Take on a podcast episode from Bite-Size Climate Tech, originally published Mon, 26 Oc. Listen: https://podcasters.spotify.com/pod/show/lydiaclinzi/episodes/The-Replacement-for-the-Replacement--Andreas-Bremen--Co-reactive-e3r3moo

TL;DR

  • Co-reactive makes a supplementary cementitious material (SCM) by carbonating milled minerals with CO2 in a tubular reactor — storage happens inside the product, not underground.
  • The pitch isn’t lower-carbon cement; it’s replacing fly ash and slag, which are vanishing as coal plants close and steel moves to direct reduction. Useful framing.
  • Scale path: 1,000 t/yr demo now, 10,000 t by end of 2027, 100,000 t before 2030. A cement plant does ~1 Mt. Honest about the gap.
  • Reaction time cut from years (ambient) to ~1 hour via milling, heat, pressure, additives. Feedstock not specified.
  • Water: 250 kg/t product, recirculated, vs ~150 kg/t for cement. Not a removal play yet — CO2 source is point-source, not air.

Lydia Chen’s Bite-Size Climate Tech sits down with Andreas Bremen, chemical engineer, mineralization PhD and co-founder of Co-reactive, for a short tour of their carbonation-to-SCM process, the 1,000 t/yr demonstration plant in Erkrath, and the go-to-market logic. Recorded 3 September 2026. Episode here.

The load-bearing argument is the “replacement for the replacement” line. Cement’s emissions sit in clinker; the industry has long diluted clinker with fly ash and blast-furnace slag. Both are structurally disappearing. Bremen’s claim is that this creates demand pull for a carbonated mineral SCM independent of any carbon price — a buyer “wants to get rid of the dependency because they know cement prices are increasing.” The product substitutes 25–50% of cement in a concrete mix depending on strength and durability requirements, and he’s explicit that performance has to match, not exceed, incumbent recipes.

The process itself: mill a mineral feedstock fine, slurry it in water, pump it through a long tube, inject CO2, let both phases dissolve and re-precipitate as carbonates, then dewater and dry. The engineering problem is retention time — ambient carbonation takes years; they claim roughly an hour. What’s missing from the conversation is the feedstock identity and the CO2 source. Both matter for anyone evaluating this as storage: the feedstock determines the tonnes-CO2-per-tonne-product ratio, and the CO2 source determines whether this is removal or avoided emissions. Bremen’s stated long-term model is co-location with cement plants and licensing, using captured flue-gas CO2 — he notes Heidelberg Materials’ Norwegian plant is the only commercial-scale cement capture in Europe. That’s carbon capture and utilisation with durable storage, not carbon dioxide removal, unless a biogenic or direct-air stream gets plugged in later. He doesn’t claim otherwise, which is to his credit.

The water exchange, prompted by a previous guest’s question, is the kind of operational detail these interviews rarely surface: 250 kg water lost per tonne of product in residual moisture, filtrate recirculated, no wastewater stream. Cement runs ~150 kg/t. Same order of magnitude, as he says.

For context, this slots into the mineralization-into-building-materials cluster alongside Paebbl, Carbon Upcycling and Neustark — the last of which does claim removal credits by using biogenic CO2 in recycled concrete aggregate, which shows what the credit-market version of Co-reactive’s process would look like. The relevant diligence questions for a buyer or investor are the ones the episode skips: tonnes CO2 bound per tonne SCM, feedstock mining footprint, and energy for milling, heating and drying at the 100,000 t scale. None of that is in the transcript, so no numbers here.

Worth 25 minutes if you cover mineralization pathways or the cement-as-storage-sink thesis and want a clear founder explanation of why SCM scarcity, not carbon pricing, is the near-term demand driver. Skip if you need removal-credit economics or measurement, reporting, and verification (MRV) detail — there’s none.