Methane – which is responsible for about one-third of warming from greenhouse gases – is a key focus for countries wanting to slash emissions quickly and slow climate change.

London-based energy think-tank Ember analysed the emission profiles of 10 major coal-mining companies in Indonesia, collectively responsible for half of the archipelago’s coal production.

It found that only four of the 10 firms included coal mine methane (CMM) emissions in their emissions inventory, indicating that the environmental impact of coal mining in the country was not being wholly accounted for.

“Failing to understand or report on these emissions appropriately undermines a company’s overall sustainability reporting. It also overlooks a potentially significant missed opportunity for emissions reduction,” the report said.

The companies’ CMM emissions “could exceed eight million tonnes of CO2 equivalent, more than a third of the companies’ potential total emissions”, Ember said in a press release.

The CMM emissions of most major Indonesian coal firms may be “on a par or greater than” their total emissions from fossil fuel combustion and purchased electricity, according to the report.

CMM, categorised as fugitive emissions or unintentional releases, refers to the methane released when coal is extracted or topsoil is removed.

Methane remains in the atmosphere for only about a decade, but it has a warming effect 28 times greater than CO2 over a 100-year timescale.

Over a 20-year timescale, it has a warming impact around 80 times greater than CO2.

Analysts urged Indonesia’s coal firms to start taking the impact of methane emissions seriously to meet sustainability standards.

“Measuring and reporting methane emissions will be crucial in coal-mining decarbonisation efforts and ensuring compliance with national and international standards,” Ember analyst Dody Setiawan said.

Indonesia is one of the signatories of the voluntary Global Methane Pledge and Jakarta says it has committed to “take comprehensive domestic actions to achieve the global reduction of methane emissions” by 2030.