While it is the carbon dioxide released by burning coal that has garnered most of the attention in the fight against climate change, methane by volume has far larger effects on atmospheric temperature in the short term. Over 100 years, the global warming potential of the colorless and odorless gas is about 25 times that of carbon dioxide. Over 20 years, the impact is about 80 times as large.
The study found that the efforts by China to dig out more coal had already released about 2.5 million tons of additional methane from mines since late last year when the government ordered more output to end an energy crunch.
New projects from the mining boom could add the same production capacity as that of Indonesia, the third-largest coal producer in the world, and could release 6 million more tons of methane a year, according to the study. Some of the projects are mines that will extract the black rock from deep underground, a process that produces more methane than surface mining.
“China’s frenzy of new mine development is creating hundreds of new sources of methane emissions. While making recent strides to meet its climate goals, China still needs to reckon with the potential fallout from a short-term mining boom,” said Ryan Driskell Tate, an author of the study.
Despite China scaling up wind and solar power sources, thermal power generators that rely on burning coal still account for the majority of the its energy supply. This model of economic growth means China is the largest emitter of carbon dioxide in the world, accounting for a third of global emissions in 2021.
Getting China, India and other countries to rein in their coal use was a major focus of the heralded environmental Conference of the Parties at Glasgow last year. China pledged to peak its emissions before 2030 and stop building coal power plants abroad but, with its fears over energy security, it is using coal more than ever.
Late last year, power shortages forced local governments to ration electricity across China as coal-fired power plants failed to keep up with soaring demand. Residential power in some cities was briefly cut, and factory activity was staggered to ration power.
The government responded with an emergency coal production plan, and China ended up with a record output of over 4 billion tons last years. China already consumes and produces about half the coal in the world.
In recent years, a growing body of research on atmospheric methane has suggested coal mining has been underestimated as a producer of the greenhouse gas and may be as consequential as leaks from oil and gas production, the other main industrial sources.
Tate said an aggressive program of capturing and using methane, where a drainage and vent system is used to extract and store the gas from mines, could reduce the damage of new projects, but there are few signs this approach is widely used.
“From the perspective of mining companies, methane is not a commercial product, it is a waste. They just want to get it out of the mine as fast as possible,” he said. “It is a global blind spot, but in China, because of the scale of their industry, the problem is huge.”
The International Energy Agency has said that coal methane must fall by 11 percent each year until 2030 to achieve net-zero greenhouse gas emissions by 2050. Part of the difficulty in estimating the scale of the problem is that mining companies do not necessarily track methane output regularly or accurately. Abandoned mines can also continue to release the gas.
Global Energy Monitor uses a project database looking at the depth and scale of mines, combined with a peer-reviewed emissions estimation methodology, to find the probable methane output. Its first global assessment, published in March, found that worldwide emissions of coal methane were over 52 million tons a year, with a climate impact similar to that of carbon dioxide emissions from all coal plants in China. The province of Shanxi produces nearly the same amount of coal methane as the rest of the world combined.
Beijing declined to sign on to a global methane reduction pledge last year, but China and the United States agreed to better monitor and control methane emissions for the rest of the decade. As part of the deal, China pledged to develop a national action plan to reduce methane emissions by 2030.
The two countries were meant to meet in the first half of 2022 to discuss measurement and mitigation of methane. While some Chinese state-owned natural gas giants have released plans to reduce emissions, there are few examples of similar plans in the coal sector, which is the main source of the greenhouse gas in China.
Faced with limited data on Chinese methane emissions, with the last official figures for annual output are from 2014, researchers are increasingly turning to satellites to track progress in curbing the greenhouse gas in the country.
A 2019 study using observation data from the Japan Aerospace Exploration Agency found that from 2010 to 2015, there was no detectable flattening or decline in methane release from coal mines during that period, despite new regulations meant to reduce emissions.
“In China in general, there is a huge emphasis, and rightly so, on air-quality problems, a lot of which are due to coal burning creating pollutants like urban smog. Whereas gases like methane, they contribute to climate change long term, but they don’t necessarily have that health impact,” said Scot Miller, an assistant professor of environmental health and engineering at Johns Hopkins University.
“The things that can be seen and have a direct impact on public health are taking on a higher priority in China compared to longer-term climate-related trends,” he added.