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Can coal be clean? Coal has several advantages as a fuel. It is abundant. It is widely distributed: countries that are short of other fossil fuels, such as Germany and South Africa, have mountains of it. As a result, it is cheap. Even though the price has risen in the past few years, it is still less expensive to run a power plant on coal than on almost anything else. But coal is also dirty. It releases lots of soot and various noxious chemicals as it burns, and so has fallen out of favour in many Western countries. Worse, coalfired plants produce roughly twice as much carbon dioxide per unit of electricity generated than those that run on natural gas. The obvious solution is to make coal fired generation cleaner. And thats what utilities in Western countries have been doing for years, to comply with ever stiffer airpollution standards. Reducing emissions of carbon dioxide, however, is another matter. In Britain, as in most rich countries, the average efficiency of coal fired power stations is about 35%. But Mitsui Babcock, an engineering firm, says its most recent designs can achieve efficiencies as high as 46%. It reckons that switching from an old design to a new one can cut fuel consumption and emissions by 23%. Many methods can reduce the various emissions produced by coalfired power stations, so that they are at least no worse than gasfired stations. But technologies also exist to make coal cleaner still, by filtering out carbon dioxide from the flue gas and storing it somehow. This is theoretically possible, but expensive. Moreover, unlike modifications that improve efficiency, there are no savings to be had by adding carboncapture technology to a power plant. As a result, no such plants have been built. | 
