Where Does Methane Come From? - Nature

When it comes to the topic of global warming, carbon dioxide (CO2) might steal most of the limelight… but methane is another serious concern for climate scientists. Although methane is around 200 times less prevalent in our atmosphere than CO2 is, and it persists in the environment for a far shorter time, it’s much more effective at retaining heat during its lifespan.

For example, methane is 28 times more potent as a greenhouse gas than CO2 over a century timescale, and a whopping 80 times more powerful over a 20-year period. What’s more, anthropogenic activity has meant that concentrations of methane have more than doubled since the beginning of the Industrial Revolution and roughly a fifth of planetary warming is thought to be caused by the gas.

It’s for this reason that methane monitoring is so important in the industrial world and among the scientific community. Nonetheless, not all emissions of methane are manmade. As a naturally occurring element in our environment, around 40% of atmospheric methane is contributed by sources that were there prior to human intervention. Here’s a quick rundown of some of the most prolific:

• Wetlands. The majority of natural methane emissions arise from bogs, marshes, swamps and other forms of wetlands. Although most microbes function in the same way as mammals (breathing in oxygen and exhaling carbon dioxide), there are many which live in oxygen-deprived locations. These organisms have adapted to their environment and breathe out methane into their soggy surroundings instead. Over time, this methane leaches out into the atmosphere. Such sources are responsible for around three-quarters of natural methane emissions and just under a third of all atmospheric methane.
• Termites. These tiny timber-eating ants gobble up the cellulose contained in plant fibres, which is then digested by micro-organisms living inside their guts. Methane is produced as a natural side-effect of this digestion process. Although each individual termite produces a seemingly negligible amount of methane, it should be remembered that this is a constant process, since termites never sleep. What’s more, they’re estimated to comprise roughly 10% of all animal biomass on the Earth. Cumulatively, they release some 23 million tonnes of methane every single year, which is equivalent to around 12% of natural emissions.
• Oceans. Oceans and seas are another chief source of methane emissions since they cover such a large percentage of the planet and gather methane from a variety of sources. The aforementioned microbes which live in wetlands also reside in seas and oceans, while they can absorb methane leaking out of natural oil and gas deposits, too. As the permafrost in the Arctic thaws each year, some methane escapes and accumulates in sediments at the bottom of the ocean floor. While it may remain in this state for many years, it can eventually escape into the atmosphere above, comprising around 10% of all natural methane emissions.

Clearly, there are plenty of natural sources of methane emissions. Nonetheless, it should be observed that many of these (such as permafrost thawing, oil and gas reserves and other causes such as forest fires) can be exacerbated by climate change, which is itself in large part due to human activity. It’s for this reason that we must take concerted steps to monitor methane emissions and do our utmost to bring them under control.

For more information on this particular area of research, the upcoming Industrial Methane Measurement conference is scheduled to take place in Rotterdam in the Netherlands on the 8^th and 9^th June 2022. All interested parties are invited to learn more by visiting the link above.