Overall: really enjoyed CDR primer but had Qs about claim that natural gas w/ CCS could power DAC w/ potential for real carbon removal.

I don't think it can. Super brief calcs: the entire 2019 US ngas production could power ~2.4-3.9 Gt CO2 removal, but emits 2.3-3.0 Gt CO2e.

Assumptions (from primer): 300-500 MW power per Mt CO2 removed, assuming 20% of it is electricity. I modeled assuming 60-100 MWe @ 20% thermal efficiency in heat-->electricity conversion & 100% cf to get to an Mt removed.

Alvarez et al. 2018 methane emissions from 2015, from a smaller system but including some that should probably be allocated to oil.

AR5 GWPs, fossil methane w/ climate carbon feedback.

EIA for the rest of it.

Big caveats: removing combustion emissions as CCS probably more efficient than DAC'ing them, plus I really appreciate the primer's point that these are "potentially" CDR systems that need to be verified with LCA.

I don't hear a ton of serious proposals to use ngas for DAC long term.

But: unless I'm missing sth, it would take *literally* the entire US ngas production to manage <1 Gt CO2 removal, and maybe actually not lead to any removal, with no other beneficial use of the gas.

Happy to share spreadsheet if anyone else cares.

Also am trying to do more calculations of totals vs. intensities in 2021. If you want to hear a rant, ask me about how product-focus in LCA has really muddied our communication about system conclusions.