Calculating the true cost of a ton of mountaintop coal

Sep 11, 2013

To meet current U.S. coal demand through surface mining, an area of the Central Appalachians the size of Washington, D.C., would need to be mined every 81 days.

That's about 68 square miles—or roughly an area equal to 10 city blocks mined every hour.

A one-year supply of coal would require converting about 310 square miles of the region's mountains into surface mines, according to a new analysis by scientists at Duke University, Kent State University and the Cary Institute for Ecosystem Studies.

Creating 310 square miles of mountaintop mine would pollute about 2,300 kilometers of Appalachian streams and cause the loss of by trees and soils equal to the produced in a year by 33,600 average U.S. single-family homes, the study found.

The study, published today in the peer-reviewed online journal PLOS ONE, is "the first to put an environmental price tag on coal," said Brian D. Lutz, assistant professor of biogeochemistry at Kent State, who began the analysis as a postdoctoral research associate at Duke's Nicholas School of the Environment last year.

While many studies have documented the severity of surface mining's impacts on local ecosystems, few have quantified the region-wide extent of the damage and provided the metrics needed to weigh the environmental costs of against 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."

To help fill the data gap, the study's authors used satellite images and historical county-by-county coal production data to measure the total area of land mined and coal removed in the Central Appalachian coalfields between 1985 and 2005.

They found that cumulative during the 20-year period totaled 1.93 billion tons, or about two years' worth of current U.S. coal demand. To access the coal, nearly 2,000 square kilometers of land was mined—an area similar in size to the Great Smoky Mountains National Park.

The team calculated the average per-ton environmental costs of this activity by using previously reported assessments of the extent of stream impairment and loss of carbon sequestration potential 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 at Duke's Nicholas School of the Environment.

That doesn't sound like much until you put it in perspective, she stressed.

"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 said.

"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 earned his PhD from Duke in 2011.

"This analysis shows that the extent of environmental impacts of surface mining practices is staggering, particularly in terms of the relatively small amount of that is produced," said William H. Schlesinger, president of the Cary Institute of Ecosystem Studies in Millbrook, N.Y. Schlesinger is James B. Duke Professor Emeritus of Biogeochemistry and former dean of Duke's Nicholas School.

"Tremendous environmental capital costs are being incurred for only modest energy gains," he said.

The new study is the latest in an ongoing effort by Duke-affiliated scientists to better understand the environmental and human health consequences of mountaintop mining. Funding for the initiative comes from the Foundation for the Carolinas.

Explore further: EPA staff says agency needs to be tough on smog

More information: "The Environmental Price Tag on a Ton of Mountaintop Removal Coal," Brian D. Lutz, Emily S. Bernhardt, William H. Schlesinger. PLOS ONE, September 12, 2013.

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1 / 5 (2) Sep 11, 2013
I'm a environmentalist who is especially fond of streams and forests and detests mountain-top removal, but even I find this ridiculous.

Losing 193 grams of carbon sequestration for every tonne (1,000,000 grams) of coal mined truly is a small price, even if it is 193 grams per year and the extraction is one-time. And truing to make it sound worse by calculating the time required for vegetation on a reclaimed mine to sequester CO2 equal to the coal removed from the mine is silly.
And 1/4 centimeter of stream length impaired for each ton of coal is small.

Coal has other problems, but the problems highlighted here are, on a per-ton basis, surprisingly modest.
1 / 5 (2) Sep 11, 2013
Check the math in the first 3 paragraphs. Why should I trust anything else the author has to say?
5 / 5 (1) Sep 11, 2013
@Roland - there is nothing wrong with the math in the first three paragraphs.

In paragraph 2: 81 days is 81*24 is just under 2000 hours = which would mean that 68 square miles is roughly 20,000 city blocks and a city block is roughly 1/300 of a square mile.
I zoomed in at random on an area of Washington DC, and pick a 1/2 mile x 1/2 mile area (which happened to be 15th NW to 7th NW by Q st NW to K st NW). I then counted the blocks and got 77.5 blocks in that area. That's close enough to 75 per quarter square mile or 300 per square mile to not find fault with their math.

In the third paragraph, 68 * 365.24 / 81 = 306 square mile per year, which is close enough to 310 not to find fault with their math.

Ahh, did you think that they meant that 68 square mile is 10 city blocks???
A bit of math will clarify what they meant:
68 square miles is the area of Washington DC, which is 81 days worth of coal.
And 68 square miles / 81 days is indeed a rate of roughly 10 city blocks per hour.

not rated yet Sep 12, 2013

And 1/4 centimeter of stream length impaired for each ton of coal is small.
Coal has other problems, but the problems highlighted here are, on a per-ton basis, surprisingly modest.

I think the general point (even though the authors do not make this explicit) is that we should not count on mountain top removal to take over the lions share of our coal production. At ~1Billion tons used in the US per year, that 1/4 centimeter of stream impairment would equate to 2500km of impairment.

Although 2500km of stream impairment is improbable, as all the surrounding streams would likely be entirely impaired before that value was reached.
3 / 5 (2) Sep 12, 2013
To meet current U.S. coal demand through surface mining, an area of the Central Appalachians the size of Washington, D.C., would need to be mined every 81 days.
That's about 68 square miles—or roughly an area equal to 10 city blocks mined every hour.

As shocking as that maybe, it's true. Mountain top removal is the most disgusting way of removing coal, but also very profitable to the anti-union coal industry ilk who have devastated vast tracks of land in Virginia, Kentucky and West Virginia. Areas so large you can see them from space. Just do google maps of Hazard Kentucky and move east to West Virginia; it's a war zone!

5 / 5 (1) Sep 12, 2013
Having had a window seat flying over the area several times on clear days, I also found the damage of mountain-top removal disgusting (but an airplane consumes enough fossil fuel that I was hardly in a position to complain).

I had expected that the damage per ton of coal was large and that this was inefficient as well as damaging as a whole. But this article shows that while the overall damage is large, the coal output is so large that on a PER-TON (per energy) basis the damage is modest, probably no worse than fracking or oil sands. Thus the problem is humanity's massive use of fossil fuels, and mountain-top removal is just a typical symptom of the problem rather than an extreme example.

Since the results of increasing energy use have helped lift humans from subsistence living to the verge of space-faring, I personally work on energy efficiency and renewable energy so that we can have both sufficient energy and an enjoyable environment.
3 / 5 (2) Sep 12, 2013
Thanks @RealScience for that additions. I think anyone who has actually seen mountain-top removal will agree that there could not be a more horrific way of extracting a 3in seam of coal than blasting whole mountains, tree's, plant's, insects, animals, fish, salamanders, frogs you name it. Then you have the effects of stream run-off etc. The worst aspect is that the mining companies never seem to the reclamation they promise. In addition you have all of the labor consequences too. It only takes one person to drive a dump truck. It 'Walmarts' the labor in the areas.
Then there are the issue of the polution and toxins released in burning the product one it is extracted.

I'll be honest, I'm surprised the technique has not outlawed given the coal companies continual violations of EPA regulations and their contempt for Labor.

5 / 5 (1) Sep 13, 2013
@Howhot - Environmentally I agree that as currently done it is pretty horrific, and that companies should be held to high reclamation standards (and NOT simply fill valleys). And I agree that there are environmental problems with burning coal as well (including mercury, CO2 and fly ash and still some SO2).

However from a labor viewpoint underground coal mining is more horrific (my great grandfather mined Appalachian coal underground, starting in grade school, and it is damned dirty and dangerous work).

Also, where does your 3 inch figure come from?
According to the article, the coal averages 11,500 tons per hectare. Even if that is imperial tons rather than metric tonnes, that's just over 10,000,000 kg per 10,000 m2 or 1000 kg/m2. With water that mass would be one meter = ~40" thick. The USGS says Kentucky coal averages a density of 1.32 so that is ~40/1.32 = ~30 inches of coal rather than 3 inches.
1 / 5 (1) Sep 14, 2013
The 3 inch seem is the nightmare scenario for a company where you blow off a mountain top and instead of finding 30+ inches, you find 3. It's a story I've heard.

I totally agree though, coal mining is not a little kids sport. Your great granddad must have been a rugged individual. My great granddad was a sod buster in the plains. Its part of that great American experience. With out your great granddad, my great granddad might not have had wagon wheels for his hay wagon.

5 / 5 (1) Sep 14, 2013
Yes, it took amazingly tough and hard-working people, both in the mines and on the plains producing food. We live so well health-wise, food-wise and materially thanks to their efforts, as well as the efforts of scientists and engineers.

We have our own challenge for the next few generations: to bring these first-world benefits (and more) to 8 to 10 billion people instead of just 1 billion, and to do so sustainably rather than through drawing down resource accumulations built up by nature over hundreds of millions of years.