Clean Coal – Not as Clean as We Thought

Is the term “clean coal” an oxymoron? That’s a hot question for politicians, the energy industry and environmentalists, alike. While the words seem intuitively clear, the meaning of the term, as well as the feasibility of improving coal’s environmental impact, are in question.

Originally, “clean coal” referred to any number of techniques to reduce the negative effects of burning coal. Up until recently, this has meant reducing sulphur dioxide and other particulates that contribute to acid rain, as well as removing minerals and impurities which reduce the efficiency of combustion. Now, with increased concern about climate change, the term is more often used to describe a process that greatly reduces carbon dioxide emissions. The most commonly referred to method is carbon capture and sequestration (CCS), in which the CO2 from coal is isolated before being emitted into the atmosphere and is disposed of in a way that prevents its escape.

While there are several ways to capture CO2 from coal, in the U.S. the most promising way is via coal gasification. This process converts the coal into a gas by heating it with steam, air or oxygen, producing hydrogen, which is used as fuel, and CO2, which can be captured. The CO2 is then transported as a gas or liquid via pipelines to sequestration sites. Options for storage include declining oil fields, saline aquifers, unmineable coal seams, and even the ocean.

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