I'm surprised by the hype around for-profit direct-air capture (DAC) companies because, unlike afforestation or biochar, which produce useful products, there is a very small market for CO2. Somewhat ironically, the biggest market for CO2 is for enhanced oil recovery (EOR), which is exactly what it sounds like: it allows for more oil to be extracted from oil wells.
There is in fact no market for CO2 separated using DAC because it costs an order of magnitude more to separate CO2 (>$100/T) than its value on the market (max $15/T). So, the real question is, who is going to pay for it?
The companies currently operating in this space (e.g. Climeworks, Carbon Engineering) are doing so at a massive loss. In the case of Climeworks, they are pumping the CO2 to a greenhouse.[0]
I don’t think DAC alone can ever make sense, there has to be a second step in the process where the CO2 is converted into a marketable product, so that product displaces emissions. This means something like converting CO2 to plastic or fuel that would otherwise be produced using petrochemicals. Carbon Engineering recently announced that they are pursuing this. Of course, in addition to two technical breakthroughs that need to occur (cheap CO2 separation from air and cheap CO2 conversion to fuel), they will somehow have to get those fuels to be cost-competitive with current fossil fuels.
The thing to keep in mind is that CO2 emissions from man-made sources total 60 GT per year (pa). And eventually all 60 GT must be removed every year. To put this into perspective, the amount of oil produced globally by weight is about 5 GT p.a. The amount of CO2 produced is truly enormous.
The market for CO2 for EOR is about 80 Mtpa (around 1000x less than CO2 emissions)[1]. EOR actually makes some sense as we will be using oil for some time, the carbon footprint of EOR-extracted oil is lower than conventional oil.
At the end of the day, CO2 capture, especially DAC, seems more like something that is run at a loss for public benefit, like public transit, not as a for-profit enterprise.
[0] On the face of it, this seems great because the CO2 is being used, but the problem is that the plants would remove the same amount of CO2 from the atmosphere whether they were grown with captured CO2 or not (they might just grow a bit faster in the greenhouse). In fact, the energy required for the carbon capture process means that the carbon footprint of the plants grown in the greenhouse using captured CO2 is likely higher than if they were grown outdoors!
[1] https://hub.globalccsinstitute.com/publications/global-statu...