Table 1.

Published air capture analyses

Refs.Steps in proposed processCost, $/tCO2Energy required, * kJ/mol CO2Second-law efficiency, %
Keith (1)NaOH scrubbing, causticization with lime, calcination, amine capture.136648 thermal and 31 work (total, 736 primary) 7.9
Baciocchi (24)NaOH scrubbing, causticization with lime, thermal calcination in a proposed oxy-blown kiln. Option A uses standard technology for the precipitation and dewatering of the CaCO3 sludge; option B uses a prospective pellet reactor.not reportedOption A: 515 thermal and 60 work (total, 686 primary)Option B: 352 thermal and 53 work (total, 503 primary)A: 10.0B: 13.5
Nikulshina (34)Aerosol-type carbonator using Ca(OH)2, solar calciner, conventional slaker. Note that the alternative configuration with H2 production is not considered here.solar calciner only, 176–2202,485 thermal2.4
Zeman (2)NaOH scrubbing, causticization with lime, thermal calcination in a proposed oxy-blown kiln.not reported225 thermal and 104 work (total, 522 primary)11.1
Stolaroff (35)NaOH spray tower, proposal, and protoype. Does not include regeneration.proposed spray tower only, 53–127§proposed spray tower only, 53–94 work§ (150–270 primary§)prototype spray tower only, 190–390 work (540–1,100 primary)insufficient information
Mahmoudkhani (36)Recover NaOH from Na2CO3 through a hypothetical two-stage crystallization/precipitation followed by titanate process. Does not include capture system.not reportedrecovery cycle only, 150 enthalpy changeinsufficient information
Lackner (14)Filter with CO2 selective sorbent (resin). Air exchange, steam flush, compression.22038 work (110 primary)50

For more details on each analysis, see SI Appendix.

  • *Does not include energy for CO2 compression after capture for transport or storage purposes.

  • Calculated in the current study based on the data provided in each publication.

  • Assuming a 35% efficiency of converting primary energy to work.

  • §Depends on the size of the tower and thus is the result of an optimization calculation.

  • Energy for compression of CO2 to atmospheric pressure included for consistency, approximate energy for further compression removed (12 kJ/mol) (37).