The concrete industry is at a pivotal moment as the world grapples with the environmental impact of this ubiquitous construction material, which accounts for approximately 8% of global carbon dioxide emissions. With an annual production of about 30 billion tons of concrete, three times more than four decades ago, innovative solutions are on the rise to create lower-carbon alternatives.

One approach involves drawing inspiration from the past. Dmat, a deep tech startup, develops self-healing concrete inspired by Ancient Roman techniques. Meanwhile, a team of researchers at Northwestern University is working on “Martian concrete” that boasts more than double the strength of traditional concrete and doesn’t require water. Over the years, researchers have also experimented with unconventional materials, such as volcanic ash, carbon black, rice husk ash, algae, and even human hair. However, while these experiments may make headlines, Professor Christopher Cheeseman of Imperial College London argues that they are unlikely to have a substantial global impact in reducing concrete’s carbon footprint. “You can take coffee grinds and put them into concrete, and maybe you can make something locally that is quite clever, but it’s going to have zero impact globally,” he says.

Cheeseman’s perspective encourages researchers to focus on readily available materials found across the globe. These materials include limestone, clay, demolition waste, and silicate minerals, which make up roughly 90% of the Earth’s crust. The primary contributor to concrete’s carbon footprint is Portland cement, a binder that requires vast energy and emits significant carbon during its production. To produce lower-carbon concrete, some companies are incorporating CO2 from the air into their concrete, while others are exploring alternative kiln energy sources, such as solar, wind, or hydrogen.

Companies like Seratech and Blue Planet Systems are replacing a portion of cement with CO2-derived silica, mitigating emissions directly from factory ducts. Brimstone, based in California, utilizes calcium silicate rocks, which are 200 times more abundant than limestone. Additionally, technologies like LC3 (Limestone Calcined Clay Cement) are gaining momentum and could reduce emissions by up to 40% compared to standard Portland cement.

While ingredients like clay and limestone may not possess the novelty of repurposed diapers or coffee grounds, their global availability is the key to addressing the concrete industry’s environmental concerns. Professor Cheeseman emphasizes that the most significant growth in concrete demand is occurring in Southeast Asian and developing countries where materials like clays are abundant and essential for building the infrastructure of tomorrow.

By Impact Lab