You are certainly right Martin but I don't think natural processes will be enough to counter the effects of CO2.
Is that the solution, I don't know, they should tell how much CO2 has been released to make the prototype (counting everything from mining to transport). They say it does not release CO2 during the process but I doubt it seriously, here again they do not count the CO2 necessary to make the fuel they use, etc.
Prototypes are usually expensive. I don't think we should worry too much about that. It is the industrial scale equipment's carbon footprint that may well be relevant.
It is easy to say "
this is not
the solution". In reality a solution is likely to involve a bit of this, a bit of that, and lots of other bits.
Eg we don't have to move to 100% wind generated electricity as our only power source. We can aim for something like 40% solar, 25% wind, 20% biomass which leaves the remaining 15% from nuclear, hydro, tidal, geothermal, wave, ocean current, air captured CO2 to fuel, carbon negative forestry and agriculture, air captured CO2 to building materials, ... When there are lots of renewables like this, each one only has to do a little.
Photosynthesis is great and we are unlikely to improve on its efficiency - but it doesn't seem to work too well in deserts. There are niche areas where such things can help albeit if this is in a small way.
Not saying this air captured CO2 to fuel will work and be useful, but I don't think we should give up on trying to make such things work.
(Prototype costs: Price of first prototype LED was something ridiculous like $900,000. Would you use that as argument to cease all research into LEDs?)