September 12, 2013
The Unseen Environmental Costs Of Surface Mining
Brett Smith for redOrbit.com - Your Universe Online
To satiate the United States’ fierce appetite for coal, miners often utilize a tactic called surface mining, which involves stripping away rock and topsoil to access the fossil fuel below.
According to a new report from researchers from Duke University just published in the journal PLOS ONE, coal retrieved from the Earth through surface mining comes at a significant cost to the ecosystem.
Study researcher Brian D. Lutz, currently an assistant professor of biogeochemistry at Kent State, said the new research is "the first to put an environmental price tag on mountaintop removal coal.”
To stress the magnitude and potential impact of surface mining, the Duke researchers noted that to meet the annual US coal demand would require converting about 310 square miles of the coal-rich Central Appalachians into surface mines. Doing such a thing would pollute about 1,400 miles of Appalachian streams and reduce carbon sequestration by affected trees and soils roughly equal to the annual emissions of almost 34,000 single-family American homes, the study found.
Previous research has looked at the surface mining's effects on local ecosystems, but few have calculated the region-wide impact of the damage and formulated metrics needed to consider the environmental costs of mountaintop mining versus its economic benefits, Lutz said.
"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."
For their study, the Duke researchers used satellite imagery and historical coal production records to calculate the total area of land mined and coal removed in the Central Appalachians between 1985 and 2005.
The team discovered that total coal production during that 20-year period was just over 1.9 billion tons, about two years' worth of current US demand. To mine the coal, more than 490,000 acres of land were disrupted – about half the size of the state of Rhode Island.
The team determined the average per-ton environmental costs of this type of mining by using previously assessed stream impairments and carbon sequestration losses associated with every hectare of land mined.
"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.
"Based on the average carbon sequestration potential of formerly forested mine sites that have been reclaimed into predominantly grassland ecosystems, 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," she added.
"Even on those rare former surface mines where forest regrowth is achieved, it would still take about 2,150 years for the carbon sequestration deficit to be erased," said Lutz, who worked on the study while attending Duke as a graduate student.
"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, a professor of biogeochemistry at Duke. "Tremendous environmental capital costs are being incurred for only modest energy gains.”