Anaerobic methane oxidation: occurrence and ecology

Area of Science:

• Environmental microbiology
• Biogeochemical cycles
• Anaerobic digestion

Background:

• Methane (CH4) is a potent greenhouse gas.
• Anaerobic oxidation of methane (AOM) is a key process in mitigating methane release.
• Understanding AOM in diverse environments like sediments and sewage sludge is crucial.

Purpose of the Study:

• To investigate the factors influencing anaerobic methane oxidation in sediments and sewage sludge.
• To quantify the rates of AOM and methane production under various conditions.
• To explore the potential for enhancing AOM in engineered systems.

Main Methods:

• Incubation of anoxic sediments and digested sewage sludge.
• Measurement of methane production and oxidation rates.
• Testing the effects of oxygen, 2-bromoethanesulfonic acid, sulfate, iron, manganese dioxide, and methane partial pressure.

Main Results:

• AOM occurred simultaneously with methane production in anaerobic environments.
• The process was temperature-dependent (optimum 25–37°C) and inhibited by oxygen.
• Sulfate and 2-bromoethanesulfonic acid affected both methane formation and oxidation, while iron and manganese dioxide stimulated oxidation.
• AOM rates increased significantly with ferrous sulfate and high methane partial pressures, reaching up to 90% of methane production in sludge.

Conclusions:

• Microbial communities in anoxic sediments and sewage sludge actively mediate methane oxidation.
• Environmental factors significantly modulate the balance between methane production and oxidation.
• Optimizing conditions, such as adding ferrous sulfate and increasing methane pressure, can enhance AOM efficiency in sludge treatment.