German start-up transforms captured CO₂ into cement additives to cut emissions

Every major city and the concrete that holds it together mask a central contradiction: the material that enables modern infrastructure is itself a major source of greenhouse gas emissions. Industry estimates put cement-sector CO₂ emissions at roughly 2.4 gigatonnes a year , about 8% of global CO₂ , with more than four fifths of that burden traced to clinker manufacture. In the United States the sector is responsible for tens of millions of tonnes of CO₂-equivalent annually, underscoring why decarbonising cement is a strategic priority for heavy industry and policymakers alike. According to analysis by McKinsey, the chemical release from calcination , the high-temperature reaction that produces clinker , accounts for around two thirds of the sector’s process emissions, making mitigation technically and commercially challenging.

A German start‑up founded in 2024 is pitching a route that addresses both emissions and raw‑material scarcity by turning captured CO₂ into a product rather than a liability. Co‑reactive, based in Düsseldorf, has developed a continuous mineralisation process that reacts CO₂ with magnesium‑ or calcium‑bearing feedstocks , from ultramafic minerals such as olivine to metallurgical slags , to yield supplementary cementitious materials the company calls CO‑SCMs. According to the company, those products deliver improved compressive strength and durability while allowing cement producers to cut clinker fractions, delivering a double dividend of performance and lower embodied carbon.

Crucially for an industry where operational continuity is paramount, Co‑reactive says its process is “drop‑in” compatible with existing cement manufacturing and concrete formulation practices. That integration focus is intended to reduce barriers to adoption by limiting the need for large plant reconfigurations and by maintaining supply‑chain traceability and quality control as the company scales.

Investment and industrialisation path

Co‑reactive closed a €6.5m seed round led by High-Tech Gründerfonds, with participation from NRW.Bank, HBG Ventures, AFI Ventures, Evercurious VC and climate‑tech business angels, and it has received public support through Germany’s Federal Funding for Industry and Climate (BIK). Industry coverage indicates the funds will be used to advance pilot activities and to build a continuous demonstration installation with a throughput target near 1,000 tonnes per annum, scheduled for the second quarter of 2026, while larger first‑of‑a‑kind plants are being designed for start‑up from 2027.

“La financiación y la investigación científica son la base, pero la transformación real solo ocurre a través de la acción empresarial”, Andreas Bremen, cofounder and CEO of Co‑reactive, told Bioeconomia. The company frames the seed capital as enabling the move from laboratory validation to industrial demonstrations and, ultimately, to multi‑kilotonne facilities that could be deployed at cement and steel complexes to mineralise biogenic or process CO₂ streams on site.

Policy and market context

The push for alternatives to traditional supplementary cementitious materials has gained urgency as coal‑fired power generation declines and the steel sector evolves, shrinking supplies of fly ash and blast‑furnace slag that historically helped reduce clinker intensity. Market signals amplify the pressure: carbon prices at record levels and tightening decarbonisation mandates raise the cost of emitting and heighten the value of low‑carbon inputs. According to the Clean Air Task Force, cement production in the U.S. alone represents a significant share of industrial emissions, and reducing both combustion and process emissions is central to national mitigation strategies.

Policy toolkits compiled by international bodies and analysts emphasise that no single technology will eliminate cement’s footprint. Rather, achieving deep decarbonisation will require a portfolio comprising energy‑efficiency measures, fuel switching, clinker substitution, carbon capture and utilisation or storage, and supportive finance and regulation. In that mix, CO‑mineralisation pathways that produce performance‑grade SCMs could be a pragmatic complement to large‑scale CCUS projects, particularly where on‑site integration and product replacement reduce logistics and lifetime emissions.

Technical and commercial caveats

Independent observers and industry analysts caution that scale, feedstock availability and lifecycle accounting will determine whether CO‑mineralisation delivers net climate benefits in practice. The OECD and other technical reviews note that clinker production dominates sector emissions, so approaches that reduce clinker percentage are among the most impactful. However, lifecycle gains hinge on the source and transport of both CO₂ and mineral feedstocks, the energy used in the mineralisation process, and the durability performance of CO‑SCMs in real‑world concrete applications.

Co‑reactive is pursuing partnerships across the value chain , from CO₂ suppliers to cement and concrete producers and standards bodies , to validate product performance and to establish certified carbon accounting. Industry reporting indicates the company is already designing modular plants intended to operate at scales from tens of kilotonnes to several hundred kilotonnes per year, a capacity range required to move beyond demonstration projects to industrial impact.

Implications for industrial decarbonisation

For professional stakeholders in industrial decarbonisation, the Co‑reactive proposition is notable for converting a regulatory cost into a potentially tradable input while addressing an emerging supply squeeze in conventional SCMs. If CO‑SCMs can be produced reliably, competitively and transparently , and if lifecycle assessments confirm substantial net CO₂ removals , mineralisation could become a mainstream lever to lower the carbon intensity of concrete without compromising structural performance.

Yet the path remains exacting. Scaling to hundreds of kilotonnes will demand secure feedstock streams, predictable CO₂ availability at competitive cost, permitting and siting for new modular plants, and acceptance by standards organisations and purchasers in conservative construction markets. That is why finance, industrial partnerships and policy incentives must move in tandem with technical validation to shift the sector’s chemistry at scale.

As regulators sharpen targets and industrial players seek low‑carbon inputs that fit existing operations, mineralisation technologies that convert CO₂ into durable cementitious materials offer a compelling alternative to both carbon storage and scarce recycled SCMs. Whether they will rewrite the carbon balance of the built environment depends on demonstration outcomes, lifecycle transparency and the ability to deploy at the industrial scales demanded by global construction markets.