Incinerator Turns Garbage into Electricity
ALEXANDRIA, Va. − Juan Murphy is perched high above a mountain of urban detritus that just keeps growing. His job is to keep carving away so the heaving trash pile doesn't overtake him.
Not a minute goes by without a garbage truck pulling into Covanta Energy's waste incinerator in Alexandria. The trucks keep coming, often occupying all of the incinerator's five bays at once.
Mattresses, campaign signs, broken office furniture, yard waste and trash bags by the thousands are deposited in sloppy heaps. "It never stops," Mr. Murphy said.
Even when trash is thrown away, it is not gone until Mr. Murphy gets rid of the vast piles once and for all. He works in a glass-enclosed cube called the pulpit, 70 feet above the dock where the trucks spill their dirty, dripping contents.
The pulpit is the best seat in the house. From it, Mr. Murphy controls a massive steel claw that lets him hoist the remnants of American life into three chutes. Each chute leads to a searing flame pit that burns the garbage.
His challenge is keeping up with the rapid pace of garbage delivery. When he started working as a crane operator more than eight years ago, that was not so easy.
"When I first came here it took a day or two to be able to control it. But it took a week before I could keep up with receiving," Mr. Murphy said.
There are 150 trucks from Alexandria, Arlington, the District and from communities in Maryland discarding up to 1,500 tons of garbage a day at the incinerator. All of it is municipal waste. They don't burn building materials, metal or items tossed into recycling bins.
All of Alexandria's and Arlington's municipal waste is delivered to Covanta.
Levers on each side of a chair in the pulpit control the claw, or grapple. One makes it go left, right, forward and back. The other guides it up and down and controls the claw so it can grab and release garbage.
The grapple, a 6,000-pound steel spider attached to a crane by four thick cables, is capable of lifting 9 tons of garbage at once.
Grapple operators learn to make the claw an extension of their hands, said Bill Rodriguez, a shift supervisor at Covanta. Four grapple operators share the job of hoisting trash into chutes, and someone is always in the pulpit.
"Trash never sleeps," Mr. Rodriguez said.
Even when Covanta is closed and doesn't accept trash -- on Sundays, Christmas and New Year's Day -- a grapple operator is in the pulpit, feeding garbage to the fires that reach 2,400 degrees.
Mr. Murphy can't toss everything directly into the chutes, which sit along the back wall of the garbage pit. Wet garbage won't burn easily, and too much dense material in a single load can slow incineration. Like industrial chefs, grapple operators lift and drop the garbage, stirring it to create a good mixture.
Some items go directly into the chutes without Mr. Murphy's aid. While he is manipulating a load of garbage with the grapple, a group of workers from the Department of Homeland Security walk through a door a floor below him and step onto a landing next to the chutes. Accompanied by a Covanta employee, they feed the fires themselves with boxes of top-secret trash.
Federal employees are common visitors. Once a group deposited million of dollars of counterfeit money into a chute.
Mr. Murphy and his fellow grapple operators must constantly fill the chutes with garbage because they can't let the fires go out.
The trash is a more valuable commodity than meets the eye. The inferno it feeds turns water into steam that powers two turbines and generates electricity.
It will take only 20 minutes for a load of garbage that is dumped into the chute to be converted into electricity, Mr. Rodriguez said.
The turbines produce up to 24 megawatts of electricity an hour. Covanta sells the energy to Dominion Virginia Power, which transfers the energy to its electric grid to power homes and businesses in the region.
Electricity generated by the burning garbage will produce enough power to supply 23,000 homes at any one time.
Covanta's plant is one of just 89 in the country using solid waste to produce energy. Waste-to-energy plants nationwide generate enough electricity to supply merely 2.4 million homes.
Burning solid waste reduces the amount of trash going to landfills, but only a few municipalities do it because typically they pay more to discard garbage at a waste-to-energy facility like Covanta's than to send it to a landfill.
Covanta charges about $61 to dispose of a ton of municipal solid waste.
That is slightly more than the cost to take a ton of solid waste to a transfer station, where many municipalities take garbage to be processed before having it delivered to a landfill, and about twice the cost to take garbage directly to a landfill.
But garbage isn't generating electricity in a landfill, Mr. Murphy said.
"To me, this is much more environmentally friendly than a landfill," he said.
Source: Knight Ridder/Tribune Business News