Substantial methane emissions from abandoned coal mines in China

Area of Science:

• Environmental Science
• Climate Change Research
• Atmospheric Chemistry

Background:

• China's abandoned coal mines are a significant, yet poorly understood, source of methane (CH4) emissions.
• Coal mines represent the largest contributor to China's anthropogenic CH4 emissions, highlighting a critical knowledge gap.
• Understanding these emissions is crucial for accurate greenhouse gas accounting and climate mitigation strategies.

Purpose of the Study:

• To estimate historical abandoned mine methane (AMM) emissions in China from 1980 to 2020.
• To project future AMM emissions in China up to 2060, aligning with national carbon neutrality goals.
• To clarify the characteristics and trends of AMM emissions for effective mitigation planning.

Main Methods:

• Utilized two distinct methodologies for estimating historical AMM emissions over a 40-year period.
• Developed projections for future AMM emissions to the year 2060.
• Analyzed emission trends in relation to coal mine closure data.

Main Results:

• China's AMM emissions surged from 0.11 ± 0.03 million tons/year in 1980 to 4.7 ± 0.94 million tons/year in 2020.
• An accelerated growth phase (approx. threefold increase) occurred between 1998-2005, coinciding with numerous mine shutdowns.
• By 2019, AMM emissions ranked as the fourth-largest anthropogenic source in China, surpassing many Annex I countries' total CH4 emissions.

Conclusions:

• Projected unabated AMM emissions to peak at 8.7 ± 2.6 million tons/year in 2040.
• AMM emissions are projected to constitute approximately one-third of China's anthropogenic carbon dioxide emissions by 2060.
• Accurate quantification and mitigation of AMM are essential for China's climate targets and global methane reduction efforts.