Low Cost Atmospheric Carbon Dioxide Removal Looks Possible

If carbon dioxide build-up starts causing unacceptable climate change then a cheap way to remove CO2 from the atmosphere might become an option.

University of Calgary climate change scientist David Keith and his team are working to efficiently capture the greenhouse gas carbon dioxide directly from the air, using near-commercial technology. In research conducted at the U of C, Keith and a team of researchers showed it is possible to reduce carbon dioxide (CO2)  the main greenhouse gas that contributes to global warming  using a relatively simple machine that can capture the trace amount of CO2 present in the air at any place on the planet. ...Keith and his team showed they could capture CO2 directly from the air with less than 100 kilowatt-hours of electricity per tonne of carbon dioxide. Their custom-built tower was able to capture the equivalent of about 20 tonnes per year of CO2 on a single square metre of scrubbing material  the average amount of emissions that one person produces each year in the North American-wide economy.

That 100 kwh per removed tonne of CO2 would be pretty good in terms of energy cost. If the electricity cost only 10 cents per kwh then the cost per tonne would be only $10. Some proposed carbon tax regimes are at $30 per tonne and up. This could be done with photovoltaics once PV becomes cheap enough. The fact that the sun doesn't shine all the time won't matter. Just run the process when the power is available. No need for transmission lines or even expensive circuitry to convert the electricity into AC power. Though materials costs and piping the CO2 somewhere might add substantial costs.

"This means that if you used electricity from a coal-fired power plant, for every unit of electricity you used to operate the capture machine, you'd be capturing 10 times as much CO2 as the power plant emitted making that much electricity," Keith says. The U of C team has devised a new way to apply a chemical process derived from the pulp and paper industry cut the energy cost of air capture in half, and has filed two provisional patents on their end-to-end air capture system. The technology is still in its early stage, Keith stresses. "It now looks like we could capture CO2 from the air with an energy demand comparable to that needed for CO2 capture from conventional power plants, although costs will certainly be higher and there are many pitfalls along the path to commercialization."

What I'd like to see: Use sunlight to drive an artificial photosynthesis process that will fix hydrogen from water to CO2 from the atmosphere. The output would be hydrocarbons usable to power cars and for other purposes. All this will come with time.

Update: See the comment by Bruce Dunn. Looks like the energy for the initial CO2 capture is a small fraction of the total amount of energy needed for this method. So this looks like a bad idea.