An Alabama plant is now churning out low-carbon concrete

CarbonBuilt kicked off production with its novel tech, which it claims can reduce overall CO2 emissions from concrete-making by 70 to 100 percent.
By Maria Gallucci

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Stacks of gray concrete blocks sit on pallets in a dusty industrial lot.
Blocks of "low-carbon" concrete sit outside Blair Block's facility in Childersburg, Alabama. (CarbonBuilt)

Concrete makers around the world are racing to reduce emissions from the ubiquitous but hard-to-decarbonize industry. This week, that global effort took an important step forward at a modest facility in central Alabama.

On Wednesday, the startup CarbonBuilt said commercial production of its low-carbon concrete has begun at a plant in the city of Childersburg. Blair Block, a local masonry manufacturer, is making the thick gray blocks using CarbonBuilt’s novel technology, which the startup claims can reduce overall carbon dioxide emissions from concrete-making by 70 to 100 percent.

This is not only a milestone for CarbonBuilt and Blair Block, but also for the broader concrete and building materials industries,” Rahul Shendure, CEO of CarbonBuilt, said in a statement. We’ve shown that it’s possible to massively reduce carbon emissions from concrete production without compromising on cost or performance.”

CarbonBuilt is among a rapidly growing group of companies and research institutions working to tackle the most carbon-intensive component of the concrete-making process: Portland cement. The limestone and clay fusion is an essential ingredient, but it emits substantial amounts of carbon dioxide when heated.

Today, the world makes more than 4 billion metric tons of cement every year. As a result, cement production accounts for between 7 and 8 percent of global CO2 emissions.

CarbonBuilt’s own alternative-cement process involves using calcium-rich industrial waste materials, which are then combined with water and aggregates. The mixture is pressed into molds and placed inside a temperature-controlled chamber. The startup then flows CO2 into the chamber, driving a chemical reaction that forms solid concrete and permanently traps carbon in the blocks.

The startup formed in UCLA’s engineering school in 2014, then spun out in 2019. The Los Angeles–based company previously demonstrated its technology at coal- and gas-fired power plants in northern Wyoming and in Wilsonville, Alabama, where the U.S. Department of Energy operates the National Carbon Capture Center. In 2021, CarbonBuilt won $7.5 million from the NRG Cosia Carbon Xprize for its technology.

An industrial facility where concrete blocks are being made
Blair Block retrofitted an existing production line to use CarbonBuilt's novel technology in Alabama. (CarbonBuilt)

Along with the Childersburg project, CarbonBuilt is participating in a new high-tech initiative in Flagstaff, Arizona, as Canary Media reported in March. Block-Lite, a local masonry business, said it plans to produce concrete by combining CarbonBuilt’s unique process with technology that removes carbon dioxide directly from the sky.

The Alabama project will source its CO2 not from fledgling direct air capture” facilities but from forestry waste that’s processed in an on-site furnace. CarbonBuilt and Blair Block retrofitted an existing commercial plant, which Shendure said cost a couple of million dollars to build. However, the low-carbon concrete blocks themselves won’t cost any more to produce than traditional concrete.

CarbonBuilt didn’t say exactly how much low-carbon concrete the facility will produce on the retrofitted line. Whatever the number is, it’s likely to barely even scratch the surface compared to the 1.5 billion concrete blocks produced in the U.S. alone every year.

The startup says the first converted line at Blair Block will avoid at least 2,000 metric tons of CO2 emissions, roughly equal to the annual emissions from 252 average U.S. homes. It will also remove another 500 metric tons of CO2 from the atmosphere through the forestry waste it uses as an input.

C&C Masonry, a leading contractor across Alabama, said it plans to use the alternative blocks for its upcoming contracts. The company is building or bidding for several projects this year that could require using up to 100,000 concrete blocks for use in large public projects around the state, a representative said by email. At 29 pounds a piece, this would translate into nearly 1,500 metric tons of low-carbon blocks.

For CarbonBuilt, the launch of its first commercial production line could help pave the way for retrofitting more of the nation’s 800 or so concrete plants. Many of them are local, family-run businesses like the companies CarbonBuilt is partnering with in Alabama and Arizona.

We look forward to replicating this success at concrete masonry plants around the country,” Shendure said in the statement.

Maria Gallucci is a senior reporter at Canary Media. She covers emerging clean energy technologies and efforts to electrify transportation and decarbonize heavy industry.