Menacing, multi-ton compactors, perched on tank-like carriages, bite deep into oozing garbage newly arrived. This morning’s waste truckloads now crackle beneath engines, mashing it to hardened waffles.
Bring it on.
Crush it down.
Repeat.
It’s not exactly rocket science, and the underlying physics principles have hardly changed since some ancient operator must have thought up trampling trash mounds with teams of oxen at Sumer or Babylon.
Run the herd over.
The pile gets smaller.
Pack it tight, in fewer passes, till it reaches optimal height; then, on to the next cell.
Key: Better Compaction
A modern how-to manual on this, titled “Landfill Airspace Utilization,” issued by the Solid Waste Association of North America (SWANA) in January 2006, gives five “must haves” for better modern compaction. All are pretty well known, but just to recap them as a reminder:
- Optimal starting depth—Set to about 2 feet.
- Heavier equipment—The higher the tonnage the more pressure is imposed per square inch at the impact point.
- Specialized wheels—For good slope traction and more concentrated compaction, custom-designs wheel are now in use, as SWANA notes, at about half its surveyed membership.
- Optimize passes—Whether with wheels or oxen hooves, three to five runs seem to give optimal efficiency.
- GPS guidance—This will boost efficiency measurably. Example: The Olina-Alpha Landfill (7,000 tons per day) in Orange County, CA, logged savings of about $3 million per year in avoided cover soil cost and credited $1.3 million for extended life of the airspace.
Typically, successful compaction roughly doubles trash density, from its incoming weight of about 600 to 1,200 pounds per cubic yard.
By a corresponding ratio, it also reduces the surface area that needs covering at the end of the workday, whether by dirt, tarp, or other material.
Here’s how a dozen industry suppliers and landfill managers have been recently advancing both the packing down and the covering up. Each is in some way advancing methodologies a step or two further, generally to eke longer service from landfills and improved work efficiency.
New Jersey: One Machine’s Big Impact
After visiting nearby landfills to see what they were up to, managers at Salem County (NJ) Improvement Authority put their heads together and decided to upgrade to a new trash compactor. The result was that SCIA’s landfill’s (500–600 tons per day, 250 acres) achieved dramatic productivity gains, which should translate into postponing the site’s “early retirement.”
During the field trips, among the eyebrow-raising discoveries was a GeoLogic GPS at Broome County, NY. SCIA site supervisor Lynn Schmidt recounts that it actually informs the operator when compaction is completed, “determines grades and slopes,” and keeps a record of where certain notable types of trash, like asbestos, were placed.
At nearby Cape May, New Jersey, the landfill was also getting impressive compaction, not only by having better guidance, but a much heavier machine; so, SCIA went out and bought one as well—the largest compactor that its preferred manufacturer BOMAG (represented by local vendor JESCO) makes: a 60-ton workhorse, standing nearly 16 feet high, which, as SCIA operator Robert Norton finds, makes it possible to “pack twice as much in less time.”
Traction up and down 3-to-1 workface slopes is also better, thanks to 72 teeth per wheel, Norton adds.
After breaking-in the piece and learning how to optimized it, assistant site supervisor Dave Cobb estimates collective productivity improvements and compaction gains at about 35%.
Tulare County, CA: Better Wheel Deals
In California’s Central Valley, landfill manager Ron Moore also bought a compactor, Caterpillar’s 826 model, to complement others in a fleet that services three county landfills. Of the trundling Cats he says, “We keep those things running all the time.”
Working-face-wise, one strategy he uses is to design working cells “with the flattest slopes we can—aiming for four-to-one or five-to-one grade,” rather than the more normal three-to-one.
Traction and slippage thus aren’t such problems, and productivity improves.
Even so, he finds that well-designed wheels are also critical site tools. He sets a premium on buying the best. Good one are relatively problem-free, easy to clean, durable, don’t get fouled by wire wrapping, and wear well—usually lasting “about 10,000 hours operating time,” he says. Maintenance wise, “we’re hardly touching them at all.”
Again, all this yields much higher productivity.
Moore buys from Caron Compactor Co., a firm located in Escalon, CA, at the north end of the same valley.
Bad wheels, of which Moore has also had experience, plug up frequently, wear badly until they round off, and do not achieve “nearly as good compaction,” he adds.
Decent product support is also key. After he once received rather “underwhelming” service from an East Coast supplier, he no longer buys wheels that are not well represented in the West, especially if the sales people don’t seem to visit often.
Word-of-mouth about good and/or disappointing wheel performance is readily shared among fellow landfill operators and, says Moore, a general consensus has formed.
As for his new Caterpillar 826, which was just newly unpacked at the time of our interview, Moore decided to order it with stock wheels. The chief appeal here was the savings, amounting to about $140,000 to $180,000 (or $60,000–$70,000 on rebuilt wheels with a trade-in), compared with the high-end Caron wheels that he likes. However, given the current economy, and to retest the value proposition, Moore is going to run the new Cat and its wheels side-by-side against a comparable compactor riding on Carons. Depending on performance, he’ll decide if the upgrade is still worth the money.
Wheel Concept Getting Some Traction
The fine points of wheels also figure into the thinking of Ernie Freeman, of HJ Industries in Avon, OH. He observers: “The biggest problem in compaction of landfills I’ve been on” is that, while the cleats on typical wheels do provide traction they also “tend to pull the trash back up, so they tend to keep losing compaction.”
Hence, his wheel manufacturing firm, which seeks to fill a niche for upgrade wheels primarily against stock Cat hardware, introduced a specialty cleat a couple of years ago. Teeth are shaped to counteract the up-pulling effect and designed to work equally well in forward and reverse, uphill or down. Freeman calls it the “Track-Pack” cleat.
Mounted on a Cat ’86, the “shoes” were being field-tested in mid-2009 at the huge Salt River Pima Landfill near Phoenix. Operations manager Kevin McGrew describes a “taller, more cutting style of cleat … in an elongated snakelike S shape,” which, he says, “would lead you to believe that compaction would be improved, because pressure point gives a distinct smaller surface area at any given time.” Although he doesn’t have formal data, early results “are certainly encouraging,” he says. “My gut tells me it’s every bit as good as the Cat Plus wheel, with improved traction, based on operator feel and handling.”
More Wheel Product Roll-Outs
Resizing stock wheels on Caterpillars to boost compaction is another strategy, one being undertaken at Terra Compactor Wheel in Plymouth, WI.
Dan Cowher, fleet manager of Veolia Environmental Services—one of the largest solid waste management organizations in North America, operating 32 landfills—is collaborating in the Terra wheel design. Caterpillar comprises the backbone Cowher’s motor pool. Although the stock wheels are adequate, he says, he anticipates a much better result will soon be delivered from the new one, anticipated to be on the job by the time this story appears.
Driving Terra’s wheel innovation is a very positive experience that has been widely reported with Rex Compactors; these are distinctive for having two small front wheels and two larger ones behind. Such an arrangement “kind of makes it like a tricycle,” Cower says. It also stacks much heavier poundage-per inch on the small front wheels, hence gaining superior compaction.
Comparatively, standard Cat wheels for its bigger compactors are sized at 55-inches diameter; Terra already makes a smallish 48-inch wheel, too small for these machines.
This would indicate a logical compromise: a mid-point size.
“We did the quick math,” Cowher recalls, and found that a reduction of just [a few] inches in diameter increases density 5%—“which is huge,” he says. “We were tickled with that.”
Adding even more focused pressure to future mounds of trash will be an enlarged wheel wrapper weighing another 500 pounds per wheel.
If performance dazzles him as expected, Cowher says this new crusher may become a standard spec in Veolia’s future, “and well worth the extra money.”
Other aftermarket accessories to make his compaction life easier include: wire guards; lots of choices for multiple width; options for many teeth; options for new, used or rebuilt wheels; and wheels optimized for sludge. Having a full menu of options allows Veolia’s many managers to fine-tune their wheel orders to accommodate local climate, topography, slope, and ground type.
And this maintenance tip: Measure wheel wear periodically, then compare deterioration to the amount of work being done; this provides a gauge of durability, value, and remaining life.
Also: “When you get more than a quarter-inch difference between front and back,” says Cowher, rotate them, typically annually, and you’ll perhaps get “another year or so” out of them.
To enhance West Coast service, Terra’s president Bob Brockway is now subcontracting with manufacturers in California (in Stockton in the north and Perris in the south) in order to save on two-way shipping, which otherwise makes deliveries and service cost-prohibitive, he notes.
In part to answer such challenges, Caterpillar recently announced it will begin offering high-quality remanufactured wheels for its 836 model, at a 35%–45% savings, yet with new-wheel warranties.
Keith Reber, commercial manager of Caterpillar’s remanufacturing division explains: “We have a keen interest in trying to keep our customers with Cat wheels and cleats, and not just for the sake of commercial sales.” Compactors, he says, are much more sophisticated than they may appear, and they take a tremendous beating. They’re designed with an integrated power train, wheel size, and cleats, and then they are exhaustively tested as systems. “But,” he says, “when people put foreign wheels or other wheels or cleats on the machine, we … don’t know what kind of stresses that might put on the final drive.” Designers sometimes tack on huge cleats for longer wear or traction, but this may entail cutting down the wheel size—then, “Once you start down that path you’re really not sure how that systems going to work any more.”
Another competitive advantage of Caterpillar’s new “reman” wheel swap program, he continues, is the elimination of certain costs and downtime. Unlike other common arrangements, in which old wheels are first removed, then temporary loaners are put on while old wheels undergo refurbishing somewhere, then later re-attached, the second-hand Cat wheels are simply be ordered through the dealer, and put on immediately, as the old ones are taken as a sort of generous trade-in.
The above-described equipment and similar innovations, together with conscientiously applied methodologies, are continually improving compaction rates, notes David Eng, of Environmental Products Inc. (EPI), makers of a ground cover product in Vancouver, BC. He cites a study, done in 2005 by the American Society for Testing Materials, which pegs the industry’s best practices improvement gains at about 40%. With such boosts, landfills will last that much longer. The ultracompacted sub-terrain also gets starved for oxygen, “so fires never start,” and thus, safety is also improved, Eng adds.
After Beating it Down, Cover it Up
Subtitle D of the Resource Conservation and Recovery Act (RCRA) requires that a landfill’s working cell be enclosed daily somehow—top, front, and sides.
The standard medium is 6 inches of soil, or certain alternatives may be applied.
There is in fact a groundswell of support for these alternative daily covers (ADCs), on the basis of simple physics and dollars: A thin, removable tarp, say, or a biodegradable plastic sheet can conserve half a foot or more of what would otherwise be displaced by daily dirt. Since landfill value is measured by its remaining airspace, anything that conserves this prolongs the value.
Randy Kozak, a colleague of Eng’s, has been selling a biodegradable geosynthetic sheet used for this purpose, principally in Europe, Australia and North America, for about 10 years. As one selling point, he cites an industry norm of six years as the waiting period for approval and construction of most new landfills. This fact puts the ADC case succinctly: “Almost anything you can do to extend the life cycle of current landfill” is justified, Kozak says. He echoes many others.
EPI’s plastic cover “positions itself,” as it were, against the competition as the labor-saver: unlike a tarp, it needs no daily retraction.
For his part, tarp vendor Marlon Yarborough of Airspace Saver in Ponchatoula, LA, sells, he says, “more and more tarps for people trying to conserve their airspace.” Business has been growing steadily every year, especially since the Tarpomatic machine came along, enabling faster and safer handling.
The only real question left, he says, is which tarp to buy—the tougher one which should last 12 to 24 months, or the cheaper, typically reordered every four or five.
Terry Pitcher, president of Mercer Motors in Mercer, ME, also makes a tarping system, aimed at smaller municipal landfills. His sales summation: “Its almost a total no-brainer … Anybody that’s not using ADC us just wasting a whole lot of money and wasting time. Putting 6 inches of dirt on a landfill every day means you’re gobbling up huge amounts of airspace.”
The value of air ranges from about $30 to $80 or more per cubic yard, depending on locality, he adds.
Tack on the cost of time, labor, dump truck, spreader, and fuel—and using dirt becomes almost impossible to cost justify, he says.
In the aforementioned SWANA report, the majority of survey takers use ADCs, with a preference for tarps. Other leading alternatives include foams, wood chips, compost, auto shredder fluff, ash, foundry sand, and slurries. These can typically be applied and/or recovered either manually or with applicator machines, and can be weighted in place, if need be, by whatever is conveniently at hand.
Rusmar Inc., for instance, offers foam generation equipment for all size venues that provides 100% vector control. Rusmar Foams are nontoxic, nonhazardous, biodegradable, nonflammable, requiring no mixing or cleanup, and available in formulations that can last up to six months.
As the following discussion with landfill operators shifts to the topic of coverings, note that each seems to encounter somewhat differing local conditions and needs, varying as to work-area dimensions, daily weather, seasons, underlying compaction quality, and odor-control issues.
For Rod Moore, in the Central Valley, day-to-day, “My guys really like the ease of tarps and how they go down,” much better than bulldozing dirt. Windy conditions call for a bit of ballast (chains or dirt); these easily suffice. Foam was tried, but quickly abandoned due to the added work.
Geosynthetics (“disposable plastics”) also have a role at his three landfills, but not for ADC as meant; rather, as a cell fills up but is not yet ready to seal, it gets covered with plastic “almost as an intermediate, or a stopgap cover,” he says. The sheeting “seem to work really good… we can leave it out [for days and even weeks], and [the local environmental oversight agency] is pretty happy,” says Moore. Again, a little dirt is strewn over, in case the wind picks up.
Fairbanks North Star Borough
Bob Jordan, solid waste manager at this 115,000-tons-per-year landfill near the Arctic Circle in Alaska reports, a bit atypically, “Our standby cover is gravel.” Locally, anyway, it is a cheap, salty medium that is always stocked as intermediate cover, and thus it is also ideal for daily use, autumn to spring.
The climate itself eliminates the need for any cover, he points out, whenever temperatures don’t reach 10°F at noon; he’s allowed to skip putting on a topping for the next three days.
But what about the need to preserve landfill life?
During the milder midyear period, tarps still aren’t viable, says Jordan, as they might be buried by the odd snowfall, making removal difficult. For these six months or so, Jordan thus uses EPI’s 1.75-mil biodegradable sheeting, which “we like very much,” he says. Easy to handle, it does indeed conserve airspace, he adds, and is very valuable for that reason alone.
Application entails a deployer on which the roll hangs overhead; as the operator backs up, it self-unrolls. Loose gravel holds it down—“and that’s the cover for the night.”
As for cost, he spends $49,000–$50,000 a year to buy 15 to 18 rolls, for topping a daily compacting area about 60 by 75 feet. This works out to a nearly identical cost for shoveling a half-foot of gravel every day. But even if the price of the sheets were to rise, the value of saved airspace will justify whatever he has to pay, he says.
Revenue-Generating Covers
ADCs may dominate, but many landfills still do use daily dirt—“probably 40% of the market,” suggests one supplier of ADCs and other products and services to landfill operators—and this preference continues, he adds, for the simple reason that dirt “is how the cover has always been done. If it works, why fix it?” asks Tony Knight, of New Waste Concepts in Perrysburg, OH.
Over the years, Knight has conducted extensive market surveys of operations and, as a result, he advises clients who still cling to their “dirty” ways, to consider applying a more rigorous analysis of landfill expenses to determine actual costs, including long-term capital. For example, the cost of building new cells, closing them, and post-closure care, can also run “as high as … eight or ten bucks a ton,” and more, his studies have found.
As a means of avoiding costs—especially deferring the high expense and amortization of constructing a new landfill—the real value of ADC over many years may actually mount up into the millions, he believes.
Another often-overlooked expense is the loss of value of a potential landfill improvement, suffered by tying up equipment and staff to do any labor-intensive dirt cover. In a survey of landfills done some years ago, Knight found that daily cover was often gobbling two or three laborers’ time for a total of 12 labor hours daily; this, he suggests, should probably be better spent doing “12 hours fixing things and developing other projects.”
As for straight-line ADC costs operationally, Knight has found that ADC saves about one-third the expense of excavating and hauling dirt, on average.
A further complicating dimension one should consider is the correct pricing of revenue generating daily cover—auto fluff, foundry sand, “fines from C&D waste disposal, ground-up stuff… and inert materials,” he says. These not only provide cover, but bring in some bucks. This fact often makes them attractive and “a pretty tough competitor” against plastics, dirt, and tarps—at least on a first glance.
However, as he hastens to add, landfills probably aren’t charging haulers of these enough, because the cover material is still eating up valuable airspace. Thus, it should not be discounted just because it is considered a cover rather than waste.
And the situation could easily get out of hand if a landfill buys too much of this cover material, the excess of which must then be disposed of as regular waste. “You start filling up your landfill with $10-a-ton material” when “you budgeted $50, $60, or $100 dollars a ton.”
Bad Idea
Also, as reported in mid-2009 at PollutionOnline.com, an ill-chosen daily cover can backfire expensively if it turns out to be hazardous. Case in point is the Warren County (NJ) District Landfill, which was charging haulers for C&D debris since the 1990s. This provided nice revenue and better drainage, and it was conveniently delivered to the working face. But in 2004, the EPA came along. Samples of the landfill’s methane were taken, hydrogen sulfide was discovered in spectacular excess—11,400 parts per million by volume (ppmv) compared with a normal 35.5 ppmv.
Bad news.
A final stop in this roundup, at the nation’s largest landfill—the Los Angeles County Sanitation Districts (13,200 tons per day by permit)—offers perhaps a representative look at daily cover applied on a very large scale.
The LACSD also shows how ADC might or might not be selected in the rare case where airspace is not a consideration.
As senior engineer Jason Ching explains, the LACSD is unusual among landfills in that its lifespan is simply set to end on a certain date—October 31, 2013—regardless of fill volume.
And, due to the current economic downturn, daily volumes have also fallen by about a third.
So, what daily cover do they pick?
“We change each day,” says Ching. “We vary it, depending.” About eight or nine days out of 10, the landfills use “a [50/50] mixture of greenwaste and dirt or just dirt,” rather than ADC, he says.
Greenwaste consists of yard trimmings, leaves, tree branches, shrubs, etc., ground up. California’s mandatory recycling law (A.B. 939) enhances the value of greenwaste when reused. Thus, to help cities offset their collection costs, the LACSD lowers its tipping-fee for it to just $14 per ton versus the usual $36.80 per ton.
Plentiful free dirt also arrives daily.
The conclusion is that when airspace is no longer a consideration—and dirt is dirt-cheap—perhaps the ADC incentive collapses, at least in Los Angeles.
Besides which, local winds across the very large working faces of local landfills discourage ADCs anyway, adds Ching; but, plastics and even foams are still on hand for rainy days—better than fighting the mud.
Summing up, McGrew in Arizona points out that competition is keen among vendors, “and anyone that stands still is going to fall behind.” Because of varying local conditions, landfills do require a variety of covers and wheels, he adds. On the latter, “Each manufacturer is trying to come up with a wheel that will satisfy a larger market share,” by straining to design products that are ever more compatible with many working faces.
Although the niche may be small, it is a very desirable one: Wheels are pricey, so sales bring good cash; better wheels bring value, so customers will pay more; word spreads, so the market rewards good products; and wheels wear quickly, so reorders are assured—just as long as the world keeps piling up trash.
A good bet.