Rising demand for housing in most major cities around the world is increasingly at odds with efforts to reduce greenhouse emissions, as the literal building blocks—concrete and cement—of the construction projects are extremely polluting.
Roughly 7% of all carbon emissions today come from cement production, making it one of the highest-emitting industrial sectors, according to the consulting firm McKinsey.
“Concrete is an essential building material,” said Claude Loréa, director of cement, innovation and ESG at the Global Cement and Concrete Association. “Three-quarters of the infrastructure that will exist in 2050 has yet to be built.”
Mirrors direct sunlight into Synhelion’s solar receiver to produce a fossil-fuel-free clinker at a trial in Spain.
About 90% of the emissions in traditional portland cement come from producing clinker—the binding agent that holds the water, gravel and sand together—that makes up nearly three quarters of the final product.
Typically, clinker is made by heating limestone and clay in a rotating kiln to temperatures above 2,700 degrees Fahrenheit. Coal is often used to power these kilns. About two thirds of the clinker emissions are released by the limestone when heated while the rest come from the combustion of fuels to create the heat.
That process has been replicated for millennia but companies now are looking to change it. Approaches to the problem include improving energy efficiency, using cleaner fuels, capturing the carbon emissions produced and switching to alternative raw materials.
One way the industry is looking to improve sustainability in cement production is by targeting efficiency gains.
British startup Carbon Re is aiming to optimize the use of fuel by employing artificial intelligence and machine learning. One of the industry’s main issues is fuel wastage, according to Carbon Re co-founder Aidan O’Sullivan, who said that differing qualities of coal mean most producers often use too much of it to produce clinker.
The startup is analyzing a number of producers’ actual fuel usage to train its machine-learning algorithm to predict the optimal fuel needed for a given fuel source and production target. “We are looking to optimize the fuel-consumption process so you use just enough energy to get the chemical reaction you need,” he said.
Small improvements can add up to a sizable emission effect. “A 2% of fuel saving translates to tens of thousands of tons of carbon per plant being saved,” O’Sullivan said. He added that the development has wider implications too: “There is a huge opportunity to use AI in heavy industry where their contribution is 20% of carbon emissions.
Others are looking to change the fuel type altogether. Cemex, one of the world’s largest cement producers, has been working with Switzerland-based Synhelion to produce clinker using solar energy rather than coal. Last year, the two companies said their trial project in Spain produced clinker without fossil fuels.
Under the approach, mirrors concentrate sunlight into Synhelion’s solar receiver which is used to heat a kiln to around 2,700 degrees Fahrenheit to create a clinker without fossil fuels. “We are eliminating combustion of fossil fuels while also having high temperature heat,” said Gianluca Ambrosetti, co-chief executive and co-founder of Synhelion.
The two companies are now working to see if the process can be done on a continuous cycle by adding thermal energy storage to its process. It aims to produce solar-powered clinker commercially by 2030.
Synhelion is also looking to add carbon capture to its model to absorb the CO2 released by the limestone, alongside cutting those emissions from the combustion to produce the heat.
The International Energy Agency considers carbon capture, use and storage as a means of reducing emissions for the industry, but at the moment uptake has been slow. In its Net Zero Emissions by 2050 Scenario, the IEA says “8% of CO2 from the sector needs to be stored globally by 2030, up from negligible levels today. But progress on deployment and investment in this area is as yet limited, with these technologies still at relatively early stages of development today.”
Heidelberg Materials, one of the world’s largest cement producers, is looking to change that. Heidelberg is currently building a carbon capture and storage facility to run alongside its plant in Brevik, Norway. It aims to start capturing emissions from production by the end of next year with the capacity to absorb roughly 400,000 tons a year when fully operational. It would be the world’s first large-scale carbon-capture site at a cement plant.
Heidelberg has opted for so-called amine capture, which uses chemical solvents to capture and absorb CO2 emissions through a chemical reaction. The CO2 is then liquefied and shipped by a new partnership of Shell, Total and Equinor to be stored under the seabed close to the city of Bergen.
“Basically, when we look at how we decarbonize, it’s one sizable lever in the [cement] industry,” said Christoph Beumelburg, director of communications at Heidelberg. “If you to want to tackle those emissions, CCUS is one technology we need to take a look at,” he added.
Another idea the industry is exploring is doing away with traditional materials altogether, thereby avoiding the clinkering process.
Delaware-based Partanna, avoids using portland cement as a binder and instead relies on natural chemistries. Co-founded in 2020 by former National Basketball Association player Rick Fox, the company uses a combination of brine from desalination plants and waste products from steel production called slag to create a new form of cement.
“We take the slag and we take brine, which are two recycled materials, put them together and mix them at just ambient temperatures, so we don’t need the excess heat that’s used to generate cement,” said Fox. In addition to creating an alternative cement, the process also absorbs carbon dioxide as the two materials react.
Partanna says the new cement is as strong as the traditional portland form and because it uses brine as a raw material, it gets stronger if exposed to seawater—a particularly useful trait for sea walls, flood defenses and walls in areas affected by storm surges or hurricanes.
Born in the Bahamas, Fox said the effects of Hurricane Dorian in 2019 on his native islands highlighted the need for stronger building materials in poorer regions that are more vulnerable to the effects of climate change. “I became interested through my own personal survival efforts as a Bahamian wanting to understand where we were in the world on the impacts of climate.”
Partanna is currently working with the Bahamian government to build 1,000 affordable homes using its cement, and is also in talks with a Las Vegas Hotelier to provide its cement for a new project.
Write to Yusuf Khan at email@example.com
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Appeared in the August 25, 2023, print edition as ‘Companies Look to Create Less-Polluting Cement.’