Coal seam fires that can burn underground for centuries pose a major threat to the environment and human health, experts say.
The super-hot fires occur naturally by spontaneous combustion caused by the right combination of sunlight and oxygen. Often they start in abandoned mines, waste piles, or coal seams ignited by fires lit above ground to clear forest for farming.
Once under way they can be impossible to put out, raging for decades or even centuries. Although few people know about the underground infernos, they release huge volumes of greenhouse gas, noxious fumes and soot into the atmosphere.
Scientists took the lid off underground coal fires at the annual meeting of the American Association for the Advancement of Science in Denver, Colorado.
Glenn Stracher, of East Georgia College, Swainsboro, said: ”Coal fires are a global catastrophe. For most people who don’t live near one of these fires, it never reaches them. There may be a little clip in the newspaper, but most people aren’t aware of the extent of the problems involved in these fires.”
The problem was most severe in countries such as China, India, and Indonesia, although smaller fires were still burning in the United States — for example, in Colorado and Pennsylvania.
Stracher’s team has determined that fires in China consume up to 200-million tons of coal a year. For comparison, coal consumption in the United States during 2000 was just over one billion tons.
Scientists fear the fires may be making a significant contribution to global and regional climate change, as well as producing health-threatening pollution. Paul van Dijk, of the International Institute for Geo-Information Science and Earth Observation in the Netherlands, told the meeting: ”One way to deal with greenhouse emission limits may be to stop coal fires.”
Toxic elements from coal fires such as arsenic, mercury and selenium could contaminate local water sources and soils, said the experts. The heat could kill above-ground vegetation and even trigger forest fires, and property was at risk from ground subsidence. The fires could be fought using a heat resistant ”grout” made of sand, cement, fly ash, water and foam, that can be pumped around burning material, the meeting heard.
Injected into cracks, vents or trenches, the material is able to seal off the fire and prevent it spreading. The grout had successfully been used in Colorado and Arizona, and talks were under way about trying it in China.
Van Dijk and colleagues have collaborated with the Chinese government to detect and monitor coal fires in the north of the country, the meeting heard. The results are helping researchers find out how the fires evolve and the best ways of dealing with them.
Alfred Whitehouse, from the U.S. Ministry of Energy and Mineral Resources Coal Fire Project, said coal fires were threatening Indonesian national parks. One of these was a site for re-introducing the endangered orangutan.
”What went up in smoke in Indonesia makes it one of the worst polluters in the world,” said Whitehouse. – Sapa-DPA