A ground-breaking development by a team of scientists and engineers at the University of Colorado Boulder, USA is all set to address the environmental impact of conventional construction by replacing the carbon-intensive Portland cement with a new zero-carbon concrete alternative.

Responding to a US Department of Defense initiative related to engineered living materials, the team used a photosynthetic biocementation process to combine naturally occurring microalgae with water, sunlight and CO2, and create a bio-cement, similar to the material used by coral to build reefs and oysters to generate their shells.

When mixed with aggregate, this bio-cement creates a zero-carbon building material with mechanical, physical, and thermal properties comparable or superior to Portland cement-based concrete.

The global construction industry is a major contributor to carbon emissions, and Portland cement accounts for 8% of the world’s total annual CO2 emissions, thanks to the carbon-intensive processes involved in the production and transportation of 4 billion tons of this building material each year.

Prometheus Materials, the manufacturer of this bio-cement, says that the product’s ability to sequester carbon during production reduces embodied carbon by approximately 90%, compared to existing Portland cement-based products.

“To prevent catastrophic climate change, we cannot simply replace fossil fuels with renewable forms of energy – we must also decarbonise the way we create building materials,” said Loren Burnett, co-founder, president and CEO of Prometheus Materials.

“By using biological rather than chemical means to create a strong, durable binding agent for aggregate, we can now offer a zero-carbon alternative to carbon-intensive Portland cement. Our bio-cement will transform architecture as we know it, by providing the construction industry with a new decarbonised building material that has environmental and mechanical properties that mirror or exceed the capabilities of concrete, wood, steel, and glass.”

In June 2022, the company closed an $8 million Series A financing round led by Sofinnova Partners, a leading European life sciences venture capital firm, with participation by the Microsoft Climate Innovation Fund, Skidmore, Owings & Merrill (SOM), GAF, and The Autodesk Foundation.

The funding is being used to commercially manufacture zero-carbon masonry units at their production facility in Longmont, Colorado.

Early this year, Prometheus Materials received foundational certifications ASTM C129 for nonloadbearing concrete masonry units (CMUs) and ASTM C90 for loadbearing CMUs for the bio-cement, achieving compressive strengths of 2400–3500 PSI.

Additionally, the ASTM C423 sound absorption testing at the Johns Manville Technical Center in Colorado revealed that the bio-concrete demonstrated a Noise Reduction Coefficient (NRC) of 0.60, which indicates 60% sound absorption or 12 times that of traditional concrete, broadening the application of the innovative technology.

Prometheus Materials’ initial pre-cast bio-concrete product line includes masonry units, segmented modular blocks and acoustic panels as well as paving stones and grass pavers. These products will be commercially available in 2024.

Branko Miletic

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