E&E Publishing recently posted a story on direct air capture, that I think shows good progress for advancing the dialogue on “DAC” and CDR more generally. I think the narrative of the DAC story could be clarified in several ways:
1. Asking the right key question. The article starts with a quote from Klaus Lackner saying: “It’s not a question of if air capture technology will be adopted; it’s a question of when.” The real question in my mind is “at what scale will DAC be adopted and for what purposes.” DAC seems best suited today to provide a valuable tool for decarbonizing sectors of the economy where eliminating carbon emissions is very expensive (today air travel and long haul trucking are good examples of such hard-to-decarbonize sectors). In these sectors, DAC could be used to synthesize liquid fuels out of ambient air, like Audi is trying to do with DAC partner Climeworks, in order to provide a carbon neutral liquid fuel. But whether DAC will ever be used to generate negative emissions on the billion+ tonne scale seems highly uncertain. Today, bio-energy with carbon capture and storage (Bio-CCS) is the leading contender to generate negative emissions cost-effectively and at scale. The article’s claim that “the sheer amount of carbon dioxide that has to be taken out of the atmosphere is too much for biomass alone to handle” is unsubstantiated, and flies against scientific literature suggesting that the biomass resource could be adequate for negative emissions so long as we also start abating GHG emissions quickly.
2. Placing DAC in the broader context of CDR. Even if biological sources aren’t large enough to achieve all necessary CDR to prevent climate change, DAC isn’t the only other option for achieving sustainable atmospheric concentrations of CO2. Mineral carbonization and the creation of carbon negative materials (like cement and plastics) could also play a key role in a portfolio of CDR solutions. Placing DAC in this context gives a more complete picture of where R&D priorities should lie.
3. Addressing some of the hard questions early on. The article concludes by quoting Lackner again, saying: “In terms of economic viability, I don’t know the answer to that; the cost of future technology is completely unpredictable.” Completely unpredictable is an overstatement. We might have large confidence intervals around our predictions, but it is important to at least formulate our current understanding of how these costs might evolve over time. This will help us prioritize research and measure the progress of that development over time. Tackling these tough questions early on helps inform the dialogue on CDR to ensure that we develop the most cos-effective and sustainable responses to climate change possible.