It’s a promising picture for the future of fuel: pulling the raw materials to produce it not from the diminishing fossil-based reserves in the ground, but from the abundant carbon dioxide in the air. Engineers at a Canadian firm have demonstrated a scalable and cost-effective way to do exactly that, which could make deep cuts in the carbon footprint of transportation with minimal disruption to existing vehicles. Their work was published today in the journal Joule.
The CO2 would be harvested via direct air capture technology, in which giant fans draw ambient air into contact with an aqueous solution that picks out and traps carbon dioxide. Undergoing heating and chemical reactions then allows the CO2 to be re-extracted and used as a carbon source for making fuel, or to be stored for future use. It can also enable the production of carbon-neutral hydrocarbons, which is a way to take low-cost, carbon-free power sources such as wind or solar and channel them into fuels that can decarbonize the transportation sector, according to study lead author David Keith.
Keith is a professor of applied physics and public policy at Harvard University, as well as the founder and chief scientist of Carbon Engineering, a Canadian CO2 capture and clean fuels enterprise. He and his colleagues claim that realizing direct air capture on an impactful scale will cost roughly $94-$232 per ton of carbon dioxide captured, which is on the low end of estimates that have ranged up to $1,000 per ton in theoretical analyses. This is good news for the prospect of integrating renewables into the energy system, which has been stymied both by cost and the fact that electricity generation from wind and solar sources is intermittent.
“We can take this energy straight from big solar or wind installations at great sites where it's cheap and apply it to reclaim and recycle carbon dioxide into new fuel," explained Keith. He’s talking about fuels compatible with the existing distribution and transportation structure, including gasoline, diesel and jet fuel.
"After 100 person-years of practical engineering and cost analysis, we can confidently say that while air capture is not some magical cheap solution, it is a viable and buildable technology for producing carbon-neutral fuels in the immediate future and for removing carbon in the long run," Keith added.