Cutting Construction’s Climate Impact with Algae Bricks

Cement—the essential binding ingredient in concrete, bricks, and mortar—is a climate nightmare. It is made by heating clay and limestone at extremely high temperatures, using carbon-polluting fuels. The chemical reaction also causes huge quantities of carbon dioxide in the atmosphere. This process is extremely carbon-intensive, and cement accounts for approximately 8% global CO2 emissions. With the world’s building stock projected to double by 2060, climate advocates are desperate for alternative materials to come to market—fast.

Longmont’s factory may be the solution. By the end of this year, it will begin churning out concrete bricks made not from cement—but from algae. Prometheus Materials was born out of research at the University of Colorado in 2021. It takes microalgae that is normally found in lakes and ponds, and grows them in bioreactors. Air is added to the microalgae so it can eat the carbon dioxide, seawater, and the light of LED lamps. The algae can then produce a cement like substance, which bonds sand to gravel and stone to make concrete. It mimics how organisms create seashells and hard coral reefs naturally.

Algae-based bricks will be available commercially in 2023. They were designed in partnership with and part-funded by U.S. architecture firm Skidmore, Owings & Merrill (SOM)—known for creating the ​​Burj Khalifa in Dubai and New York’s One World Trade Center.

According to Loren Burnett, Prometheus Materials CEO, making bricks emits only tenth the amount of CO2 as conventional concrete block production. Burnett says that when the company has completed installing solar panels for its manufacturing plant, it will be carbon neutral and in three years carbon negative. “There’s virtually no CO2 emitted during the process and we actually sequester CO2,” he says. “Because the algae absorbs it through photosynthesis, and we then embed that algae into our building materials.”

Prometheus’ production timeline puts it near the forefront of a movement to replace carbon-intensive conventional building materials, like steel and concrete, with materials derived from plants and other organisms. The so-called “bio-based” materials sector is still in its infancy. But supporters say it has the potential to transform the construction industry from one of the world’s biggest emitters—responsible for 11% of CO2 emissions—to an absorber of carbon. This is a change from climate villain to part of solution.

New era in plant-based building

It is not a new idea to use nature for construction. For thousands of years, people have used the organic material and plants around them to build structures. Straw has been used to create cob from South Africa, England and Afghanistan for thousands of years. Bamboo is strong and fast growing, which makes it a crucial component of traditional East Asia architecture. Timber has maintained its popularity throughout history in many countries. In the United States, 90% of all new homes are still built with wooden frames. Environmental campaigners have been pushing for carbon-absorbing materials in small-scale and residential construction over the past few decades.

Ban Muangkeo Village has traditional bamboo houses that are built from stilts on stilts.

Wolfgang Kaehler—LightRocket/Getty Images

However, it has been difficult to build large-scale structures with natural materials (though some high-profile wooden skyscrapers have appeared in certain cities). Researchers are working to develop a new type of organic-derived material that is strong enough to replace the carbon-intensive concrete and steel. To stimulate those efforts, in June, the U.S. Department of Energy announced $39 million in grants for 18 projects working on “technologies that can transform buildings into net carbon storage structures.” The University of Colorado team behind the algae bricks is one of the recipients. A grantee also works on insulation materials made from fungi that could be retrofitted to homes. A third wants to add microbes to wood to create a “living” material “with the strength of steel.”

Continue reading:The Netherlands now offers a lower-cost mortgage for houses made of straw and fungi

A handful of bio-based products have been released to the market. BioMason is a Durham-based company that feeds bacteria calcium and CO2 in order to create bio-cement. It currently sells tiles across Europe and the U.S. Basilisk is a Dutch biotech company that sells concrete made with limestone-producing bacteria. They also offer concrete mixes that can be used on existing buildings. Concrete will self-heal and not need to be reconstructed or demolished.

Bio-based material companies face many of the same problems as any other climate-friendly technology: They still struggle to increase their laboratory successes to a scale that is commercially viable, and at prices comparable to carbon-polluting alternative technologies. Others need to discover how they can obtain large amounts of organic matter from small farms without competing with agriculture, the restoration and conservation projects, or renewable energy.

How would you make algae bricks mainstream?

But Brant Coletta, a partner at SOM, who worked with Prometheus to design their bricks, claims the technology’s “easy scalability” was the main draw for the architecture firm. Initially Prometheus will grow its algae—which can double in volume every four to six hours—at its Colorado plant, to produce its cement-like material, turn it into bricks, and ship them to customers. Within 18 months, they will start shipping a dried, light-weight version of the bio-cement, so that customers can turn it into bricks—without expensive equipment or highly trained staff.

Prometheus provides microalgae seawater, CO2, light and other nutrients to make a cement-like substance.

Brooks Freehill

To convince Coletta of that last point, one of Prometheus’ co-founders sent him a few bricks in the mail along with photos of his young children making them in their backyard. “Quality control probably wasn’t the strongest in that, but it demonstrates how this is a product that can find its way into the global market,” Coletta says.

Safety certification of Prometheus’ algae bricks, by the American Society for Testing and Materials, should be complete by the end of the year, along with construction of the manufacturing plant, according to Burnett. He says the plant will immediately begin producing “tens of thousands” of bricks and quickly scale up to a “significant” amount—though he would not disclose projected volumes, citing commercial reasons. Burnett did not reveal the final price of the bricks, but the company has a good idea of their costs. “Our goal is to not have any green premium attached to our blocks,” he says.

Even if the cost of the bricks proves to be comparable to conventional concrete blocks, it may take architects and developers a few years to trust that “they will perform and have limited-to-no cost impact on projects,” Coletta says. There’s not much data on how prevalent organic-derived materials are in the construction industry. Experts estimate that around 3% are bio-based in the Netherlands. This country has been a leader in sustainable building practices over recent years.

SOM however, which is known for its green architecture leadership and keenness to offer low-carbon solutions to clients, plans to add bricks to their material list as soon safety certification has been completed. “We’ve had clients come in and they see us working on this and say they want it in their project right away,” Coletta says. “It’s hard for me to hold my design teams back.”

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