Greenhouse gas emissions from green waste composting windrow

Area of Science:

• Environmental Science
• Climate Change Research
• Waste Management

Background:

• Composting green waste generates greenhouse gases (GHG) contributing to climate change.
• Understanding seasonal variations in GHG fluxes from compost windrows is crucial for mitigation strategies.

Purpose of the Study:

• To monitor and quantify seasonal GHG emissions (CH4 and N2O) from field-scale green waste compost windrows.
• To identify key environmental factors influencing GHG fluxes.
• To estimate the contribution of green waste composting to statewide GHG emissions.

Main Methods:

• Field-scale monitoring of three green waste compost windrows over a one-year period.
• Measurement of seasonal greenhouse gas fluxes (CH4 and N2O).
• Analysis of environmental factors including oxygen concentration and moisture content.

Main Results:

• Wettest/coolest conditions yielded highest CH4 emissions (254±76gCday⁻¹ DW Mg⁻¹).
• Driest/hottest conditions resulted in highest N2O emissions (342±41mgNday⁻¹ DW Mg⁻¹).
• Oxygen and moisture content consistently predicted N2O and CH4 emissions.
• CH4 contributed more to global warming potential (GWP) than N2O.

Conclusions:

• Methane (CH4) is a significant contributor to the global warming potential of green waste composting.
• Moisture and oxygen control in compost windrows are key to mitigating GHG emissions.
• Green waste composting accounts for an estimated 789,000 Mg CO2 eq. annually in California.