POSTED 22 MARCH 2007
Global warming: Can we just stash the carbon dioxide?
Global warming is the nightmare that just won't quit. Fearing the biggest environmental catastrophe since the ice age, many scientists say the goal of the Kyoto agreement — slowing the increase in greenhouse gas emissions — will not do the job. Rather, we need to drastically cut dumping carbon dioxide into the atmosphere.
The past weeks have been a good one — at long last — for the gathering struggle against global warming. There was the symbolism of the Oscar for Al Gore's movie "An Inconvenient Truth." (On Mar. 21, Gore called global warming a "planetary emergency" in testimony to the U.S. House of Representatives). But there are other signs of new thinking, even in the foot-dragging United States, which remains the largest source of greenhouse gases — and the biggest opponent of cuts in those gases.
Last fall, California passed a landmark law to "cap" carbon dioxide emissions. Other states are considering similar measures.
Within the past two weeks, "the chief executives of America's largest automobile companies — General Motors, Ford, Chrysler and Toyota North America — pledged to support mandatory caps on carbon emissions, as long as the caps covered all sectors of the economy," according to The New York Times (see #1 in the bibliography).
On March 19, giant institutional investors met in Washington to press Congress for mandatory controls on carbon dioxide. "Joining a rising corporate chorus itching to sink money into clean energy projects, big investors will press the U.S. Congress on Monday to pass laws attempting to tackle global warming," wrote Reuters (see #2 in the bibliography). "The dozens of investors include Merrill Lynch, The Capital Group, which manages $850 billion in mutual funds, and the California Public Employees Retirement System, the largest U.S. pension fund, said a source at Ceres, a Boston-based coalition of investors and environmentalists."
Australia, a major source of coal — and big-time greenhouse-gasser — is funding two large pilot plants to store carbon dioxide deep underground.
TXU, a giant Texas utility, scrapped plans for eight coal-fired generators in favor of conservation, efficiency, and underground carbon dioxide storage.
Taken together, these are promising signs of a new seriousness toward the unpleasant but undeniable truth: The fuel we burn is cooking our planet by causing the reflection of heat back to the surface.
The scientific community is practically unanimous: The predicted warming is occurring, and is in full gallop in the Arctic. A warmer world will see more fires, more droughts, more giant hurricanes, more flooded coastlines, and more environmental refugees.
Maybe you know of another habitable planet in the universe, but we haven't heard the news. So for now, the smart money says "Take the sure bet: Save the only planet you got."
To slow global warming, we could use energy more efficiently, switch to non-carbon energy sources like biomass, nuclear, wind and solar, and grow more trees to soak up carbon dioxide.
Courtesy James Hansen, GISS
So here's another low-carbon idea: How about bottling carbon dioxide at power plants and burying it? Variously called "carbon capture and storage," "carbon sequestration," or the "low-carb diet," this idea may sound too good to be true, but it is gaining traction. Just this month, American Electric Power Co., the largest coal-burner in the country, announced an effort to capture and store carbon dioxide from a coal-burning generator in West Virginia (see #3 in the bibliography). (Coal is the focus of these storage discussions because it is almost pure carbon, and therefore makes more carbon dioxide per kilowatt-hour than other fuels.)
Experts say geologic storage sites a kilometer or more belowground might be able to hold more than a thousand billion tons of carbon dioxide, and many believe the gas is likely to stay put once it gets belowground.
A done deal?
So problem solved? Not exactly. Carbon storage remains experimental; not a single large generating plant is now injecting carbon dioxide. Underground storage depends on capturing large amounts of carbon dioxide, which is an enormous challenge in its own right. Smoke at a coal generating plant contains only 13 to 15 percent carbon dioxide, and concentrating, transporting and storing huge tonnages of carbon dioxide could cost a raft of money and a bargeload of extra energy.
Carbon storage is a huge job. In 2004, humans produced about 27 billion tons of the waste gas, a number that is rising every year. A new study from MIT posed the task in these terms: "If 60 percent of the CO2 produced from U.S. coal-based power generation were to be captured and compressed to a liquid for geologic sequestration, its volume would about equal the total U.S. oil consumption of 20 million barrels per day."
And that's just for a part of the carbon dioxide from coal-fired generators...
Global Energy Sources
Data from MIT.
Furthermore, carbon storage is only suitable at large power plants: Nobody will be capturing CO2 behind a train, airplane or scooter. So the low-carb storage diet will not solve the whole greenhouse warming problem — much of which is rooted in transportation fuels.
Significant carbon storage must await the conclusion of large experiments on cost, technology and environmental impact, during which time hundreds of new coal-powered generators will each begin spewing millions of tons of carbon dioxide each year. Refitting a plant for carbon capture can be almost as expensive as building a new one, so the sooner carbon capture and storage technology can be proven, the sooner utilities can include the necessary capture equipment.
Speed matters, given the rapid rate of warming. According to Curtis Oldenburg, of the earth sciences division at Lawrence Berkeley National Laboratory, "We really need to get started at some scale to learn more. It's being done in a few places, and so far it looks like everything is fine, but we'd like to do it in even more places," and at a much larger scale.
Public acceptance of carbon storage cannot be assured, and there are risks: about 1700 people died in Cameroon in 1986 during a massive outgassing of natural carbon dioxide. And unless we test for slow leaks, carbon storage could amount to a big waste of energy and money; a smokescreen rather than a solution to global warming.
Photo by Jack Lockwood, USGS
Finally, governments need to enact a mechanism to persuade or force generators of carbon dioxide to start reducing their emissions, and then to start monitoring the effectiveness of reductions and storage. Anyone who has witnessed the long, sorry story of Kyoto knows how difficult those negotiations may be.
Scoring for storing
In the face of all these hurdles, why even consider carbon capture and storage? Because no single solution will, by itself, stop global warming. Because carbon storage could preserve some use of those extremely versatile fossil fuels. And because storage could be cheap: some estimates anticipate a rise of just 2 cents in the cost of a kilowatt hour of electricity.
Now, you could go low-tech and start planting trees, which metabolize carbon dioxide into cellulose and other organic compounds. But trees eventually burn or decay, releasing the carbon dioxide. A second low-tech approach is to store more carbon in the soil, which also improves soil fertility and raises crop production. But land is limited, and trees and soil cannot store the gigatons of carbon dioxide released every year.
And that brings us back to the idea of returning the carbon from fossil fuel back to the Earth, and especially the carbon from coal. As David Hawkins, a climate expert at the Natural Resources Defense Council, told the New York Times, "Under any plausible scenarios of global coal use, we are going to need carbon dioxide capture and storage."
Is anybody injecting carbon dioxide deep underground right now?