Assessing the climate change mitigation potential from food waste composting

Area of Science:

• Environmental Science
• Waste Management
• Climate Change Research

Background:

• Food waste in landfills is a major source of greenhouse gases.
• Limited data exists on commercial-scale composting emissions and their drivers.

Purpose of the Study:

• To quantify methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) emissions from commercial-scale food waste composting.
• To identify biogeochemical drivers influencing these emissions.
• To compare composting emissions with landfilling and assess mitigation potential.

Main Methods:

• Utilized a non-invasive micrometeorological mass balance approach for commercial-scale windrow piles.
• Employed continuous sensors for oxygen (O2) and temperature.
• Conducted intensive sampling for biogeochemical processes.

Main Results:

• Methane emission factors ranged from 6.6 to 8.8 kg CH4-C/Mg wet food waste, influenced by redox and watering.
• Nitrous oxide emissions were low (0.01 kg N2O-N/Mg wet food waste).
• Overall composting emissions were 38-84% lower than landfilling, with potential savings of 1.4 MMT CO2e for California by 2025.

Conclusions:

• Food waste composting is an effective strategy for greenhouse gas emissions reduction.
• Optimizing turning frequency and reducing watering can further minimize composting emissions.
• Composting offers a viable alternative to landfilling for climate change mitigation.