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Low quality coals – key commercial, environmental and plant considerations

Stephen Mills

September 2016
Around half of the world’s estimated recoverable coal reserves comprise coals of low quality and value. These are predominantly subbituminous and high-ash bituminous coals, and various grades of lignite. All are important for power generation and/or cogeneration, by far their biggest market. However, on a more localised basis, some are also used for various residential, commercial and industrial applications. Each coal type brings its own combination of advantages and disadvantages. Despite the latter, a number of countries have turned increasingly to the use of such coals.

The use of low quality coals was last examined in detail by the Clean Coal Centre in 2011. The international supply and demand situation for these types of coal has evolved since. In some parts of the world, there has been a significant increase in the amount used as utilities have switched to lower quality sources, largely for commercial reasons. In the last decade, subbituminous coals and coals with higher ash content have been introduced into the market and traded in increasing quantities. As reserves of some better quality export coals have been depleted, there has been a shift towards the greater use of variants of lower quality. Often, the motive has been cost saving measures instigated by utilities. However, switching can, potentially, reduce power plant efficiency, increase emissions, and escalate plant maintenance requirements.

A number of major economies rely heavily on indigenous resources of lower quality coals, particularly for power generation. In some cases, these comprise the only significant energy resource available. Such coals are often mined relatively inexpensively via large-scale opencast techniques. They are of strategic importance, providing a secure source of energy and helping minimise dependence on imported supplies.

This report examines the current production and use of these three categories of coal and discusses what the future may hold. For each, the situation in the biggest coal producers and/or users is examined. Despite moves away from coal in some economies, on a global basis, all three are expected to continue to play a major role in energy production for some time.