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 short-term effects on atmospheric temperature. Over a 100-year period, the global warming potential of the colorless and odorless gas is about 25 times that of CO2. Over 20 years, the impact is about 80 times as large.
The study found that China’s efforts 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.
Newly proposed projects from the mining boom could add the same production capacity as that of Indonesia, the world’s third-largest coal producer, and threaten to release an additional 6 million tons of methane per year, a 10 percent increase of the global total for coal mine methane, according to the authors’ estimates. Some of the projects are mega-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, co-author of the study.
Despite China’s rapid scaling up of wind and solar power sources, thermal power generators that rely on burning coal still account for the majority of the country’s energy supply. This carbon-intensive model of economic growth means China is the world’s largest emitter of carbon dioxide, 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 much heralded environmental Conference of the Parties at Glasgow in 2021. 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 the country 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, causing China to hit a record output of 4.07 billion tons for 2021. China already consumes and produces about half the world’s coal.
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’s a waste. They just want to get it out of the mine as fast as possible,” he said. “It’s a global blind spot, but in China, because of the scale of their [coal] industry, the problem is huge.”
The International Energy Agency has said that coal mine 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-level database looking at the depth and scale of individual mines, combined with a peer-reviewed emissions estimation methodology, to find the probable methane output.
Its first global assessment, published in March, found that global emissions of coal-mining methane were about 52.3 million tons per year, with a climate impact similar to that of carbon dioxide emissions from all China’s coal plants. China’s leading coal-mining province, Shanxi, produces nearly the same amount of coal-mining methane as the rest of the world combined.
Beijing declined to sign on to a global methane reduction pledge in Glasgow last year, but China and the United States agreed to jointly work to better monitor and control methane emissions in the 2020s. As part of the deal, China pledged to develop a national action plan to reduce methane emissions by 2030.
The two nations 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-mining sector, China’s main source of the greenhouse gas.
Faced with limited data on Chinese methane emissions — the last official figures for annual output are from 2014 — researchers are increasingly turning to satellites to track the nation’s progress in curbing the greenhouse gas.
A study using observation data from the Japan Aerospace Exploration Agency published in 2019 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’s 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.
Lyric Li in Seoul and Pei Lin Wu in Taipei contributed to this report.