All four of today’s stories come down to one question: which tonnes count. The physical limits on carbon removal are not the binding constraint right now. The accounting rules are.
That shows up in the EU, where a plan for 250 Mt of removals inside the Emissions Trading System depends entirely on eligibility definitions. It shows up in the UK, where the government’s answer to its greenhouse gas removal (GGR) review is mostly a set of rules about what qualifies for support. It shows up in the science, where the honest answer to “how much can enhanced rock weathering remove” is “it depends on what you can measure.” And it shows up in Klaus Lackner’s long-running argument that scale is a manufacturing and policy problem, not a chemistry problem. The ceiling on CDR this decade is a definitions problem.
The EU’s 250 Mt only exists on paper until the eligibility rules are written
Captain Drawdown’s daily CDR Log #281 looked at the EU plan to bring removals into the Emissions Trading System (ETS), the cap-and-trade market that covers power, industry and aviation. The headline number is 250 Mt of removals. The catch is that the number says nothing about which removals.
The distinction matters more than the total. Permanent removals, meaning geological storage via direct air capture or bioenergy with carbon capture and storage (BECCS, where biomass is burned for energy and the CO₂ is stored underground), behave like a true offset against fossil emissions. Land-based removals from forests and soils are reversible, and they are already counted under the EU’s separate land accounting rules for land use, land-use change and forestry (LULUCF). If the same tonne is credited in both systems, the 250 Mt shrinks in practice while growing on paper.
So the real policy work is in the fine print: permanence thresholds, whether temporary storage gets a discount or a different unit, and how the removals link to the EU’s existing certification framework. A 250 Mt headline with loose rules does less than a 100 Mt headline with tight ones. The number is not the policy. The definitions are.
Lackner’s case for scale rests on manufacturing, not on a breakthrough
The second take covered Klaus Lackner, the Arizona State researcher who proposed direct air capture decades before it had a market. His argument against the “CDR can’t scale” myth is deliberately unglamorous. The chemistry of pulling CO₂ from air is known. The cost comes from building the same unit thousands of times and learning as you go, the way solar panels and wind turbines came down the cost curve through volume rather than invention.
Two caveats he does not skip. First, DAC at scale needs cheap, low-carbon energy, and that energy competes with direct decarbonisation. Second, none of this is a reason to slow fossil-fuel phase-out. Removal only makes sense for residual emissions that cannot be cut, and Lackner has been consistent on that point. The myth he is debunking is “it can never scale,” not “we don’t need to cut emissions.” Those are different claims, and conflating them is how CDR gets misused.
Enhanced weathering’s real number is bounded by measurement, not by rock supply
The third take, with Derry, asked how much CO₂ enhanced rock weathering (ERW) can actually remove. ERW spreads crushed silicate rock such as basalt on farmland; rain and soil acids react with it, and the CO₂ ends up as dissolved bicarbonate that eventually reaches the ocean.
The theoretical potential is large because basalt is abundant and farmland is already managed. The practical number is smaller and uncertain for a specific reason: the removal happens slowly, underground, and partly downstream, so measurement, reporting and verification (MRV) has to track carbon that leaves the field. Field trials from different groups give different weathering rates depending on soil pH, rainfall, rock grain size and how the carbon is traced. The data cannot yet distinguish a fast-weathering site from a site where the signal is measurement noise.
That is the ERW lesson for today’s pattern. The gigatonne-scale estimates are a supply calculation. The creditable tonnes are an MRV calculation. Until those converge, buyers will keep paying for the second number, not the first.
The UK’s GGR response is also a rulebook
The fourth take, with James Screen, went inside the UK government’s answer to its GGR review. The substance is a framework for which removal methods get supported, how permanence is defined, and how the business model for engineered removals links to existing carbon pricing.
The same questions from Brussels reappear in London: does biomass-based removal count the same as geological DAC, how are land-based tonnes treated, and what level of monitoring is enough to issue a credit. The UK has moved earlier than most on contracts for engineered removals, which gives it a chance to set definitions others copy. Whether that happens depends on the detail, and the detail is still being written.
What’s next
Watch the EU eligibility text. The question is whether permanent and land-based removals get separate units in the ETS, or one blended category. Separate units would preserve the integrity of the 250 Mt. A blended category would quietly erode it.
Watch for ERW MRV convergence. The sign of maturity will be two independent field programmes reporting weathering rates that agree within a factor of two, measured by the same method. Until then, treat any single-site number as a single-site number.
The physical case for removal is settled enough. The accounting case is where the next two years get decided.