M E T H A N E
Alessandro Volta, the Italian chemist and physicist is best known for inventing the electric battery in 1800, a seminal moment in the development of electrical energy storage. What are less well known are Volta’s extraordinary adventures with ‘flammable air’. At various swampy locations around the lakes of northern Italy, he managed to collect bubbles of gas rising from the depths and much to his surprise, discovered they were flammable. Thus was methane discovered. If Volta were alive today, he would, I’m certain, be thrilled to know that modern battery technology is playing a major role in combating climate change. He would be less thrilled to discover that methane was a potent greenhouse gas.
Alessandro Giuseppe Antonio Anastasio Volta
Since the beginning of the Industrial Revolution, the methane concentration in the atmosphere has increased by about 260% due almost entirely to human activities. By 2019, global methane concentrations had risen from 722 parts per billion (ppb) in pre-industrial times to 1866 ppb, the highest value in at least 800,000 years.
Figure 1
It won’t have escaped your notice that methane concentrations in the atmosphere are measured in parts per billion. Why, then, are climate scientists raising the alarm about a gas which is 200 times less abundant than CO2? The answer: because in terms of its global warming potential (GWP), methane is far more potent than CO2. What complicates methane’s GWP is the fact that methane emitted today will only exist for around a decade – it breaks down in the atmosphere. Nonetheless, compared to CO2, methane’s GWP is 84 times greater over a 20 year period and 28 times greater over 100 years. (Confusing, eh?)
And yet, methane concentrations only rarely make the news. Before long, they most certainly will.
Over the past 40 years, methane concentrations in the atmosphere have followed a similar trend to those of CO2.
Despite its trace concentration in the atmosphere, methane has been responsible for 23% of climate forcing (extent to which global temperatures are increased).
Figure 2
By NOAA Public Domain
This annual increase trend since 2005 is more clearly seen in Fig. 3. 2021 saw the largest methane increase since records began.
By NOAA Global Monitoring Laboratory - Public Domain
Figure 3
Methane comes from both natural sources and human activities. Natural processes account for 40% of methane emissions, with wetlands being the principle source. The other 60% is anthropogenic in the following proportions:
33% - Fossil fuel production. The largest proportion of anthropogenic emissions come from methane released during oil and gas extraction, the result of flaring and pipeline leakage. (More on this in the natural gas section.)
27% - Livestock. 'Enteric fermentation' by bacteria in the intestines of cattle and sheep releases methane. A single cow can emit 99kg of methane in a single year.
18% - Plant agriculture. Both food and biomass production release methane with rice cultivation being by far the greatest contributor. Waterlogged paddy fields provide an ideal environment for microbes to produce methane in a process called 'methanogenesis'.
16% - Waste. The decomposition of organic waste in landfills and waste water treatment plants produces methane.
4% - Biofuel burning. Huge amounts of wood, agricultural waste and dung are burnt for heating and cooking. Frequently this burning is incomplete and releases methane.
2% - Other.
Two fairly depressing facts emerge from this section on methane. First – the atmospheric concentration of methane is rising quickly. Second – methane has a powerful global warming potential. But! There is good news on the horizon. 159 countries have signed up to the Global Methane Pledge (GMP) whose goal is to cut methane levels 30% below 2020 levels by 2030. This is a far less painful road towards net zero. Cutting the waste methane from the fossil fuel industry is a win/win measure. Of course, natural gas is 70-90% methane and contributes to atmospheric CO2 when burnt. That’s why the Pledge is targeting every anthropogenic source of methane.
Oil-flaring in China
