Influence of organic composition of biomass waste on biochar yield, calorific value, and specific surface area

Abstract

The complexity of biomass waste makes it difficult to study the effects of individual constituents on the yield and properties of the pyrolysis product (biochar). In this work, rice husk, bamboo sawdust, coffee residue, and tea leaf were selected for biochar production by a two-step pyrolysis process. To assess the effects of organic composition, ash-free values were applied for comparison. The results showed that different organic compositions of biomass waste had distinct influences on the biochar yield, calorific value, and specific surface area. Extractives contributed little to the biochar yield and calorific value, but their distribution states in the biomass waste affected the specific surface area of the biochar. High lignin content favored a high biochar yield and calorific value, but it did not have a substantial influence on the specific surface area of the biochar. Cellulose was the main factor that determined the specific surface area of the biochar. These results suggest that a desired biochar can be obtained by pyrolysis of a suitable biomass waste. Biomass waste with higher lignin and lower extractive contents is recommended for biochar with higher yield or higher calorific value, while for the application as the absorbent, pyrolysis of biomass waste with a high cellulose content is preferred.