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The seed money approach is not a bad approach. This would allow small research groups that the US government has decided to starve for cash to continue their w

The seed money approach is not a bad approach. This would allow small research groups that the US government has decided to starve for cash to continue their work for a few years, and it also creates a bit more of a incentive, i.e, successive funding rounds. The approach does look more like a VC route than a federal agency approach, which has some benefits. The stories about how it takes six months and half a dozen reviews at a government agency to purchase some inexpensive lab equipment that was needed yesterday are not entirely apocryphal. This approach seems interesting: > "Heirloom, a company working on capturing CO2 directly from the air, recently made headlines after raising $53 million in venture capital. For the XPRIZE, Heirloom teamed up with a company called Carbfix, which specializes in turning CO2 into stone. Carbfix is already demonstrating its technology at a working carbon removal facility in Iceland." Note also that there's a real tie-in with SpaceX here, which runs rockets on a variety of fuels, i.e. RP1 which is essentially highly refined jet fuel, and methane, CH4. Mastering carbon capture and conversion technology, i.e. running processes like CO2(atm) + H20 -> C + H -> CH4, long chain hydrocarbons (RP1), would be critical to synthesizing fuel on Mars for example, which has an atmosphere of CO2 and apparently, water ice in the subsurface. This could also make SpaceX independent of fossil fuels: imagine a giga-scale carbon capture and methane synthesis factory in Texas providing all the fuel Starship needs. Also, in a fossil-fuel free world, international air travel would require jet fuel, and that's possible with DAC and water-hydrogen, via a modified Fischer-Tropsch process, first used with coal gas / steam as inputs.

mbbutler 5y ago
The tech for Direct Air Capture (DAC) is already quite efficient at removing CO2 from the atmosphere (80%+ depending on the particular process). At best, new innovation on the chemistry of the removal process can only increase the efficiency by 25%. The real issue with DAC is that it is incredibly difficult to innovate around the fact that CO2 in air is just immensely dilute. You need to process enormous amounts of air to remove an appreciable amount of CO2 and, even worse, as the plant operates and recirculates processed air, the local air around the plant becomes more and more devoid of CO2 leading to a decreased amount of CO2 captured per unit volume of air. The only real improvement that I could see occurring in this space is coming up with a process that creates less back-pressure against the fans pumping in unprocessed air which could bring down the energy cost per ton of CO2 removed. But even in that case the back pressure created by a DAC process is normally caused by flowing air through a porous catalyst, which is essential for high efficiency. So there's a trade-off there as well. Ultimately I am not very sanguine about DAC and I have been disappointed to see news agencies reporting as if DAC is even in the top 10 technologies most important to reduce carbon emissions.
- photochemsyn 5y ago
  Staggered extraction cycles, where each round leads to a 10X increase in concentration, is one option. If you look up how D2O (heavy water, where the hydrogens are replaced by deuterium) is produced, the first step is often done that way. The initial stage is the concentration of HDO from H2O, which is naturally found at about 1 part in 3200. 400 ppm CO2 is 1 part in 2500, so it's comparable. Proof-of-process for Starship fueling would be generating a stream of pure CO2 from air at a rate sufficient to feed into a methane production facility (which would require a similar stream of hydrogen from water processing) to produce around 500 tons of liquid methane in a reasonable amount of time. Possible?

mbbutler 5y ago

The tech for Direct Air Capture (DAC) is already quite efficient at removing CO2 from the atmosphere (80%+ depending on the particular process). At best, new innovation on the chemistry of the removal process can only increase the efficiency by 25%. The real issue with DAC is that it is incredibly difficult to innovate around the fact that CO2 in air is just immensely dilute. You need to process enormous amounts of air to remove an appreciable amount of CO2 and, even worse, as the plant operates and recirculates processed air, the local air around the plant becomes more and more devoid of CO2 leading to a decreased amount of CO2 captured per unit volume of air. The only real improvement that I could see occurring in this space is coming up with a process that creates less back-pressure against the fans pumping in unprocessed air which could bring down the energy cost per ton of CO2 removed. But even in that case the back pressure created by a DAC process is normally caused by flowing air through a porous catalyst, which is essential for high efficiency. So there's a trade-off there as well. Ultimately I am not very sanguine about DAC and I have been disappointed to see news agencies reporting as if DAC is even in the top 10 technologies most important to reduce carbon emissions.

photochemsyn 5y ago
Staggered extraction cycles, where each round leads to a 10X increase in concentration, is one option. If you look up how D2O (heavy water, where the hydrogens are replaced by deuterium) is produced, the first step is often done that way. The initial stage is the concentration of HDO from H2O, which is naturally found at about 1 part in 3200. 400 ppm CO2 is 1 part in 2500, so it's comparable. Proof-of-process for Starship fueling would be generating a stream of pure CO2 from air at a rate sufficient to feed into a methane production facility (which would require a similar stream of hydrogen from water processing) to produce around 500 tons of liquid methane in a reasonable amount of time. Possible?