2.13: On the NAS report on negative emissions
As mentioned above several times, in 2018, the US National Academy of Sciences released a detailed, interesting and important report on negative emissions technologies which can be read in full online.
“Safe” achievable scales <$100
With “current technology and understanding”, they estimate a “safe” achievable scale of at best only ~10 GigaTonnes of CO2 annually around the globe across all currently available technologies, in their Table S.1:
Potentials for plant based solutions
Of note, their Box 3.1 is more optimistic on bioengineering-enhanced plant based approaches, with potentially 11 GtCO2/yr achievable just with plant based solutions and “frontier technology”
The NAS report also projects ~0 safe scaling of industrial direct air capture at this moment (see Table S.1), citing economics (cost) and practical barriers for safe scale-up. I think perhaps they basically just noted that this is expensive at present, and thus could inflict an economic damage and thus not be “safe” in a broad sense.
But this says little about the possibilities in a scenario where a) society considered the need to be more dire, or was richer, and thus could bear a larger economic cost, and/or b) where the technology has advanced further — indeed, they are just using this as a statement of the current state of the art, before going into a whole set of recommendations for new R&D to improve things. Everyone interested in this should read their outline of proposed research at the end of this summary document.
Overall, their Table S.1 pasted above deliberately undershoots — which makes sense given that it has “with current technology and understanding” in the title, and is assembled from a consensus of many expert views — what would be technically feasible with next-gen technology and research, and with realistic but aggressive deployment possibilities. That gives an optimistic picture overall, I think, if the technology development and cost reduction curves are pushed hard enough.