Cement might be crucial to construction, but it’s "a climate nightmare,” as Ciara Nugent put it in TIME. Making concrete is a carbon-intensive process that involves melting limestone and clay, which requires large amounts of fossil fuels to achieve heat levels. In fact, cement is responsible for 8% of global CO2 emissions. The number of buildings in the world is estimated to double by 2060, making cement a particularly pressing climate issue.

That’s where Prometheus Materials comes in. The Colorado-based manufacturer has developed an innovative solution: bricks made of algae rather than cement. The Prometheus factory can grow microalgae in bioreactors, feed it carbon dioxide, and the algae secrete a substance that resembles cement. Making these bricks emits a tenth of the CO2 used to make typical concrete blocks. Because manufacturing algae bricks sequesters carbon, there’s even a chance the process is carbon negative, especially if the manufacturing plant relies entirely on renewable energy. 

The Prometheus Materials algae brick fits with a larger trend of researchers and innovators turning to the sea for solutions to the climate crisis. Start-ups have been exploring seaweed farms that can sequester carbon and even remove methane from the atmosphere. Meanwhile, planting mangrove forests and kelp in the sea and fertilizing oceans with dissolved iron can help the ocean absorb even more carbon than it does currently.