The US generated more of its electricity from gas than from coal for the first time ever in April — in a sign of how the shale boom is putting mounting pressure on the country’s mining industry. Plunging prices for natural gas, which have fallen alongside oil since last summer, led to it being used to generate 31 per cent of America’s electricity in April, while coal contributed 30 per cent. This was the first month in US history that gas-fired electricity generation surpassed coal-fired generation, according to SNL Energy, a research firm — although it came close in 2012 when gas prices were also very weak. In 2010, coal provided 45 per cent of US power. Since then, competition from cheap shale gas — unlocked by the rise of horizontal drilling and hydraulic fracturing — plus a growing regulatory burden on coal-fired power plants, has squeezed out coal […]