A local food resource circulation model combining anaerobic digestion and rice cultivation in Japan: impacts on climate change and nutrient use

Abstract To address the environmental burdens caused by greenhouse gas emissions and heavy nitrogen use from agri-food systems, anaerobic digestion of food waste has been proposed as an alternative source of fertilizer and waste management strategy. This study estimated greenhouse gas emissions and nitrogen flows in four scenarios (S0–S3) to evaluate an integrated resource circulation system combining anaerobic digestion and digestate application to rice paddies. Greenhouse gas emissions were mitigated by 6–8% while crop yields were maintained by −0.52–+47 kg rice/ha in alternative scenarios through waste management changes, owing to source separation and increased energy efficiency. Anaerobic digestion process conserved 53% of the nitrogen (0.64 t N/y) embedded in food waste. However, when digestate was applied alone, 23.4 kg N/(ha·y) was estimated to be exhausted from the rice paddy system due to ammonia volatilization from the digestate. Nevertheless, under mixed fertilization, a 0.71 kg N/(ha·y) increase or 9.8 kg N/(ha·y) decrease was observed depending on the scenario. Therefore, the integrated resource circulation system in this study shows a stable yield, is effective against climate change on a local scale, and may guide circular society planning.