Meta, Holcim, and other investors ink deals to clean up concrete

The United States makes some 90 million metric tons of cement every year to bind together the nation’s concrete buildings, bridges, and other infrastructure. In the process, U.S. cement plants generate huge amounts of planet-warming emissions — equivalent to those from 16 million gas-powered cars.

Decarbonizing cement and concrete is necessary to deal with climate change, but it’s a complicated task. Doing so requires both using cleaner technology to run scorching-hot kilns and reconfiguring the long-standing chemistry of cement itself. The industry is searching for low-carbon solutions at the same time that it faces rising demand in general from the builders of data centers, warehouses, housing, and much more.

Globally, constructing and operating buildings accounts for more than a third of total greenhouse gas emissions every year. Of that share, about a fifth are ​“locked into the construction materials” themselves, Luke Herbert of Climate Group, an international nonprofit, said during a Climate Week NYC event held in late September.

“But here’s the twist,” Herbert added. ​“As electricity becomes greener and our buildings more efficient, operational emissions are set to drop very significantly, meaning the materials that we put into those buildings will become a much greater issue.”

That challenge has led several major construction firms, building owners, and investors to partner with or pour money into a growing number of startups — some of which are already operating facilities, while others are still testing innovations in the lab. In recent years, ​“clean concrete” companies have raised more than $750 million in venture capital funding, Crunchbase estimated in August, and the activity isn’t letting up.

Here’s a look at four of the latest developments in this emerging space.

Meta invests in CarbonBuilt 

Meta, the parent company of Facebook, is investing in the startup CarbonBuilt to help reduce the embodied carbon of the tech giant’s data centers, the companies announced last week.

Los Angeles–based CarbonBuilt is working to replace the industry-standard Portland cement — cheap, ubiquitous, and extremely carbon-intensive to produce — with its alternative cement ​“binder.” CarbonBuilt’s first customer, Blair Block, uses the binder to make thousands of tons of concrete blocks every month at its retrofitted masonry plant in Alabama.

The startup plans to install its technology at a masonry facility in the western U.S. and at another in the east-central region by year end, Rahul Shendure, CEO of CarbonBuilt, told Canary Media this week.

Meta and CarbonBuilt didn’t disclose specifics about their collaboration. Shendure said only that Meta is injecting ​“catalytic capital that is pushing these next plants to happen sooner than they otherwise would.” The tech giant is ​“very motivated, when they see things that are promising, to help shift the shape of that [adoption] curve so that it goes faster,” he added.

Typical Portland cement is a fusion of limestone and clay that binds together sand, gravel, and water to form concrete. When baked, the limestone breaks down into its constituent parts of calcium oxide and carbon dioxide. This chemical process, called calcination, is responsible for about 60 percent of the industry’s overall emissions.

CarbonBuilt, a spinout from UCLA’s engineering school, uses calcium-rich by-product materials from industrial sources for its binder. At the Alabama plant using CarbonBuilt’s tech, Blair Block combines the material with water and aggregates, presses the mixture into molds, and places them inside a chamber. CO₂ from an on-site biomass furnace then flows into the chamber, helping drive a chemical reaction that forms solid concrete and permanently traps carbon in the blocks.

The company claims its novel approach can reduce carbon emissions from concrete-making by up to 70 percent, compared to industry baselines, for roughly the same price.

“Concrete as well as other key hard-to-abate industries represent a big chunk of the embodied emissions associated with data center infrastructure,” John DeAngelis, Meta’s head of clean technology innovation, said during Climate Week NYC. The deal with CarbonBuilt is an effort to target ​“emissions at the source” and to help drive ​“deep decarbonization” in the concrete sector.

CRH, Holcim place big orders with Sublime Systems 

Sublime Systems, another leading cement startup, said last week that it had secured $75 million in combined investments from CRH and Holcim, two of the world’s largest building-material providers.

Sublime, a spinout of the Massachusetts Institute of Technology, makes cement by running an electrical current through a bath of chemicals and calcium silicate rocks. The process avoids using limestone feedstocks and eliminates the need for fossil-fueled, high-temperature kilns, resulting in what Sublime calls ​“fully electrified, ​‘true-zero’” cement.

Today, Sublime makes its cement from a 250-ton-per-year pilot plant in Somerville, Massachusetts. Earlier this year, the startup was selected for an $87 million grant from the U.S. Department of Energy to build its first commercial-scale plant in Holyoke, on the site of a former paper mill. Sublime hit another milestone in May when construction workers began applying concrete made from its novel cement at an office park project in Boston.

Since then, the company has been working to line up customers for the 30,000-ton-per-year Holyoke facility, which could open as soon as 2026. The $75 million in funding from CRH and Holcim includes both equity investments and binding, prepaid agreements to purchase some of the low-carbon cement from the forthcoming manufacturing plant.

“If Sublime is to have a swift and massive impact on climate change, our breakthrough technology must be paired with manufacturing operations, logistics, and distribution — areas the building materials leaders excel in,” Leah Ellis, CEO and co-founder of Sublime, said in a press release on the new investment.

Cocoon nabs $5.4 million with early-stage, flexible tech 

The startup Cocoon is in a much earlier stage of development than CarbonBuilt or Sublime Systems. Its technology aims to serve not one but two heavy industrial sectors: cement and steel.

The London-based company recently raised $5.4 million in pre-seed funding from a group of climatetech investors, including Gigascale Capital, the VC firm led by former Meta executive Mike Schroepfer. Cocoon plans to use the funding to expand its research-and-development capabilities in London and to test its technology at a research steel plant in northern England starting at the end of this year.

Cocoon is developing a type of supplementary cementitious material, or SCM, that can partly replace Portland cement to help drive down CO₂ emissions. SCMs are frequently used in the global construction industry, and many come from the waste streams of coal-fueled facilities such as ironmaking blast furnaces.

Cocoon is repurposing a trickier industrial byproduct: the slag from electric arc furnaces, which melt iron and scrap metal to make steel. As steelmakers work to clean up their polluting industry, companies are building more of these electricity-powered furnaces in the U.S. and globally. But there’s a hitch. Unlike blast furnace waste, the by-product they produce — given its high iron content — can’t be used to supplement cement.

Eliot Brooks, co-founder and CEO of Cocoon, said the startup has developed a system that can fit directly into the slag pits of electric furnaces. A two-step chemical process then ​“overcomes the challenges” of the iron content and allows the slag to work like any other SCM, though Brooks didn’t provide more specific details about the patent-pending approach.

When used in cement-making, the treated slag could potentially fetch higher prices — and deliver greater CO₂ reductions — than the iron-rich original, which today is mainly used as a low-value road aggregate. Brooks said he hopes Cocoon’s process can incentivize the steel industry’s shift toward facilities that use clean electricity and green hydrogen, not coal, by allowing companies to sell more-lucrative SCMs.

“We need to decarbonize these industries in sync,” he told Canary Media.

Carbon Limit’s carbon-removing approach

Carbon Limit, based in South Florida, is taking a different approach with its supplementary materials. The company has developed a powdery mineral additive that it claims can enhance the natural ability of concrete to directly soak up and store CO₂ from the atmosphere.

Carbon Limit launched in 2021 and now has several projects underway to test and verify the carbon-capturing ability of its products. In August 2022, the startup partnered with the Minnesota Department of Transportation to lay 35 new pavement mixes on a quarter mile of a major U.S. interstate as part of a three-year case study. Carbon Limit has also deployed its concrete mixes on walkways at Google’s Innovation Center in Sunnyvale, California.

Meanwhile, the startup is developing additives that could drive down CO₂ emissions through other means. Last month Carbon Limit unveiled a new material that it says can improve concrete’s ability to reflect sunlight and limit heat absorption, keeping buildings cool and, ideally, reducing overall energy use from running fans and air conditioners.