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Holcim unveils carbon sink concrete in Venice

By Richard High, 31 July, 2025
Holcim's Basic Services Unit prototype in Venice. The Basic Services Unit prototype in Venice showcases Holcim’s biochar concrete, designed to permanently store CO₂ and enable low-impact construction.

Holcim has revealed a new carbon sink concrete using biochar technology, in collaboration with Pritzker Prize-winning architect Alejandro Aravena and his firm ELEMENTAL. The system was presented during the 2025 Architecture Biennale in Venice in a full-scale Basic Services Unit housing prototype that demonstrates how construction can actively remove CO₂ from the atmosphere.

The biochar-enhanced concrete is designed to deliver net-zero carbon performance in production (A1-A3 phases) and is fully circular, incorporating 100% recycled aggregates. The prototype housing unit uses precast modular panels to deliver essential living functions like sanitation and cooking, following ELEMENTAL’s well-known incremental design model that has already been replicated over 4,000 times in Latin America.

Biochar is produced through pyrolysis, a low-oxygen thermal process that converts organic waste into a stable carbon form, preventing the release of up to 3 kg of CO₂ for every kilogram of biochar used. Holcim has incorporated this material into low-carbon formulations of cement, mortar and concrete, with no reported compromise in performance.

“Holcim’s new decarbonisation technology allows us to address the scale and speed of the housing crisis' demand without putting a strain on the environment,” said Alejandro Aravena, founder of ELEMENTAL.

“In Venice, we are bringing incremental housing to its core: a structural sanitation unit using precast panels takes care of the basic needs of inhabitation.”

Holcim CEO Miljan Gutovic added: “Through our partnership with Alejandro Aravena and the ELEMENTAL team, we have demonstrated how Holcim’s new carbon sink technology can shape the future of construction.”

The project forms part of the Time Space Existence exhibition organised by the European Cultural Centre and runs from 7 May to 23 November 2025.

Prototype Basic Services Unit on display at the 2025 Venice Biennale, showing biochar concrete’s architectural potential. Image: Holcim. Prototype Basic Services Unit on display at the 2025 Venice Biennale, showing biochar concrete’s architectural potential. Image: Holcim.
Precast concrete panels being craned into place during construction of the prototype. Image: Holcim. Precast concrete panels being craned into place during construction of the prototype. Image: Holcim.
Early visualisation of the unit’s modular design, based on incremental housing principles. Image: Holcim. Early visualisation of the unit’s modular design, based on incremental housing principles. Image: Holcim.
Refined version of the prototype, integrating biochar concrete with visible services and stair access. Image: Holcim. Refined version of the prototype, integrating biochar concrete with visible services and stair access. Image: Holcim.
Final evolution of the Basic Services Unit concept, adaptable to different urban layouts. Image: Holcim. Final evolution of the Basic Services Unit concept, adaptable to different urban layouts. Image: Holcim.
A aerial view of the prototype being exhibited at the 2025 Architecture Biennale in Venice. Image: Holcim. A aerial view of the prototype being exhibited at the 2025 Architecture Biennale in Venice. Image: Holcim.

 

Why this matters to the UK concrete sector

Biochar-enhanced concrete could offer a practical pathway to carbon-negative materials, with immediate relevance to the UK’s push for net-zero construction.

As the industry embraces offsite, modular, and precast approaches in social housing, infrastructure and retrofit schemes, Holcim’s technology signals a scalable solution that may soon reach commercial markets. Its compatibility with standard concrete applications — including infrastructure, industry, and buildings — is especially significant as UK contractors seek verified methods to meet carbon disclosure and ESG targets.

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