Thermophilic methane production and oxidation in compost

Area of Science:

• Microbiology
• Environmental Science
• Biogeochemistry

Background:

• Methane cycling in compost heaps remains under-investigated.
• Composting processes can produce significant methane emissions.
• Understanding microbial methane oxidation is crucial for mitigating greenhouse gases.

Purpose of the Study:

• To investigate methane oxidation in compost of varying ages.
• To quantify methane oxidation rates and identify responsible microorganisms.
• To assess the potential of compost microbial communities to reduce methane emissions.

Main Methods:

• Incubation of compost material (4, 8, and >10 weeks old) to measure methane oxidation.
• Analysis of methane concentration profiles within compost heaps.
• Isolation and characterization of thermophilic methanotrophic bacteria.
• 16S rRNA gene sequencing for microbial identification.
• Determination of optimal temperature for methane oxidation.

Main Results:

• Thermophilic methane oxidation was observed in compost, with rates between 2.6 and 4.1 micromol CH4(gdw)(-1)h(-1).
• Methanotrophic bacteria oxidized 46-98% of produced methane, with populations estimated at 10(9) cells (gdw)(-1).
• A thermophilic methanotroph, strain KTM-1 (genus Methylocaldum), was isolated and showed optimal activity at 45-55°C, matching compost temperatures.

Conclusions:

• Compost heaps harbor active thermophilic methanotrophic communities capable of significant methane oxidation.
• The isolated Methylocaldum strain is well-adapted to compost conditions and contributes to methane mitigation.
• Compost microbial activity offers a promising biological pathway for reducing methane emissions from organic waste.