Extensive fires burning underground in the many coal-producing countries are a little known "global catastrophe", scientists warned on Friday. These largely hidden conflagrations are an important source of air pollution, particularly in Asia, and they contribute significantly to global warming.
|
|
The world's coal fire experts, who met at the American Association for the Advancement of Science conference, said new data from heat-sensing satellites and ground-based geological surveys showed that the problem was more serious than environmental scientists had previously realised. Thousands of fires are burning in the world's coalfields - and there is no easy way to put them out.
In China, the leading coal producing nation, underground fires are believed to consume up to 200m tonnes of coal per year, said Glenn Stracher of East Georgia College. That would release as much carbon dioxide per year as all the road vehicles in the US - equivalent to 2 to 3 per cent of carbon dioxide emissions from global fossil fuel burning.
Science briefing |
|||
|
Go there |
Coal seams near the surface occasionally catch fire naturally - the right combination of sunlight and oxygen can cause spontaneous combustion or the coal may be ignited by heat from forest fires started by lightning. But most burning today results from human activity, particularly mining. Once a fire starts it may smoulder on for decades or even centuries.
The most notorious US coal fire started in a mine close to Centralia, Pennsylvania, in 1962. The town was abandoned in the 1970s when pollution became intolerable - and the coal is still burning today. Last year a historic coal mine fire near Glenwood Springs, Colorado, sparked a forest fire that destroyed 12,000 acres of trees and destroyed almost 30 homes.
In Indonesia, there is a particularly pernicious interaction between forest fires and coal burning, said Alfred Whitehouse, a US government expert seconded to the Indonesian government. Fires started deliberately to clear forest for farming have ignited coal seams close to the surface, which can in turn start more forest fires. As a result, some of Indonesia's national parks - and a nature reserve used as a reintroduction site for orangutans - are threatened.
Of the 20,000 orangutans estimated to remain in the wild, 15,000 are in the Kalimantan region threatened by coal and forest fires.
Most Indonesian coal fires are relatively easy to extinguish, given sufficient resources, because they are close to the surface. A hundred have been put out by excavating the earth around the burning coal and pouring in water, Mr Whitehouse said, but he estimated that as many as 3,000 coal fires are still burning in Indonesia.
Gary Colaizzi, a US mining engineer, has invented a high-tech means of putting out coal fires. His company, Goodson and Associates, uses a heat-resistant grout - a mixture of sand, cement, ash, water and foam - that can be pumped around the burning coal and shut off its oxygen supply. It has been used successfully to put out 25 fires in the western US, he said.
