Zero Carbon Cement

In the small town of Holyoke, Massachusetts, bulldozers have been removing a paper mill. The new ground on the banks of the Connecticut River will soon be home of a large industrial experiment. If it pays off, Paper City may soon become Clean Cement Capital. A startup, Sublime Systems has developed a process for producing cement without releasing any carbon emissions.

CEO and co-founder, Leah Ellis says, “It’s poetic justice. We’re excited about bringing clean technology to this community which has been damaged by a legacy of pollution from the old industry that used to happen there.”

Cement is the key ingredient in stuff that gets mixed and poured and hardened into sidewalks, roads and buildings. It is the glue that binds together sand, water, and gravel to form a fabric in our world. It’s also a major source of carbon emissions. By some measures as much as 8% of carbon emissions occur from the making of cement.

Scientist often make a distinction between the carbon we know how to eliminate such as from power generation, home heating and automobiles. And then there’s a group called “hard to decarbonize” stuff - emissions from industrial activities where clean solutions are in early stages and not cost effective. Cement is one of the main culprits of this kind of pollution.

Half of the emissions from cement comes from a chemical reaction that’s intrinsic to its production. Cement consists of lime, silica, and water. It’s made by first heating up limestone in a kiln to more than 1,400 degrees Celsius (2,550 degrees Fahrenheit). This reaction creates lime. The problem is the limestone contains carbon, and as it heats up, that carbon is released as a gas.

Sublime Solutions has found another way. They have developed a new way to make reactive lime that does not require limestone. Instead of heating rocks in a kiln, they use a chemical process that is driven by electric currents. By doing this, they avoid using limestone altogether, using a variety of other raw materials that do not contain carbon to produce lime.

The technology Sublime Systems uses in its chemical process is a device calkled an electrolyzer and has become much cheaper. This technology has recently benefited fro economies of scale as interest in using them for applications like clean hydrogen production have grown.