A physics professor at Harvard University and CEO of Carbon Engineering, Calgary, Canada, is building a machine that could pull tens of thousand of tons of carbon out of the air in an effort to reduce the amount of greenhouse gases in the atmosphere. It relies on processes developed years ago to extract small quantities of pure CO2 for industrial purposes.
In the first step, air is blown over the air contactor which contains a cascade of a liquid that readily absorbs CO2. (The liquid being used in the prototype is sodium hydroxide.) That CO2-rich solution is sent to a crystallizer or causticizer where solid carbonate precipitates out and gets sent to a kiln. The kiln burns the solids at 900°C, causing them to release a stream of pure CO2. The kiln could run on natural gas and any CO2from burning the gas also gets sent to the contactor to prevent its release into the atmosphere. The burnt solids are pumped to a mixing tank where they react with water to reform the hydroxide solution. The solution returns to the contactor to capture more CO2.
The kiln also generates excess heat, which the inventor wants to use to make electricity to run fans in the air contactor and mixers in the mixing tank.
The recovered CO2 can be sold for industrial applications, permanently buried deep underground, pumped underground to make it easier to extract oil, or used to make hydrocarbon fuels with lower life-cycle carbon emissions than gasoline. It is hoped that a company could make money by selling the CO2 the machine removes from the atmosphere.