Coal mine methane emissions are highly concentrated in the world's productionheavy and gassy coal deposits (Figure 3). The major emitters in GEM's data, measured in million tonnes of CO 2 e100 and CO 2 e20, respectively, remain clustered in the world's major coal producers (Figure 4). But the data also demonstrate the nuances . COAL MINE METHANE. Coal. 30. methane. .