The hemp fields sprouting in a part of Canada best known for its giant oil patch show how climate change is disrupting the construction industry. Six years after setting up shop in the shadow of Calgary’s tar sands, Mac Radford, 64, says he can’t satisfy

the greenhouse gases behind global warming.

Around the world, builders are putting modern twists into ancient construction methods that employ the hearty hemp weed. Roman engineers used the plant’s sinewy fibers in the mortar they mixed to hold up bridges. More recently, former White House adviser Steve Bannon weighed in on using so-called hempcrete to build walls. Early results indicate it’s possible to tap demand for cleaner alternatives to cement.

“We have way more demand than we can supply,” Radford said from his plant in Airdrie, which is undergoing expansion and soon expects to churn out enough Lego-like hemp bricks each year to build 2,000 homes.

Greener alternatives to cement add to the pressure on companies, including Lafargeholcim and Votorantim Cimentos, as the global economy pivots toward dramatically lower emissions.

Cement makers are responsible for about 7% of global carbon dioxide emitted into the atmosphere every year, with copious volumes entering via limestone kilns needed to produce the material. Manufacturers say they’ve struggled to find markets for greener alternatives, giving easy entree to entrepreneurs like Radford who cater to customers concerned about their impact on the Earth.

“They love it once they understand it,” Radford said of the builders who’ve adopted the modular, interlocking bricks he invented for their projects. “Our old practices, we have to change.”

While architects and developers have traditionally concentrated on the energy used by their buildings once they’re standing, it’s actually the materials required in their construction that represent the brunt of a structure’s lifetime carbon footprint. Replacing high-carbon-intensity materials like cement with greener alternatives like hemp can dramatically reduce or even offset greenhouse gas pollution.

Hemp fields absorb carbon when they’re growing. After harvest, the crop continues to absorb greenhouse gases as it’s mixed with lime or clay. Hempcrete structures also have better ventilation, fire resistance and temperature regulation, according to their proponents.

Numbers across the industry vary depending on the process, but Justbiofiber says that its hemp captures 287 pounds of carbon dioxide for each cubic meter it builds. Those structures made with their bricks will sequester more greenhouse gases than they emit in production. By contrast, each ton of cement produced emits half a ton of carbon dioxide, according to the European Cement Association.