Do compost-based landfill biocover systems designed for methane oxidation emit nitrous oxide in significant amounts?

Area of Science:

• Environmental Science
• Microbiology
• Climate Change Mitigation

Background:

• Landfills are major sources of methane (CH4), a potent greenhouse gas contributing to climate change.
• Compost-based biocover systems can oxidize CH4, mitigating emissions from landfills.
• Composting processes can generate nitrous oxide (N2O), another strong greenhouse gas, raising concerns about biocover effectiveness.

Purpose of the Study:

• To evaluate the climate benefit of compost-based biocover systems by comparing CH4 oxidation to N2O generation.
• To determine if N2O emissions from biocover systems compromise the CH4 mitigation efficiency.

Main Methods:

• Field studies were conducted at three full-scale biocover systems at Danish landfills.
• Measurements included surface screenings, surface flux measurements, and gas composition analysis.
• CH4 removed and N2O generated were quantified and compared in CO2-equivalent units.

Main Results:

• Both individual location assessments and overall biocover performance analyses indicated no negative impact of N2O emissions on CH4 mitigation.
• The ratio of N2O emitted to CH4 oxidized (in kg CO2-eq per day) was consistently low, less than 2.3% and often below 1%.

Conclusions:

• Compost-based biocover systems are effective for mitigating landfill CH4 emissions.
• The generation of N2O during the composting process does not undermine the climate benefits achieved through CH4 oxidation in these systems.