Methodology for identifying cost-effective food waste-resource circulatory strategies toward zero-carbon cities: Linking valorization technologies with byproduct reutilization pathways

Many cities seek to understand the intersection between food waste (FW) resource circularity and urban zero-carbon goals. However, currently available FW analytic tools focus only on FW valorization technologies in the current energy system, and do not analyze various byproducts reutilization pathways towards urban decarbonization. Our paper contributes by combing: a) Life cycle assessment of six advanced carbon valorization technologies in a future zero-carbon grid, with: b) Cost-effectiveness analysis of alternative byproducts reutilization pathways that contribute to urban decarbonization, including heating transitions through biogas reutilization in residential furnaces, neighborhood-scale district energy systems (DES), and regional-scale power generation to support heat pumps, as well as transportation fuel transitions and farm-application of digestate and biochar. Among six advanced technologies (beyond composting), anaerobic digestion (AD) with and without biochar amendment delivered maximum carbon mitigation (∼230–270 kg CO₂-eq/tonne FW), while AD-only has the most energy savings (∼24 therms/tonne FW). Among reutilization pathways, direct use of biogas in existing neighborhood DES yielded the lowest decarbonization cost-effectiveness (-$1000/tonne CO₂-eq), much lower and cost saving than the next option of biomethane as transportation fuel ($40/tonne CO₂-eq). The methodology, applied to a cold climate city of St Paul, MN, can be generalized elsewhere and to different resources/byproducts, quantifying for the first time cost-effectiveness of the combined valorization-reutilization resource circularity cycle toward urban decarbonization.