A SCIENTIFIC LOOK AT “CLEAN” COAL
Can Captured Carbon Save Coal-Fired Power? Extracting carbon dioxide from power plant exhaust and storing it underground may be the only hope to avoid a climate change catastrophe caused by burning fossil fuels
David Biello, June 22, 2009 (Scientific American)
It is no wonder the dream of “clean” coal is so seductive. The use of coal as a fuel causes 40% of all greenhouse gas emissions (GhGs) in the world. Yet coal is especially abundant in the world’s biggest GhG-generating nations, China and the U.S.
Many of the same scientists whose opinions form the foundation of the climate science validating global climate change, like the International Panel on Climate Change (IPCC), also believe the only way climate change can be stopped is by using carbon capture and sequestration (CCS) technology, or “clean” coal, to eliminate the GhG spew.
There are important and prominent exceptions. James Hansen, the NASA climate scientist who first called public attention to the significance of atmospheric GhG accumulations in the 1980s, staunchly opposes the use of coal in any form and has courageously committed acts of civil disobedience to stop it.
The seductiveness of "clean" coal's promise is irresistable to politicians. Leaders in the EU and Australia have directed big investments in its development. The Obama administration’s economic stimulus package allotted $3.4 billion for “clean” coal R&D and H.R. 2454, the landmark energy and climate bill just approved by the U.S. House of Representatives, allocated $60 billion more for “clean coal” test projects.
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Recognizing that the coal plants that began operating after 2000 will generate more GhGs in their 50-year lifetimes than all the human coal burning between the middle of the 18th Century and the turn of the millennium, even the Natural Resources Defense Council (NRDC), the Environmental Defense Fund (EDF) and the Clean Air Task Force back legislation that funds “clean” coal R&D. Their dream is of a technological breakthrough that will "solve the problem" of coal.
The Sierra Club and Greenpeace have their doubts. To bring the world’s GhG-concentration to 80% below 1990 levels by 2050 – the IPCC’s prescription – requires immediate action. “Clean” coal does not presently exist as a solution to rising GhGs and climate change. New Energy and a whole science of Energy Efficiency are available right now. Investing in them will build an emissions-free New Energy infrastructure immediately and grow technologies that actually exist right now instead of spending money on a seductive technology that may someday be of great service.
Why is there no “clean” coal? Because it is too expensive. The International Energy Agency (IEA) says bringing CCS technology up to speed will take at least $20 billion and 10 years. The American Coalition for Clean Coal Electricity (ACCCE), a coal industry mouthpiece, says it will take $17 billion and 15 years.
But the seductive promise of "clean" coal keeps the coal industry fired up.
There are 2 distinct parts to “clean” coal: (1) Capture and (2) Sequestration. Both have been shown to be possible - at a price.
Norway’s StatoilHydro, with experience working the North Sea oilfields since the 1980s, began taking the carbon dioxide (CO2) out of natural gas at its North Sea Sleipner field and pumping it back below the 250-meter-thick band of sandstone formations 1,000 meters under the ocean in 1996. About 12 million metric tons of CO2 has been pumped into the sandstone, which has a relatively impermeable 200-meter-thick layer of shale and mudstone over it. Statoil monitors it closely. There has been no leakage in over a decade.
The Sleipner experiment. (click to enlarge)
In 1986 at Lake Nyos in Cameroon, 2 million metric tons of naturally sequestered CO2 spontaneously vented, pushing away the oxygen in the air and suffocating 1,000 nearby villagers.
Sonogram monitoring shows the once liquid CO2 beneath Sleipner is now a thin layer on the sandstone using 0.0001% of the available sequestration area. Statoil recently began a similar sequestration project at the Snøhvit natural gas field in the Barents Sea, using a 150-kilometer pipeline to inject CO2 into the seabed.
In 2004, BP partnered with Statoil and others on the In Salah natural gas field in Algeria. They are pumping captured CO2 into the underlying saline aquifer to stabilize the fields. Where gas has been removed, there has been 6 millimeters of subsidence. Where CO2 has been pumped back in, the elevation rose 10 millimeters.
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For decades, the oil industry has used CO2 like this, pumping it back into wells to push up more oil. It is called Enhanced Oil Recovery (EOR). There have been cases of the CO2 venting, but it has always dispersed too quickly to do any harm.
The Lake Nyos incident was a dreadful conjunction of a lot of CO2 and a uniquely low-lying area where the CO2 pooled. Other sequestration sites have been demonstrated to be stable, even under the stress of earthquakes. But nothing is conclusively proven regarding sequestration over decades, or centuries, except that sites must be carefully chosen, closely monitored and not be considered absolutely safe.
Storage may be the simplest part of CCS.
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At Vattenfall’s 1,600-megawatt Schwarze Pumpe coal plant in Spremberg, Germany, uses the oxyfuel process of burning coal in pure oxygen to render the CO2 byproduct in a form that can be captured and channeled to other uses. The process successfully traps over 90% of the greenhouse gases - but of only 30 megawatts of the plant’s capacity. This suggests the possibilities of the process but proves nothing about doing it at utility scale. The cost of this operation makes coal-generated electricity about 5 times the market price.
There are 2 other proposed CO2 capture processes. One uses chemistry. Amines are special membranes or ionic liquids that act as ammonia scrubbers. They pull CO2 out of the gas plume coming off burning coal. The other is gasification. The coal (or oil) is turned into synthetic natural gas, from which CO2 can be more readily removed.
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None of the 3 methods solve the problem of cost. Trials have cost as little as $5 per metric ton (In Salah) to more than $90 per metric ton (gasification).
A new power plant burning pulverized coal and using amine scrubbers, according to a U.S. Department of Energy (DOE) May 2007 estimate, could capture 90% of its CO2 and generate $114 per megawatt-hour (MW-h) electricity. Plants without CCS generate $63 per MW-h electricity. DOE estimated that the gasification method would generate $103 per MW-h electricity. This would add about $0.04 per kilowatt-hour (KW-h) to a consumer’s utility bill, making coal as expensive or more expensive than wind- or natural gas-generated electricity.
At these high prices, there are small plants capturing their CO2 (the 180-MW Warrior Run power plant in Maryland, the Kingsport power plant in Tennessee). There are more such small-scale projects planned. Vattenfall will expand the Schwarze Pumpe operation and convert Janschwalde in Germany and Nordjylland in Denmark by 2015. Australia (ZeroGen) and China (GreenGen) are both building what they hope will be zero-emissions plants using gasification (IGCC) technology.
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The Obama administration plans to resurrect the FutureGen project, a 275-megawatt IGCC plant that would theoretically capture 90% of its GhGs. It was cancelled under President Bush because of the cost. But DOE now has stimulus money and energy/climate bill money and a loan guarantee program to foster CCS R&D projects like FutureGen, regardless of the cost.
Duke Energy will spend $2.35 billion on a 630-megawatt IGCC plant in Edwardsport, Ind., that could be the first utility-scale CCS project. But it will only capture 18% of its GhGs by 2013. It will likely cost a lot more to be more efficient.
American Electric Power will capture 3% of the GhGs from its 1,300-megawatt Mountaineer Power Plant in West Virginia later this year. It will inject the captured CO2 3 kilometers underground. (The locals, already organized to fight mountaintop removal mining processes, are not pleased.)
The Erora Group (Kentucky), Summit Power (West Texas), Tenaska (Taylorville, Ill., and Sweetwater, Tex.), BP and Southern Company also have projects in the works, though many previous planned projects were set aside when the planners confronted the real costs involved. Things may be different now, however. A lot of federal support is available and 2 federal policies, one requiring utilities to obtain emissions-free energy and another putting a price on emissions, make new projects potentially more economic.
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The U.S. is thought to have 100-years of storage capacity in its geologic reservoirs of permeable sandstone and deep saline aquifers. Much of that storage capacity is near where many of the 4,600 large industrial consumers burn coal in the U.S., in the Midwest, Southeast and West.
Sequestration of CO2 may be relatively safe, as advocates contend. The CO2 seems to dissolve into the substance of the sandstone and saline formations or, over longer spans, form carbonate minerals with the surrounding rock. Because of this chemistry, some attempts to pump out CO2 from trial sequestration sites failed completely.
But no commercial insurance company has yet volunteered to take long-term financial responsibility for sequestration sites. If only governments will insure sequestration, the question of the cost – like the question of insuring nuclear power plants - comes into play. Competing and much safer New Energies will appear more expensive if the value of "clean" coal's federally underwritten insurance is not included in cost calculations. This is one of the ways the nuclear energy industry has deceptively created the impression its electricity is cost-competitive.
The IPCC’s 2005 special report on CCS said a properly selected sequestration site should securely store at least 99 percent of the sequestered CO2 for more than 1,000 years. That’s going to be hard to validate, much less insure.
IGCC gasification. (click to enlarge)
There are many potential sequestration sites, but if the world intends to continue relying on “clean” coal indefinitely, it will surely run out of affordable storage. It can also count on running out of economically recoverable coal, probably by the middle of this century, if not sooner. Both of these limitations will make CCS coal-generated electricity more and more costly.
On the other hand, the New Energies that are now just barely competive with GhG-spewing sources will only get technologically more sophisticated and cheaper – at least until the world starts running out of sun and wind and waves.
In the near term, both Statoil and BP expect to offset the costs of CCS by selling their captured CO2 to the oil industry. Enhanced oil recovery (EOR) has been effective at increasing oil industry production over 10% a day for over 3 decades. There are 100+ oil fields using the technique, so BP and Statoil have a built in market (including their own oil operations).
Calculations show using captured CO2 to enhance oil recovery does reduce overall GhG emissions 24%. The extra captured oil, of course, generates GhGs when it is burned. But even though every recovered barrel of oil causes 0.42 metric tons of CO2, the recovery process requires 0.52-to-0.64 metric tons of CO2. EOR could cut U.S. GhGs 4%. Unless one of the sites leaks.
Another part of the CCS seduction is how much industry wants to be able to use it in the coming carbon-constrained economy. Cement production, steel making, aluminum smelting, glass plants, chemical industries and many other crucial business processes generate large volumes of GhGs. Finding a way to capture and resell their waste would be invaluable to such businesses and industries. They are no doubt very enthusiastic about governments' willingness to do R&D on their behalf. They might even be inclined to invest in the effort to perfect the technology if a cap&trade system imposed a penalty for not having it and a reward for having it.
Or they might decide it makes better business sense to invest in New Energy and Energy Efficiency than in a seductive promise 15-to-20 years away and prohibitively expensive.
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- Steve Caldwell, coordinator for regional climate change policy, Pew Center on Global Climate Change: “There is the potential for the U.S. and other countries to continue to rely on coal as a source of energy while at the same time protecting the climate from the massive greenhouse gas emissions associated with coal…”
- Staffan Görtz, CCS spokesperson,Vattenfall: “[The $100-million CCS demonstration boiler at Schwarze Pumpe] makes nine metric tons of CO2 per hour at full load…we don’t have a storage site yet.”
- Olav Kaarstad, CCS adviser, Statoil: “We aren’t really much worried about the integrity of the seal and whether the CO2 will stay down there over many hundreds of years…”
- Susan D. Hovorka, geologist, University of Texas: “We’re not going into a salt cavern; we’re not going into an underground river. We’re going into microscopic holes…Add it up, and it’s a large volume…”
- Sally Benson, hydrologist/director of the global climate and energy, Stanford University: “There are at least 100 years of CO2 sequestration capacity and probably significantly more…”
- James Dooley, senior research scientist, Pacific Northwest National Laboratory/ IPCC lead author: “If it took all that energy to shove [the CO2] into that sandstone, it’s going to take a lot of energy to get it out…Like an oil field, where we get out half or less of the original oil in place, a lot of the CO2 gets stuck in there. It’s immobilized in the rock.”
- Kaarstad, Statoil: “It costs a fraction of the tax…We are actually making money out of this.”
- Kurt Waltzer, carbon storage development coordinator, Clean Air Task Force: “The Dakota gasification project is creating synthetic gas and taking the CO2 from that process…[by piping it to the Weyburn oil field]… In effect, you have demonstrated all the components of doing a CCS project.”
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- Mark Brownstein, managing director in the climate and air program, Environmental Defense Fund (EDF): “Environmentalists are talking about coal not because we love coal…It’s because we have to deal with coal to achieve the kind of CO2 reductions we need to make in the timeframe we need to make them.…[T]he first CCS project that is done badly is the last CCS project that will be done…In this respect, it is very similar to nuclear power.”
- Kaarstad, Statoil: “…[P]ower plants are an order of magnitude more difficult with regard to capturing CO2.”
- Rajesh Pawar, CO2 sequestration project leader, Los Alamos National Laboratory: “In terms of total cost, they want to shoot for $10 per metric ton of CO2…We are closer to the $50 per ton range right now.”
- Greg Kunkel, vice president for environmental affairs, Tenaska: “…There are at least two billion tons of domestic emissions from pulverized coal power plants…You can’t tackle the larger problem [of climate change] unless you deal with those plants in some way.”
- George Peridas, engineer and scientist, NRDC: “The next 25 years of investment would produce 34 percent more emissions than all previous human use of coal…This is a massive legacy, and we cannot afford to let that happen.”
- John Thompson, coal transition project director, Clean Air Task Force: “If we don’t address the problem of coal, it’s game over for climate change…”
- Howard Herzog, research engineer, Massachusetts Institute of Technology: “We may have by 2020 a handful, maybe even close to 10 CCS-capable coal plants…If your goal is 80 percent cuts [in CO2 emissions] by 2050, then it’s not big enough.”
- Gardiner Hill, CCS manager of technology and engineering, BP Alternative Energy: “[But] every five years of inaction ... requires an extra gigaton of reductions…Unless we get started now, we don’t get the advantage of CCS and the emissions reductions we need.”
- Friedmann, Lawrence Livermore: “We’re going to have to do it, the same as adding wind, solar, nuclear power and conservation…It’s a climate imperative, so let’s get on with it.”