Cement is one of the world’s most commonly used manmade materials. It is also one of the largest industrial sources of carbon dioxide; producing cement generates about 8% of global carbon dioxide emissions.

In a new paper in the journal ACS Energy Letters, researchers report a new kind of cement that cuts energy use by 70% and carbon dioxide emissions by as much as 98% compared with traditional cement-making methods.

The new process incorporates an electrochemical conversion step before heating the limestone to reduce the extreme heat needed later. The researchers also utilize recycled cement and concrete to further cut carbon emissions.

Making cement is an inherently carbon-intensive process. The emissions come from two routes. First, the process requires heating limestone (calcium carbonate) and silica at temperatures of over 1,450°C, the energy for which traditionally comes from burning fossil fuels.

Second, the chemical reactions themselves produce carbon dioxide. That’s because the heat converts the limestone to lime by driving off carbon dioxide. The lime then reacts with silica to form calcium silicate clinkers that are used to make cement.

Instead of cooking limestone and silica in a high-temperature kiln, Curtis Berlinguette and colleagues designed an electrochemical reactor that converts limestone and silica into a compound called calcium silicate hydrates. This conversion happens at a temperature of only 60°C. Then the researchers convert the hydrate to calcium silicate mineral in a kiln at 650°C, less than half the temperatures used in traditional methods.

Because of the electricity use and lower temperatures, the new method reduced the energy required by 70% compared to traditional processed. It also cut carbon emissions.

Then, the team went a step further. Instead of using new limestone, they tested their process on recycled waste cement. They found that it could also serve as a source of calcium carbonate in their electrochemical reactor to produce calcium silicate hydrate.

Using recycled cement dramatically slashed emissions, resulting in only about 20 kg of carbon dioxide emitted per ton of clinker produced, a reduction of almost 98% compared to the production of ordinary Portland cement.

The work presents a credible path for dramatically reducing the carbon footprint and increasing the circularity of one of society’s most ubiquitous materials, the researchers say.