This American duo wants to tackle Europe’s green cement demands

Cement is responsible for 8 percent of global emissions, making it one of the biggest climate challenges – but also a massive business opportunity for those who can crack the code for lower-carbon production.

In Europe, startups like Sweden’s Cemvision and Paebbl, Ireland's Ecocem, and the UK's Material Evolution are making significant strides in developing low-carbon cement solutions. However, how quickly they can scale these innovations to make a substantial global impact remains unclear.

Brimstone, based in Oakland, California, has been grappling with the same problem since it launched nearly six years ago. But the company has grown rapidly and now has 55 employees.

Impact Loop meets co-founder Hugo Leandri as he glides confidently through the halls of Norrsken House in Stockholm, one of three global impact hubs run by the Norrsken Foundation, a non-profit founded by Niklas Adalberth, co-founder of Klarna, to support startups tackling global challenges.

Brimstone landed a spot on Norrsken’s Impact 100 – a list of the world’s most promising impact startups – a few years back, and the company has kept in touch with the foundation ever since. Now, Leandri is in the Swedish capital as part of a European tour to meet partners and investors.

While he acknowledges that low-carbon cement is a growing industry in Europe, he is confident that Brimstone’s model is unique.

"There are several ways to reduce the climate impact of cement production, and all of them are needed," Leandri says, before adding:

"But we’re the only ones producing Portland cement in a sustainable way."

A volcanic rock solution

Portland cement is the most common type of cement used globally and a key ingredient in concrete. Simply put, making this kind of cement usually generates emissions in two ways. First, through the chemical process itself – when clinker, the hardened material that forms the backbone of cement, is produced from limestone, large amounts of carbon dioxide are released. Second, through the heating of kilns, which often rely on fossil fuels.

Brimstone chose to focus on cutting process emissions and began exploring the possibility of replacing limestone with another material. Cement requires calcium and silicon dioxide, and the founders discovered that calcium silicates in volcanic rock could do the job.

"Cement is a commodity industry, which means cost efficiency is key. Conventional production is efficient but unsustainable. We offer a new raw material that allows for the co-production of both the binder and the cement itself."

But, Leandri stresses, Brimstone isn’t a cement producer.

"We’re a tech company with patents on our process. That means we can work with all kinds of players across the sector."

We’re a tech company with patents on our process

Sourcing the raw materials

Brimstone primarily sources its volcanic rock from existing quarries in the US, where these materials are abundant. By partnering with the right industry players, the company aims to establish production facilities directly next to these quarries, streamlining the supply chain.

The process involves breaking down the rock into its essential components—calcium, silicon dioxide, aluminium, iron, and magnesium—before recombining them in the precise ratios needed for cement production. This method, which Brimstone holds a global patent for, allows them to produce Portland cement without the carbon-heavy step of limestone calcination, explains Leandri.

The energy factor

Achieving zero-emission cement also depends on energy use. While Brimstone says its solution can eliminate the bulk of the 60 percent of emissions that come from the chemical process, the remaining 40 percent comes from heating—and that requires access to cheap, renewable energy.

"Our method makes it possible to use lower temperatures and more electricity than usual. And it’s likely that a producer adopting our technology would also rethink their energy mix to further reduce their climate impact. So in a future where we have an abundance of cheap, green energy, cement production will be more or less emissions-free."

A billion-dollar, three-phase plan

Brimstone is still in the development phase, with three ongoing projects under evaluation. The first, a pilot facility in Oakland with a price tag of €4.6 million [$5 million], aims to provide critical insights into the path forward. Next up is Reno, Nevada, where a small-scale commercial facility will be built for €14–18 million [$15–20 million].

Once the technology is fully validated, Brimstone will move to the third phase, backed by the US Department of Energy, which is covering half of the €370 million [$400 million] project cost.

"When these three steps are complete, we’ll hopefully have produced 100,000 tonnes of material that we can sell on the market."

An added bonus, he explains, is that the new cement process would not require additional permits or licences.

"The beauty of our technology is that the end product is exactly the same material used in regular Portland cement. The final product is no different in any way."

So far, Brimstone has raised around €55 million [$60 million], with a Series B round set to launch in 2025. That’s also part of the reason Leandri is currently in Stockholm.

"There are many skilled investors here who really understand the issue and want to contribute to Europe’s climate transition. And it’s a great market for sustainable cement startups – Cemvision is just one of several exciting players."

Indeed, Norrsken alone has already helped spawn numerous Swedish green transition startups. Norrsken VC, the venture capital arm of the foundation has electric plane manufacturer Heart Aerospace as part of its portfolio, alongside battery manufacturer Northvolt. Flower, one of Brimstone's competitors in the sustainable cement space is also an alumni of Norrsken House.

There are many skilled investors here who really understand the issue

Money lessons from history

Leandri shares that he and and his friend Cody Finke originally came up with the idea for Brimstone while studying at Caltech (the California Institute of Technology), a prestigious US university known for its cutting-edge research in science and engineering. After a few half-successful ventures, they started analysing past industrial revolutions.

"Technological breakthroughs only take off when they’re more efficient and cheaper than the alternative. We quickly realised that cement was an industry in urgent need of that kind of transformation."

But Leandri stresses that true cost reductions require large-scale production.

"You can’t rely on subsidies or sustainability premiums forever – that’s not particularly sustainable in itself. The key is to find a method that works and scale it properly so that costs drop to the same level or below market price. That’s when we can make a real impact."