New method reduces the cost of scrubbing CO2 from the atmosphere

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.

“As we continue to search for ways to cut emissions and slow down the effects of climate change, our best shot may just be using a method that clearly “sucks”.” – @dctrjack on our #directaircapture technolgy in @CNET. Full story here: #airtofuels

— Carbon Engineering Ltd. (@CarbonEngineer) June 8, 2018

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 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 et.al.

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.

Thank you @MattMcGrathBBC for the story on our big step forward in cutting the cost of #carbonremoval. Read it here: @BBCWorld #airtofuels #directaircapture

— Carbon Engineering Ltd. (@CarbonEngineer) June 7, 2018

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.”