A Pacific Northwest landfill captures a valuable energy source
I approach the open pit of Lane County, Oregons Short Mountain Landfill on olfactory alert, mouth-breathing in case the odor is as overpowering as I expect an acre of open trash to be. I take a tiny, furtive sniff. Not bad. I inhale less tentatively, to be sure, and then finally, take a healthy, uninhibited snort. Its a sour smell, like a film of old milk on the inside of an empty plastic jug, but on a grander scale. Its unpleasant, but surprisingly, not nauseating. The view, on the other hand, is pretty offensive.
I am standing at the edge of a huge pit, a third of which is covered by trash, a ragged spread of barely discernable, soiled material. Two gigantic yellow bulldozers with eight-foot-high, knobbed steel wheels rumble around down in the pit, compacting the spongy surface. Thirty feet above the pit, a dingy blue and yellow compactor truck backs up to the ramp. Its convex rear door pops open, erupting trash a waterfall of black plastic bags, Styrofoam, and wood scraps. Its hard to identify objects, but I think I see a mattress tumble through the stream. Before I can find it in the conical mound that forms below the truck, though, one of the giant dozers gouges the pile with its 10-foot-high blade, pushing buoyant debris before it like a breaking ocean wave.
Whats most notable about the trash is that it is overwhelmingly plastic. Looking over the pits surface, I spot a scrap of cotton clothing here, a tattered newspaper there, an occasional soiled plush toy, but thats about it. The lack of anything organic isnt surprising though Lane Countys recycling and composting programs divert 52 percent of the waste stream, from newspapers to grass clippings to food scraps, before it reaches Short Mountain Landfill. While that efficiency 27 percent better than the national average saves space at the dump, it has a surprising downside: The facility’s landfill gas-powered electric plant is now running at only a little more than half of its capacity.
Short Mountain is one of 375 landfills in the United States that tap the methane created by decomposing garbage and burn it to generate electricity. At Short Mountain, the putrid gas supplies enough electricity to power 1,300 nearby homes, but in the 13 years since the landfill’s power plant was constructed, gas output has steadily declined. Instead of powering all four of the facility’s locomotive-sized generators around the clock as it once did, there’s now only enough gas to run two engines full time and a third during work-day hours. That shortfall, say the plant’s managers, is attributable to one thing: a decreasing percentage of organics in the county’s trash.
As Doug Hoover presses buttons on the Gem 2000, the phonebook-sized gadget emits shrill beeps similar to the sounds a microwave makes while being programmed to cook miniature pizzas. Instead, and far less savory, Hoover is preparing to sample the gaseous emissions from a million-ton garbage stew. He’ll hook the machine up to lines from a half-dozen of Short Mountain’s 101 landfill gas wells for a routine check of output and gas content. It’s a warm, sunny morning in April, atypical for Oregon, but par for a winter and spring that has produced only 39 percent of normal precipitation. While no one likes to work in the rain, this dry weather actually makes Hoover’s job as power plant operator all the more critical as he tries to coax as much gas as possible out of the landfill to replace the anticipated shortage of hydro-generated energy from low river flows.
Dressed in jeans, a gray T-shirt and work boots, Hoover has the solid build you’d expect of a man running a power plant. His hair is cut short, his moustache is trim, and his arched eyebrows give him an alert, intelligent look. Hoover has been with the project since its inception and is one of two employees of Eugene People’s Utility District (EPUD) – the public utility that owns the electric plant – working full-time at the landfill.
We are walking along Short Mountain’s perimeter road, at the far end of the landfill from the open pit. Above us rise a pair of pyramids wrapped in black plastic, 100-foot-high garbage ziggurats, their hearts a potpourri of lawn furniture, kitchen utensils, and shower curtains. These are phases one and two of Short Mountain, the latter closed only since November. Like giant black pincushions, each of the mountains is perforated every 75 feet by one of the wells’ eight-inch-diameter PVC tubes, which are sunk up to 100 feet into the trash pile. The wells are linked by a mile-long system of plastic tubing to the power plant, where the methane that naturally burbles up from the decomposing garbage is filtered, cooled, and then fed directly into the thrumming yellow engines.
Beside us is the main gas pipeline, an 18-inch diameter black plastic tube that snakes along the road like a giant boa constrictor digesting an unfortunate villager. Because the black plastic expands and contracts with temperature fluctuations, the 3,000-foot long pipeline can gain and lose hundreds of feet in length over the course of a day. “It does its own thing,” says Hoover, continuing to fiddle with the electronic device. “Sometimes you come out here in the summer and you can actually hear the pipe scraping across the road as it lengthens.”
We stop at a junction where tubing from one of the wells meets the pipeline, a valve marked C8 with white paint and topped by a red-handled knob. Hoover kneels down to attach the Gem 2000 to couplings on the valve casing via two clear plastic tubes. He presses a button and the machine makes a small whirring noise, vacuuming in a gas sample for analysis. After about a minute, the numbers flickering on the screen stabilize. The reading: 50.8 percent methane, 33.4 percent carbon dioxide, four percent oxygen, and a balance of 11 percent (mainly nitrogen).
The methane is what he’s after. Methane is a dense, flammable gas, the main ingredient in so-called natural gas burned by stoves and hot water heaters in millions of American homes. Methane is formed by anaerobic decomposition, primarily in swamps, but also in trash heaps – the byproduct of billions of bacteria digesting organic matter like leather shoes, paper cups, and chicken bones. In addition to being flammable, methane is a potent greenhouse gas, and the EPA is so concerned with its effect on global warming that each landfill with over a million cubic feet of garbage (Short Mountain is an average-sized landfill at nearly 6 million cubic feet) is required to capture its methane and burn it. The combustion converts methane to the far more benign carbon dioxide, 21 times less potent as a greenhouse gas. If that combustion is used to fire generators as at Short Mountain, then there is a tidy double ecological net of greenhouse reduction and alternative energy production. Unfortunately, only 16 percent of the nation’s 2,300 landfills harness that mandated combustion for energy – at the remainder, the potential electricity literally goes up in smoke.
The EPA’s Landfill Methane Outreach Program has identified 610 other landfills where methane could be harnessed for secondary use cost effectively. In Oregon alone, the EPA estimates that seven eligible but untapped facilities could generate more than 34 megawatts of electricity, enough to power over 16,000 homes. Chris Voell, program manager for the EPA’s Landfill Methane Outreach Program, says the slow adoption of landfill gas plants has to do with economics and ignorance. Some landfills are just too far away from potential users to make development financially worthwhile. But, he adds, perception is often the problem. “People just have mental blocks when it comes to landfills,” he says. “They just don’t want to consider it.” For most people, the less they think about the bloated, toxic piles of refuse, the better. To combat that sentiment, a big part of Voell’s job is giving landfill gas-promoting presentations around the country.
system has been installed,
much of the landfill's odor
has been eliminated.
flammability is one of the principle reasons Hoover has to use the
$8,000 Gem 2000. In 1986, a fan at a Steve Winwood concert at San
Francisco’s Shoreline Amphitheater, which was built atop a closed
landfill, was scorched when, possibly calling for an encore, he flicked
his cigarette lighter, which ignited a methane seep and sparked a
five-foot high column of flame. While such a flare is unlikely in a
landfill tapped by wells, smoldering fires can still spontaneously
ignite if high oxygen levels meet with the estimated 180-degree
temperatures common in decomposing landfills. “We had a few in the
early days,” Hoover says. One fire melted the well, and had to be
extinguished by digging it up with a backhoe.
“That was before we had this, though,” he says, indicating the device. “Back then, no one used them because they cost $30,000 and were unreliable.”
The reliable, economical machine is currently whirring again, even though we are walking along the road to the next well, 125 feet ahead. “It’s just purging itself,” explains Hoover. We stop at the next well, G23, and Hoover again kneels to connect the sampling tubes. Again the machine whirs, and again the numbers flicker on the screen.
I’m watching for is a high nitrogen reading,” he says, pointing at the
“Balance” line. “If it gets up over 20 percent, that means we’re
getting too much air into the landfill.” That excess oxygen can lead to
not only landfill fires, but also a retardation of methane production –
it kills off the bacteria whose digestion creates anaerobic
decomposition. If Hoover sees that he’s getting too much air into the
trash, he’ll close off the valves on the wells just a bit to stop
“pulling” them. For all practical purposes, Hoover is a bacteria
rancher, trying not to drive his herd too hard.
The reading for G23: Methane, 63.1; carbon dioxide, 36; oxygen, 0.7; balance, .2. This is a good well, yielding high methane, possibly sunk into a rich pocket of organic material, such as the tankers full of rotting eggs that a local poultry farm periodically dumps, the worst stuff Hoover says he’s seen go into the landfill. “It’s just a gooey mess,” he says. “The smell is unbelievable. You see that truck coming and you just clear out for a while.”
Hoover says the smell of the landfill doesn’t really bother him anymore, and for the most part, since the methane collection system has been installed, much of the odor has been eliminated, another benefit of the power plant for the surrounding community.
The chicken eggs highlight one of the general
difficulties of landfill gas generation – working with wet garbage.
When Hoover hooks the Gem 2000 up to the wells, he must closely watch
that no liquid gets drawn into the machine. As it is whirring at our
next set of valves, the adjacent pipe suddenly starts slurping. Hoover
kicks that tube, and the noise stops. “Leachate,” he says.
Leachate is the liquid that drains out of the trash pile, a mixture of curdled organics and rainwater brewed into a ripe tea of oil, grease, and household products like paint and bleach. Leachate is considered hazardous waste and landfills are required to drain the stuff off and treat it. Elaborate systems drain the leachate from below, but inevitably, some of it percolates into the methane wells.
The water entering isn’t all bad, though. According to Hoover, 20 to 30 percent moisture content is optimum for methane production. Landfills in dry parts of the country typically have much slower rates of methane production, and in fact some inject water or leachate into the pile to speed decomposition. “Obviously,” says Hoover, “we have the opposite problem.” In very wet climates like western Oregon, the tarps that cover the landfills not only reduce odor, but also keep rainwater out. Even so, wells often become saturated. Only about half of the 101 wells at Short Mountain are currently producing methane. The rest are too saturated with leachate, or clogged with refuse.
I point to the first valve in the current group, G5, whose line is severed, asking if it is one of the saturated wells. “That one is what we called ‘retired,’” Hoover says. A few years back it began emitting a caulk-like substance that was clogging up the power plant’s filters. “One of the mills probably dumped a bunch of resin into that part of the landfill, stuff they were using to glue plywood together,” says Hoover. “We drained it a few times, but finally just cut it off. You never know what you are going to get in there.”
At our last test wells of the day, a thicket of green thistles barricades the valves. Hoover begins to mash the spiky leaves out of the way with his work boot. “Even though it’s a landfill I can’t use Roundup,” he says, referring to the chemical herbicide. “It’s just one of those rules about using chemicals on public lands.” He pauses a beat, and then, with an arched eyebrow and a smile adds, “So we use inmates instead.”
As if on cue, a group of four rangy young men appear on the slope above us. They are dressed in the convict’s gear – orange T-shirts and hats, with jeans, boots, and work gloves. They amble over the black plastic tarp, ignoring us, walking with the big, loose steps of cocky teenagers. The tallest wears his cap with the brim cocked to the side and shakes a can of spray paint in his right hand. “They mark any holes they find in the tarp,” says Hoover. The holes grow larger when buffeted by the wind, eventually letting too much rainwater into the trash pile.
A few vultures soar on thermals created by the rising heat.
collects the final readings, and we hop in the truck to head back to
the power plant. We drive the remainder of the perimeter road, the
capped trash pile squatting massive and black to our right, heat
already shimmering off its black flanks at 10:30 in the morning. A few
vultures soar on thermals created by the rising heat. We pass the
leachate treatment plant below on the left and then make the turn to
pass between the peaks and the open pit. There we pause and watch the
bulldozers spreading the trash. Clouds of dust rise in their wake
and small starlings flit up before them as they push the trash into the gentle grades that Hoover requests as optimum for his horizontal wells.
At first the wells were drilled with a corkscrew and set into the trash pile vertically, but it turns out that laying the wells into the growing layers of garbage as they go is more effective. The process is simple: A backhoe digs a trench into the trash, which is then filled with rounded river rock and layered with a filtering membrane. Seventy-five to 100 feet of perforated plastic piping is then laid among the stones and covered with about 40 feet of garbage. Then they wait for the bacteria to do their work. While the naturally expanding gas would flow into the piping of its own accord, a light vacuum at the power plant helps it along. As we pass the dumping ramp we watch a truck spill its load down into the pit. Amid the falling refuse some large green pine boughs are brightly visible. "There's something you never see anymore," says Hoover, "greenery. It all gets processed for mulch now." I ask him how he feels about the fact that the recycling and compost programs are cutting into the methane production. He admits that he'd like to be running all four engines, but, "as a member of the community, I'm glad that they are saving so much landfill space. This landfill is going to be able to stay open a lot longer because of recycling."
I think about a previous afternoon when I'd visited the landfill. I'd watched a pickup truck pull in alongside the 16-ton garbage-spewing compactor trucks. It backed up a small wooden trailer to the edge of the ramp and stopped. A middle-aged man appeared beside the trailer and opened its tailgate, revealing something big, furry, and dead. He climbed in, grasped the thing by the hooves and rolled it over the edge. A black-faced sheep fell through the air, bounced on the trash's spongy surface and lay with its stiff legs in the air. The sight of something so natural atop the salad of mangled plastic refuse was startling – but only for a moment. In the next instant, one of the huge dozers turned and headed straight for the sheep. I cringed as the dozer ran over the spot with its vicious steel-knobbed wheels. But when the machine passed, there were no mangled remains, no blood on the wheels. The sheep had been pressed deep under the surface of the trash layers, a bit of organic material for Hoover's wells.
Frederick Reimers, former managing editor of Paddler magazine, freelances for Outside, National Geographic Adventure, Sports Illustrated and Men's Journal. He attends graduate school at the University of Oregon.