Pyrolysis behaviour of herbaceous and woody biomass for producing chars suitable for biocoke production

Biocoke production, sustainable agricultural waste management, and the value addition of biochar are increasingly important for the steel, coal, and agricultural industries. Although biochar has been explored as a blending material in coal for cokemaking, limited research has examined the combined influence of biomass type, preparation methods, and pyrolysis conditions on char properties as it relates to coking behaviour when blended with coal. This study investigates the effects of biomass structure, preparation method, and pyrolysis temperature on biochar properties derived from banagrass and wheat straw (grass-type) and acacia (hardwood). Five preparation methods were evaluated at pyrolysis temperatures between 400°C and 800°C. Raw and pelletised acacia chars showed high densities (665-950.8 kg /m³ at 800°C) and high surface areas (up to 338 m²/g at 800°C), reflecting the preservation of their lignified cellular structure during pyrolysis. In contrast, pelletised banagrass chars showed lower surface areas (as low as 2.38 m²/g) while maintaining high densities (up to 630 kg/m³ at 800°C). Pelletisation increased banagrass char density (~228 to ~596 kg/m³) and yield (~28 to ~32 daf wt%), while washing reduced banagrass ash content from 14-11 wt% to 5-11 wt%. The results demonstrate that low surface area, high density chars can be produced from herbaceous biomass through crushing and pelletisation, whereas the woody biomass tends to preserve its structural cohesion and pore network during pyrolysis, leading to chars with high surface areas even after pelletisation.