I think another way we could look at things is finding "cheap" forms of carbon that would have otherwise been burned/left to rot and reprocess those into building materials.
- It's primarily a tech solution which allows for scale. If you build one Machine you can build a million. It won't actually require very much space, it need access to cheap energy and abilities to store/sequester the CO2 captured.
- Technology have the benefit that can be optimized and optimized and optimized to the point where the cost is not very high. The less tech the less changes for optimization
- There is a big risk many countries won't meet their responsibility. Getting wealthy democracies onboard is hard enough. We need a scalable way to solve this that doesn't require everyone to help because they prob won't after all
- Any negative emission solution that requires a large land-mass will create other problems (dealing with land-owners etc).
The return on investment for a lot of Carbon capture/sequestering is not lucrative (or at least the business models are not yet apparent). The long term VC angle for air to fuel seems straight forward.
- Mars alone will be a huge market for such technology. Driving a lot of demand 100-200 years out (if not a big market in 20-40 years).
- Shanghai, et-al, need air filters. Now imagine a filter which also generates a sellable resource; fuel. I imagine that machine would sell quite well in those markets.
- With the right level of efficiency, a new era of "sail" boats could be powered by reclaimed fuel from air. Imagine the market for a cargo/cruise ship leaving port with an empty fuel tank, and days later reaching the destination port with a full tank and its goods delivered.
- With the right level of efficiency, this only improves the efficiency of coal plants. Burning coal for electricity but also reclaiming the CO2 for fuel.
CO2 -> fuel consumes energy (that is stored in the fuel). Fuel -> CO2 releases it.
I agree in all of the cases I mentioned there would always need to be some energy source.