Carbon Engineering [1] seems to be making good progress toward this goal. They even published a paper about their process and its economics in Cell [2].
"We describe a process for capturing CO2 from the atmosphere in an industrial plant. The design captures ∼1 Mt-CO2/year in a continuous process using an aqueous KOH sorbent coupled to a calcium caustic recovery loop. We describe the design rationale, summarize performance of the major unit operations, and provide a capital cost breakdown developed with an independent consulting engineering firm. We report results from a pilot plant that provides data on performance of the major unit operations. We summarize the energy and material balance computed using an Aspen process simulation. When CO2 is delivered at 15 MPa, the design requires either 8.81 GJ of natural gas, or 5.25 GJ of gas and 366 kWhr of electricity, per ton of CO2 captured. Depending on financial assumptions, energy costs, and the specific choice of inputs and outputs, the levelized cost per ton CO2 captured from the atmosphere ranges from 94 to 232 $/t-CO2."
Whoa, gasoline produces 20 pounds of CO2 per gallon burned. So 100 gallons per ton of CO2. At $2/gallon, that's $200/t to produce. And then we have to spend potentially more than that to clean up the pollution. Planetarily, we iz a stupid.
But for the record, I absolutely don't believe it's that cheap to take CO2 out of the air at scale. So this whole thing is a pipedream.
If I'm doing my (very bad) math right, I think that works out to around a max of 60 cents per liter of gas, if you want to offset it with direct carbon capture using this method. That's not completely insane.
However, How many plants (and at what cost for building these plants), would there need to be, in order to make a meaningful difference? For example, would a $100 billion dollar investment over the next five years make a meaningful impact?
"We describe a process for capturing CO2 from the atmosphere in an industrial plant. The design captures ∼1 Mt-CO2/year in a continuous process using an aqueous KOH sorbent coupled to a calcium caustic recovery loop. We describe the design rationale, summarize performance of the major unit operations, and provide a capital cost breakdown developed with an independent consulting engineering firm. We report results from a pilot plant that provides data on performance of the major unit operations. We summarize the energy and material balance computed using an Aspen process simulation. When CO2 is delivered at 15 MPa, the design requires either 8.81 GJ of natural gas, or 5.25 GJ of gas and 366 kWhr of electricity, per ton of CO2 captured. Depending on financial assumptions, energy costs, and the specific choice of inputs and outputs, the levelized cost per ton CO2 captured from the atmosphere ranges from 94 to 232 $/t-CO2."
[1] https://carbonengineering.com/ [2] https://www.cell.com/joule/fulltext/S2542-4351(18)30225-3