What is methane? Greenhouse gases

Methane, a compound with the chemical formula CH4, a common fuel source, is the main component of natural gas. As it is relatively abundant on Earth it is an attractive fuel. However, capturing and storing it poses challenges because of its gaseous state under normal conditions for temperature and pressure.

It is also a powerful greenhouse gas – it is one of the gases that drives climate change (global warming). Environmentalists are concerned about methane because if it is allowed to get into the air from leaky natural gas pipes and agricultural livestock it absorbs the Sun’s heat and warms up the atmosphere.

Methane CH4 gasMethane – or CH4 – consists of one atom of carbon and four atoms of hydrogen. (Image: adapted from uoregon.edu)

Methane vs. carbon dioxide emissions

People often ask whether methane is as important as carbon dioxide regarding greenhouse gas emissions.

Methane does not linger as long in the air as carbon dioxide (CO2) does. However, it absorbs heat much more effectively than CO2, so initially, it is a major greenhouse gas.

For the first twenty years after it is released, methane is between 25 and eighty-four times more potent than CO2 (figures vary depending on which study you look at).

So, although over the long-term CO2 matters more, methane emissions, because the gas is so potent over the short term, need to be controlled too.

Sources of MethaneThe largest source of methane from human activity after agriculture is the oil & gas industry. According to climate-change-knowledge.org: “What makes food production such a large source is that livestock is the big source of methane emissions and most deforestation is clearing land for livestock and industrial scale food production.” (Image: adapted from climate-change-knowledge.org)

Where do methane emissions come from?

According to the United States Environmental Protection Agency (EPA), more than sixty percent of total CH4 (methane) emissions come from human activities. It is emitted from agriculture, industry, and waste management activities.

Industry: the largest source of emissions from industry in the developed nations is natural gas and petroleum systems. Some methane is emitted to the atmosphere when natural gas is produced (taken out of the ground), processed, stored, transmitted and distributed.

Agriculture: domestic livestock including cattle, sheep, goats, buffalo and camels produce large amounts of methane as part of their normal digestive processes, i.e. burps and farts.

Methane is also produced when animals’ manure is managed or stored in holding tanks or lagoons. The agriculture sector is the main source of CH4 emissions globally. A study found that dosing cattle with antibiotics increases the release of methane from cow dung.

Waste from Businesses and Homes: as waste decomposes in landfills methane is generated. The same occurs in the treatment of wastewater. In the US, landfills are the third largest source of methane emissions.

US Methane EmissionsThe United States has seen methane emissions decline by 6% over a 24-year period. (Image: epa.org)

Methane also comes from several natural sources. The largest natural source are wetlands, which emit CH4 from microorganisms (bacteria) that decompose organic materials in the absence of oxygen. Smaller sources include wildfires, volcanoes, sediments, oceans and termites.

Many countries are reducing methane emissions. In the US they declined by 6% between 1990 and 2014. During that 24-year period emissions grew from sources linked to agricultural activities, but fell considerably from sources related to the oil & gas industry.

Video – Methane: The other important greenhouse gas

This video, published by the Environmental Defense Fund, talks about methane gas and what we can do to reduce emissions.