Take on a podcast episode from The CDR Policy Scoop, originally published Tue, 27 Oc. Listen: https://shows.acast.com/the-cdr-policy-scoop/episodes/minings-untapped-removals-opportunity-with-cara-maesano

TL;DR

  • Almost any carbon removal pathway can run on a mine site; only ex situ mineralization with metal recovery truly requires one. Useful framing.
  • Headline potential (>1 Gt/yr) and $80–300/t range are theoretical and price-based, not cost-based. Maesano says so herself; treat accordingly.
  • Thetford Mines hub (Frontier, Carbon Removal Canada) targets ~800 Mt of Quebec asbestos waste. Research only, no projects announced yet.
  • Arca claims ~100x reactivity from microwave activation of tailings. Lab result, not field data.
  • Environmental liability reduction, not credit revenue, is the current driver for miners. Likely the most actionable insight here.

Eve Tamme and Sebastian Manhart host Cara Maesano, lead author of RMI’s August report on mining and carbon dioxide removal, now scientific and technical director at CDR 2030, on this episode of The Carbon Removal Scoop. The ~30 minutes cover which removal pathways fit mine sites, how surficial mineralization of tailings works and is being accelerated, what the report’s scale and cost numbers actually rest on, and why permitting and risk aversion slow adoption more than land area would suggest.

The most useful part is Maesano’s taxonomy. Surficial mineralization is “ideal for” mine sites because the reactive waste and the flat storage facilities are already there, but it could happen elsewhere. The one pathway that genuinely needs a mine is ex situ mineralization in a reactor that simultaneously extracts metals the first pass missed. She also flags in situ mineralization variants that circulate fluid back up after it has leached target metals — effectively mining and storage in one loop, potentially viable at deposits too lean to justify a conventional mine. On acceleration: untouched tailings piles carbonate only in the top layer exposed to water and CO2. Arca’s Australian trial used rovers to churn the material and expose fresh rock; its newer microwave activation reportedly makes material “100 times more reactive” in the lab. Maesano is careful: “that’s to be seen in the field.”

The hosts press on the numbers, and the answer matters for anyone citing this report. The >1 Gt/yr figure is an upper bound derived from calcium and magnesium content in estimated waste volumes. The $80/t floor is Frontier’s own estimate, stated when it announced its second near-billion-dollar offtake tranche with surficial mineralization as a priority. The upper end relies on third-party techno-economic analyses because, as Maesano puts it, “getting cost information from startups is really challenging.” She calls the estimates “very squishy.” That’s a candid framing you won’t find in most report summaries.

On adoption, the interesting claim is that miners’ per-tonne-of-CO2 profit is too low to buy durable removals, but their environmental remediation costs are enormous and well understood internally. Anglo American’s enhanced weathering work in Brazil started from a waste mountain explicitly labelled “a liability.” Carbonating tailings may also stabilize heavy metals against leaching — shown at small scale, not yet at scale. Permitting is the counterweight: mines are licensed to handle waste in specific ways and rarely deviate, so building removal in from day one (Canada Nickel is the cited example, with a seven-year permitting path versus 15–20 typical) may be easier than retrofitting.

For context, this builds on Frontier’s stated prioritization of surficial mineralization and Arca’s roughly 300,000-tonne Microsoft offtake mentioned in the episode, and sits alongside Naim Jawad’s Carbon Curve interview with Canada Nickel that Maesano references directly. Captain Drawdown has previously covered the enhanced weathering feedstock sourcing question; this episode is the mine-side mirror of that conversation.

Worth an hour for geochemical CDR developers, buyers weighing surficial mineralization offtakes, and anyone who needs to know what the RMI headline numbers do and don’t support before quoting them.