Is it possible to change how the most ubiquitous building material on earth is made — one so dirty that it accounts for nearly a tenth of greenhouse gases, yet so cheap to produce that it costs less per kilogram than bottled water? 

Researchers at MIT think so. They describe in the journal PNAS a new process for making cement without emitting greenhouse gases.

Cement manufacturing is a dirty business, achieved by grinding up limestone, which is then typically cooked using coal at high heat with sand and clay. As the underlying ingredient in concrete, cement accounts for 8% of global greenhouse gas emissions. If cement were its own country, it would be the third-highest greenhouse gas emitter. For every kilogram of cement produced, an equal amount of carbon dioxide is released into the atmosphere.

Business is booming: the annual growth rate of cement production is 2.5%, with 3.6 billion metric tons produced per year, according to Utpal Nandy, managing director of BU Builders and Consultants, a development company based in India.

And cement is extremely cheap to make — a single kilogram costs only 13 cents, according to Yet-Ming Chiang, the Kyocera Professor of Materials Science and Engineering at MIT who led the research team. 

The team’s method involves the use of an electrolyzer to produce cement via an electrochemical process that, when powered by renewable energy sources, can be contained in a closed loop that produces nothing but water vapor.

The process is simple, and scalable, but faces the challenge of persuading a thriving industry to change its established way of doing things. Just as importantly, demand for so-called “green cement” is muted because of the cost, Jens Diebold, head of sustainability at LafargeHolcim, a Swiss manufacturer of building materials, told Bloomberg in June.

The way to getting cement producers to convert is to move “in a stepwise fashion,” Leah Ellis, the MIT paper’s lead author, said in an interview with MIT News. Improve the cement manufacturing chain one process at a time, she said.

The Risks and Cost of Change

Leaving aside cost, changing a process that traces to ancient Rome, however, won’t be easy. As Jeremy Gregory, the executive director of MIT’s Concrete Sustainability Hub research center, told Karma, engineers working with concrete are slow to adopt new innovations  because no one wants to take chances on something as critical as a building’s foundation.

“There are companies that want to put out that they’re located in a sustainable, LEED-certified building, even if doing so adds more cents to every dollar of expense.”

California lawmakers encountered this in the process of writing the state’s Buy Clean California Act, which went into effect this year. The measure requires state agencies to consider the carbon footprint of materials like steel and glass and use low-emissions materials where possible. Cement originally was intended to be included in the bill, but was removed because developers couldn’t agree on a specific low-emissions type to use in projects, Gregory said.

The key to getting the industry to adopt new sustainable building practices like MIT’s is certification, according to Sam Adams, CEO and co-founder of Vert Asset Management. In 2017, Adams helped launch one of the first environmental, social and governance-linked real estate investment funds, the Vert Global Sustainable Real Estate Fund.

Speaking to Karma, Adams said he’s found that companies “that want to wear their commitment to sustainability on their sleeves” will embrace innovation in sustainable building — even if it doesn’t pencil out in terms of cost — if it’s baked into a system like the U.S. Green Building Council’s point-based LEED model.

“There are companies that want to put out that they’re located in a sustainable, LEED-certified building, even if doing so adds more cents to every dollar of expense,” he said.

Indeed, companies like Prologis, the largest global owner of warehouses, have ESG goals to own or convert existing buildings to be 100% sustainable certified. For Prologis, that would mean 521 million square feet of warehouses would be certified as sustainable, or 4,493 acres worth of buildings. The company’s portfolio does contain dozens of LEED-certified buildings, including facilities in New Jersey, Washington, Mexico and China.

Cleaner cement is on the radar of some companies. Earlier this month, HeidelbergCement, one of the world’s largest cement manufacturers, signed a memorandum of understanding with the state-owned Norwegian firm Group Equinor to expand carbon capture processes in cement plants. The plan calls for captured carbon dioxide to be transported and permanently stored at empty oil and gas fields beneath the North Sea.

The process outlined by MIT will be closely watched in the sustainable building space, especially if it proves effective at production scale, Adams told Karma.

“People tend to think, ‘I want to save the planet by investing in sustainable energy.’ But buildings use 40% of the world’s energy — they should be up there with renewable energy and transportation in the conversation about impact investing,” he said.