(9d) Life Cycle Assessment of Underground Coal Gasification

Increasing energy demand, impending oil and natural gas resource depletion, and relatively low cost of energy production, have allowed coal to remain an important source of energy. However, increasing awareness of climate change has led to public resistance against the operation and new construction of coal-fired power plants. As a result, there is a growing interest in coal gasification as a more environmentally friendly alternative to traditional coal combustion.

Underground coal gasification (UCG) is a promising technology where unmined coal is converted, in-situ, into valuable synthetic gas (syngas) via the injection of oxidants into the coal seam. The syngas can then be collected above ground for further processing via numerous routes. For instance, via the Fischer-Tropsch process, it could be processed into synthetic fuels, or the hydrogen and carbon monoxide can simply be combusted to provide power to electricity generating turbines.

Whilst there are obvious advantages to not being required to extract the coal, there are potential impacts from UCG that need to be considered when assessing the viability and sustainability of the process. These in turn must be considered alongside other issues, such as energy security and human health and well-being.
UCG employs the techniques developed for oil and gas industry, it not only has the potential of reducing the cost of energy generation from coal, but also opens the possibility of generating energy from coal previously too deep to be mined in an economically feasible manner.

This study uses a life cycle assessment methodology to investigate the environmental impacts, to assess possible process improvements, including costs, and ascertain the competitiveness of the technology via comparison with alternative process routes. It also investigates how the environmental impacts and resource flows change with different potential end products of UCG.