Landfill Compactors and Heavy Equipment
Compact, compact, compact—and save landfill airspace. It’s an old song and we all know the words.
It is a basic assumption that most landfills will have a compactor. But there’s more to successful compaction than just having a compactor—you must have the right compactor, and then provide your crew with the training and resources they need to use it productively.
This brings to mind the story of the old woodcutter who’d used a handsaw and ax for 30 years, until a chainsaw salesman talked him into upgrading. The woodcutter tried the newfangled chainsaw for a week and then finally returned it, saying, “I could cut more wood with my old saw. This miserable thing doesn’t work.” Puzzled, the salesman took hold of the saw, gave the rope starter a pull and fired it up. The old woodcutter leaped back, wide-eyed and exclaimed, “What’s that noise?”
We can laugh about the woodcutter, but it would be a mistake to suppose we know all there is to know about landfill compaction. The role of compactors has changed within this industry, and it continues to change. The very existence of landfill compactors is a relatively new phenomenon.
But I’m moving too quickly. Before we run down the road of how to use a compactor, let’s look back a ways and see why we use compactors in the first place. Yes, we use compactors primarily to maximize landfill airspace … but, “Why?” Why is airspace important? Why does it become more important each year? Why is the average landfill today five times larger than the average 1988 landfill? What drives this industry toward an ever higher awareness of the need to compact trash? And why are manufacturers creating larger and larger compactors?
To understand landfill compaction, we must step back in time, 40 years or so. Ours was an unregulated industry with many, many dumps spread across the country. Every town had at least one, and open burning was the accepted method of operation.
Through the mid-1960s, few landfills could be called sanitary. Recognizing the problems associated with solid waste, Congress passed the Solid Waste Disposal Act in 1965, which provided money for researching and improving landfill methods.
In 1968, The US Department of Health, Education and Welfare prepared a National Solid Waste Survey. This report found that only 6% of the landfill disposal sites in the US were adequate. And this was a time before liners or groundwater monitoring requirements. Remember, in 1968 there was no EPA. The industry was in rough shape, but thanks to some brave visionaries, change was coming.
One of those visionaries, coauthor of the 1968 National Solid Waste Survey, was Lanny Hickman, who also served as the executive director of SWANA (formerly GRCDA) from 1978 to 1996. Beginning in 1968, he and other solid waste experts developed and ran a training program on the Principles of Sanitary Landfills. This program toured the country, providing training on the state level.
According to Hickman, early efforts to raise the bar for landfills were directed toward basic public health issues related to air, water and vectors. Daily cover requirements, for example, were implemented primarily as a fly control measure.
Today we’re still working toward those primary goals of protecting human health and the environment.
As our awareness of waste-related problems increased, more regulations followed, resulting in much higher standards for solid waste disposal … and the closing of thousands upon thousands of dumps across the country.
This started a trend: to eliminate small, problematic dumps and replace them with larger, more sophisticated regional landfills. The push toward consolidation had begun.
Several major regulatory milestones help to maintain that momentum. These include the following:
- The formation of the Environmental Protection Agency in 1970
- The Resource Recovery Act of 1970
- The Resource Conservation and Recovery Act of 1976 (RCRA)
- The Hazardous and Solid Waste Amendments of 1984 (HSWA)
- Subtitle D—promulgated in 1991
The latest and perhaps most significant major regulatory change was the EPA’s subtitle D, which required, among other things, landfills to construct base liners and monitor groundwater. Subtitle D was promulgated on October 9, 1991, marking (for the most part) the beginning of the end for unlined, loosely regulated landfills in the US.
Let’s look at a summary of how this has changed the characteristics of landfills.
According to the EPA, in 1988 the US recycled approximately 30 million tons of the 194 million tons of municipal solid waste generated in the US. Most of the remaining 164 million tons was distributed to the approximately 8,000 active landfills. Based on those numbers, and assuming 260 operating days per year, the average landfill in 1988 handled 79 tons of waste per day.
Note: This estimate does not account for alternative waste disposal methods such as incineration or composting.
Similarly, in 2006, the US recycled 82 million tons of the 251 million tons generated. Again, much of the remaining 169 million tons of waste went to landfills. But by 2006, there were only 1,754 active landfills. Using earlier assumptions, the average landfill in 2006 was handling 371 tons of waste per day,
Continuing a trend that began in the 1960s, the average size of landfills in the US has increased at a rate of 9% per year since 1988.
The increasing size of the average landfill has brought about other changes as well. In the late 1960s, my grandfather worked as an equipment operator for the county road department. Every month or so, he’d transport the dozer to the local dumps scattered across the county and clean them up. One of those infamous dumps was just a mile or so down the road from our house. It was located in an old gravel pit, next to the creek. Classic, huh? For us country kids, it was exciting to watch grandpa push trash into the pit, set it on fire, and then watch as things exploded and the rats scattered. Remembering back, I like to think we stayed safely upwind, but I can’t say for sure.
In those days, compaction was not an important issue. In fact, it wasn’t an issue at all. If the current pit filled up, so what? The inventory of gravel pits far exceeded that of trash—and few people really cared or even thought about landfill airspace or compaction.
Then, in 1972, the EPA published Sanitary Landfill Design and Operation. Within this document was the statement: “…the field density of most compacted solid waste within the cell should be at least 800 pounds per cubic yard.”
Waste compaction was finally becoming an operational benchmark, but with bulldozers being the most commonly used machine, landfills were not properly equipped to achieve peak performance. This fact too, was recognized and soon to be addressed.
The 1972 EPA document also referenced a study where, “…the in-place dry density of solid waste compacted by the steel-wheeled compactor was 13% greater than that effected by the crawler dozer and the rubber-tired compactor.” A practical means of improving waste compaction had been identified.
While the industry plodded along, primarily using bulldozers, there were again a few visionaries looking into the future and making plans. Innovation and experimentation were rapidly advancing the state of the landfill. Equipment manufacturers and landfill operators created hybrid compactors by installing steel wheels on loaders and log skidders. They converted soil compactors to trash compactors by changing wheels and installing protective guarding. These compaction “wildcatters,” had opened the door to a whole new type of machine: the Landfill Compactor.
Around this same time, in 1972, Caterpillar released its first landfill compactor, an 816 model weighing 40,900 pounds—roughly the same as a modern D6 bulldozer. Six years later they released the 826C, which—for nearly 2 decades—helped set a standard in the landfill industry. But Caterpillar was not the first or the only company to manufacture a landfill compactor in those early years.
In the 1960s, Fred Caron, founder of Caron Compactor Co., developed a landfill compactor referred to as the Pactor. The rights to this machine were later sold to Rexworks, then to CMI, and finally in 2001, to Terex. The modern versions of that machine have evolved into much heavier, more powerful machines that are now manufactured by Terex. The Terex machines are modern and sophisticated, but they come from pioneer stock and have a rich history in the solid waste industry.
But change is a process, and it took many years for landfill compactors to effectively permeate the industry. So, even as waste compaction became an important operational yardstick for sanitary landfills, operators still had to make do with what they had, which was, in most cases, a bulldozer.
Using crawlers to compact waste, operators developed an industry-accepted method of compaction: Push uphill and work on as steep a slope as possible. Over a couple decades, this procedure for compacting with a crawler-tractor became a standard method of operation in the landfill industry.
Today, based on the widespread use of landfill compactors, the accepted practice is to spread waste and work on a flatter surface, providing a more stable orientation for the equipment operators, and allowing the compactors to move quickly, make more passes, more tooth penetrations per day, and ultimately, achieve a much higher rate of compaction.
This brings us to the modern era, where we stand, not on the top, but simply on the next step up the hill. Today’s compactors are heavier and more powerful than ever. Landfills without compactors have become more the exception than the rule. And the science of landfill compaction has truly become a science.
In the same way that 19th-century prizefighter Jem Mace became a champion by bringing science to the boxing ring, some progressive landfills are knocking the socks off their competition when it comes to compaction.
In extreme contrast to the “800 pounds per cubic yard” referenced by the EPA in 1972 in its Sanitary Landfill Design and Operation manual, some modern landfills are achieving amazing compaction rates in the range of 1,500 to 2,000 pounds per cubic yard! This finally, may be what you’ve been expecting: How to achieve peak performance from a landfill compactor. Let’s take a look.
Select the Right Machine
It all starts here, and like ordering a drink at Starbucks, sifting through the choices and then making a decision is by far the hardest part of the deal. Start by looking at the size of your operation—generally measured in tons per day, and specifically in tons per hour. Production rates vary from one compactor to another, based primarily on the size (weight) of the machine. Keeping in mind that there are many variables and every landfill is unique, we can use the following equation as a starting point for selecting a compactor.
W = weight of compactor (in pounds)
T = average tons of waste per hour
For example, suppose a landfill receives 800 tons of waste per day and is open 10 hours per day. On average, it receives 80 tons of waste per hour (T is 80). The equation becomes (750 x 80) + 20,000, resulting in an answer of 80,000. Thus, the landfill in this example should start by considering a compactor in the 80,000 pound range.
Compactors range in weight from around 50,000 to nearly 130,000 pounds. Use this equation to get in the ballpark, but remember: This is just a starting point. Other variables include type of waste, type of supporting equipment, operating style, and styles of wheel and tooth.
Pick and Choose
Identifying different types of waste within your wastestream and then handling them appropriately is another important step toward a goal of exceptional compaction. To a novice, trash is trash. But to an experienced landfill operator, there are many types of garbage—some easier to compact than others. A good first step here is to eliminate bulky materials that cannot be compacted. If they can’t be eliminated, segregate them into a specific part of the daily cell and then fill around them as effectively as possible. Avoid distributing bulky items randomly throughout the cell because they will tend to bridge over certain areas and prevent the compactor from fully compacting the surrounding waste.
In addition to managing bulky items, it’s also important to take full advantage of good garbage. From a compaction standpoint, good garbage is easily compacted and trimmed to a smooth, well-graded finish. Generally, trash delivered by front-loader and rear-loader route trucks is “good,” and material that arrives in roll-off bins, contractor trucks or self-haul vehicles is not. One of the key characteristics of good garbage is moisture.
When it comes to achieving the highest possible compaction, there’s nothing better than a little moisture...unless it’s a lot of moisture.
A savvy landfill operator can utilize moisture in a variety of ways. Here’s a quick rundown on common sources of moisture and ways to get the most benefit from it.
Wet loads—Even in dry climates, there will likely be some relatively wet loads entering the landfill. Typically, these arrive via packer trucks servicing routes that include schools, restaurants, hotels, grocery stores or other customers generating lots of food waste. By carefully spreading and mixing the wet trash with the trash containing mostly dry paper (i.e., office building routes), the dry paper will be able to absorb moisture, greatly enhancing its achievable density. When mixing dry and wet loads, it’s important to allow adequate time for moisture absorption before making the final compactor passes. Usually 20–30 minutes is adequate. Other sources of wet loads include: sludge, cannery or various agricultural wastes. During the wet season, rain or snow may also cause certain loads to be wetter than usual.
Leachate recirculation—For landfills with sufficient containment systems and appropriate permit approval, recirculating leachate back into the active, working face can provide a tremendous increase in compaction density, often in the range of 15-20%. Under the right conditions, any other water source could provide similar benefits.
Compact Until Done
Achieving optimum compaction isn’t just a matter counting passes. The compactor’s effort varies widely depending on the type of waste, its moisture content, the size and type of machine, operator technique, slope and many other factors. Some material reaches optimum density in one or two passes, other material might take six or more. The key to success is to continue compacting up to the point of diminishing return – where the additional cost of making another pass exceeds the benefit of whatever incremental density will be achieved. The equation shown earlier can be rewritten and used to estimate a compactor’s optimum production rate as shown here:
Applying this equation to an example, an 80,000 pound compactor (W) could handle approximately 80 tons (T) of trash per hour.
To apply the results of this example, if the landfill received 520 tons of waste per day, the compactor would be expected to work 6.5 hours per day (520 ÷ 80 = 6.5). Remember, the compactor’s optimum production rate is based on the machine handling a constant, steady flow of material.
Waste compaction can’t be managed if it isn’t measured. Knowing this, many landfills measure waste compaction density on a frequent basis, but there are also many landfills that don’t measure it at all. The latter method of, “Working until it’s full,” is sure to provide some interesting surprises when the landfill runs out of soil or when the liner fills up faster than the budgeters assumed.
There are two ways to measure waste density.
The first is to conduct a short-term compaction test. This entails surveying an area on the landfill, placing in it, a known quantity of compacted waste, then resurveying. The before and after surveys can be compared to calculate the change in volume and tonnage records provide the weight of trash placed. A simple calculation provides the resulting density, measured in pounds per cubic yard. The benefit of this method is that it provides quick results. A typical test can take a week or less. The drawback is of course, that it’s just a snapshot and may not represent the landfill’s overall performance.
The second method for tracking compaction is to create quarterly or annual topographic maps of the landfill, calculate volumes between them, compare to inbound tonnage, and then come up with a density figure. This method provides the most accurate measure of overall waste density.
Over the years, regulatory changes have pulled—and sometimes pushed—the solid waste industry toward better protection of human and the environment. But it wasn’t the standards alone that brought about improvement. It was the creative effort of operators and equipment manufacturers that help support those desired changes with practical solutions.
Throughout those years of change, equipment manufacturers have continued to produce bigger, better and more productive machines. The current heavyweight landfill champ is the Aljon Impact 600, weighing in at a massive 126,000 pounds. Lesley Bailey, Inside Sales Manager for the Solid Waste Division at Aljon, affirms that, like other machines, Aljon’s history can be traced back many years, to the late 1970’s, when they designed and manufactured a 35,000 pound machine, the LF-350, and later on the LF-450 and LF-750, weighing 45,000 and 75,000 pounds respectively.
These were the first hydrostatic landfill compactor. Designed from the ground up, it featured greater ground clearance, a heavy-duty frame, tighter turning radius (hydrostatic requires no axles) and an air-cooled Deutz engine. Those early machines were innovative and based on lots of observation and many comments from landfill operators. Lesley goes on to say, “we listen carefully to our customers.” Based on what they hear, many of the early Aljon features have been carried through into the current models.
Regardless of the make, model or size compactor you use, you can be assured that the machine you buy today stands on the foundation of decades of experience and thoughtful planning.
The changes and improvements in compaction equipment and technique are positive. However, those of us in the industry must keep up with those changes or there can be negative impacts. For example, consider a landfill owner, who contracts with someone else to operate the facility. Many of those agreements have a bonus/penalty clause, whereby the contractor is rewarded for achieving higher than expected density …or penalized for lower-than-expected performance. If the compaction performance standard is based on an outdated assumption, one party or the other may be placed in an unfair position.
Also, the performance of a specific compactor will not be constant at all landfills. As waste stream varies, so too will the optimum achievable density. Track your performance and communicate with manufacturers, landfill operators and others in the industry. What we learn today will help strengthen the foundation for future improvements.
Author's Bio: Neal Bolton is a consultant specializing in landfill operations and management.