Rachel's Democracy & Health News #984, November 6, 2008
GREEN COAL?
[Rachel's introduction: When we compare coal-burning technologies to the 12 principles of green engineering and the 12 principles of green chemistry, how does coal stack up?]
By Peter Montague
As we search for solutions to global warming and toxic contamination, we can compare technologies, intending to select the least harmful. In recent years, scientists have developed two sets of criteria that we can use to judge the "greenness" of competing technologies. The first is called "The 12 principles of green engineering" and the second is "The 12 principles of green chemistry."
Both sets of principles were developed by teams of technical experts and published in peer-reviewed journals. They are now widely understood and endorsed. Most importantly, they offer ordinary people, as well as experts, a way to decide which technologies are worth supporting and which ones should be phased out or never developed at all.
You can find both sets of principles listed at the end of this article.
Is Coal Green?
Don't laugh. There are major environmental groups who have received major grants to convince the public that "clean coal" is just around the corner and that we should be investing many billions of dollars each year in "clean coal." These groups include the Union of Concerned Scientists [2 Mbyte PDF], the Clean Air Task Force, and the Natural Resources Defense Council [1 Mbyte PDF].
There are roughly 500 coal-fired power plants in the U.S., burning a total of about 1.05 billion tons of coal each year to produce half the nation's electricity.[1] These plants emit 1.9 billion tons of carbon dioxide (CO2) each year, which is 1/3 of the nation's annual total CO2 emissions. Most proposals for "clean coal" focus narrowly on this CO2 problem, intending to capture CO2 and bury it in the deep earth, thus converting it from our problem to our children's problem.
The "other" wastes from burning coal
In addition to 1.9 billion tons of CO2 released by coal-burning power plants each year, another 120 million tons[2] of toxic wastes are created (so-called coal ash, or coal combustion waste [ccw]). These 120 million tons of waste, produced annually, will remain toxic forever, and they have to be put somewhere.
"Clean coal" advocates tend to give lip service to this other 120 million tons of toxic waste. Their preferred solution for these toxic wastes is to capture them and bury them in shallow pits in the ground called landfills or "surface impoundments." Unfortunately, all landfills and surface impoundments eventually release their contents into the local environment, so storing coal wastes in landfills and surface impoundments is just another way of passing these problems along to our children. [See "EPA says all landfills leak, even those using best available liners," Rachel's News #37 (August 10, 1987).]
How toxic is this toxic waste? The 1.05 billion tons of coal we burn each year contain 109 tons of mercury, 7884 tons of arsenic, 1167 tons of beryllium, 750 tons of cadmium, 8810 tons of chromium, 9339 tons of nickel, and 2587 tons of selenium.[3] These are tremendous quantities of toxic materials and they are produced each year, year after year. Where do these toxic materials go?
As coal is prepared for burning it is crushed and washed. The coal wash water is "disposed" of at the mine site, meaning it is dumped into a large bathtub in the ground. Of course sooner or later it leaks out the bottom of the bathtub, carrying with it each year an estimated 13 tons of mercury, 3236 tons of arsenic, 189 tons of beryllium, 251 tons of cadmium, and 2754 tons of nickel, and 1098 tons of selenium.
During combustion, coal-fired power plants emit into the air each year 52 tons of mercury, 47 tons of arsenic, 8 tons of beryllium, 3 tons of cadmium, 62 tons of chromium, 52 tons of nickel, and 184 tons of selenium.
However, as air pollution control technology improves, more of these airborne toxicants are captured in the form of a finely divided ash. Coal ash (also called coal combustion waste, or CCW for short) contains large quantities of toxic metals: 44 tons of mercury, 4601 tons of arsenic, 970 tons of beryllium, 496 tons of cadmium, 6275 tons of chromium, 6533 tons of nickel, and 1305 tons of selenium. Many of these elements are toxic to humans and other life-forms in microgram quantities.
The ash containing these toxic metals is buried in shallow pits near the coal plants that produced it. There, rain filters through the toxic ash year after year, leaching out the toxic metals and moving them downward (pulled relentlessly by gravity) into the soil and eventually into the groundwater below.
You might ask, what's the big deal? These toxicants started out below ground in coal and now they're ending up below ground again? So what?
You can understand the problem by thinking of a cup of coffee. If you pour water over a few coffee beans, you don't extract much coffee. The result looks pretty much like a cup of hot water. The good stuff remains locked up in the beans. But if you grind up the beans into a finely divided powder, then pour water over them, presto! You get a rich, thick cup of coffee. What has happened is that the surface area of the coffee beans has been enormously increased by grinding them up -- thus exposing a much larger surface to the water, allow the good stuff to be leached out into your cup.
Coal is the same. Coal underground is like coffee beans. Water filtering through a solid seam of coal does not extract much of those toxic metals. But once you mine, crush and burn the coal, turning it into a finely divided ash (like grinding up the beans, vastly increasing the surface area that can come into contact with water), then filter rainwater through it year after year after year -- presto! You get a rich, thick, toxic waste capable of poisoning your underground water supply. Placing that finely divided waste into a hole in the ground with a double liner beneath it -- a modern landfill -- does not prevent, but merely delays, the release of the toxicants, allowing the present generation of decision-makers to pretend all is well, but saddling our children with a stupendously large legacy of toxic materials and contaminated water.
If the total weight of coal combustion waste is 120 million tons per year in the U.S., then each of our 500 coal-fired power plants is producing, on average, 240,000 tons of toxic waste each year. If a power plant runs for 40 years, it leaves behind just about 10 million tons of toxic waste (9.6 million tons to be exact). This does not include the "overburden," as it is called -- all the dirt that must be removed to get at the coal. (In the western states, where most of U.S. coal is mined, as much as one ton of overburden waste is created for every ton of coal mined. In Appalachia, where 7% of U.S. coal is mined, 450 mountains have been destroyed by mountain-top- removal coal mining. So far, 700 miles of streams have been filled in (destroyed) by mountain-top-removal wastes in Appalachia.)[4] Then there is acid mine drainage that sours streams below mines for centuries after mining stops. down. The waste produced by coal mining is enormous and enormously destructive.
The 120 million tons of toxic waste also does not include the pollution produced by transporting coal from mine to power plant. About 40% of all rail freight in the U.S., by weight, is coal.[5]
Another serious waste problem created by coal mining is methane gas. Methane is a greenhouse gas that, pound for pound, has a warming potential 23 times as great as CO2. Since 1750, human industrial activities have roughly doubled the natural amount of methane in the atmosphere, and each year for the past 15 years atmospheric methane has been increasing about 1% per year. Ten percent of this methane is contributed by coal mines.
So how does coal measure up against the green principles? Principle 2 of "green engineering" says, "It is better to prevent waste than to treat or clean up waste after it is formed." And Principle 1 of "green chemistry" says the same thing, "It is better to prevent waste than to treat or clean up waste after it is formed." Could it be any clearer?
Given the mountains of unmanageable toxic waste produced year after year by coal mining, transport, and combustion, we can see right away that coal does not measure up to the standards of "green engineering" or "green chemistry." Not even close. Even if all the carbon dioxide from coal plants could be captured and handed off to our children to worry about, clean coal (and "green coal") would remain nothing more than a public relations gimmick, a fiction, a fraud, a ruse.
Coal is not green. Coal is the color of death.
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The 12 Principles of Green Engineering
[First published in Paul T. Anastas and J.B. Zimmerman, "Design through the Twelve Principles of Green Engineering", Environmental Science & Technology Vol. 37, No. 5 (March 1, 2003), pgs. 95A-101A.]
Principle 1: Designers need to strive to ensure that all material and energy inputs and outputs are as inherently nonhazardous as possible.
Principle 2: It is better to prevent waste than to treat or clean up waste after it is formed.
Principle 3: Separation and purification operations should be designed to minimize energy consumption and materials use.
Principle 4: Products, processes, and systems should be designed to maximize mass, energy, space, and time efficiency.
Principle 5: Products, processes, and systems should be "output pulled" rather than "input pushed" through the use of energy and materials.
Principle 6: Embedded entropy and complexity must be viewed as an investment when making design choices on recycle, reuse, or beneficial disposition.
Principle 7: Targeted durability, not immortality, should be a design goal.
Principle 8: Design for unnecessary capacity or capability (e.g., "one size fits all") solutions should be considered a design flaw.
Principle 9: Material diversity in multicomponent products should be minimized to promote disassembly and value retention.
Principle 10: Design of products, processes, and systems must include integration and interconnectivity with available energy and materials flows.
Principle 11: Products, processes, and systems should be designed for performance in a commercial "afterlife".
Principle 12: Material and energy inputs should be renewable rather than depleting.
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The 12 Principles of Green Chemistry
[First published in Martyn Poliakoff, J. Michael Fitzpatrick, Trevor R. Farren, and Paul T. Anastas, "Green Chemistry: Science and Politics of Change," Science Vol. 297 (August 2, 2002), pgs. 807-810.]
1. It is better to prevent waste than to treat or clean up waste after it is formed.
2. Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
3. Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
4. Chemical products should be designed to preserve efficacy of function while reducing toxicity.
5. The use of auxiliary substances (e.g., solvents, separation agents, and so forth) should be made unnecessary wherever possible and innocuous when used.
6. Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure.
7. A raw material or feedstock should be renewable rather than depleting wherever technically and economically practicable.
8. Unnecessary derivatization (blocking group, protection/deprotection, temporary modification of physical/chemical processes) should be avoided whenever possible.
9. Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
10. Chemical products should be designed so that at the end of their function they do not persist in the environment and break down into innocuous degradation products.
11. Analytical methodologies need to be developed further to allow for real-time in-process monitoring and control before the formation of hazardous substances.
12. Substances and the form of a substance used in a chemical process should be chosen so as to minimize the potential for chemical accidents, including releases, explosions, and fires.
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[1] Barbara Freese and others, Coal Power in a Warming World (Cambridge, Mass.: Union of Concerned Scientists, 2008), pg. 5.
[2] Barbara Freese, cited above in note 1, pg. 7.
[3] Martha Keating and others, Laid to Waste; The Dirty Secret of Combustion Waste from America's Power Plants (Washington, D.C.: Citizens Coal Council, 2000), pg. 2. [1.3 Mbyte PDF]
[3] Barbara Freese, cited above in note 1, pg. 7.
[4] Barbara Freese, cited above in note 1, pg. 6.