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

Why this matters now

Enhanced rock weathering (ERW) has spent 2025 and early 2026 winning offtakes on a story about co-benefits: spread crushed silicate rock on farmland, farmers get liming and micronutrients, buyers get durable CDR. This week a CDRXIV preprint from Olagaray, Lambert and Thorlakson argues the co-benefit ledger has been kept with one column missing. Nickel, chromium and cobalt from basalt and dunite feedstocks accumulate in soils on the same timescales as the carbonate formation buyers are paying for, and most methodologies treat that accumulation as a compliance checkbox rather than a dose-response variable. If you are buying ERW tonnes in 2026, this is your critique to steel-man.

What is it?

ERW crushes silicate rock (usually basalt, sometimes the more reactive dunite) and spreads it on agricultural land. The rock reacts with CO2 and water, forms bicarbonate, and eventually stores carbon as dissolved or precipitated carbonate. Feedstock chemistry varies by quarry across orders of magnitude. Dunite in particular is nickel-rich. Every tonne of rock that dissolves to release calcium and magnesium also releases whatever trace metals rode along in the mineral lattice.

Who’s involved?

The Olagaray et al. framework is the first structured risk-assessment tool aimed squarely at metals. Beerling’s group at Sheffield published UK field data this month showing ERW alters soil gas fluxes across land uses in ways that complicate carbonate accounting, and by extension the transport pathways for co-released metals. Registries issuing ERW credits today, including Puro.earth’s methodology under which Eion’s Twinterstellar facility is listed, treat metal loading as a threshold check, not a monitored curve. UNDO, the largest operator by farm footprint, reports 60 farms visited across 31 farmers. Deployment is ahead of standardized metals MRV (measurement, reporting, verification).

What just happened?

The CDRXIV preprint dropped this week alongside the EGUsphere soil gas paper. Read together, they are a structural critique: Jessen et al. on arXiv show subsoil acidity can delay carbonate formation for decades. The same residence time applies to co-released metals. Slow carbon means slow, concentrated metal exposure in the same soil horizon.

The parallel is uncomfortable. As Josh Gabbatiss noted on Bluesky about carbon capture and storage, (@joshgabbatiss.bsky.social), “CCS is considered by the IPCC to be ‘critical’… But its development has been slow. The IEA has scaled back its projections as the technology consistently fails to live up to expectations.” ERW is at the stage where “critical” framing can outrun measurement. Metals monitoring is where that gap will show up first.

Open questions to track

  • Will Puro.earth, Isometric, or the EU Carbon Removals and Carbon Farming (CRCF) regulation add quantitative per-hectare cumulative metal loading thresholds in their next ERW methodology revision?
  • Does the first regulatory intervention come from a carbon registry worried about durability, or an agricultural agency worried about soil quality? The latter would reprice existing credits fast.
  • Does dunite deployment slow, or do operators shift to lower-nickel basalts and eat the reactivity penalty?
  • Who audits the loading curve, and does long-tail liability sit with the landowner or the offtaker? Current contracts I have seen are silent.

Further reading

Ask your supplier for the loading curve in writing. If they cannot produce one, you are underwriting the gap.

Citations

  1. Cdrxiv — CDRXIV preprint from Olagaray, Lambert and Thorlakson
  2. DOI-resolved paper — ERW alters soil gas fluxes across land uses
  3. Puro.earth — Puro.earth’s methodology under which Eion’s Twinterstellar facility is listed
  4. LinkedIn — reports 60 farms visited across 31 farmers — LinkedIn post
  5. arXiv preprint — Jessen et al. on arXiv — preprint
  6. Bluesky — @joshgabbatiss.bsky.social — Bluesky post