Cement has an emissions problem. Can tech that mimics coral fix it?

Literally and figuratively, cement is the glue that holds our cities together. Each year, humans use more than four billion tons of this material — the key ingredient in concrete — to build homes and offices, roads, and sewer systems. Concrete, for its part, is so ubiquitous that there is only one material on Earth that we use more of: water.

But the cement industry also has a major climate problem. It’s responsible for 8 percent of the world’s carbon dioxide emissions — that’s roughly three times more emissions than all aircraft combined.

San Jose–based startup Fortera is aiming to change that.

While a small percentage of the cement industry’s carbon emissions comes from burning fossil fuels, most of its emissions are the byproduct of a chemical reaction that transforms limestone into cement. Fortera has developed a new cement production process that actually absorbs carbon dioxide, rather than emitting it.

“Concrete is not going anywhere,” Fortera CEO and co-founder Ryan Gilliam told Canary Media. ​“So to manufacture it in a way that’s better for the environment, that’s really the solution.”

Fortera’s unique approach is gaining traction worldwide.

Already, the startup has worked with ready-mix suppliers to provide its cement for projects with Caltrans, the City of Santa Cruz, and the City of Berkeley, alongside various California-based contracting companies. Last year, Fortera received $85 million in series C funding to expand operations beyond its plant in Redding, California. Since then, it has begun engineering an expanded plant at an undisclosed location in the Western U.S., with the capacity to produce 400,000 tons of cement per year. (The Redding plant produces 15,000 tons per year.)

Then, in December, it announced a new partnership with multinational cement corporation Sumitomo, whose venture capital arm was also an investor in the earlier funding round. This collaboration will allow Fortera to expand into Asia, where 73 percent of the world’s cement is produced. The firm is also in the early planning stages for 30 new plants in the United States, Mexico, Asia, and Europe.

There is increasing demand for green cement and desire within the industry to decarbonize, according to Ben Skinner, a manager on the Cement and Concrete team at clean energy think tank RMI. That’s especially true in places like the European Union that offer incentives to companies to cut down on emissions.

“Fortera is one of several innovations that we are really excited about,” he said.

In search of nature’s cement

The inspiration for Fortera came from the oceans.

In the early 2000s, entrepreneur Brent Constantz, who holds a PhD in geography and biological sciences, became fascinated by corals, tiny creatures that make up the ocean’s colorful reefs. Corals absorb carbon dioxide from the sea as they build their hard skeletons — the structures we think of when we imagine coral — and these skeletons are made of calcium carbonate, cement’s essential ingredient. Constantz wanted to know: If corals can build sturdy structures while cleaning up the environment, why can’t we? He founded the company Calera in 2007 aiming to do exactly that. In 2019, the company was rebranded as Fortera.

“Calera was founded on the principle, when we make cement we make CO2, when nature makes rocks it absorbs CO2,” said Kas Farsad, who joined Calera at its inception as a materials scientist and now works as the Chief Strategy Officer for Fortera. ​“You had this compass that something is possible.”

To form their skeletons, corals undergo a cascade of fleeting chemical reactions. Unstable carbonate chemicals react to form new, more stable carbonates, each of which exists for only a few milliseconds. Scientists at Fortera wanted to find a way to hit ​“pause” on this natural process so that they could isolate an intermediary that can act as cement. Then, if that ​“paused” substance is later mixed with water, sand, and other aggregates, it would be like hitting ​“play”— it would become cement. Between 2007 and 2009, scientists at Calera tried thousands of times to produce one of those intermediaries. ​“It failed miserably for 18 months,” Farsad said.

Eventually, they found their intermediary: a mineral called vaterite, produced by mixing lime and carbon dioxide from limestone under the right conditions.

The concept was initially controversial, with many scientists expressing skepticism that the idea would work. While Calera did develop a product, the idea didn’t take. In 2011, Constantz stepped down from his position as CEO and in 2015 the company shelved its patents. The concept was largely forgotten until 2019, as public concern about climate change mounted. ​“People started calling and saying, ​‘Hey, that original technology, is it worth revisiting?’” said Gilliam, who at that point had taken the helm of the company under its new name, Fortera.

But although the underlying technology, inspired by coral, is the same, Fortera has a different business model than its predecessor.

Calera saw itself as a carbon capture and sequestration company. Its first partners and investors were coal plants. Fortera, in contrast, is working with manufacturers of traditional cement, also called Portland cement. Brand-new Fortera plants, called ReCarb plants, are bolted onto already existing Portland cement plants. Fortera’s technology then takes the carbon dioxide emitted by the existing plant and incorporates that gas into its product, ReAct Cement. This cement can then be used on its own or mixed with Portland cement to form a hybrid product.

One element of Fortera’s process that’s particularly attractive to manufacturers of Portland cement: It eliminates a lot of waste.

To make Portland cement, you heat limestone in a kiln. The limestone then undergoes a chemical transformation in which nearly half of it is lost as carbon dioxide. ​“By actually capturing that, we effectively double the amount of product,” Gilliam said. That allows cement manufacturers to lower production costs while eliminating the ​“green premium” that can make it more difficult to sell sustainable products.

It’s a win-win situation: Fortera’s production method allows cement companies to double production, raise profits, and cut down on emissions. 

“We figured out how to take that technology that we’d already proven out but do it in a way that actually works with the cement industry,” Gilliam said.

Transforming an Industry

ReAct isn’t a zero-carbon product — yet. The ReCarb facility and Portland cement plant form a closed-loop system. By sequestering the CO2 produced when limestone is heated to form Portland cement, the process cuts down carbon emissions by 70 percent. However, it doesn’t eliminate emissions from using fossil fuels to run both the plants.

Fortera isn’t the only company that aims to transform cement.

Some Portland cement manufacturers are taking it upon themselves to lower emissions by decarbonizing the energy supplies used to heat their kilns or employing carbon capture. Meanwhile, startups like Brimstone and Sublime Systems have developed their own chemical processes that eliminate or lower carbon dioxide emissions. Both companies received industrial demonstrations grants from the U.S. Department of Energy earlier this year.

“There are a variety of solutions that need to be deployed to reach our net-zero targets by 2050,” said Skinner. ​“We’re going to see a lot of variety based on market preferences, regional availability of materials, what the existing infrastructure looks like.”

Skinner believes that Fortera is playing an important role in this pivot, because of the competitive price of its product and the fact that it can be mixed with traditional cement. ​“This is a great near-term solution,” he said.