Sucking out the warmth

After a decade of work, his shower-sized prototype whirs away inside a warehouse in Tucson, Arizona, each day capturing about 10 pounds of the heat-trapping greenhouse gas as air wafts through it.

Only a few billion tons to go.
In the battle against global warming, technology has long been seen as the ultimate saviour, but Lackner’s machine is a clunky reminder of how distant that dream is. He estimates that sucking up the current stream of emissions would require about 67 million boxcar-sized filters at a cost of trillions of dollars a year. The orchards of filters would have to be powered by complexes of new nuclear plants, dams, solar farms or other clean-energy sources to avoid adding more pollution to the atmosphere.

The potential of technology has pushed scattered groups of scientists to work on massive schemes to re-engineer the planet. One idea is to block sunlight, either by constructing artificial volcanoes to blast sulfur particles into the atmosphere or by launching millions of tiny satellites into space and arranging them into a giant mirror. Another concept is to sprinkle iron over the oceans to nurture plankton colonies that would absorb carbon dioxide from the air and transfer it to the depths.

But while the science of dialing back the planet’s thermostat is straightforward, the execution is fabulously expensive, complex and grandiose on a mindboggling scale. “Nobody doubts it is possible to take CO2 out of the air,” said David Keith, a professor of engineering and economics at the University of Calgary in Canada and one of several scientists around the world working on the problem. “The issue is, ‘What does it cost?’”

Some policy experts contend that blind faith in technology is a harmful distraction from the hard sacrifices needed to control global warming. “The temptation is to say, ‘Let’s get John Wayne on horseback or Bill Gates … and solve this problem,’” said Dale Jamieson, director of environmental studies at New York University.

But some scientists say that the potential of such ideas cannot be ignored given the world’s political paralysis on controlling emissions and its myopic addiction to cheap and dirty coal. “There are not that many alternatives,” Lackner said.

Among the options, carbon filtering is the most direct and best understood. If industrialisation is a process of transferring carbon stored in the earth to the atmosphere, filtering seeks to put it back. The technology is decades old. Bottled oxygen used in hospitals started out as plain air before nitrogen, carbon dioxide and other gases were filtered out. Space capsules and submarines extract carbon dioxide to maintain breathable air for crew members.

The process for removing atmospheric carbon involves putting one compound, usually a hydroxide, in contact with the air, setting off a reaction that grabs CO2 and incorporates its carbon atoms into a carbonate compound. Then, in a reaction that requires a large input of heat, the carbonate compound is broken apart, reconstituting and trapping the carbon dioxide.

Researchers propose pumping the captured CO2 into the ground, a practice used to increase the pressure in oil wells. Geologists say there is room in subterranean rock formations to lock it away forever. The beauty of carbon capture is that it scrubs the planet without intruding on it, unlike artificial volcanoes and sun reflectors, which could cause enormous planetary damage in the form of acid rain or giant shadows that stunt crops.

The filters could be placed anywhere in the world, because carbon dioxide disperses throughout the atmosphere.

For all its appeal, the process is hideously inefficient. Carbon dioxide makes up less than 0.04 percent of the atmosphere, and removing climate-changing quantities of it requires filtering massive amounts of air. Lackner calculated that sucking up all 28 billion tons of CO2 released worldwide each year would require spreading out his machines over an area the size of Arizona.

That seems like a reasonable sacrifice to save civilisation, until you consider the expense. Experts estimate it would cost as much as $200 a ton to filter and store CO2 from the air. That means the yearly vacuuming bill could reach $5.6 trillion.

The enormous cost raises the question: Who would pay? It is the same impasse that has stymied efforts toward a global agreement to reduce emissions. China claims that the West should foot the bill because it created the problem over the last two centuries. The United States says China must accept its share of responsibility as the world’s new top polluter.

For now, Lackner’s machine, a solitary prototype, continues to hum away in Tucson. With no good place to store the carbon dioxide it traps, the gas is simply released back into the air.
-Alan Zarembo (Los Angeles Times)