The diagram above schematic shows how CO2 sequestration might be achieved in conjunction with UCG. A rolling programme of UCG gasification along a coal seam would leave highly porous cavities and stressed strata in its wake. As these areas cool down, the abandoned cavities would be accessed by directional drilling or through the existing production boreholes. CO2 would then be injected at high pressure for storage and retention. For permanent CO2 sequestration, the depth and strata conditions must be suitable and this is an area for further investigation.

Coal gasification, both surface and in-seam, is at the forefront of cleaner coal technology. Utilisation of the product gas in combined-cycle gas turbines can provide significantly higher generation efficiencies, the gas can be cleaned and CO2 capture from Syngas using amine solutions is a well proven technology.

The CO2 capture and sequestration option is now a topic of major research interest around the world. The US DOE has embarked on a large programme to support its "Pathway to Stabilisation" Scenarios and the EEC has included CO2 capture and sequestration in the 6th Framework proposals.

UCG is a particularly suitable target for research in this area. It has the same advantages as surface gasification for CO2 capture, and can access potential underground storage locations for CO2 through its association with drilling underground strata.

The combination of UCG and CO2 sequestration is an area of growing research interest.