Coal gas has (had) a Calorific Value between 10 and 20
Natural Gas from the N Sea double that at 39
Petrol about 45 and commercial butane 118.
It will not have escaped your attention that not much coal is being produced in the UK - not since 1985 and the miners' strike - so coal gas is rare.
http://www.kayelaby.npl.co.uk/chemistry/3_11/3_11_4.html
As reported in the DTI Energy Review 'Our Energy Challenge' January 2006 North Sea gas resources have been depleted at a faster rate than had been anticipated and gas supplies for the UK are being sought from remote sources, a strategy made possible by developments in the technologies of pipe-laying that enable the transmission of gas over land and under sea across and between continents. Natural gas is now a world commodity. Such sources of supply are exposed to all the risks of any import. There are still substantial coal reserves in the UK and this fact prompts the thought that at some time in the future, coal gas may once again be used as a reliable indigenous source of energy.
Natural Gas flame is about 1960°C
Coal Gas flame is about 1977°C - a tad hotter
But natural gas has twice the heat for the same volume - try not to confuse heat with temperature - a hot brick is cooler than a match flame but it has more heat.
Research is good for the soul...
March 2015