Slag is the molten effluent produced when producing steel in traditional blast furnaces. The material has been touted as a greener alternative to cement for making concrete, the most abundant man-made material on Earth. But as the steel industry turns to greener production methods, the effluent is facing supply chain problems.
As steelmakers in the U.S. and Europe turn increasingly to electric arc furnaces (EAFs) that are smaller, more energy-efficient and run on electricity rather than coal, Cocoon is a new startup founded on the belief that producing greener steel or generating concrete slag doesn't have to be an either/or proposition.
Despite concerns about concrete production, demand is only growing. Although cement only makes up about 10-15% of the concrete mix, it's responsible for about 90% of emissions, so the industry is constantly looking for greener alternatives. Cocoon is developing a solution called “e-slag,” a processed by-product of steel production that acts as an energy-efficient replacement for cement.
Image credit: Cocoon
“The challenge with steel slag is that it has a high iron content, which is one of the things that limits its reactive ability as a cementitious material,” co-founder and CEO Eliot Brooks tells TechCrunch. “We have a two-stage process that addresses the high iron content and the challenges that it brings, and then gets the reactivity of the cement in the other stage of the process.”
Though still in the testing phase, the UK-based company's technology is designed to be integrated into existing steel production workflows. A standard system uses slag pots mounted on rails or on the front of a lorry, from which molten material is discharged into a large pit. The slag is then cooled, crushed, and sent to the cement manufacturer. Cocoon's solution is housed in a shipping container that is installed in the pit to collect the molten material that flows out of the slag pots.
The company recently raised $5.4 million in pre-seed funding, with participation from Wireframe Ventures, Celsius Industries, Gigascale Capital and SOSV. SOSV has previously backed Cocoon, and Brooks works part-time at SOSV's newly opened HAX facility in Newark, New Jersey. The founders were also present when TechCrunch toured the facility in April.
The new funding will be used to build an R&D facility in London, with initial testing to take place at a steelworks in the north of England, followed by testing in the U.S. Brooks hopes to have Cocoon's technology integrated into a pilot plant sometime in the second half of 2025.