Concrete is used in the construction of buildings, roads, bridges, sidewalks, and more. But making all of the cement that is used as the binder in concrete is not only incredibly energy-intensive but the process also releases billions of tons of carbon dioxide into the atmosphere each year. What if someone could change that by incorporating recycled materials and making it not just carbon neutral but carbon negative, meaning that it absorbs more CO2 than was used in its production? That's exactly what Tucson-based inventor David Stone is doing with his invention called Ferrock.
One of the materials that Stone incorporates into Ferrock is waste steel dust, which is currently not recycled and is available at no cost. Another ingredient is recycled glass. Stone has been working with Richard Pablo, a member of the Tohono O’odham Nation, to collect discarded bottles from drinking sites on the reservation. “Cleaning the desert and picking up those bottles, it kind of gave me an energy, a positive outlook,” Pablo recalls. The bottles are run through a glass crusher and become part of the aggregate used to make Ferrock.
“The glass cullet and the steel dust,” Stone explains, “are mixed with minor ingredients that promote iron corrosion (rusting) and carbonate formation. Then water is added to make a wet paste that is similar in consistency to ordinary concrete. It can be poured and troweled like concrete to make the same kind of products. Finally, we expose the mix to carbon dioxide gas, which diffuses into it and reacts with iron to form iron carbonate. This mineral keeps growing for about a week into a solid matrix that binds all the glass together. The result is a hard, durable material that is as strong as concrete but greener because it is truly carbon negative and is composed almost completely of recycled wastes.”
“Through this project,” Stone reports, “we have transformed the discarded bottles into a green building material that in turn has been used to make a variety of products including tiles, pavers, and blocks as well as bigger structures such as benches, sidewalks, slabs, and walls.” Stone pledges, “When the time comes and the world wants to build with new materials that are carbon-neutral or carbon-negative, I will be able to step forward and say, yes, I have such a material.”
In 1998, John Warner and Paul Anastas published the ground-breaking book, Green Chemistry: Theory and Practice. The road to this achievement was not linear for Warner. Growing up in a blue-collar family in Quincy, Massachusetts, he originally saw himself as a musician and went to college to study music. But it all changed when he saw what could be invented in a chemistry lab.
Completing advanced degrees in chemistry, Warner went to work at Polaroid and was headed for a successful career in industry. Then personal tragedy struck when a birth defect claimed the life of his young son. Unsettled by the thought that his work as a chemist might have been connected to his son’s birth defect, Warner realized that, in all of his studies, he had never been taught about the dangers of toxic chemicals for people and the environment.
Warner left Polaroid and set out to change the way chemistry is taught in universities across the country. And in 2007, he founded the Warner Babcock Institute for Green Chemistry as an invention factory to create technologies and processes that are functional, cost-effective, and environmentally benign.
Learn more about the 12 principles of green chemistry . . .