Coal the dark gold of the UK. The resource that caused the standstill of pits and the riots of vast mining areas of the UK during the seventies is set to make a comeback.

The United Kingdom is well placed within Europe in having large reserves of indigenous coal both onshore and offshore in the southern North Sea.

These reserves have the potential to provide security of future energy supplies long after oil and natural gas are exhausted.

Traditional mining methods however are not suited to working offshore reserves,and development and infrastructure costs of new mines can render the exploitation of landward reserves uneconomical.

The concept of gasifying coal underground and bringing the energy to the surface as a gas for subsequent use in heating or power generation has considerable attraction.

Underground coal gasification (UCG) has the potential to provide a clean and convenient source of energy from coal seams where traditional mining methods are either impossible or uneconomical.

UCG is the partial in-situ combustion of a deep underground coal seam to produce a gas for use as an energy source.

It is achieved by drilling two boreholes from the surface,one to supply oxygen and water/steam,the other to bring the product gas to the surface.

This combustible gas can be used for industrial heating,power generation or the manufacture of hydrogen,synthetic natural gas or other chemicals.

The gas can be processed to remove carbon dioxide (CO2) before it is passed on to end users,thereby providing a source of clean energy with minimal green house gas emissions.

Government policy is to encourage the development of cleaner coal technologies for application both at home and in overseas markets.

The potential for UCG in the UK relates not only to reducing environmental emissions but also to ensuring security of energy supply and maintaining an acceptable level of diversity of energy supply.

The basic feasibility of UCG has been proven in previous trials.Further detailed studies are required to prove the technology of precision drilling process control over sustained periods of operation and to fully evaluate any possible environmental impact on underground aquifers and adjacent strata.

An EU trial,sponsored in part by the UK's Department of Trade and Industry (DTI),has demonstrated the feasibility of UCG at depths typical of European coal.

The DTI concluded that the UCG process has potential for UK coal reserves, particularly when considering the large quantities of offshore coal potentially available.

Technology targets for UCG were set in DTI Energy Paper 67 and a programme of studies has taken place with industry to critically assess the commercial feasibility of UCG.

The technology,if successful, has export potential to countries such as China and India where coal reserves considerably exceed oil and gas reserves.