Economic and environmental viability of biofuel production from organic wastes: A pathway towards competitive carbon neutrality

Production of renewable C1 transport biofuels (such as biomethane and biomethanol) through the integration of anaerobic digestion (AD) with carbon capture, utilization and sequestration technologies may offer a solution to reduce greenhouse gas (GHG) emissions. This paper presented a detailed techno-economic and environmental assessment of four cases for biomethane or biomethanol production by incorporating AD, CO2 utilization via biomethanation (CU), solid digestate pyrolysis (Py) and methanol synthesis (MeOH). The results reflected the current state of technologies and potential future scenarios within a mature market. Under optimistic scenarios (scaled-up systems and reduced hydrogen price of 1 €/kg), the minimum potential GHG abatement cost for the AD-Py-CU case was −111.1 €/t CO2-eq when biomethane was sold at 1.03 €/Nm3 (a contract gas price in 2022), while the abatement cost rose to −58.2 €/t CO2-eq when H2 was purchased at 3.40 €/kg. When methanol was sold at 425 €/t (global weighted average value), the marginal abatement cost for the AD-Py-CU-MeOH (with H2 at 1.0 €/kg) case was 136.5 €/t CO2-eq, which is higher than current carbon credits at 33.5 €/t CO2. This study suggests that biomethane produced by incorporating AD, CO2 biomethanation and pyrolysis technologies may be economically and environmentally competitive over natural gas. [Display omitted] •Minimum selling prices of 0.50 €/Nm3 CH4 were modelled with H2 purchase of 1.0 €/kg.•Minimum selling prices of 661 €/t MeOH were modelled in the optimistic scenario.•The minimum marginal abatement cost for the CH4 system was −114 €/t CO2.•With H2 purchase of 3.40 €/kg the marginal abatement cost of CH4 rose to –62 €/t CO2.•The marginal abatement cost of biomethanol is higher than proposed carbon credits.