sentences:  With an output of 56.8 million tonnes of coal in 1985, the Bogatyr Mine entered the Guinness Book of World Records for being the world's largest single coal mine.Since then this level of production was not sustained, and in 2007 the production of the mine was 40 million tons of coal.Together with the neighbouring Severnyi mine, the oldest mine in the Ekibastuz coal basin, they hold reserves estimated at 4.5 billion ton of coal, which at the current production rate give them a residual lifetime of over 100 years.