Carbon capture’s net CO2 additive---their studies don’t assume that captured carbon is used for oil production or recycled back into the atmosphere

*CCS = Carbon Capture and Storage, EOR = Enhanced Oil Recovery, DAC = Direct Air Capture

Neither of the two principal industrial carbon removal (ICR) methods being promoted and subsidized by governments meets the collective biophysical need of atmospheric CO2 reduction, and both are net CO2 additive as presently practiced. These are point-source capture in which the captured carbon is used for oil production, and direct air capture when wholly fossil fuel powered and all emissions produced by the process are accounted for. Point-source CCS cannot reduce atmospheric CO2, since it can never store more than it captures, and as currently practiced is also net additive (with only rare and minor exceptions where the captured CO2 is simply injected underground). Point-source CCS even at its theoretical best is somewhat net CO2 additive. (Indeed, CCS is not normally considered a “negative emissions technology.”) DAC, when fossil fuel powered and the full process and emissions are accounted, is also net CO2 additive. That is, in both cases the processes add more CO2 to the atmosphere than they remove, emitting—in the case of point-source capture—from 1.42 to 4.7 tons of CO2 to the atmosphere for each ton removed (see Table 3) and—in the case of direct air capture—emitting from 1.46 to 3.44 tons of CO2 for each ton removed.6 Nevertheless, as explained in the “Discussion” section, some studies, through their methodological choices, report point-source capture and direct air capture to be climate mitigating or net CO2 reductive—by leaving out part of the life cycle process, by assuming low or zero-carbon power sources, by invoking an emissions-discounting “displacement” assumption or by ignoring that, in real-world practice, captured CO2 is primarily used for oil production. Captured CO2 is primarily used for oil production— “enhanced oil recovery” (EOR) in which CO2 is injected into partially depleted oil reservoirs to extract residual oil. In the United States, which is the world leader in CCS, virtually the only use of the captured carbon is EOR (Foehringer Merchant 2018). EOR is also the primary use of captured CO2 globally—the vast majority of captured CO2 that has been injected for subterranean storage worldwide was frst used for oil extraction via EOR (Global CCS Institute 2018). An analysis of the “Facility Data” on the Global Carbon Capture Institute website also indicates that most captured CO2 is used for EOR.7 As Dismukes et al (2018) stress: “The use of EOR changes the nature of carbon from being a pollutant to a valuable commercial input…” EOR is the predominant use of CO2 not only in point-source capture, but also is emerging as the predominant use in DAC (Blum 2019; Storrow 2020), something that is not generally acknowledged in the technical literature on DAC. Scientifc and technical papers commonly argue that captured CO2 could be “utilized” for a variety of products other than oil, including synfuels, chemicals, building materials, and cement (e.g., Sandalow et al. 2017; Davis et al. 2018; Soltof 2019; Hepburn et al. 2019). However, there is no climate-signifcant level of alternative demand for captured CO2 at this time or in the foreseeable future because utilization volumes fall far short of sequestration need (Bennett et al. 2014; Schäfer et al. 2015; Mac Dowell et al. 2017; Foehringer Merchant 2018; Center for International Environmental Law 2019; van Renssen 2020; Global CCS Institute, undated) and most of these uses would result in the CO2 soon being recycled back into the atmosphere. For details see Online Appendix 1. In principle, it may be possible for DAC to be net CO2 reductive if powered by a non-carbon energy source and if the captured carbon is stored underground and not used for commercial production. Operationally there are only extremely small-scale pilots (e.g., Climeworks experiments in Switzerland and Iceland). We found no analyses of a fullscale, renewables-powered DAC process based on a full life cycle (see Fig. 1) and including embodied emissions and emissions from chemicals (e.g., sorbent) manufacture. Yet, the major, but generally ignored, policy issue about subsidizing renewables-powered DAC is whether renewable energy should be channeled for carbon removal rather than used directly to reduce carbon emissions by powering homes, industry, businesses, and transport.