Search is on way to trap planet-heating carbon dioxide
Cox News Service
Friday, August 19, 2005
WASHINGTON — With the world poised to generate huge volumes of carbon dioxide in the next 25 years, experts say the need to capture the planet-heating gas and store it in safe places is becoming urgent — and increasingly feasible.
Using available technologies, carbon dioxide (CO2) can be captured and pumped into geologic formations deep underground, scientists say.
The technique might add as little as 25 cents to the cost of a gallon of gasoline or $40 a month to a typical residential electric bill, a Princeton University scientist estimates, and the cost would be expected to fall as innovations are developed.
A group at Arizona State University is investigating another approach, with estimated costs that are considerably higher but coming down. It would involve combining CO2 with plentiful minerals to form substances that would be chemically stable for millions of years.
The cost of allowing the heat-trapping gas to remain in the atmosphere could be far higher.
Nearly all atmospheric scientists believe that increases in CO2 and other "greenhouse gases" have caused the Earth's surface temperature to rise.
Many fear the concentration is approaching the point known as "dangerous anthropogenic interference," when altered weather patterns, rising and acidified seas, and other unforeseen changes could bring about global havoc.
Nevertheless, projected economic growth over the next few decades imply drastic increases in the atmospheric concentrations of the dominant greenhouse gas, CO2, which is produced by the combustion of coal, petroleum and natural gas.
The scale of the imminent increases is illustrated by a United Nations projection that the amount of electricity produced in the world's coal-burning power plants will double between 2002 and 2030.
Robert H. Socolow of Princeton University has calculated that the pollution produced by these plants during those 28 years will include approximately 501 billion tons of CO2.
That's almost as much CO2 as scientists believe coal burning has vented into the air since the turn of the 17th century, the time of William Shakespeare.
"If we're going to build that many coal plants, we're going to make one hell of an impact on the planet," Socolow said. "I think it's obvious that a substantial fraction of that carbon dioxide should not be allowed to enter the atmosphere."
Socolow and ecologist Stephen Pacala, co-directors of the Princeton Carbon Mitigation Initiative, say the world must move rapidly to develop a combination of strategies, from the use of carbon-free alternative energies to the capture and storage of CO2, in order to reduce the buildup of greenhouse gases.
Removing CO2 from power plant emissions is not as difficult as it might sound.
About 15 percent of the flue gas from a traditional coal-fired power plant is carbon dioxide, Socolow said.
If droplets of chemicals known as amines are sprayed through the flue gas in a chamber known as an absorption tower, the CO2 will stick to the amines, he said.
Then, under heat, the amine-CO2 combination breaks apart, freeing the amine chemical to be routed back into the absorption tower to collect more CO2.
The next step, Socolow said, is to compress the CO2 into what's called a "supercritical" fluid, almost as dense as water.
Socolow said a 1,000-megawatt coal plant would produce about 50 million barrels of supercritical carbon dioxide per year.
Several ways of storing the captured gas are being explored.
In one strategy, being explored by physicist Andrew Chizmeshya and chemist Michael McKelvy at Arizona State University, the supercritical CO2 would be combined with abundant surface rocks to form permanent carbonate compounds.
If a common rock called serpentine is ground and mixed with water and supercritical CO2 in a solution Chizmeshya likens to "dirty soda pop," the CO2 combines with the serpentine to form magnesium carbonate, or magnesite, he said. The mineral is stable for millions of years.
The procedure would add $200 to the cost of using a ton of coal, but Chizmeshya said this is dramatically below the estimated cost when they started working on the system five years ago.
He and McKelvy said they believe they have the solution to a problem that could lower the cost even more.
The alternative approach of injecting the captured CO2 underground would not be a totally new technology.
In fact, the energy industry now injects compressed carbon dioxide into the ground to pressurize oil or gas reserves and make it easier to get the fuel out of the ground.
Also, Norway uses a deep below-ground disposal system for carbon dioxide removed from natural gas in a purification step.
Socolow said new technologies like carbon dioxide storage, sometimes called carbon sequestration, will not work unless society decides to put a price on simply venting the gas into the atmosphere.
"Investment in technology is, I think, necessary, but there will be no actual the large-scale implementation of the technology until it is cheaper to put it underground than to pay the tax to emit it," he said.
That would imply caps on emissions or a carbon tax, both of which have been non-starters with the Bush administration.
However, Energy Secretary Samuel Bodman recently announced that the government would spend $100 million on moving "sequestration technology from the laboratory to the field." He said that would bring the country "a step closer to significantly reducing greenhouse gas emissions while maintaining the important role coal plays in America's energy mix."
Socolow said experts have calculated that the cost of pumping the gas into deep caverns would be about $25 a ton, or about $60 for every ton of coal.
By the time the cost is passed through the coal and power industries to the consumer, the cost of a kilowatt hour of electric power would probably go up 20 percent, or $40 on a $200 monthly home power bill, he said.
But that's too much, said Paul N. Cicio, executive director of the Industrial Energy Consumers of America.
"If my members' energy cost goes up 20 percent, they're out of business," he said.
He says his industry supports Bush administration initiatives to develop new technologies and energy efficiencies, but costly CO2 capture and storage efforts will work only if competing economies such as China and India do likewise.
John Topping, founder of the Climate Institute, an environmental organization devoted solely to climate change issues, agreed with Socolow and Pacala that a combination of strategies is urgently needed.
"We need to find ways to make renewable fuels and nuclear power more competitive, and to get these coal plants to start sequestering CO2, and to develop a clean hydrogen fuel system and do a lot of other things," he said.
"It may be a little bit here and a little bit there, but if something is not done soon, we're just going to be piddling into the wind," he added.
On the Web:
CO2 storage animation: www.statoil.com/statoilcom/svg00990.nsf/web/sleipneren?opendocument
Jeff Nesmith's e-mail address is jeffn(at)coxnews.com
