Enhanced in-situ biomethanation of food waste by sequential inoculum acclimation: Energy efficiency and carbon savings analysis

The increasing rate of food waste (FW) generation globally, makes it an attractive resource for renewable energy through anaerobic digestion (AD). biogas recovered from AD can be upgraded by the methanation internally produced carbon dioxide, CO2 with externally sourced hydrogen gas, H2 (biomethanation). In this work, was added to reactors processing FW in three successive phases, digestate preceding phases recycled succession addition fresh inoculum enhance acclimation. concentration increased succeeding phases: 5%, 10% and 15% reactor headspace Phase 1 (EH1), 2 (EH2) 3 (EH3), respectively. utilisation biomethane yields as acclimation progressed EH1 EH3. Biomethane yield controls: EH1_Control, EH2_Control EH3_Control were 417.6, 435.4 453.3 NmL-CH4/gVSadded accounting 64.8, 73.9 77.8% And test EH1_Test, EH2_Test EH3_Test 468.3, 483.6, 499.0 NmL-CH4/gVSadded, 77.2, 78.1 81.0% A progressive in-situ biomethanation could lead production that meets higher fuel standards gas-to-grid (GtG) injections vehicle – i.e. >95% CH4. This would increase savings compared conventional upgrade methods. For example, GtG 7.3 MWh/tFW 1343 kg-CO2e savings, which is better than physicochemical options (i.e., 4.6–4.8 846–883 savings).