New method reduces the cost of scrubbing CO2 from the atmosphere

Posted Jun 13, 2018 by Karen Graham
A Harvard professor announced on June 7, 2018, that his company, Carbon Engineering, has found a method to cheaply and directly pull carbon-dioxide pollution out of the atmosphere and turn it into fuel.
The core purpose of the pellet reactor system is to take the CO2 that has been absorbed from the air...
The core purpose of the pellet reactor system is to take the CO2 that has been absorbed from the air into liquid at the air contactor and transform it into a solid pellet.
Carbon Engeering
Vast amounts of carbon dioxide, a greenhouse gas (GHG) are being pumped into the atmosphere every minute of the day and night - and there is no indication it will be halting anytime soon. The daily CO2 reading from Mauna Loa Observatory, Hawaii (Scripps UCSD) was 411.03 ppm on June 11, 2018.
In response to the rising CO2 emissions, Carbon Engineering - a Squamish, British Columbia, Canada-based clean energy company, founded by David Keith, a professor of applied physics at Harvard, and funded by Bill Gates, has produced a study that details engineering and a cost analysis for a 1 Megaton-CO2/year direct air capture plant.
The study was published in the new scientific journal Joule on June 7. In the study, Keith and his team propose the design of a large industrial plant that is capable of capturing carbon dioxide from the atmosphere at a cost of $94 to $232 per ton.
The new method would mean it would cost between $1 and $2.50 to remove the carbon dioxide released by burning a gallon of gasoline in a modern car. If this is possible, the new method would be considerably less than the estimated cost of $600 per ton suggested by a team of experts in 2011.
“I hope to show that this as a viable energy industrial technology, not something that is a magic bullet … but something that is completely doable,” says Keith. Carbon Engineering is seeking funding to build a commercial-scale demonstration plant for its process following successful tests at its pilot plant in B.C.
A calcium loop (right) drives the removal of carbonate ion and thus the regeneration of the alkali c...
A calcium loop (right) drives the removal of carbonate ion and thus the regeneration of the alkali capture fluid (left). Boxes with titles show the names of the four most important unit operations. Each box shows the chemical reaction with reaction enthalpy at STP in kilojoules per mole of carbon and the reaction number for reference elsewhere in the paper. Note that water is liberated in reaction 1 and consumed in reaction 4, balancing the process.
David W. Keith
The process, in a nutshell
Basically, Keith and his team grafted a cooling tower onto a paper mill. And while chemically complicated, the process for removing CO2 does not rely on out-of-this-world science. According to the study, the technology makes synthetic fuels using only water, air, and renewable power. There are three major steps involved.
In the first step, air is sucked into the facility's giant "contactors," resembling cooling towers. There, it is exposed to an alkaline liquid. Because CO2 is mildly acidic, says Keith, "it wants to be in the base."
In step two, the watery liquid - containing carbon dioxide - is brought into the factory, where using a series of chemical reactions, the acid is separated from the base. The acid is then frozen into pellets, then heated and converted into a slurry. “Taking CO2 out of a carbonate solution is what almost every paper mill in the world does,” Keith told The Atlantic.
Lastly, using a chemical process called the Fischer-Tropsch process - something used by oil companies to convert hydrocarbon gases into liquid fuels every day, the carbon dioxide is combined with hydrogen. And this last step is the key to Carbon Engineering's success. It means the company can produce carbon-neutral hydrocarbons.
“What we’ve done is build a (direct-air capture) process that is—as much as possible—built on existing processes and technologies that are widespread in the world,” Keith says. “That’s why we think we have a reasonable possibility of scaling up.”
What does this all mean?
One big thing this study clears up is the cost the direct capture of CO2 from the atmosphere. If this does prove to be cost-saving, it would shoot down the nay-sayers who have said direct carbon capture would never be viable. This same process could be used for carbon sequestration, where CO2 is captured and stored underground.
But there aren't many investors lining up to store carbon and this new process at least will make the facility profitable. “The main, near-term market is making carbon-neutral hydrocarbon fuels,” Keith says. “We see this as a technology for decarbonizing transportation.”