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COAL The prospects for Underground Coal Gasification 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. U nderground 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. John Kessels from the International Energy Agency (IEA) clean coal centre, UK, says that UCG, also referred to as in- situ gasification and which originated out of the Soviet Union, has seen many trials in that region as well as the USA, Europe and Canada. All these have led to technology improvements. In recent years these improvement have been successfully applied to several UCG projects that have led to global interest. However, Kessels says the technology is nowhere near commercialisation. “This could happen in five to ten years, or sooner at high risk if UCG goes the route of fracking.” The evolutions that have furthered the technology include progress in horizontal and directional drilling, in-situ monitoring, improvement in UCG reactor environment and the development of techniques to exploit different kinds of coals. One of the reasons coal remains so popular an energy carrier is that it is widely dispersed compared with other fossil fuels. For example, while some 52% of the world’s oil resources is controlled by 2% of the planet’s population and 54% of the world’s gas resources is controlled by 3% of the global population, 50% of the world’s coal resources falls under the control of 42% of the global population. Kessels says that the drivers for UCG are numerous. One of these is the steady decline in the quality of the coal produced worldwide, and exhaustion of reserves of higher grade coals. “It means many countries are turning increasingly The piping of the underground coal gasification project next to the Majuba power station in South Africa. 26 ESI AFRICA ISSUE 4 2013