Methanismen

Methanismen refers to the set of processes that govern methane (CH4) in the Earth system, including its production, consumption, transport, and fate. Methane is a potent greenhouse gas and a key component of the global carbon cycle. Its atmospheric concentration has risen since preindustrial times, contributing to climate forcing alongside carbon dioxide and nitrous oxide.

Natural sources of methane arise from anaerobic environments where microorganisms produce methane as a metabolic byproduct. Major natural sources include wetlands, termites, and the anaerobic sediments of lakes, rivers, and oceans. Geological methane can also originate from natural seeps and some fossil fuel reservoirs. Human activities add substantial methane emissions, notably from enteric fermentation in ruminant livestock, rice paddies, fossil fuel extraction and distribution (leaks from natural gas and oil systems), landfills, and manure management.

Methane production is largely carried out by methanogenic archaea in anaerobic conditions, a process known as methanogenesis. Methanotrophs, methane-oxidizing bacteria and related organisms, consume methane in aerobic or microaerophilic environments, serving as a biological sink. In the atmosphere, methane reacts with hydroxyl radicals (OH), leading to its eventual removal over a timescale of about a decade to a dozen years. Methane’s global warming potential is higher than carbon dioxide over short timescales, making it a focus of climate mitigation efforts. Methan clathrates in marine and permafrost settings represent potential, long-term methane reservoirs that could release under warming conditions.

Mitigation measures focus on reducing leaks in fossil fuel systems, improving manure management and rice cultivation practices, and capturing landfill gas, alongside strategies that enhance methane oxidation in soils.