FROM the lip of the Hanson Permanente quarry, on the eastern slope of the Santa Cruz Mountains in Cupertino, the Santa Clara Valley stretches out in panorama. Few cement plants in California are this close to this many people. Most of the state's 11 kilns are well away from population centers, close enough for workers to commute, but otherwise out of sight. Here, suburbia reaches right up to the edges of the Permanente land, homes suddenly giving way to an industrial road leading up to the expansive plant and the limestone mining operation behind it.

As a result, engineers and executives will have to figure out how to make an essentially dirty process clean—or at least cleaner.

As California tries to fight global warming—with or without the rest of the country—cement manufacturing remains one of the trickiest industries to regulate.

"I don't think there's any [industry] quite like cement," says Mike Tollstrup, one of the state officials overseeing California's effort to fight global warming. "There are not a lot of facilities. Cement is used everywhere. There are significant issues of leakage. If we don't do it right, the potential for increasing emissions is a real concern."

In 2006, California adopted Assembly Bill 32, a law mandating that by 2020 the state cut greenhouse emissions to 1990 levels. Tollstrup's agency, the California Air Resources Board, which will oversee implementation, released a Proposed Scoping Plan a couple of months ago mapping out how the state will reach its goal.

Cement is one of the industries singled out by regulators because, as Tollstrup says, it's both necessary and necessarily polluting. Unchecked, carbon emissions from the cement sector would rise 23 percent, from 9.7 million metric tons in 2004 to 12.6 million metric tons in 2020, according to state statistics.

Demand for building materials moves in concert with population growth, and California's population continues to grow. By 2030, the U.S. Census projects it will exceed 46 million people.

"Long-term trends look promising if you're a cement maker," says Andy O'Hare, vice president of regulatory affairs for the Portland Cement Association. "First and foremost, any economy is going to need cement from somewhere to continue to grow. We're working from that premise, and state government seems supportive."

Magic Dust

Concrete is a blend of materials—cement plus fine and coarse aggregates and water—that harden into a firm structure. Cement is the glue holding it all together. In dry form, it's a chalky powder. At every stage of cement production, there is something to evoke an environmentalist's worst nightmare.

It starts with limestone. Behind the Permanente plant, an open quarry funnels down 750 feet into the hillside. Twice a week, mining crews detonate a series of explosives set into the rock face. Water trucks hose down the loose gravel.

Raw ore moves by conveyor belt through grinders until each chunk reaches a uniform size, about a cubic centimeter. Turning limestone into lime is the main source of carbon emissions in the cement-making process. The mined rock must be heated to 2,700 degrees Fahrenheit. That uses massive amounts of fuel.

The most common fuel in cement plants is coal, though Permanente doesn't use it. This plant relies entirely on petroleum coke, a byproduct of oil refinement. "Pet coke" isn't any better for the air than coal (chemically, it's similar), but it disposes of otherwise troublesome waste.

Heating limestone turns it into lime, releasing carbon dioxide in the chemical reaction. What comes out is called "clinker," which is ground into a fine powder.

The oft-cited measure of cement's impact on global warming is 1 ton of carbon dioxide for every ton of cement produced. California plants, on average, are about 10 percent cleaner, putting out .895 tons of CO2 for each ton of cement. The state would like to see that number drop to .80.

The danger, say all involved, is that cement production could shift out of state. While California's plants continue to clean up, if their products become too expensive, local builders could cut costs by buying from out of state, negating any emissions gains made here. At the moment, China is the biggest supplier of cement, as well as the world's largest source of greenhouse gases.

To combat production leakage, the A.B. 32 scoping plan proposes to apply a carbon intensity standard to all cement sold in California, not just what's produced here. When measuring the carbon footprint of imported cement, regulators say, they would count every part of the process, from mining to calcination to shipping.

Manufacturers see this as the best part of the state's plan. Counting the 20 percent increase in emissions resulting from transport, California kilns maintain an edge.

California consumes more cement than it produces, so some cement is always imported. In a good year (which 2008 was not), the state's 11 kilns can put out 12 million to 13 million metric tons a year. Builders use as much as 16 million tons.

"We think that we can set limits that would apply to out-of-state and out-of- country facilities, too," Tollstrup says. "That way, if you want to sell cement in the state of California, you have to meet that requirement."

California has done this before, Tollstrup says, pointing to the rule that all gasoline sold in the state must contain an oxygenator—a requirement that led refiners to add MTBE, and later ethanol to fuel blends. But the state tried applying local emissions standards to automobiles, too, provoking a multiyear fight with the federal Environmental Protection Agency and the Bush Administration, which tried to block California's tailpipe rules. With George Bush about to leave office, Tollstrup is optimistic.

Cold Hard Cash

In theory, cleaning up will be good for California business. In 2020, according to an economic analysis of A.B. 32 commissioned by the Air Resources Board, the state's economy will have increased production activity by $27 billion, and overall personal income by $14 billion.

For cement makers, better energy efficiency and smoother production processes should save money, the state says. Industry-wide, California expects cement plants to save $3.4 million annually, spread over the next 12 years.

From the state's perspective, there's only so much that can be done to reduce cement's carbon footprint. Roads and bridges built over the next decade may require alternative ways to make concrete.

Tom Pyle, an engineer with CalTrans, deals with such issues every day.

When CalTrans builds a bridge, he explains, its primary concerns are safety, structural longevity and cost. Solving global warming isn't the agency's goal (though Pyle counts himself an environmentalist). He and other concerned builders have been trying something that addresses both issues.

In large-scale projects, Pyle says, a common problem is a kind of rust that eats away at the strength of concrete. For a building, it's a cancer. "One way to stop it is to put fly ash in," he says. "From an engineering point of view, it's a medicine that stops this cancer." Fly ash is a byproduct of burning coal, so it's not entirely clean, but many see it as a step forward.

At the Permanente plant, there is also talk of using the kiln's leftover heat to generate electricity, something happening in other parts of the world, but which no other facility in California does.

"Back in the '40s, most cement plants created their own power, only because we didn't have a stable utility sector," Shane K. Alesi, a Heidelberg executive, said.

O'Hare, of the Portland Cement Association, says the use of concrete in home construction can save on heating bills That's something that Pyle sees as well.

"I believe the cement industry is seeing opportunity," the engineer said. "As our world starts to change, we're going to start to look for sustainability. To me, as a concrete geeky kind of engineer, sustainability means building things that are going to last more than a generation. And for CalTrans, what we're looking at is extending the life of our roads and bridges.

It's hard to predict where the cement industry will be in 12 years. Emissions will probably be lower. If the state's plan works out, those greenhouse gases will be gone, not just displaced.

Marvin E. Howell, director of land use planning at Hanson Aggregates (now also part of Heidelberg), said the big changes won't occur at cement plants. Instead, A.B. 32 is "going to mean changes in how people use the product."

"Everybody is going to have to change," Howell said. "It's not just us."

Tollstrup paints the most optimistic picture of the industry in 2020. "I expect that the facilities in California will be the most efficient in the world," he says."They're just going to be ultraclean facilities by the time we get to the end game here."

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