Underground coal can be exploited by drilling into coal seams and extracting the methane that naturally occurs within coal. The methane can be used directly for generating electricity or for heating. Such extraction, known as coal bed methane (CBM), is relatively non-intrusive, i.e. there is no coal mine and it leaves the coal unaltered so it could be mined by traditional methods in the future.
There are already a number of CBM projects in the UK. BGS is investigating the distribution, depth, thickness and gas content of coal seams suitable for CBM exploitation.
Underground Coal Gasification (UCG) is the conversion of coal with a controlled combustion (in situ underground) into a synthetic gas that is then extracted and processed to provide fuel for power generation or fuel oils.
The gas contains both methane and hydrogen and it can be processed into a high quality diesel using the Fischer-Tropsch method. This syn-diesel has greater environmental benefits than diesel derived from oil since it has a higher octane value and produces less nitrogen oxides and particulates when used.
UCG has several advantages compared with conventional coal mining. It can be employed in areas where surface or underground mining is unable to exploit coal deposits, for example at great depths, where surface or underground mining is unacceptable or not possible, or to exploit structurally complex, or unreachable, deposits that would normally be unworkable.
The BGS led a study to explore the resource available from new coal exploitation technologies. The study found that the coal resource potentially suitable for UGC was an extra 17 billion tonnes, enough to last for several hundred years — see UK Coal Resource for New Exploitation Technologies 6.5 MB pdf. The BGS are currently interested in quantifying the UCG resource with 3D modelling and researching the effect on the stability of surrounding rocks during the burn process.
For further information please contact Dr Jonathan Busby.