Captain Drawdown’s daily logbook on every CDR story, paper, and expert voice — so you don’t have to read them all.
On Wednesday, Zeke Hausfather posted a thread that quietly reframed the most expensive argument in carbon removal procurement. “We have a new paper out on the value of reversible carbon storage in a zero-emissions world,” he wrote. “We try and answer the question of when it makes sense to ‘rent’ vs ‘buy’ CDR” (@hausfath on Bluesky).
Rent versus buy. That is not science vocabulary. That is procurement vocabulary. And it is the tell.
Hausfather has spent the last decade as one of the most-cited climate scientists working at the science-policy boundary. Berkeley Earth. Breakthrough Institute. Climate research lead at Stripe. Science lead at Frontier Climate, the buyer consortium that has committed roughly a billion dollars in offtakes for durable carbon removal through 2030. He also co-leads Carbon Brief’s new Cited newsletter, which amplifies climate research to a policy audience. The man has distribution.
That biography is the tension. The person advising the largest durable-only CDR buyer in the world just co-authored a paper, with Allegra Mayer, Jennifer Pett-Ridge, Jerome Dumortier and Dimitar Slessarev in ACS, arguing that pure-durable portfolios are likely not the cost-optimal path.
Here is the dollar claim, in his words: “The main takeaway is that using reversible CDR as a bridge to durable CDR is potentially more cost-effective than perpetual maintenance of reversible CDR or an immediate transition to durable CDR” (@hausfath on Bluesky).
Translate that. The cheapest dollar-per-ton-of-warming-avoided path is neither pure forestry nor pure direct air capture. It is a sequence. Buy reversible storage now, when it is cheap. Buy durable removal later, when costs have come down. In between, use the reversible tons to hold warming flat while the durable supply scales.
This is a direct economic challenge to the removals-only, durable-only orthodoxy that Robert Höglund and others have framed as the highest-integrity buyer choice. Höglund’s argument is moral and integrity-first. Hausfather’s is unit-economic. Both can be right about different things, but procurement committees do not run on moral arguments. They run on cost curves and defensibility memos.
The lens Hausfather brings is what makes him consequential. He is not a forestry partisan. He has spent years criticizing low-quality avoided-emissions credits. And he is not a DAC maximalist either, despite his Stripe and Frontier Climate roles. He holds both critiques at once, which is why his framework forces both camps to update. To the reversible-CDR sellers, he is saying your tons have a defensible role. To the durable-CDR sellers, he is saying: “Durable replacements don’t emerge whole cloth out of the ether; near-term investments in durable CDR are needed alongside reversible CDR to help scale the technology and drive down costs” (@hausfath on Bluesky).
He is also explicit about the risk. “Institutional commitments to maintain reversible CDR projects cannot be guaranteed. Reliance on reversible CDR as a bridge to durable CDR therefore carries an unknown amount of risk” (@hausfath on Bluesky). That hedge is what keeps him credible to durable-only buyers. The paper does not tell them they were wrong. It tells them the portfolio math is more interesting than they assumed.
Look at where the buyer market is right now. TD Bank just signed two ten-year offtakes with Climeworks and Deep Sky for more than 18,000 tonnes of durable removal (@pembina on Bluesky). A Canadian bank, picking DAC at premium prices, when cheaper reversible volume was available. That is exactly the procurement choice Hausfather’s paper now gives the next bank a defensible reason to revisit. Not abandon. Revisit. Mix.
The economic implication is concrete. If you sell forestry, biochar, or soil carbon, you now have a peer-reviewed citation to bring to buyers who previously dismissed you on permanence grounds, a point we have argued from a different angle in Why Carbon Removal Needs More Than Trees. If you sell DAC, mineralization, or biomass with carbon removal and storage, you need a sharper answer to why your offtake premium is justified against a credible rent-first-buy-later alternative. And if you are a buyer, “rent or buy” likely becomes a standing question in every CDR procurement memo within twelve months.
The bet Hausfather is making is that the integrity debate has hit a ceiling and the next decade of CDR allocation will be decided on cost-per-warming-avoided, not credit category. He is moving the conversation from category fights to portfolio math. That favors buyers who can hold both timeframes in mind at once.
Watch the next Frontier Climate or Microsoft announcement. If either explicitly cites a bridge rationale for including reversible volume, that is the moment the paper becomes a purchase order. Until then, Hausfather has done what very few researchers manage. He gave the procurement teams new vocabulary, and the vocabulary will outlast the paper.
Citations
- Bluesky — @hausfath on Bluesky — Bluesky post
- Carbonbrief — Cited newsletter
- Bluesky — @hausfath on Bluesky — Bluesky post
- Bluesky — @hausfath on Bluesky — Bluesky post
- Bluesky — @hausfath on Bluesky — Bluesky post
- Bluesky — @pembina on Bluesky — Bluesky post