Wednesday, March 25, 2009

A look at how construction debris is recycled--when there's stuff to recycle.

Posted By on 03.25.09 at 10:16 AM

Bob Kalebich, a 27-year veteran of the garbage business, recalls when interest in recycling first exploded in the 1980s. “Most waste haulers thought it was going to be a fad and didn’t get into it,” he says.

Instead, as Americans kept producing more and more stuff, recycling grew into a $236 billion-a-year industry that employed more than a million workers. As I’ve written before, the reasons are fairly simple: recycled materials are in demand because they tend to be cheaper than "virgin" products and thanks to technology the costs of sifting them out of the garbage have dropped considerably.

Last summer Kalebich’s employer, Allied Waste, one of the biggest waste companies in the country, opened a new plant in Chicago’s Pilsen neighborhood to sort and recover the wood, paper, metal, concrete, rock, drywall, and other stuff generated by area construction and demolition work. Demand for this material has swelled over the last few years—the use of recycled products helps qualify buildings for LEED certification and other "green" designations, which helps developers market them to environmentally conscious clients. 

And there’s typically a big supply of it. In recent years about half of the 8.2 million tons of waste produced annually in the city of Chicago has been C & D debris, as it’s known.

But since the economy tanked and construction slowed down—construction starts fell 7 percent in 2008 and are predicted to fall 39 percent this year—the plant has been receiving far less than the 1,500 tons it can handle each day. Kalebich says it has to pick up again at some point. “Right now it’s one of those ‘if you build it they will come’ things.”

Even so, it offers an example of how, in a slightly healthier economy, technology can make conservation economically viable. Here's how it's done.

 

 

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Trucks dump C&D debris in the plant yard, where a crane scoops it up and drops it into a giant industrial shredder that chops it into smaller parts. From there it’s plunked onto conveyor belts that shoot it into the plant.

 

 

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Inside, workers grab unusable junk off the piles—plastic rings, plastic bottles, bags, pieces of carpet or insulation. When operating at full capacity and handling lots of heavy material, there's work for 17 employees at a time. The whir and grind of machines requires a near-shout to be heard.

 

 

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Lately the loads that have come in have been dominated by light material like cardboard, which is produced at the end of the construction cycle, another sign that the building industry is in a huge slowdown. But as Kalebich and operations manager Gary Dyke showed me around, heavier—and far more lucrative—material like concrete and rock came rumbling down the conveyor belts. Kalebich slapped me on the back and said I must be good luck. “What are you doing tomorrow?” he asked. “Can you come back?”

 

 

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Workers also pull drywall and cardboard off the conveyor belts, but science handles much of the sorting. Magnets grab the iron and steel, and the “water bath” pictured above separates wood from rock and concrete by applying the simple principle that the heavy stuff sinks and the light stuff floats. After bathing, the wood is dried with a blower and sent to another shredder. The 4,500 gallons of water are reused for three to six months before being flushed.

 

 

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The shredded wood falls into giant bins that will be trucked to companies that make mulch, wood chips, or fuel products. 

 

 

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The mixed rock drops to its own conveyor belt. Eventually it’s crushed and sold to firms that turn it back into concrete or other construction material. 

 

 

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Cardboard and other paper waste ends up in its own pile before being baled and shipped off for recycling.

The whole process takes less than ten minutes.

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