Biochar physicochemical properties: pyrolysis temperature and feedstock kind effects

TLDR

Biochar, produced by pyrolyzing biomass, is used for pollution remediation, soil fertility, and carbon sequestration, and its properties—pH, surface area, pore volume, CEC, volatile matter, ash, and carbon content—vary with pyrolysis temperature and feedstock composition. This review examines how pyrolysis temperature and biomass type influence biochar’s physicochemical properties and its impact on soil fertility. These property changes arise mainly from extensive organic matter decomposition during pyrolysis, which alters biochar’s structure and composition. Higher pyrolysis temperatures produce biochars with greater surface area, porosity, pH, ash, and carbon but lower CEC and volatile matter, while animal‑derived feedstocks yield lower surface area, carbon, and volatile matter and higher CEC compared to crop and wood feedstocks.

Abstract

Abstract Biochar is a pyrogenous, organic material synthesized through pyrolysis of different biomass (plant or animal waste). The potential biochar applications include: (1) pollution remediation due to high CEC and specific surface area; (2) soil fertility improvement on the way of liming effect, enrichment in volatile matter and increase of pore volume, (3) carbon sequestration due to carbon and ash content, etc. Biochar properties are affected by several technological parameters, mainly pyrolysis temperature and feedstock kind, which differentiation can lead to products with a wide range of values of pH, specific surface area, pore volume, CEC, volatile matter, ash and carbon content. High pyrolysis temperature promotes the production of biochar with a strongly developed specific surface area, high porosity, pH as well as content of ash and carbon, but with low values of CEC and content of volatile matter. This is most likely due to significant degree of organic matter decomposition. Biochars produced from animal litter and solid waste feedstocks exhibit lower surface areas, carbon content, volatile matter and high CEC compared to biochars produced from crop residue and wood biomass, even at higher pyrolysis temperatures. The reason for this difference is considerable variation in lignin and cellulose content as well as in moisture content of biomass. The physicochemical properties of biochar determine application of this biomaterial as an additive to improve soil quality. This review succinctly presents the impact of pyrolysis temperature and the type of biomass on the physicochemical characteristics of biochar and its impact on soil fertility.