Cement is a way of life for Bryan Kalbfleisch. “I was born and raised in the ready-mixed concrete business,” says the New Jersey-based general manager, explaining that his father worked in the industry for 40 years. “I was the kind of kid who knew how to operate heavy machinery before I could drive. “

Now he’s doing something he never imagined: developing a new kind of concrete that can store carbon dioxide to help fight climate change.

The start-up Solidia Technologies that he heads is among a growing number of people trying to solve one of heavy industry’s most difficult problems: how to make concrete without producing a lot of gas emissions. greenhouse effect.

Concrete is one of the most widely used raw materials in the world, just after water, and among the most polluting. Industry accounts for about 2.6 billion tonnes of carbon dioxide each year, or about 6% of global emissions. If it were a country, it would be the fourth emitter, just behind India, ahead of Russia and Japan.

Startups trying to produce low-carbon cement are attracting some of the most prominent tech investors, such as Bill Gates’ Breakthrough Energy, Amazon’s Climate Pledge Fund, as well as venture capitalist John Doerr, of Kleiner Perkins. More than $ 100 million in venture capital has been allocated to cement start-ups in the past 12 months.

Large cement manufacturers, including Holcim in Switzerland and HeidelbergCement in Germany, are also working on the problem.

“We are really interested in this area because it is a big problem that needs to be solved,” explains Jonah Goldman, managing director of Breakthrough Energy, which recently invested in three cement start-ups: Solidia, CarbonCure and Ecocem.

“There are different ways of approaching it, because it seems like such an unaffordable problem. It is intrinsically a product emitting greenhouse gases, ”he explains. “The natural process of its creation releases carbon into the atmosphere.”

Why is cement so difficult to decarbonize?

The basic chemistry of cement makes its decarbonation very difficult: the main ingredient is clinker, made from limestone heated in a kiln. When limestone heats up, it releases a lot of carbon dioxide and changes its molecular structure.

This chemical reaction accounts for up to 70 percent of emissions from cement manufacturing, and the remaining 30 percent comes from the energy to heat the kiln. For every 10 tonnes of cement produced, 6 tonnes of carbon dioxide are found in the atmosphere.

When every step of the concrete supply chain is considered, the industry’s carbon footprint is among the worst.

Ian Riley, chief executive of the World Cement Association, says the industry has already cut emissions by more than a fifth over the past two decades, through traditional means, such as the use of more efficient furnaces, cleaner sources of energy for heating and making cement with less clinker.

Industry can cut emissions by an additional 30 percent using these methods, he estimates, but not down to zero. “Much of the fruit on hand has already been picked,” says Riley. “That still leaves 70% of the emissions we haven’t dealt with – and for that 70% we really need new approaches. “

Whoever finds the winning solution will benefit greatly from an industry worth $ 300 billion a year.

Solidia produces concrete pavers by hardening the material in a carbon dioxide chamber

Rob Niven, head of CarbonCure, aims to store 500 million tonnes of carbon dioxide per year © J Yanyshyn / VisionsWest

CarbonCure, a start-up based in Canada, has developed a complementary machine that injects CO2 to the point of mixing cement with water and sand to create concrete. This permanently stores CO2 and makes the concrete stronger.

Rob Niven, founder and CEO, says his goal is to store 500 million tonnes of carbon dioxide per year. Its equipment is used at more than 400 concrete mixing sites and it is supported by investors such as Mitsubishi, Microsoft and Amazon.

CarbonCure earns revenue from licensing fees from construction companies that use its technologies, as well as from the sale of carbon credits for the CO2 captured.

“Our job is to create value from CO2 molecules and store them permanently, so that they never end up in the atmosphere and contribute to climate change,” explains Niven.

At Solidia, Kalbfleisch takes a different approach – one that produces concrete pavers, like those used in landscaping, by curing the material in a carbon dioxide chamber.

“Solidia cement reacts with CO2, it uses very little water in the prefabrication process, compared to traditional concrete,” explains Kalbfleisch. “About 3-5% of the weight of the finished product is solid carbon,” he adds.

Another start-up, CarbonBuilt, linked to the University of California at Los Angeles, is developing concrete blocks that use less carbonaceous raw materials and are hardened with the CO2 from the fumes.

Rahul Shendure, managing director, says the process requires an initial investment of around $ 1 million for each block production line, the idea being that companies save money over time by using raw materials. less expensive. “Once you invest the capital expenditure, it’s cheaper to manufacture than traditional concrete,” he says.

A challenge for all “green” cement start-ups is that at present, large cement companies have few financial incentives to reduce their emissions.

Europe is an exception, where cement factories have to buy allowances to cover their CO2 emissions and can save money if they produce less. But in many other countries, like the United States, policies are not yet in place to encourage cement companies to pay for greener alternatives.

“It’s not so much that there are regulations today [that require emissions cuts], says Riley. “It’s just that at some point the social license to operate will depend on [producers] do something like that.

Many of the world’s biggest cement makers are also rushing to crack the formula in anticipation of tougher rules that may be imposed on them.

Magali Anderson of Holcim works with different materials to make cement with less emissions © Elisabeth Real

Holcim’s low carbon concrete

At Holcim, the goal is to reduce emissions of cement-like materials from 561 kg of CO2 per tonne in 2019, to 550 kg by 2022, and to 475 kg by 2030.

Magali Anderson, its sustainability manager, explains that Holcim works with different materials, such as calcined clay, to make cement with less emissions, in addition to other approaches. Holcim is also partnering with Solidia to produce concrete in the United States.

While these changes will help meet his short-term emissions goals, Anderson says the use of carbon capture solutions will be necessary in the long term. Holcim has over 20 pilot projects underway to test different ways of capturing carbon from the cement process.

Even if these technologies improve, it will still be expensive to produce carbonless cement. With sectors such as aviation and shipping, cement is quite simply likely to remain one of the most difficult industries to decarbonize, says Lord Adair Turner, chairman of the Energy Transitions Commission.

“With cement, our calculation was that [reaching net zero] could double the cost of cement, resulting in a 30% increase in the cost of concrete, ”he says. “And that could increase the cost of construction by 3%. It is therefore small, but it is not trivial.

“So that raises questions about who will pay for it, who will be willing to pay more for a zero carbon cement building. It’s more of a challenge than for cars and steel.


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