Source filtering can definitely be done more cost-effectively, quite dramatically so. https://encyclopedia.pub/entry/19427 https://encyclopedia.pub/entry/19427

Source filtering can definitely be done more cost-effectively, quite dramatically so. https://encyclopedia.pub/entry/19427 https://encyclopedia.pub/entry/19427 has a lot of details and citations on various processes that achieve this. Just to give an idea of the different scale - they quote a few simulations showing $55/ton on a 300MW coal plant (capturing 60kg per second) and $35/ton on natural gas power plants - which means your bill for total decarbonisation would be under £500 for the year. The only issue is that, ironically, source capture is a limited resource. Once that 60kg/s worth of cheap carbon offsets are bought up, the next person has to buy offsets from a slightly more expensive source capture setup. Eventually all the output of all the power plants will be captured in this way and you have to start capturing from smaller sources like vehicles. I don’t know the state of the art in automobile exhaust capture but I do recall the math on a basic temperature swing adsorption system for diesel trucks that relies on waste engine heat to avoid performance penalties and could capture 90% of CO2 emissions. A full tank of diesel emissions is roughly one ton of CO2 and you needed something ridiculous like ten tons of adsorbent to capture that. (I am sure it is possible to do much better.) It probably makes sense for ships, maybe for trucks, probably not for cars, and I can’t see it ever being sensible for aircraft. The nice thing about direct air capture is that it provides a simple economic limit. You don’t need to figure out how to do carbon capture on a plane, you just capture it from the air after the fact.