CO2 Capture and Conversion in Anaerobic Digestion of Organic Wastes for Enhanced Methane production: Demonstration Project in Bologna WWTP

Currently the limiting of greenhouse gases emissions is the focus of international negotiations. As a consequence, innovative technologies and alternatives to geological and deep-ocean long-term CO2 sequestration are necessary to reach the greenhouse gas reduction targets. The present work aimed at combining CO2 capture with its use in anaerobic digestion. CO2 was captured from the local sludge incinerator flue gas and recovered as a concentrated stream. A Two-Phase Anaerobic Digestion (TPAD) process was successfully established and maintained, leading to specific microbial adaptation and selection and to a sharp phase separation. CO2 acted as booster and substrate in the acidogenesis phase of this TPAD context. By enhancing the hydrolytic and fermentative steps, CO2 injection leads to efficient biomass degradation and increase in VFA production. Moreover, CO2 intake in the acid phase has a positive impact on the overall GHG balance. The overall result is that the integrated approach of CO2 capture from combustion gas and its use in anaerobic digestion has improved the economic and environmental features of biomethane production. In constant association with lab-scale and pilot trials, the project is focused on demonstration activities directly on the operative sites of industrial partners.