Call him cement man.

[GLT]

Green cement may set CO2 fate in concrete

Carrie Sturrock,San Francisco Chronicle Staff Writer

Tuesday, September 2, 2008



(09-01) 19:18 PDT -- Call him cement man.

Back when Stanford Professor Brent Constantz was 27 he created a high-
tech cement that revolutionized bone fracture repair in hospitals
worldwide. People who might have died from the complications of
breaking their hips lived. Fractured wrists became good as new.

Brent Constantz, at his pilot factory in Moss Landing (Mo...One of the
tanks that will be used to make green cement a...The making of green
cement. (Todd Trumbull / The Chronicle)
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Now, 22 years later, he wants to repair the world.

Constantz says he has invented a green cement that could eliminate the
huge amounts of carbon dioxide spewed into the atmosphere by the
manufacturers of the everyday cement used in concrete for buildings,
roadways and bridges.

His vision of eliminating a large source of the world's greenhouse
CO{-2} has gained traction with both investors and environmentalists.

Already, venture capitalist Vinod Khosla is backing Constantz's
company, the Calera Corp., which has a pilot factory in Moss Landing
(Monterey County) churning out cement in small batches.

And Carl Pope, executive director of the Sierra Club, says it could be
"a game changer" if Constantz can do it quickly, on a big scale and at
a decent price.

"It changes the nature of the fight against global warming," said
Pope, who has talked with Constantz about his work.

That might sound like hyperbole, but the reality is that for every ton
of ordinary cement, known as Portland cement, a ton of air-polluting
carbon dioxide is released during production. Worldwide, 2.5 billion
tons of cement are manufactured each year, creating about 5 percent of
the Earth's CO{-2} emissions.

When Constantz learned about the high CO{-2} levels, he thought he
could do better. After all, the majority of his 60 patents have to do
with medical cement.

He claims his new approach not only generates zero CO{-2} , but has an
added benefit of reducing the amount of CO{-2} power plants emit by
sequestering it inside the cement.

To make traditional cement, limestone is heated to more than 1,000
degrees Celsius, which turns it into lime - the principal ingredient
in Portland cement - and CO{-2}, which is released into the air.

Constantz uses a different approach, the details of which remains
secret pending publication of his patent.

At his pilot factory, a former magnesium hydroxide facility that made
metal for World War II bombs, magnesium crunches underfoot as
Constantz, wearing a pressed, blue button-down shirt with rumpled
shorts and sandals, outlines how the process works.

He pointed to two enormous smokestacks billowing flue gases full of
carbon dioxide next door at Dynegy, one of the West's biggest and
cleanest power plants.

Constantz takes that exhaust gas and bubbles it through seawater
pumped from across the highway. The chemical process creates the key
ingredient for his green cement and allows him to sequester a half ton
of carbon dioxide from the smokestacks in every ton of cement he
makes.

Constantz believes his cement would tackle global warming on two
fronts. It would eliminate the need to heat limestone, which releases
CO{-2}. And harmful emissions can be siphoned away from power plants
and locked into the cement.

The same process can also be used to make an alternative to aggregate
- the sand and gravel - that makes up concrete and asphalt, which
would sequester even more carbon dioxide from power plants.

"The beauty here is we're taking this old industrial polluting
infrastructure and turning it into something that will save the
environment," Constantz said.

On a per-person basis, the United States is the world's worst CO{-2}
polluter from all sources. But according to the Netherlands
Environmental Assessment Agency, China just surpassed the U.S. for
total carbon dioxide emissions.

China is expected to produce 47 percent of the world's 2.5 billion
tons of cement this year, Constantz said.

To power its new buildings and sustain its building boom, China
constructs at least one coal-fired power plant a week. Each one
belches out enough CO{-2} to cancel the benefits of every hybrid on
U.S. roadways, said Constantz.

A CO{-2} molecule can travel from Beijing to San Francisco in less
than a day through atmospheric circulation, he said. So even with
California mandating that CO{-2} emissions fall to 1990 levels by
2020, a crisis remains.

"Carbon dioxide is a global problem, not a regional problem," he said.

As far as cost, Constantz estimates his cement would retail for $100 a
ton versus roughly $110 for Portland.

The reason no one invented it before now, he said, is that people
didn't truly understand the dangers of CO{-2} until less than a decade
ago.
Skeptics question product

He has skeptics.

Portland cement has a track record of more than 100 years, and any new
material would have to get incorporated into building codes, noted
Rick Bohan, director of construction and manufacturing technology for
the Portland Cement Association in Skokie, Ill.

And Tom Pyle, a Caltrans engineer who serves on the cement subgroup of
Gov. Arnold Schwarzenegger's Climate Action Team, acknowledged that
the technology is possible, but he still wants to examine Constantz's
cement.

"We hope they have a carbon-reducing viable construction material," he
said. "They need to show up with a bag of this so we can test it."

Constantz is confident he will prove himself. Initially, he proposes
mixing his new invention with Portland cement to ease a conservative
industry into a new product. Concrete bigwigs have invited him to
speak about Calera cement at their annual World of Concrete in Las
Vegas next February.
Power plant partnerships

Constantz envisions building cement factories next to power plants the
world over. A team is scouting out U.S. locations. While Dynegy has
supplied Constantz with some flue gas, it hasn't entered into a formal
agreement.

"As we're looking into the future, we're very interested in technology
that would help capture CO{-2} from the flue gases and turn it into a
product that offers a benefit," said Dynegy spokesman David Byford.

It could be good for business. California has mandated emissions
reductions. And Congress is working on legislation that would allow
high polluters to buy credits from those with low emissions. Power
plants would have a huge incentive to sequester their CO{-2} in
cement.

But even if Constantz succeeds, the world would still need to do much
more to fight CO{-2} emissions, said Chris Field, director of the
department of global ecology at the Carnegie Institution for Science
at Stanford. "It's a big, long complicated game," he said. "As we
develop each new segment of the solution we need to embrace it and
deploy it and work hard to develop the next segment of the solution."
Coral basis of idea

Big ideas can form in haphazard ways. The one for bone cement began
during a televised football game, when Constantz read an osteoporosis
article in the New England Journal of Medicine. Three weeks later, as
he studied a coral reef, it occurred to him he could maybe synthesize
coral skeletons in human bones.

His new cement mimics how coral reefs form, too. Coral uses the
magnesium and calcium present in seawater to create carbonates much as
he's using CO{-2} and seawater to make carbonate.

This latest invention took 18 months to conceive and execute. He feels
it's one of the most important things he's ever done.

"Climate change is the largest challenge of our generation," he said.

Who is Brent Constantz?

Profession: An associate consulting professor in Stanford's department
of geological and environmental sciences and founder of the Calera
Corp. Created and sold three other companies - Norian Corp., Corazon
Technologies Inc. and Skeletal Kinetics.

Education: UC Santa Barbara, bachelor's of science (1981); UC Santa
Cruz, doctorate (1986)

Family: Married and father of four.

Pastime: Surfing and rock climbing.
Concrete facts about cement

2.5 billion tons of hydraulic cement is produced worldwide annually.
Add sand and gravel and that makes more than 9,000 million cubic yards
of concrete. That's more than enough concrete to pave an eight-lane
highway from the Earth to the moon and back again - twice.

If you stayed on the planet, that same eight-lane highway would circle
the Earth almost 40 times.

Source: Portland Cement Association