[defrost]

Of course coal "leaks" .. it's a major issue worldwide.

https://www.osmre.gov/programs/mine-fires

    Due to thermal insulation and the avoidance of rain/snow extinguishment by the crust, underground coal-seam fires are the most persistent fires on Earth and can burn for thousands of years, like Burning Mountain in Australia.

~ https://en.wikipedia.org/wiki/Coal-seam_fire

[ZeroGravitas]

Coal mines also leak methane.