Coking coal can be replaced by other carbon sources, though coal itself was used to replace charcoal, derived from wood.

The World Coal Association states "721 million tonnes of coking coal was used in the production of steel" in 2010.

http://www.worldcoal.org/coal/uses-of-coal/coal-steel/

Total global coal extraction in 2010 was 3547.8 Mtoe, or ~5,068 tons of coal (BP 2014 annual energy review). Coking coal is 14% of that total.