Captain Drawdown’s daily logbook on every CDR story, paper, and expert voice — so you don’t have to read them all.

Four European CDR modeling papers hit arXiv in a single week, and read together they expose an uncomfortable truth: the headline cost numbers for direct air capture and CO2 removal portfolios are governed less by chemistry or geology than by undisclosed assumptions about future carbon prices. Those assumptions diverge by an order of magnitude across teams, and almost none of the papers treat the divergence as the headline variable.

Start with the most explicit of the four. Chiani and co-authors, in The Uncertain Policy Price of Scaling Direct Air Capture, show that DACCS deployment trajectories are not really a function of capex (capital expenditure) learning curves. They are a function of which carbon-price pathway modelers assume governments will deliver. Uncertainty in that single input swamps technology cost uncertainty. The paper essentially tells the rest of the modeling community: stop arguing about sorbent chemistry, start arguing about the policy floor.

Now contrast that with the Aarhus group. Their twin papers, Near-optimal solutions for carbon capture, conversion, storage, and removal strategies and Exploring carbon dioxide removal strategies to help decarbonise Europe using high-resolution modelling, frame European climate neutrality as a residual-emissions management problem. DACCS and CCS volumes drop out of system optimization. The trouble is the word “near-optimal” hides how sensitive the optimum is to the assumed carbon-price scaffolding underneath. Change the price path and the optimal portfolio mix shifts hard.

The fourth paper, Bernecker and Müsgens on Direct Air Capture in Europe, catalogs the “wide variety of cost estimates” in the DACCS literature. They attribute the spread to siting, heat integration, and storage routing. That is true. But the ranges only become bankable once paired with a policy-price floor, and none of the four papers agrees on what that floor should be.

Ken Caldeira (@kencaldeira.com on Bluesky) put the strategic risk this way: “We may need to reduce costs more to make the endgame cheaper, but questions about the endgame should not cause us to blunder our opening moves.” That is exactly what the arXiv cluster keeps colliding with. Endgame cost curves are being cited to justify or defer opening moves, when in fact the cost spread is mostly about which policy price modelers slot into the spreadsheet.

David Ho (@davidho.bsky.social on Bluesky) framed DAC as temporal arbitrage, pulling future emissions back. He joked that his own piece could have been called “DAC To The Future.” That arbitrage only prices if a future carbon price exists. Which is the variable each arXiv team assumes differently.

Here is the tension. Four independent European modeling teams shipped serious CDR strategy work in seven days. The supply side of the literature is producing impressive output. But Robert Höglund’s read-across in Markets are more important for novel than conventional CDR reminds us the demand side is also waiting on a price signal. Both sides are waiting on a price the other expects to materialize. And the communications layer between them is thin. Dirk Paessler (@dpaessler.bsky.social on Bluesky) recently pointed to his own AI agent as the European CDR explainer of record. That is not a complaint, it is a measurement. Four papers landed and the discourse around them ran through a handful of individuals.

So what does this mean if you are buying, supplying, or regulating CDR right now? Any European DACCS cost estimate you quote is a function of an assumed carbon price that varies wildly across the literature. Treating these ranges as technology forecasts rather than policy forecasts will keep producing offtake decisions and roadmaps mispriced for the world that actually shows up. Germany’s recent CCfD allocation is one data point on that price curve. The arXiv cluster is showing you the curve has no agreed shape. Our earlier piece on how DAC scales leaned on capex learning. After this week, that framing needs a policy-price annotation.

What to watch: whether the next wave of EU-funded CDR modeling adopts a common policy-price sensitivity protocol, or whether the Aarhus, RFF-CMCC, and Cottbus groups keep publishing in parallel with incompatible price scaffolding. If the latter, buyers will pick whichever cost curve flatters their procurement strategy, and the modeling literature will become a menu rather than a guide.

Citations

  1. arXiv preprint — The Uncertain Policy Price of Scaling Direct Air Capture — preprint
  2. arXiv preprint — Near-optimal solutions for carbon capture, conversion, storage, and removal strategies — preprint
  3. arXiv preprint — Exploring carbon dioxide removal strategies to help decarbonise Europe using high-resolution modelling — preprint
  4. arXiv preprint — Direct Air Capture in Europe — preprint
  5. Bluesky — @kencaldeira.com on Bluesky — Bluesky post
  6. Bluesky — @davidho.bsky.social on Bluesky — Bluesky post
  7. Substack (marginalcarbon) — Markets are more important for novel than conventional CDR — Substack post
  8. Bluesky — @dpaessler.bsky.social on Bluesky — Bluesky post