By Joel Warner
By Michael Roberts
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The belt moves slowly at first, gradually gaining speed as the sorters get accustomed to the pace. It's a bit like watching Lucille Ball try to keep up with the chocolates on a classic episode of I Love Lucy, a reference that Herrera has heard more than once but finds elusive. ("A lot of people have mentioned that to me," he sighs. "I've never seen it.") At its peak, the plant processes thirty to forty tons of material an hour.
A few feet past the pre-sort, the first screen awaits, a spinning whirligig of large, star-shaped discs. The principle is simple: big stuff goes over the top, everything else falls through. At this juncture, the big stuff tends to be cardboard, which ends up on its own belt, Conveyor 15, headed toward the baling machines. But the system is far from flawless; smaller scraps of cardboard can fall through, while some plastics might be stuck to cardboard and go over the top. So there are quality-control folks waiting beyond the screen to pull non-cardboard off Conveyor 15 and return it to the stream via another conveyor, and so on.
Adding commercial clients has more than tripled the amount of cardboard the plant sees, Herrera says. And going to single stream has more than quadrupled the workforce in the plant. "There used to be three or four sorters, one baler, one forklift operator," he recalls. "Now we have twenty sorters, two balers, four lift operators -- and that's on fiber alone. The container line runs another ten people."
The next screen has smaller stars, with tighter gaps between them. It's designed to send most of the newspaper hurtling over the top to its own belt. Some large containers make it over, too, and will have to be retrieved and sent back into the main stream, but the critical objective at this point is to get the paper away from the increasingly fragmented glass, which falls through the screen. "Glass is the worst contaminant we can have on newspapers," Herrera says. "The worst."
In theory, the remaining paper products are winnowed out at the third sort, where a screen with a different pattern of stars is hooked up to a blower that helps to propel the paper over the top, while containers made of plastic, glass and metal fall through. In practice, there's a return belt for the containers that fly over the top and some additional sorting on the container line for paper that falls through. But most of the paper is now headed for balers on one side of the plant. The blocks of newspaper that emerge from the back of the plant, destined for paper mills, will sell for around $125 a ton, and cardboard commands a similar price. The mixed paper will probably be shipped overseas and sell for around $75 a ton. (Waste Management has a second plant in north Denver that deals primarily in high-grade office paper and cardboard; it also offers public drop-off for phone books, cardboard and, for a fee, electronic waste.)
On the opposite side of the plant is a further network of belts, platforms, screens and catwalks, where the feverish separation of containers commences. A powerful magnet sucks tin cans into their own silo. A device that Herrera calls an eddy current exerts a magnetic field that repels aluminum cans; while the rest of the materials drop off the belt to another system below, the cans hurtle through a chute and are spat out in a cage, with sound effects like a popcorn popper gone berserk. Plastics whirl through a vortex designed to send the heavier materials downward while the lighter stuff, fugitive fiber and aluminum, heads elsewhere.
When it's over, Waste Management has a bunch of other well-sorted commodities for the loading dock. Clear plastic beverage bottles, which go for as much as $340 a ton, thanks to the hike in oil prices. Colored plastic, around the same price. Milk jugs, maybe $600 a ton. Aluminum, $1,900 a ton, but it's a small percentage of the total volume.
What's left? At the far corner of the plant, emerging from the noise and dust and seeming chaos of the sort process, is a fine rubble of busted glass, tattered labels and caps. A waterfall of glass, pouring from a final conveyor belt into its own bunker and headed for the Denver landfill, which is located in Arapahoe County and run by Waste Management.
The plant is able to sell 300 to 400 tons a month of intact bottles or large fragments to Rocky Mountain Bottle, a manufacturer half-owned by Coors. But most of the glass emerges from the plant too fine, too mixed up with ceramics, rock or other contaminants, to be of any commercial value. Every month, Waste Management hauls a thousand tons of the stuff to the landfill. Herrera says it's used as landfill cover because it's cheaper than dirt.
"There's a guy on the line pulling the big pieces of glass we send to Coors for recyling," he says. "But it's impossible, for the volume we handle, to manually sort the rest and produce the kind of quality they can accept."