Comparative carbon accounting of multi-stream food waste management: insights from a megacity case study

Abstract

Background: Food waste (FW) management can contribute to emission reduction when low-carbon pathways such as anaerobic digestion or composting are adopted instead of landfilling. Methods: This study quantified emissions across four treatment modules for five household (HHFW), one kitchen (KW), and two fruit and vegetable (FVW) waste sites. Results: Baseline operations emitted 66,086.2 t CO2, with HHFW and KW contributing 69.9% and 22.9%, respectively. Pollutant treatment dominated (93.4%), mainly from residue and sewage management. FW intensities ranged from 54.34–162.13 kg CO2/t-HHFW, 122.1 kg CO2/t-KW, and 59.2–84.3 kg CO2/t-FVW. Resource recovery presented both offsets and burdens: grease recycling avoided up to −10.87 kg CO2/t-KW, while composting added 74.7 kg CO2/t-FVW. Compared to landfill disposal, the project reduced carbon intensity 7–16 fold, exceeding 800 kg CO2/t at top-performing sites (V1 and H4). Relative to incineration, reductions were smaller and site-dependent, though most treatment streams still achieved net savings. Scenario optimization highlighted the transformative potential of advanced interventions: a Moderate pathway integrating anaerobic acid production (AOP) cut emissions 1.6–1.7 fold, while optimistic pathways, anaerobic digestion (AD) and insect bioconversion (BSFL), achieved net-negative emissions of −308.4 kg CO2/t for HHFW and −117.41 kg CO2/t for FVW, respectively. Conclusion: These findings demonstrate that source separation, targeted resource recovery, and coupling bioenergy with value-added products can convert FW management from a carbon source to a net sink, supporting deep decarbonization strategies.