Surface mining required to meet America’s coal demand equates to an area the size of Washington DC every 81 days
Pic: flickr / David Hoffman
By Sophie Yeo
An area the size of Washington DC will have to be mined every 81 days to meet current US coal demand, scientists have calculated.
This means that 310 square miles of the Central Appalachian mountains are required to supply the US with coal for one year.
These are findings of scientists from Duke University, Kent State University and the Cary Institute for Ecosystem Studies, who say they wanted to “put an environmental price tag on the mountaintop removal of coal”.
Currently, the US holds the world’s largest estimated recoverable reserves of coal, and produced more than a million tons in 2012. 81% of this was used by US power plants to generate electricity. But due to the switch to natural gas in 2007, its contribution to net generation has fallen from 50% in 2007 to 37% in 2012.
Mountaintop removal is a method of extracting coal that involves blasting the top off a mountain in order to expose the seams of coal beneath. The practice, which was first tested in the late 1970s, is cheaper and less labour intensive than underground mining.
The study allows the environmental costs of this method of mining to be weighed against its economic benefits, says Brian Lutz, an assistant professor of biogeochemistry at Kent State.
While many studies focus on the impact of surface mining on local ecosystems, few have documented the region-wide extent of the damage.
“This is a critical shortcoming,” Lutz said, “since even the most severe impacts may be tolerated if we believe they are sufficiently limited in extent.”
“This analysis shows that the extent of environmental impacts of surface mining practices is staggering, particularly in terms of the relatively small amount of coal that is produced,” said William H. Schlesinger, president of the Cary Institute of Ecosystem Studies.
“Tremendous environmental capital costs are being incurred for only modest energy gains,” he said.
The US has been exporting more and more of its own coal supplies, which indicates that the emissions avoided by the switch to the cleaner natural gas have in fact merely been exported – more than half, according to the Tyndall Centre for Climate Change Research in Manchester.
The 310 square miles of mountaintop mine that it would take to provide one year of the US coal supply would pollute 2,300km of Appalachian streams. It would produce the same volume of greenhouse gases as 33,600 average homes, due to the loss of carbon sequestration by trees and soils.
“Given 11,500 tons of coal was produced for every hectare of land disturbed, we estimate 0.25 centimeters of stream length was impaired and 193 grams of potential carbon sequestration was lost for every ton of coal extracted,” said Emily S. Bernhardt, associate professor of biogeochemistry at Duke’s Nicholas School of the Environment.
She stressed that this might not sound like much until you put it into perspective.
But, she says, “We calculate it would take around 5,000 years for any given hectare of reclaimed mine land to capture the same amount of carbon that is released when the coal extracted from it is burned for energy.”