Abstract

Shagufta Gaffar*, Vanessa Kertesz, Krishnaswamy Jayachandran

Biochar - a porous, carbon-rich material produced through thermochemical conversion of organic biomass under oxygen-limited conditions - is increasingly applied in soil amendment, environmental remediation, and climate change mitigation. Its properties, and ultimately its utility across these contexts, are determined by the feedstock from which it is produced. This review examines how feedstock classification and compositional characteristics shape biochar properties including yield, elemental composition, surface area, porosity, pH, cation exchange capacity, and contaminant content, drawing on proximate and ultimate analysis, FTIR, BET, and SEM evidence. Seven major feedstock categories are evaluated: Agricultural residues, woody biomass, herbaceous and energy crops, animal manures, slaughterhouse wastes, sewage sludge, and algal biomass. Lignocellulosic feedstocks - particularly wood and crop residues-consistently produce biochars with high carbon stability and well-developed surface area, whereas manureand sludge-derived biochars are nutrient-rich and strongly alkaline but carry elevated risks of heavy metal accumulation and organic contaminant transfer. Pyrolysis temperature modifies but does not override feedstock-driven property differences: High temperatures raise aromaticity and surface area yet suppress cation exchange capacity and nutrient retention - a trade-off central to rational biochar product design. Application-specific performance in soil amendment, carbon sequestration, heavy metal immobilization, and water remediation is reviewed with feedstock-specific examples, revealing that the optimal feedstock is application-dependent and cannot be determined without reference to the target system.