What are the Main Sources of Methane Emissions?
Methane is known as a greenhouse gas. This means that rather than reflecting and redirecting solar radiation within the atmosphere, it traps it, contributing to a warming effect that has the potential to cause climate change and instability. While carbon dioxide is the most commonly discussed greenhouse gas due to the sheer volumes created, methane is actually 25 times more potent than carbon dioxide when it comes to trapping heat close to the Earth’s surface.
Sources of atmospheric methane
Methane is a naturally occurring gas, and it has a low level background presence in the atmosphere. At these atmospheric concentrations it is completely non toxic and doesn’t cause environmental issues. Modern industrial and commercial practices, as well as climate change, have, however, caused a sharp increase in the amount of methane being released into the atmosphere throughout the 20th Century and into the 21st.
Natural sources of methane are numerous, and many do not pose an environmental risk while they remain undisturbed. One example of a natural source of methane is the gas that is locked away within permafrost. This methane will remain in the ground for as long as ground temperatures remain below freezing, but climate change is increasing the rate at which this permafrost is melting. As it melts it releases the once trapped methane, becoming a source of atmospheric methane emissions.
Where it is practical, methane can be extracted from these natural sources and used as a combustible fuel. Around 40% of industrial operations and 80% of households use natural gas as their main source of heating and electricity. It burns much more cleanly than other fossil fuels such as coal and oil, and it is easy to transport, making it the preferred option for many.
Methane is constantly being produced through natural bacterial activity. Decomposition of waste materials in landfills is a major source of methane emissions, and as global populations increase, so does the amount of waste we produce. This poses a significant problem when considering methane’s role as a potent greenhouse gas. Gas capturing systems which syphon off the methane produced by decomposing waste can redirect this resource to provide heating and generate electricity, making it a highly effective way to reduce emissions from this source.
One of the largest and most challenging sources of methane emissions is agriculture - livestock farming in particular. Living beings create methane in their guts as they digest food, and in ruminants such as cattle, huge amounts of methane can be expelled every day. Growing populations mean a higher demand for meat and dairy produce, and this leads to agriculture being responsible for an increasing volume of methane emissions every year.
Due to the stresses it places on land and water use, as well as the emissions it generates, livestock farming is one of the leading contributors to environmental damage. In the UK there is a growing trend for sustainably produced foods, many of which contain little or no animal-derived ingredients. Reducing consumption of meat and dairy produce, as well as introducing mitigating measures such as tree planting initiatives can help to reduce the environmental costs of agriculture.
The use of biofuels produces around 12 million tonnes of methane every year. Biofuels are any kind of biomass which is burned in order to produce energy, and when the materials are incompletely combusted, methane is released. While the vast majority of biofuels are used domestically for cooking, heating, and lighting, low tech manufacturing also makes use of them. Brick and tile manufacturers, traditional food producers and transportation are other users of biofuels which release methane.
What are methane sinks
Methane sinks are the exact opposite of methane sources. The most significant methane sink is the troposphere - the lower level of the atmosphere which is adjacent to the surface. Unfortunately, if methane is allowed to escape into this sink, it traps solar radiation and contributes to rising global temperatures. Over time, atmospheric methane reacts with radicals to create carbon dioxide and water vapour, both of which are also considered greenhouse gases due to their ability to trap heat. Soil is also a methane sink, as are large bodies of water which allow the dissipation of gases in either direction.