Quantifying global warming potential of alternative biorefinery systems for producing fuels from Chinese food waste

Biorefining of Chinese food waste (FW) into transport fuels was assessed in terms of amount of fuel produced and over all Global Warming Potential (GWP) for six different scenarios including biogas, biomethane, bioethanol and biodiesel in different combinations. The life-cycle perspective used included GWP aspects of material and energy use, emissions during biorefining and management of residues, as well as substitution of fossil fuels according to the energy content of biofuels. All of the six FW biorefineries revealed savings in GWP ranging from -19 to -138 kg CO₂ eqv. per ton of wet FW. Compared to the reference scenario with only anaerobic digestion (S0), introducing biogas upgrading to biomethane (S1) improved the GWP by 37%; while producing bioethanol prior to anaerobic digestion (S2) decreased the savings in GWP. Introducing biodiesel prior to anaerobic digestion (S3) revealed around 60% improvement in GWP, while combining biodiesel and biomethane gave the largest improvement in GWP, 84% compared to the reference scenario, and the most fuels (around 2400 MJ in terms of 30 kg biodiesel and 35 kg biomethane per ton of wet FW). A sensitivity analysis revealed that the electricity production based on the biogas was an important parameter and appears in all refineries, while the results was less sensitive to the production of biodiesel and biomethane. The residue management contributed also to the GWP, but did not vary much among the biorefinery scenarios.