California: Scientists Hunt For Green Building Materials
By Michael Torrice, Mercury News
The plank looks like a polished piece of plywood, and someday people may build coffee tables with it. But this wood was not grown in a forest — it was born from the greenhouse gasses seeping from landfills.
The Stanford University researchers who produced this wood alternative are part of a movement to support greener buildings by developing construction materials that are created and disposed of in an environmentally friendly way.
Green buildings are not only about replacing standard light bulbs with fluorescent bulbs or toilets with low-flush alternatives. Because manufacturing traditional building materials requires large amounts of energy and emits greenhouse gases, finding green alternatives will improve a building's overall environmental footprint.
However, inventors still must convince the construction industry that these products can replace centuries-old building materials.
"When it comes to construction and the environment, structural engineers make a mess and environmental engineers clean it up," said Sarah Billington, the Stanford researcher who leads the wood project. "We wanted to fix the mess from the start."
Building materials are responsible for about 20 percent of the greenhouse gasses emitted by a building during its lifetime, said Brent Constantz, founder of Calera, a company that is producing green cement.
To reduce these environmental costs, engineers have searched for alternatives that require less energy to produce, can be recycled easily, use renewable raw materials and emit less greenhouse gases.
Billington's green wood can be recycled more efficiently and replenished faster than natural wood. After recycling, wood loses its original strength and trees can take more than a decade to regrow.
Layered like lasagna
The Stanford team's solution is a combination of hemp fibers and biodegradable plastic that they layer like lasagna. Once pressed together and heated, the layers bond. The material is as strong as wood, but when buried in land fill it degrades faster.
More importantly, the wood creates more raw materials as it breaks down.
Bacteria make this cyclic process possible. Microbes produce methane gas when they decompose this wood substitute and other debris thrown into landfills. Another type of bacteria absorbs this gas and turns it into plastic that can be used to create a new wooden plank. Then the process can start over.
"Everywhere there are people, you have waste," Billington said. "So you have a continuous source of raw materials."
But this new wood is not ready for construction sites yet. The material is heavier than real wood and it takes more force to pound a nail into it. These issues would be a deal-breaker for the construction industry, Billington said.
"The construction industry likes to use the tools their grandfathers used," she said. "If it doesn't work the same or use the same screws and nails, then it won't be adopted."
Training builders to use new materials and buy new tools requires time and money that many companies cannot afford, said Cheryl O'Connor, chief executive officer of the Home Builders Association of Northern California. "It would be like starting over for many companies," O'Connor said. "And that's real tough to do in bad economic times."
Builders also want to ensure new materials are as durable as traditional materials, O'Connor said. They worry that if new materials fail prematurely, they will be liable for replacing them.
"We have to test new materials before we know the materials will last as long as a house does," O'Connor said.
Currently, many of the green building products on the market are used for architectural finishing, such as flooring and cadenzas, said Oswald Chung, a professor of civil engineering at Kansas University.
"These materials are easy to replace, because they don't have to carry any weight," he said. "But they're only 5 to 10 percent of building materials used."
Replacements for structural materials, such as concrete, are more difficult to find, Chung said.
Concrete is particularly dirty. To make Portland cement, the main component in concrete, manufacturing plants must release copious amounts of greenhouse gas. One ton of cement equals one ton of carbon dioxide spewed.
Bruce Constantz at Calera, based in Los Gatos, decided to take on the concrete challenge. His company developed a green method to produce both cement and aggregate, another component of concrete.
Instead of releasing carbon dioxide into the air, their method sequesters it from power plant flues and mixes the gas with seawater to produce the mineral raw materials of concrete. For every ton of green cement Calera manufactures, it not only doesn't create carbon dioxide, but actually removes a half ton from smokestacks of coal plants to create the cement.
"We're taking carbon dioxide that would normally go into the atmosphere and putting it into cement," Constantz said.
Calera has started a pilot plant next to the Moss Landing Power Plant, where it produces five tons of green cement every day, which is only enough material to run structural tests on.
At Stanford, Billington's team is now testing their green wood to see if it will meet building codes.
Her graduate student places small samples of the material in a machine, called a weatherometer, that simulates extreme weather conditions — blasts of UV light, scorching temperatures and drenching rains. Passing these tests will move their biodegradable alternative closer to adoption.
"In the long run," Billington said. "I hope it will replace everything used by wood at a construction site."
Contact Michael Torrice at mtorrice at mercurynews.com or 408-920-5064.