Biochar Addition for Enhanced Biomethane Production from Food Waste: Process Performance and Techno Economic Assessment

Anaerobic digestion (AD) is a sustainable waste-to-energy technology that contributes to the circular bioeconomy and zero-waste goals. However, its efficiency is often constrained by process instabilities such as volatile fatty acid accumulation, ammonia inhibition, and pH fluctuations. Biochar intensifies the biogas production rate and methane content from AD by enhancing buffering capacity, adsorbing inhibitors, promoting biofilm formation, and facilitating direct interspecies electron transfer. Objective of this study is to evaluate the effect of sugarcane bagasse-derived biochar on improving the stability, kinetics, and techno-economics of AD of food waste. In this study, sugarcane bagasse-derived biochar produced through pyrolysis has been applied to the AD of food waste. Based on modified-Gompertz and first-order kinetics determined through lab-scale experimental results, techno-economic analysis has been performed for 10,000 metric tonnes/year. Compared to the control, 29% higher cumulative methane yield of 352 L/kg VS is obtained from biocharassisted AD. Methane concentration is also improved from 58% to 65%, while the biodegradability index increases to 81.03% against 62.65% for control. Kinetic modelling confirms enhanced process performance with a shorter lag phase and higher hydrolysis rate. Economic analysis indicates that biocharassisted AD generates higher annual revenue ($184,695 vs. $156,687) compared to the control. Higher investment cost for the digestate storage system is responsible for negative net present values (NPVs) in both scenarios and needs further analysis. The novelty of this work lies in the combined experimental– kinetic– economic assessment of biochar-assisted AD. This study also suggests that utilization of biochar within the AD plant ensures carbon circularity and improves profitability through the production of energyrich by-products like bio-oil and syngas through digestate-valorization. The outcomes of the research support policies to achieve sustainable deployment in line with the Sustainable Development Goals (SDGs) through the production of valuable additives and by-products from AD waste, i. e., digestate.