Coal production in the United States is plummeting to levels not seen since a crippling coal strike 35 years ago, according to a report released by the Energy Department on Friday. The coal industry in recent years has been plagued by bankruptcies as power utilities increasingly moved to replace coal with cheap natural gas and renewable sources, like solar and wind energy. Coal was once the dominant source of the nation's electricity generation, but consumption of the fossil fuel has declined by nearly a third since its peak in 2007. Once gradual, the decline in coal mining appears to be picking up momentum. Coal production in the United States of 173 million tons for January through March was the lowest in any quarter since 1981. The Energy Department noted [broad] forces at play in its brief report. "Coal production has declined because of increasingly challenging market conditions for coal producers," the report said. "In addition to complying with environmental regulations and adapting to slower growth in electricity demand, coal-fired generators also are competing with renewables and with natural gas-fired electricity generation during a time of historically low natural gas prices." As recently as early 2008, coal was the source of roughly half the electricity generated in the United States; this year, that figure has fallen to roughly 30 percent.