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Natural causes of air pollution: Methane Emissions

Methane is an odorless, colorless greenhouse gas with the chemical formula of CH4. It is mainly used as a component of natural gas.

Natural sources create 36% of global methane emissions, long before humans existed there has been methane emissions into the atmosphere. However, methane expulsion is mainly man-made, in activities such as landfills and livestock farming. As a fact, it may seem interesting to know that daily methane emissions from cows (through belching and flatulence) and from cars are pretty similar.

It can lead to severe asphyxiation if someone is highly exposed to methane gas in the air. Building construction must take into account this factor, since the presence of methane in the airways of the building can lead to dire consequences.

Methane levels have more than doubled over the last 150 years. This is because of human activities like fossil fuel use and intensive farming. Before the Industrial Revolution, natural sinks kept methane levels in a safe range.

Methane is twenty times more powerful greenhouse gas than carbon dioxide when released into the ozone layer. It is also highly inflammable when it combines with other elements in the air and it massively contributes to global warming. Bellow you will find the main natural sources of methane.


A wetland is a distinct ecosystem that is inundated by water, either permanently or seasonally, where oxygen-free processes prevail. The primary factor that distinguishes wetlands from other landforms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play numerous roles in the environment, principally water purification, flood control, carbon sink and shoreline stability.

Wetlands are the largest natural source of methane producing 78% of natural methane emissions. Microbes need environments with no oxygen and abundant organic matter, thus wetlands are perfect for them to be born.

Wetlands are estimated create 147 million tonnes of methane each year. Part of these emissions are absorbed by methane-consuming microbes. However, the majority of these emissions are released into the atmosphere and the ozone layer.


Termites are eusocial insects that you probably know due to they can break into your house and destroy all the wood structures. However, do you know these little insects produce large amounts of methane?

Termites eat cellulose, but rely on micro-organisms in their gut to digest it. During the normal digestion process of a termite, methane gets produced.

Photo by Jared Belson

At this point you are probably thinking: no way, this tiny insect cannot produce amount of methane I should worry about. You are right if you have just one termite, but if you take into account the total population of termites numbers add up.

Termites produce 12% of natural methane emissions, being a total of 23 million tonnes of methane per year. Surprising right? If you have termite infestation at home, be aware that you and your family can be highly exposed to methane.


Everyone knows what an ocean is, but almost nobody knows these are a major natural source of methane. In fact, oceans don’t produce itself methane, but these are the perfect environment for microbes to live and emit this type of pollution gas.

According to scientists from the University of Illinois and Institute for Genomic Biology, the ocean-based microbe Nitrosopumilus maritimus produces methane through a complex biochemical process the researchers referred to as “weird chemistry.”

Oceanic methane emissions often gets produced in deeper sediment layers of productive coastal areas. The methane created by these microbes mixes with the surrounding water. After some time in the water, it gets emitted to the atmosphere from the ocean surface.

At the end oceanic methane emissions are 10% of natural methane emissions and 19 million tonnes of methane per year.

Arctic’s methane issue

It is estimated that there are billions of cubic metres of natural methane gas trapped underneath huge areas of permafrost in Siberia, and under the frozen wastes of the Arctic. When methane is enclosed in frozen water it is called methane hydrate.

The Arctic has warmed more quickly than any other area of the planet. As the ice has melted, naturally formed methane gas, which would otherwise be trapped under the ice, is bubbling to the surface.

Currently, there are thousands of sites in the Arctic where methane gas is being released into the atmosphere and it could have serious ramifications for global warming.

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