When trash stacks up, it presents a problem for landfills, most of which are only permitted to reach a limited height. That’s why so many landfill operators are willing to pay in the vicinity of half a million dollars apiece for massive machines that squash piled-up trash down again. In the words of Mark Welch, factory marketing representative for Caterpillar landfill compactors, “Compactors compact trash. The objective is to get the most waste in the least amount of space. Air space is money to a landfill operator.“

These massive machines trundle on spiked steel wheels all over landfills across the country and around the world turning air right back into money for landfill operators. There are just four major United States landfill compactor manufacturers including Aurora, Illinois-based market leader Caterpillar. Their primary competition consists of the bulldozers that landfills already have.

Bulldozers’ wide track treads give them great traction, but spread out the load of their weight in a manner that works against the goal of smashing trash flat. Compactors employ various wheel schemes, attempting to balance the goals of pressing down a wide footprint, and focusing the weight in a narrow footprint to maximize gravitational force. Compactor wheels also commonly feature wire-cutting wheel attachments to reduce downtime due to wheels wrapped in landfill wire. Recent introductions include GPS positioning devices to make it easier for operators to know which areas in a landfill they have already compacted and where to go next.

Weight is the first distinguishing characteristic for a landfill compactor. Generally, higher-volume landfill operators prefer heavier machines and are willing to absorb the higher purchase and operating costs. Some lower-volume landfills acquire two or more lighter compactors, which can help spread and compact peak flows of trash better than a single larger machine.

Al-jon Inc. of Ottmuwa, Iowa, makes three different sizes. “The Vantage 500 is the smallest. It starts at 81,000 lbs.,” says R.B. Bernie Melcher, vice president of solid waste products at Al-jon. “Our medium-sized machine is the Vantage 525, it goes up to 110,000 lbs. and the Vantage 600 is the largest compactor in the world, weighing up to 126,000 lbs.”

Al-jon employs a hydrostatic transmission that applies constant torque to the steel wheels. “That allows that machine at full throttle to change direction without any detriment to the machine or loss of power,” Melcher says. He adds that machines’ high ground clearance — 30 inches at center on the small machine — reduces wire wrapping and increases compression ability because only the compactor’s wheels are touching down.

Taking a different tack, Caterpillar emphasis a mechanical approach to converter drives. “Cat landfill compactors have steel driving steel, from the torque converter to the transmission through the differential and final drives to the tips on the wheels,” says Mark Welch, factory marketing representative.

Cat compactors also can be fitted with the company’s computer-aided earthmoving system, which employs GPS, onboard sensors and control systems to improve efficiency. Caterpillar’s three models, from smallest to largest, include the 52,000-lb. model 816F, the 81,000-lb. 826H and the 118,000-lb. model 836H.

BOMAG, based in Kewanee, Illinois, emphasizes the wheel design of its four models. “One-piece, chill cast teeth feature a high-strength, wear-resistant material in the upper three-quarters, or contact area, of each tooth to enhance component life,” explains BOMAG’s Doug Zoerb, marketing communications administrator. “The lower quarter of the tooth is constructed of a softer material for ease of welding to the wheel.”

Wheels affect not only machine life, operating costs and downtime, but also can make for more effective compaction when, for instance, longer teeth penetrate more deeply into the trash pile, the company says. BOMAG wheels feature adjustable scraper bars to block trash buildup and achieve maximum tooth penetration, as well as built-in wire cutters to guards against wire wrap-around. BOMAG’s four models include the BC672RB at 71,000 lbs., the BC772RB at 81,205 lbs., the BC972RB at 101,630 lbs. and the BC1172RB at 120,000 lbs.

Recent technological trends in the industry include an emphasis on fuel economy and ability to meet emissions regulations. Al-jon plans to have all its compactors meet Tier III emissions standards by the end of this year, according to Melcher. Prices for satellite position-tracking equipment have halved in the last two years, he adds, making those helpful add-ons much more appealing. “If the price continues to fall,” he says, “that’s going to be pretty attractive.”

The market is shifting somewhat as well. Landfill operators who took forays into balers are reevaluating compactors as less expensive ways to get more use out of their limited space. Melcher reports a shift in customers as government buyers, who once represented 80 percent of sales, have dropped to about 65 percent as the private waste industry has consolidated into bigger players. Finally, the four top American manufacturers — Al-jon, Cat, BOMAG and Oklahoma City-based Terex — may soon be contemplating competition from Japanese equipment maker Komatsu, a significant presence on the international scene that so far has declined to market its compactors here.