The Oil Drum | DrumBeat: November 18, 2006

115 comments on DrumBeat: November 18, 2006

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oilmanbob on November 18, 2006 - 9:49am

The coal mine acreage is dependent on the thickness of the seam and how much other rock is between the layers. The estimate uses no calculation of the energy requirement of the mining machines or the comparative BTU content of the coal or its water content. Coal can also be mixed in a slurry and pumped in a pipeline. IMHO the figures are spurious.

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Substrate on November 18, 2006 - 11:58am

Which figures do you believe to be false?

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Just some rough noodling with numbers to see what happens:

From here: Anthracite coal is 1506 kg/m^3

From a brief look around I'll assume an average coal seam to be approximately 4.57 meters

Which means that for every 1 m^2 of surface area, there are 4.57 m^3 of coal beneath, or 6882 kg of coal beneath for every square meter above.

From google: 1 acre = 4,046.85642 m^2

(4046 m^2/1 acre) X (6882kg/m^2) = (27844572 kg/acre)

or (61,386,773.3 lbs/acre) or (30,693 short tons/acre)
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Now this is probably where you think the numbers are bogus, but I'll use them for now anyway... "A 1,400 MW generating plant near here burns 550 tons an hour and would burn up a mile-long train load of coal in a bit over 15 hours."

So let's say 1,400 MW consumes 13,200 tons of coal per day (550 X 24) or 4,818,000 tons per year. That 1,400 MW plant would "destroy" roughly 157 acres per year. (Using the aforementioned assumptions. My feeling is that I was optimistic on my assumptions. If someone else would like to take the torch and punch out some more accurate numbers/correct any mistakes, please do so)

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Laurence Aurbach on November 18, 2006 - 1:16pm

So, let's assume your calculations are in the ballpark. Over a 30-year period, coal mining "uses" the same amount of land as a 1980s-era solar thermal plant. The SEGS plant has a 30-year delivery contract; it has been in operation for 20 years and 15 years additional working life is expected.

In addition, the company that manufactured the SEGS plant claims that its latest-generation technology is 50 percent more efficient than the SEGS technology. That would imply a proportional reduction in the acreage requirement for an equal amount of electricity generation.

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Substrate on November 18, 2006 - 2:56pm

The tricky thing about that, is that after 30 years...the coal fired plant will continue to destroy land, whereas a solar plant will be fixed. I also just did a "worst case" number crunch below and assuming an 18 inch coal seam would put the yearly land use at 1,568 acres per year as compared to 157 acres per year... or ten times as much. So the coal plant may catch up to the land usage and begin surpassing that of the solar plant in as little as three years.

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Squalish on November 18, 2006 - 1:24pm

I'm don't know much about coal, but here's two points I've picked up:

Anthracite is now a quite small portion of the coal industry, and its primary deposit in eastern Pennsylvania has been mostly depleted.

Mountaintop mining often doesn't glean anywhere near that much - I seem to recall a National Geographic caption about removing a hundred feet of rock for an 18 inche thick seam.

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Substrate on November 18, 2006 - 2:43pm

I biased it towards the optimistic for two reasons in particular. 1: Since I probably couldn't come up with exhaustive numbers it's safer that way and would also help "fudge" in some things like underground mines...2:If even the optimistic case turns out pessimistic, you really know it's bad.
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18 inches = 0.4572 meters

1 m^2 of surface area, yields 0.4572 m^3 of coal beneath, or 689 kg of coal beneath for every square meter above.

1 acre = 4,046.85642 m^2

(4046 m^2/1 acre) X (689 kg/m^2) = (2,787,694 kg/acre)

or (6,145,813 lbs/acre) or (3,073 short tons/acre)

1,400 MW consumes 4,818,000 tons per year.

So... 1,568 acres per year assuming a 0.4572 meter thick seam. Ten times as much - ouch. (That, I imagine, should set the worst case boundry)

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Laurence Aurbach on November 18, 2006 - 3:14pm

Based on this EIA DOE chart, the majority of coal production comes from mines with coalbed thickness around 4-6 feet. But there's a good 42% of production that comes from coalbeds 10 feet thick or greater.

Here's a record of some BLM sales that puts the coal/land ratio in Wyoming around 110 tons/acre. If your 30 tons/acre is true for 58% of the U.S., and 110 acres is true for 42% of the U.S., then the national average might be around 64 tons/acre.

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Laurence Aurbach on November 18, 2006 - 3:18pm

Correcton: ... BLM sales that puts the coal/land ratio in Wyoming around 110,000 tons/acre. If your 30,000 tons/acre is true for 58% of the U.S., and 110,000 acres is true for 42% of the U.S., then the national average might be around 64,000 tons/acre.

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Substrate on November 18, 2006 - 4:11pm

wow...thanks for digging this up. I'm surprised at the 110,000 tons/acre figure...no wonder Wyoming pumps out the coal.

Underground - 368,612 (thousand short tons)
Surface - 762,190 (thousand short tons)

I'm guessing "surface" means strip mining?

Gotta go I'll take a closer look at this later

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Laurence Aurbach on November 18, 2006 - 3:48pm

Sheesh, that was some correction. I'll try again.

... BLM sales that puts the coal/land ratio in Wyoming around 110,000 tons/acre. If your 30,000 tons/acre is true for 58% of the U.S., and 110,000 tons/acre is true for 42% of the U.S., then the national average might be around 64,000 tons/acre.

Note, however, that the Kentucky Geological Survey says that bituminous coal will yield 1,800 tons/acre foot. At a five foot coalbed thickness, that's 9000 tons/acre. Quite a range of estimates! I'm hoping someone with expertise in this field can weigh in.

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Substrate on November 19, 2006 - 12:20am

A can of worms has definitely been opened. This interests me for sure. Only time will tell if it can battle my Americanized gnat-like attention span though. I too hope someone with expertise will weigh in (aka TOD faeries). But hope can be helped by giving it a chance, so I'll attempt to keep the motivation up, distill what's been learned today and expound a little, and probably drop it into Monday's drumbeat in the hopes of catching a wider audience. With luck there'll be someone there with some insight.

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Substrate on November 19, 2006 - 10:25am

Electricity - production: 3,892,000,000,000,000 Wh (2003) https://www.cia.gov/cia/publications/factbook/geos/us.html

Coal is ~50% of the mix. So 1,946,000,000,000,000 Wh attributed to Coal.

http://www.eia.doe.gov/cneaf/coal/page/acr/table4.html
68% of mines appear to be "surface" mines, so 1,323,280,000,000,000 Wh attributable to surface mined coal.

If a 1,400 MW (continuous duty plant) consumes roughly 13,200 tons of coal per day, which is (33,600 mWh/13,200 tons) or (2.54 mWh/ton).

(1,323,280,000,000,000 Wh) X (tons/2,540,000 Wh) = 520,976,378 tons of coal per year for "surface mined" coal.

Which best case 110,000 tons/acre: (520,976,378tons)X(acre/110,000tons)= 4,736 acres/year

Worst case 3,000 tons/acre (18" seam): (520,976,378tons)X(acre/3,000tons)= 173,659 acres/year

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Substrate on November 19, 2006 - 10:46am

Vermont is 9,250 miles^2 or 5,920,000 acres.

Best case it would take 1,250 years to destroy a Vermont

Worst case it would take 34 years to destroy a Vermont

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oilmanbob on November 18, 2006 - 1:45pm

Most of the coal being hauled on trains to Texas is bituminous, sub-bituminous and lignite. Anathracite was nearly exhuasted in the middle of the last century. Coal goes down thousands of feet, although commercially mineable coal coal seems to be above 500 ft subsurface. Coal contains varying ammounts of water which must be removed and disposed of to make the best fuel. I don't think we can easily calculate or predict commercial near surface deposit thickness or than guess its suitability for mining without some core drilling. I'm not saying this stuff can't be analysed. Its a job I be I just don't know how without a bunch of data and time.
This is great thought and an interesting idea. Thanks for bringing it up! I hope my criticisms helped clarify your thinking, not throw cold water on a good idea.

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Laurence Aurbach on November 18, 2006 - 3:34pm

Anthracite is the best case in terms of tons/acre foot. Bituminous, sub-bituminous and lignite yield less coal per unit area, so Subtrate's figures are conservative in that respect. The Kentucky Geological Survey gives these figures:

Anthracite: 2,000 tons/acre foot
Bituminous: 1,800 tons/acre foot
Subbituminous: 1,770 tons/acre foot
Lignite: 1,750 tons/acre foot

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AlanfromBigEasy on November 18, 2006 - 6:49pm

Minor point. Lignite has too low an energy value (and too dirty when burned) to be railed long distances.

Most lignite that is mined & burned is typically conveyer belted to a nearby power plant.

Alan

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totoneila on November 18, 2006 - 2:40pm

Hello Substrate,

To foster a desire in people to conserve electricity: at some carefully predetermined and constantly readjusted billing rate--money will not be accepted anymore, but physical labor will be required. You pay your bill by helping shovel spilled coal, working at a recycling center or community food bank, picking up trash along a road, weeding in a community garden, helping insulate homes for the elderly and poor, mentoring at a school, etc.

If someone wants to burn alot of juice to heat their pool or power their McMansion, then they can plan ahead on required community service of some kind. No exceptions or substitutions allowed! Just another wild and crazy idea of mine-- I am full of them.

Bob Shaw in Phx,Az Are Humans Smarter than Yeast?

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