Greenhouse gas emissions from regional food waste circulation schemes utilizing anaerobic digestion for 2030-2050: a...

Agri-food systems are major greenhouse gas (GHG) emitters, requiring integrated waste and resource management. Anaerobic digestion (AD) offers a multifunctional solution by treating waste, generating energy, and producing fertilizers. However, few studies have examined region-wide systems incorporating multiple AD reactors at varying capacities. Here, we assessed GHG emissions, nitrogen circularity, crop yield, and costs under alternative scenarios for Kyoto Prefecture (2030-2050), integrating AD between waste-to-energy and rice cultivation processes. Using Tier 2 estimations with regional parameters, we designed scenarios to represent simple fertilizer substitution, yield maximization, and GHG minimization. Compared with the baseline, the alternative scheme reduced GHG emissions by 12-21%, retaining up to 89% of nitrogen, and lowering costs by 13-16%, while achieving sustainable crop yields with balanced performances. The findings highlight the potential of AD as a practical policy pathway to reduce emissions and costs, while maintaining crop yields, supporting transition to greener agri-food systems.