SOURCE: Carbon Brief

DATE: March 24, 2020

SNIP: Methane emissions from coal mines could be more than double previous estimates, according to a new study.

The fossil-fuel industry is understood to be one of the biggest sources of atmospheric methane, primarily due to leaks from the production of oil and gas.

However, a new paper published in the Journal of Cleaner Production suggests that coal mining may actually be a bigger contributor to levels of the greenhouse gas, with emissions set to grow considerably in the coming years.

This is even more pronounced when accounting for the impact of old coal mines that continue to seep methane long after they have been abandoned. To date, attempts to curb methane emissions from mines have been limited.

While there is considerable uncertainty around the contribution from fossil fuels, which makes up around a fifth of the total, previous work has suggested oil-and-gas production is the biggest contributor.

Meanwhile, coal, which releases 75% more CO2 than gas per unit of energy, has been relatively overlooked when it comes to methane, a far more potent greenhouse gas.

But coal can be a source of methane, too. The gas escapes from coal seams and is often siphoned off through ventilation systems to ensure a safe environment for miners.

The IEA coal mine emissions estimate also comes to around half the 79Mt it estimated for oil-and-gas operations in 2018.

However, the new study estimates that CMM in 2020 will be much higher than this, some 135bn cubic metres (bcm), equating to roughly 92Mt of methane.

The authors also note that, for the first time, they developed a methodology for estimating global methane emissions from old mining sites, suggesting a considerable role for abandoned mine methane (AMM), which in the past has been largely ignored. When factoring this in, coal methane emissions in 2020 rise to 114Mt.