Integrated Valorization of Bamboo waste via Integrated Torrefaction and Anaerobic Digestion: Energy Recovery and Techno-Economic Assessment

This study investigates an integrated valorization pathway for bamboo waste by combining torrefaction and anaerobic digestion to recover energy from both solid and liquid process streams within a circular economy framework. Bamboo’s high lignin content (24-27 wt%), low ash content (<3 wt%), and favorable volatile composition enable enhanced thermochemical upgrading and subsequent biochemical energy recovery. Torrefaction at 290 °C for 60 min increased the bio-coal higher heating value from 17.6 0.4 MJ/kg to 25.4 1.5 MJ/kg with ~66% volatile matter reduction and lignin enrichment. The aqueous condensate containing biodegradable organic acids with low inhibitor concentrations, achieved a biomethane potential of 493 1.7 mL-CH4/g-VS during anaerobic digestion. The integrated process delivers a net energy recovery of approximately 21 GJ/ton, exceeding that of rice husk and rice straw under identical conditions. A techno-economic assessment of a 50,000 t/y integrated torrefaction-anaerobic digestion pilot plant facility in India indicated economic feasibility with an internal rate of return of 15.8% and a payback period of 6.5 years. By enabling near-complete utilization of bamboo residues, the proposed pathway supports sustainable resource utilization, circular economy principles, and UN Sustainable Development Goals 7, 12, and 13.