Production and characterization of eight biochars originating from agricultural waste in Cameroon

Biochar physicochemical properties vary greatly depending on the origin of the residues. The present study contributes to leveling the scientific gap on biochar properties. We produced and characterized the chemistry of 8 biochars from agricultural crop residues (corncobs, bean straws, cocoa pod husks, coconut shells, palm kernel shells, palm mesocarp fibers, rice husks, and cassava peels), for assessing their suitability as organic amendments, and their potential to sequester carbon dioxide in the soil. Bean straws and cocoa pod husks exhibited higher total nitrogen and phosphorus, exchangeable bases, and electrical conductivity. Ash content was highest in biochar from rice husks (43.8%). Coconut shells and corncobs had the highest total carbon concentration of 77.4% and 75.6%, respectively. Coconut shells exhibited the greatest carbon dioxide reduction potential (374.6) among all studied biochars. According to the International Biochar Initiative (IBI) standard, heavy metal concentrations were low in all tested biochar. Therefore, biochars from bean straw and cocoa pod husks were the most promising as agricultural amendments and biochar from coconut shells had the best carbon dioxide reduction potential. The advantages highlighted by this chemical characterization should be tested in field soils for validation.