Underground Coal Gasification

Underground Coal Gasification (UCG) is a process by which coal that is unable to be mined for economic and technological reasons can be converted to a product gas while still in the ground (van der Riet, 2008). The coal is ignited in situ and oxidants are injected into the seam at high pressure to convert inaccessible coal into a gas that can be easily extracted through drilling technology similar to that used for fracking. The main gaseous products that come from this process include methane, carbon dioxide, carbon monoxide and hydrogen (Cui, 2014) that can then be used to produce power and chemical/liquid fuels.

UCG offers an opportunity to extract energy from coal reserves while avoiding many of the health and environmental impacts involved in mining (Greg and Edgar, 1978). It eliminates the dangers that go with conventional mining and has minimal above ground disturbances while producing low-cost energy, it also reduces the need to transport and expose of ash. However, this is a developing industry so there are many disadvantages and problems with method and tests. Many of the major trials have be conducted in the USA, Russia, China and Europe but site criteria has not yet been established (Coach, 2009). Despite 50 years of development there are still only 3 active UCG projects in the world (see map below). There are still many concerns with groundwater contamination and ground subsidence but the Chinchilla project in Australia reported neither of these impacts just 20,000 tonnes of cheap coal (Sury et al., 2004). The British Geological Survey has estimated that there could be 17 billion tonnes of coal eligible for UCG in the UK which has the potential to sustain our energy needs for 289 years.

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There has been a lot of public opposition towards UCG due to its similarity to fracking but with a moreharmful resource. It has been known to cause a lot of the same environmental impacts while still emitting greenhouse gases  and the only advantage is its low cost.

For more detailed information on UCG see Bahl et al. (2014).