Conscious Living

Decarbonizing Concrete with Algae

Decarbonize Concrete with Algae

Concrete is the most widely used substance on Earth in the civil construction industry, forming the foundation of modern development while strengthening buildings and structures. However, due to its extensive use, concrete production is a huge contributor to greenhouse gas emissions. In fact, approximately 8% of carbon dioxide (CO2) released into the atmosphere comes from the concrete manufacturing process. 

With increasing environmental and economic concerns, regulators, engineers, developers, and owners are seeking innovative concrete solutions that conserve non-renewable resources. The global demand for regulating concrete production waste stems from these growing environmental and economic issues.

Reducing Cement’s Carbon Footprint

Researchers have been working on various alternatives to reduce the energy consumption and environmental impact during the concrete fabrication process. Cement plants have started testing carbon capture technologies and electric kilns to lower emissions. However, carbon capture is costly, and scaling the technology to meet the demand of the cement and concrete industry is quite challenging. 

One interesting alternative is the use of algae. Algae can be used as a biofuel to heat cement kilns, and algae cultivation systems have been linked with cement production to capture carbon. It naturally utilizes sunlight, water, and dissolved carbon dioxide to produce large amounts of new calcium carbonate, which is the primary material in limestone.

A team at the University of Colorado Boulder, along with their colleagues at the Algal Resources Collection at the University of North Carolina Wilmington (UNCW) and the National Renewable Energy Laboratory (NREL), is exploring the use of all-natural microalgae to tackle the cement industry’s biggest emissions problem. Their innovative work has earned them a $3.2 million grant from the U.S. Department of Energy’s (DOE) Advanced Research Projects Agency-Energy (ARPA-E). The research team was recently selected by the HESTIA program (Harnessing Emissions into Structures).

“This is a really exciting moment for our team,” says Wil Srubar, the lead principal investigator on the project and an associate professor at the University of Colorado. “Now is the time to solve this very challenging problem for the industry. We believe that we have one of the best solutions, if not the best solution, for the cement and concrete industry to address its carbon problem,” he adds.

The idea of growing limestone came to Srubar while snorkeling in Thailand in 2017. He observed that calcium carbonate, the main component of limestone, grows naturally in the ocean.

Typically, to make Portland cement, which is the most common type of cement, limestone is extracted from large quarries and burned at high temperatures, releasing substantial amounts of carbon dioxide. The research team discovered that replacing quarried limestone with biologically grown limestone, a natural process completed by some species of calcareous microalgae through photosynthesis (similar to growing coral reefs), offers a net carbon-neutral way to produce Portland cement.

Ground limestone is often used as a filler material in Portland cement, typically replacing 15% of the mixture. By using biogenic limestone instead of quarried limestone as the filler, Portland cement could not only become net neutral but also carbon negative. It would pull carbon dioxide out of the atmosphere and store it permanently in concrete.

“If all cement-based construction worldwide were replaced with biogenic limestone cement, we could prevent 2 gigatons of carbon dioxide from being released into the atmosphere each year. Additionally, we would pull more than 250 million additional tons of carbon dioxide out of the atmosphere and store it in these materials,” explains Srubar.

The researchers are also working on optimizing algae growth, and a startup called Minus Materials, which emerged from this research, has already made small quantities of the material available with plans to expand. Minus Materials previously won the university-wide Lab Venture Challenge pitch competition and secured $125,000 in seed funding and hopes to begin pilot-scale production within 12 to 24 months. It’s already beginning to supply small samples to partners in the cement industry and companies, such as Microsoft, that are searching for new ways to decarbonize. Srubar envisions eventually forming a network of global production sites that can supply the biogenic limestone locally, around the world.