Conference on Environmental Science and Technology

This study presents a waste-to-energy strategy that integrates CO₂ capture and biological methanation, contributing to renewable energy production from waste streams. The system combines zero-valent iron (ZVI) and anaerobic granular sludge (AnGrSl) to biologically convert CO₂ to CH₄ under mild conditions. Sodium bicarbonate (NaHCO₃), formed via CO₂ absorption in NaOH, enhances both buffering and soluble carbon availability, facilitating microbial uptake and methanogenesis. Two ZVI dosing strategies were tested: a single 50 g/L dose and a staggered 10 g/L × 4 addition. Results showed that the one-time high-dose maintained consistent CH₄ yields, while staggered additions showed initial gains but limited long-term performance. The process supports a closed-loop cycle by regenerating NaHCO₃ through re-flushing the NaOH solution with CO₂, making it a promising example of circular bioenergy production. This system exemplifies environmental biotechnology by enhancing methane yields through microbial and chemical synergy. Its low-energy demand and resource recovery potential make it well-suited for decentralized applications in wastewater and sludge treatment. The process aligns with circular economy principles and climate action by converting captured CO₂ into renewable methane, reducing emissions while producing valuable energy.