Coal's longevity as a major source of primary energy production has so far confounded predictions that ‘old king coal' might someday be dethroned. After oil, coal remains the second source of primary energy globally and the largest source of power, satisfying 40% of the world's electricity needs, according to the Paris-based International Energy Agency (IEA).

Although the continuing appeal of the dirtiest fossil fuel is not welcomed by environmental campaigners, it is good news for the coal