As the world’s cities expand at faster and faster speeds, so does its use of cement. One oft-quoted statistic shows that China alone used as much cement in the last three years as the US used in the last 100. Just one problem: Cement is responsible for pushing a hell of a lot of carbon dioxide into the world.

The process of making cement is resource-intensive and heat-intensive—that’s why it creates so much CO2. And that’s why researchers are interested in finding ways to trap or sequester that CO2, and why the research project of a University of Arizona student in the early 2000s is garnering so much interest. A recent PBS report introduced us to Stone—now Ph.D—whose product was made in a lab by accident, while he was experimenting with iron:

It was bubbling and spitting. And I thought, well, that — that didn’t work. The next day, when I came in and I found it and rescued it from the garbage, I realized, this just didn’t get hard. It got very hard, glassy hard.

For the past 13 years, he’s built a business around the glassy stuff he calls Ferrock. It’s made from the waste of steel mills (steel dust) and doesn’t use the same heat-intensive production process of cement. It’s also more durable and stronger than cement.

But that’s not actually biggest selling point. That would be the fact that this mixture of chemicals actually sucks up CO2 and traps it, as University of Arizona explains:

Conversely Ferrock™ only hardens when exposed to high concentrations of carbon dioxide, which is absorbed and trapped, making it a carbon negative material. This greenhouse gas diffuses into the wet mixture and reacts with the iron, creating iron carbonate and becoming part of the material’s mineral matrix.


Sounds great, right? What’s stopping the world from adopting Ferrock to replace cement? Well, making a massive paradigm shift in one of the biggest industries on Earth isn’t as easy as demonstrating a breakthrough. We’re talking about an industry that accounts for as much as $250 billion in profits a year. Check out the full PBS mini-doc above for more.