3) specific surface functional groups for greater sorption affinity and stronger interactions (Rajapaksha et al 2016).…”

The Contribution of Integrated Polytechnic Regional College (IPRC) Musanze in Creating Valuable Uses to Tomato Crop Farm-Leftovers

“…At elevated temperature, those materials are broken down in simple compounds and this process is known as thermochemical depolymerization reactions. The thermochemical decomposition "pyrolysis" of biomass, generally, takes place in an oxygen-free environment within a temperature range of 300-500 °C to produce the char (Sakhiya, Anand and Kaushal, 2020). This bio decomposition process converts low-energy-density biomass into a high-density liquid product called "bio-oil", medium caloric value gas called "synthesis gas", and high-density solid product called "biochar".…”

“…The activation here means a technique applied physically or chemically to biochar to improve its physical characteristics (i.e. specific surface area) and absorption capacity (Sakhiya, Anand and Kaushal, 2020). The activated biochar serves multiple purposes like soil amendment in agriculture, absorbent of contaminant and pollutant in aqueous solutions; it can be used also as catalysts of chemical reactions, fuel alternative, used as an additive, used in the construction sector.…”