Critics' Voices

There's little doubt that this idea would work — the chemistry is well established — but the major objections to this proposal are cost, practicality and the difficulty of disposing of sequestered carbon dioxide.

Professor Keith hopes to build several carbon pumps, for use around the world. In Keith's design, each scrubber would be the size of a power station — nearly 400 feet high and occupying perhaps an acre of land. A full-scale pump would capture 10,000 tons of carbon dioxide per year.

Clearly, it's difficult to imagine that wide-scale construction of the scrubbers will ever happen. However, the counter to any pessimism is that the technology is still being developed. Mobile phones, computers and many other technologies were large and cumbersome at first — now they are thousands of times more powerful, but a fraction of the size.

However, with each carbon pump capturing a mere 10,000 tons of CO2 per year, that's a drop in the ocean, as critics point out. Fossil fuel burning amounts to 26 billion tons of CO2 per year — so if the idea were adopted, then we'd need more than 2 million of these monster machines around the globe.

Another objection focuses on the carbon footprint of the entire process. These carbon scrubbers will require a huge amount of electricity to run. However, Professor Keith is confident that the amount of C02 taken out will exceed the carbon required to run the scrubber — otherwise, executing this experiment would be pointless.

Although far from cost-effective, the technology does exist to capture carbon dioxide at coal-fired electric plants. But nothing yet exists to capture CO2 from mobile sources such as cars and planes, which account for about one-third of emissions. Carbon dioxide circulates around the globe, so capturing carbon directly from the atmosphere precludes the need for cumbersome — and impractical — storage devices on vehicles and planes. This technology could both offset emissions from human activity and remove greenhouse gases accumulated in the atmosphere since the Industrial Revolution.

It could also allow civilization to burn through the estimated 100 to 200 years' worth of coal reserves without disastrously changing the climate.

The most serious objection is the difficulty of disposing of the sequestered carbon dioxide. A number of schemes are in development for disposal of sequestered CO2. For example, some scientists have plans to turn surplus C02 into rock and bury it in land previously mined for coal or oil; one scientist even dreams of expelling it into outer space.

There's one, final objection. Others think that, because it's likely many years away from functional deployment, the mere suggestion of such technology at this point is a distraction, and could divert resources away from more concrete steps that could prove effective in the near term.