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This cement alternative absorbs CO2 like a sponge

April 13, 2015 at 6:30 PM EDT
Cement has been called the foundation of modern civilization, the stuff of highways, bridges, sidewalks and buildings of all sizes. But its production comes with a huge carbon footprint. Environmental chemist David Stone was seeking a way to keep iron from rusting when he stumbled upon a possible substitute that requires significantly less energy. Special correspondent Kathleen McCleery reports.
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GWEN IFILL: Climate change has prompted scientists to search for new ways to reduce greenhouse gases in all kinds of fields.

Now an Arizona inventor has discovered an alternative to the unlikely cause of fully 5 percent of the world’s carbon dioxide emissions.

Special correspondent Kathleen McCleery has the story, part of our Breakthroughs series on invention and innovation.

DAVID STONE, Inventor: I have here the last surviving bit of an experiment that went wrong.

KATHLEEN MCCLEERY: Thirteen years ago, David Stone was a Ph.D. student studying environmental chemistry.

DAVID STONE: It was the corner lab right up here.

KATHLEEN MCCLEERY: In a lab at the University of Arizona in Tucson, he hunted for a way to keep iron from rusting and hardening up.

DAVID STONE: It got hot. It started to steam. 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.

This one was cast by hand.

KATHLEEN MCCLEERY: Stone — that’s his real name — began to think his discarded rock just might be a substitute for a very common product: cement.

It’s been called the foundation of modern civilization. Portland cement, the generic name, is the glue that allows concrete to harden. And concrete is everywhere, in highways, bridges, sidewalks, buildings of all sizes, and much more. Four billion tons of cement are manufactured each year worldwide, a half-ton for every person on Earth. It has a huge carbon footprint.

Steve Regis is senior vice president at CalPortland, one of the nation’s top 10 cement producers.

STEVE REGIS, CalPortland Company: This plant, if it’s making about a million tons a year of cement, will emit roughly 800,000 tons a year of CO2 carbon greenhouse gases.

KATHLEEN MCCLEERY: One reason is the extremely high heat, about 2,800 degrees Fahrenheit, needed to process the limestone used to make cement.

STEVE REGIS: In making cement, we actually make new minerals. And that uses a lot of heat to cause that chemical reaction to occur. This plant here, when they’re making a million tons a year, is burning on the neighborhood of 20 tons per hour of coal.

KATHLEEN MCCLEERY: David Stone uses a very different formula.

DAVID STONE: This is the basic recipe, if you will.

KATHLEEN MCCLEERY: One that doesn’t require high heat and recycles materials from other industries.

DAVID STONE: The whole process is green.

KATHLEEN MCCLEERY: A key ingredient is iron, something he gets from steel mills.

DAVID STONE: I discovered that there was this material called steel dust that is not recycled. So, it typically goes straight to the landfill.

KATHLEEN MCCLEERY: Silica is added to the mix, and that comes from ground-up glass. Finding that wasn’t hard either. Stone connected with the community college at the Tohono O’odham Nation, a Native American reservation the size of Connecticut in Southern Arizona.

There, he met Richard Pablo, a recovering alcoholic looking to turn his life around. Pablo knew where to find plenty of used glass.

RICHARD PABLO: Cleaning the desert and picking up those bottles, it kind of gave me an energy, a positive outlook. And then I started thinking about that there’s a power behind that, a spirit behind that, even behind that bottle.

KATHLEEN MCCLEERY: Stone’s material, called Ferrock for the iron, has another environmental plus.

DAVID STONE: You can say we are walking on trapped CO2.

KATHLEEN MCCLEERY: It’s a kind of carbon sponge. Stone adds CO2, which makes it harden, for example, into concrete paving slabs like these.

DAVID STONE: We’re stepping down on climate change. This is a carbon-negative process that helps trap the greenhouse gas, carbon dioxide.

KATHLEEN MCCLEERY: That caught the eye of the Environmental Protection Agency. Then EPA Administrator Lisa Jackson came to the reservation and she, too, walked on Ferrock…

DAVID STONE: This is a steel wire support structure.

KATHLEEN MCCLEERY: … and gave grants of more than $200,000 to build demonstration projects, which employed tribe members like Pablo.

The prospect of jobs on the reservation has made Stone’s work attractive, says Casey Thornbrugh, project director for the Land Grant Office of Sustainability at the community college.

CASEY THORNBRUGH, Tohono O’odham Community College: As projects come up, such as campus buildings, homes, businesses that want to use the material, that’s where the jobs come in.

KATHLEEN MCCLEERY: Stone won a prize for his invention while a student. The University of Arizona helped him secure a patent and later licensed the technology to him. And now he’s formed a company called Iron Shell.

Experiments on Ferrock’s strength are under way at Arizona State University in Phoenix.

Professor Narayanan Neithalath, a civil engineer who develops sustainable materials, is testing Ferrock.

NARAYANAN NEITHALATH, Arizona State University: When you talk to anybody about concrete, the first thing that they will ask you is, what’s the strength? We have found out in our work that this is about five times tougher than your conventional Portland cement concrete.

KATHLEEN MCCLEERY: That strength might help protect a building from an earthquake, a tornado or even a bomb, like the one that brought down the federal building in Oklahoma City in 1995.

NARAYANAN NEITHALATH: What happened in Oklahoma City bombing was the explosion demolished all the columns of the building and the building crashed because of the weight of it and the columns not being able to support them.

But if I have a blast-resistant material, so something made out of this material, what you will have is the — the columns will still become weaker. But it won’t collapse just like that, and you will save loss of lives and loss of property.

KATHLEEN MCCLEERY: At CalPortland cement, officials say their product has stood the test of time for more than 100 years. They have won Energy Star awards from the EPA for 11 years running for their energy-saving efforts.

Among the achievements: using alternative fuels such as old tires and recouping some of the CO2 emissions.

Steve Regis says his company is always on the lookout for new ways to make cement, but says Ferrock isn’t practical for a large-scale operation.

STEVE REGIS: Dave’s idea, I think it has a good niche market for — for nonstructural block, yard art, benches. But consider the scale of that compared to a 200-mile six-lane freeway eight inches thick or a runaway.

KATHLEEN MCCLEERY: Stone is well aware he’s David to a very big Goliath, but he thinks there will be a market for Ferrock eventually.

DAVID STONE: I’m doing my part, as best I can, to respond, so that 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.

KATHLEEN MCCLEERY: A material he hopes will one day make a lasting impression.

DAVID STONE: Here it is.

KATHLEEN MCCLEERY: I’m Kathleen McCleery for the PBS NewsHour in Tucson, Arizona.

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