Great question. We believe it becomes an issue of storage, logistics, supply chains, transport, and so on. We approach it this way: if we build & install 1,000,000 decentralized car-sized capture systems that capture, say, 1 ton of CO2 a year, that is going to require 1,000,000 CO2 absorption/desorption systems (cost/energy/embedded CO2), 1,000,000 high-pressure compression systems (cost/energy/embedded CO2), as well as installation, delivery, system maintanance & repair, etc. Then we have to collect the CO2 when the decentralized units are full - again, not easy, since CO2 likes to leak when stored/transported under pressure. When deployed over a large geographic area, the problem gets more complex since it must be monitored & managed with many nodes in the system.

That's not to say a decentralized system can't be done. If someone can do it & it costs less than us, that's good for the world. But coming from years in the chemical manufacturing world, we believe that humans have learned a lot, especially over the past 2-3 centuries, how to build huge chemical production facilities that make (relatively) efficient use of power & resources to process ton-scale quantities of materials. We have experience in bulk-scale chemical facilities for other chemical processes, and know that when they work, they can work really well. So we believe that bulk industrial scale is the fastest/cheapest way for CO2 removal from air in a way that can be deployed fast enough & in an economically-sustainable way to meet existing/forecast demand for voluntary CO2 credits & eventually to tip the needle through large-scale deployment.

There was an art project a couple of years ago to clean up smog.

https://www.studioroosegaarde.net/project/smog-free-project

This would be equivalent to trees, where you then store the tree forever before it dies, and even assuming you can plant and then store those trees using 0 energy it really doesn't make much of a dent.