(Bloomberg) — The most astonishing thing about cement is how much air pollution it produces.
Manufacturing the stone-like building material is responsible for 7% of global carbon dioxide emissions, more than what comes from all the trucks in the world. And with that in mind, it’s surprising that leading cement makers from LafargeHolcim Ltd. in Switzerland to Votorantim Cimentos SA in Brazil are finding customers slow to embrace a greener alternative.
Their story highlights the difficulties of taking greenhouse gases out of buildings, roads and bridges. After wresting deep cuts from the energy industry, policymakers looking to extend the fight against global warming are increasingly focusing on construction materials and practices as a place to make further reductions. The companies are working on solutions, but buyers are reluctant to pay more.
“There is so far too little demand for sustainable materials,” said Jens Diebold, head of sustainability at LafargeHolcim. “I would love to see more demand from customers for it. There is limited sensitivity for carbon emissions in the construction of a building.”
While architects and developers concentrate on the energy used by their buildings, it’s actually the materials supporting the structure that embody the biggest share of its lifetime carbon footprint. Cement’s contribution to emissions is especially immense because of the chemical process required to make it.
About two-thirds of the polluting gases that come from cement production stem from burning limestone. Kilns are heated to more than 1,400 degrees Celsius (2,600 Fahrenheit), about four times hotter than a home oven set to the self-clean cycle. Inside the kiln, carbon trapped in the limestone combines with oxygen and is released as CO2, the most abundant greenhouse gas.
A ton of cement yields at least half a ton of CO2, according to the European Cement Association. That’s more than the average car would produce on a drive from New York to Miami. And a single mixer truck can carry about 13 tons. Hundreds or even thousands of tons go into ordinary office buildings.
The scale of the problem has drawn the attention of research groups like the IEA and Chatham House along with policymakers from the C40, which represents the world’s largest cities. The IEA estimates cement production will rise 12% to 23% by 2050, though it could cut emissions with a series of actions. All the groups are looking for levers to prompt change.
“It’s very difficult,” Shirley Rodrigues, deputy mayor for London and a C40 board member, said in an interview. “What we can do is to start to send a signal. We’ve got a new requirement for developers that they must develop a circular economy statement to show how they will reduce, reuse and recycle materials.”
Cement makers are responding but have found customers hesitant. LafargeHolcim, the second-largest maker by capacity, once launched a carbon-free product. It was more expensive and used a different production process. Customers were “very price sensitive” and didn’t show interest, Diebold said. Buyers acknowledge that cost is crucial.
“There are cement products with lower environmental impact, but they usually cost more than the normal ones,” said Lennart Henriz, chairman of the sub-commission on environment at the European Construction Industry Federation. “There are many types of strict targets on the European construction sector. But sometimes there is a lot of talking but low action.”
Cost is a problem because greener forms of cement can cost triple what the traditional mix does. Researchers led by Brett Tempest at the University of North Carolina at Charlotte found a yard of geopolymer cement may reach $161, while the most commonly used Portland variety is $51, their 2015 paper in the PCI Journal published by the Precast Concrete Institute.
What comes out of the kiln is called clinker, the key raw ingredient of cement. It’s the substance that, when mixed with gypsum and water, binds with gravel to harden and form concrete. Many companies are working to cut the amount of clinker in their cement, which requires new and sometimes untested recipes.
Others are looking at substitutes. Those include fly-ash, which comes from the chimneys of plants that burn coal, or slag from steel-making blast furnaces. They trigger a chemical reaction and form what’s known as a geopolymer binder.