Mrv

Last week we published a long write-up of the first CDI Symposium, where a room of soil scientists picked apart the world’s most-measured enhanced-rock-weathering experiment and landed on an uncomfortable conclusion: the rock dissolves, but the expected carbon-removal signal often doesn’t show up — and whether it does depends heavily on the specific soil. Enhanced rock weathering (ERW), the symposium suggested, is not a universal climate fix but a context-dependent one, and measuring it honestly is the whole ballgame. ...

Near the end of the first-ever Carbon Drawdown Initiative (CDI) Symposium, the man who paid for the whole thing stood up to thank everyone and said something you almost never hear from a project’s funder: “It’s now five years ago since we literally spread the first ton of rock on the field… and I still cannot tell if we’ve done CDR since then. That drives me nuts. And it’s just one field.” ...

Most CDR efficiency claims are framed as a ratio. They should be framed as a balance. A ratio of 1.1 — 100 tonnes emitted across the lifecycle to capture 110 tonnes — is a vanity metric. The number that matters is the net balance: gross capture minus embodied plus operational emissions. That is what we mean when we say a pathway is “85% net.” For every 100 tonnes of CO2 pulled out of the air or fixed in stable form, 85 tonnes survive after you subtract everything the project emitted to make those 100 tonnes happen. The 15 tonnes you are losing went into making steel, running compressors, trucking rock dust, or heating a sorbent. That is what credible buyers should pay for: the 85, not the 100. The credible registries already refuse to issue credits for anything else. ...

A new Nature paper maps the uncertainties of Enhanced Rock Weathering — from toxic trace elements to carbon tracking gaps. Here’s what it means for CDR.