Underground coal gasification has been undergoing pilot trials for some 50 years, but no commercial operations exist – however the potential excites because it could change the prospects of the 83% of global coal resources that are currently unmineable.
Underground coal gasification (UCG) converts coal in-situ into synthetic natural gas. The process involves the drilling of wells into a coal seam with oxidants in the form of air/oxygen or steam injected into the seam to serve as a fuel for the underground combustion and gasification process. The combustion process decomposes the coal to generate a syngas which consists of carbon dioxide, hydrogen, carbon monoxide, methane and hydrocarbons. A separate production well is used to bring this gas to surface.
One of the problems faced by UCG is that it is hard to convince governments it is a solution, and it is often referred to as the ugly sister of emerging technology options. People easily confuse UCG with coal bed methane and hydraulic fracturing. However, while one can already see anti-coal energy lobbyists having a field day with an energy form which can be described as setting alight underground coal fields and tapping the gases for power generation, there are also some very good reasons this technology is generating increasing excitement worldwide.