Quantification of - And determining factors affecting - Methane emissions from composting plants

Area of Science:

• Environmental Science
• Climate Change Research
• Waste Management Studies

Background:

• Methane is a potent greenhouse gas, and accurate data on emissions from the waste management sector are vital for national greenhouse gas budgets and climate mitigation.
• Quantifying methane emissions from composting facilities is essential for understanding their contribution to climate change.

Purpose of the Study:

• To quantify total methane emissions from five commercial composting plants in Denmark.
• To characterize temporal and operational patterns of methane emissions.
• To identify factors influencing methane emission rates and emission factors.

Main Methods:

• Methane emissions were measured over a one-year period using the tracer gas dispersion method.
• Emission rates were quantified in kg CH4 h-1.
• Emission factors were calculated in kg CH4 Mg-1 of treated feedstock.

Main Results:

• Methane emission rates varied from 8.0 ± 0.1 to 42.5 ± 1.5 kg CH4 h-1.
• Emission factors were highest for combined anaerobic digestion and open windrow plants (4.51-5.21 kg CH4 Mg-1), followed by open windrow plants co-composting garden/park waste, sewage sludge, and straw (3.49-3.76 kg CH4 Mg-1).
• Lowest emission factors were observed at open windrow plants treating only garden/park waste (1.56-3.24 kg CH4 Mg-1). Emissions were higher during working hours and in spring/summer compared to autumn/winter.

Conclusions:

• Methane emissions from composting plants are significantly influenced by feedstock type, composting technology, operational patterns, and season.
• The study provides critical data for refining national methane budgets and developing targeted climate mitigation strategies within the waste management sector.
• Seasonal variations and operational factors, such as time of day, play a significant role in methane emission levels.