Imagine no restrictions on fossil-fuel usage and no global warming! (EH Update).

Researchers at the U.S. Department of Energy's Los Alamos National Laboratory are studying a simple, cost-effective method of extracting carbon dioxide directly from the air. The method could allow sustained use of fossil fuels without global climate change.

Researchers would harvest carbon dioxide from the air, reducing buildup of the so-called "greenhouse gas" in the atmosphere and allowing it to be converted into fuel.

Los Alamos researcher Manvendra Dubey says that "Fossil fuel supplies are plentiful, and what will limit the usage of fossil fuels is the potential climatic and ecosystem changes you may see as a result of rising [CO.sub.2] levels in the atmosphere. If you can capture atmospheric carbon dioxide, then you limit the environmental impact of fossil fuels."

While many scientists are working on capturing or sequestering carbon, the method being explored by Dubey and his colleagues differs because it works on a dilute stream of [CO.sub.2] in the atmosphere as opposed to capturing more concentrated forms found in power plant exhausts. The method uses ordinary air with its average carbon dioxide concentration of about 370 parts per million, and it is the only means available of capturing [CO.sub.2] generated from transportation sources and the small, dispersed sources that account for nearly half of all carbon dioxide emissions.

The method works as follows: Wind and natural mixing transport [CO.sub.2] to a removal site. The air is passed over an extraction agent (e.g., a solution of quicklime, the active agent in some cements). As the air passes over the extraction structure, the carbon dioxide in the air reacts with the quicklime and becomes converted to calcium carbonate (limestone), a solid that falls to the bottom of the extractor.

The calcium carbonate is then heated to yield pure carbon dioxide and quicklime, which is recycled back into the extractor. The purified and liberated carbon dioxide can be sequestered as a gas by direct injection into the ground, or it can be reacted with minerals to form a solid. Carbon dioxide gas also can be sold commercially to the petrochemical industry, which uses large quantities of it to extract fossil fuels.

Because this process uses existing air, it does not need to be located near any particular elevated source of carbon dioxide, It captures carbon dioxide from all sources by harnessing wind as a no-cost transportation vector.

Because the treated air is discharged, the overall concentration of carbon dioxide in the atmosphere gradually decreases over time. If this method is used on a large enough scale, it may be possible to return atmospheric carbon dioxide levels to pre-Industrial-Age concentrations, according to Dubey.

The cost of the entire process is equivalent to about 20 cents per gallon of gasoline. A typical extraction facility that could extract all current carbon dioxide emissions would require an area of 1 square yard per person in the developed world. A facility of sufficient size could be located in arid regions; discharged air that is deficient in carbon dioxide could have consequences for nearby plant life, but large expanses of desert would not be affected by the [CO.sub.2] deficit.