Baling out Small Landfills

David J. Montague and John T. Baker

When seeking to extend a landfill's life, managers of small sites are discovering that baling waste can be a viable alternative to traditional loose waste disposal.

Other pluses of baling at small sites include: reduced operational costs, increased efficiency and improved site aesthetics.

Could baling be the solution for your landfill? Read on.

If you have a loose-waste landfill, your site's waste density is determined by the thickness of the lift being compacted, the number of passes the equipment makes, and the weight and configuration of the compaction equipment (plus environmental factors and waste characteristics).

The typical equipment used at landfills to compact the waste are:

* track-type tractors and track loaders which can achieve compaction densities of 800 to 1,000 pounds per cubic yard and

* steel-wheeled landfill compactors (those with operating weights over 45,000 pounds can achieve compaction densities of 1,200 to 1,400 pounds per cubic yard).

While a landfill compactor provides the greater compaction, this equipment's use often would not be feasible at a small site since it only would be needed for a few minutes at a time.

A more practical choice would be to use a track-type tractor or track loader, which also could be used to excavate, haul, and place cover soil, and repair ditches and roads.

The in-place density of baled waste depends on the baler's configuration and waste characteristics. Balers which provide a greater working pressure in the bale chamber generally can produce a bale with a greater density.

However, as this working pressure increases, the baler's size and cost increases as well. Therefore, when selecting a baler, consider the following:

* waste received daily;

* compaction density desired;

* whether or not recyclables will also be baled;

* future waste volumes predictions; and

* budget.

Small balers are made which can manage small landfill waste volumes and also provide a bale density similar to those found at a loose-waste site.

Such balers' densities are reported by the manufacturers to range from 1,025 to 1,620 pounds per cubic yard. However, these densities are based on the weight and dimensions of the bale in the chamber. Once outside of the chamber, bales tend to expand. There is also an air space between the bales when they are placed in the landfill.

These factors add an average of six inches to the bale's width and length. (Bale height actually decreases almost immediately when placed in the landfill due to the weight of overhead bales.)

With the actual field dimensions, smaller balers' densities can range from 875 to 1,270 pounds per cubic yard.

Let's compare the differences between loose and baled waste disposal. Using the example of six-inch cover soil on a three-foot compacted lift, loose waste disposal produces a 3.5:1 waste-to-soil ratio. Here, only 78 percent of the total cell volume is waste.

However, four to five waste bales can be stacked in a column with only six inches of soil needed to cover the top bale. This soil covers baled waste every 12 to 15 feet. Thus, the waste-to-soil ratio is about 9:1, which means that 90 percent of the total cell volume is waste.

The Cost of Baling Waste Your site's waste densities and waste-to-soil ratios will help you determine if baling waste is feasible for your operation.

The design life affects the construction financing terms and the annual dollar amount needed for closure and post-closure.

In order to determine a particular method's feasibility, first specify the cell's design life (i.e. 15 years). Then, calculate the cell volume, taking into consideration the primary disposal method, the percent of soil in a cell, waste in-place density and waste volume or tonnage received.

Next, select a disposal method (loose or baled waste) to calculate the required cell volume. Finally, determine the cell life for the other disposal type for comparison purposes.

Using this calculation method, a 15-year loose waste cell should last about 1711/42 years in a baled waste operation. The additional cell life gained with baled waste is due to the reduced volume of soil used in this operation.

With the exception of equipment building design, construction and closure will be the same with loose or baled waste. Loose waste demands only a simple on-grade slab and overhead doors large enough for landfill equipment. On the other hand, baled waste requires an on-grade slab with a pit for the conveyor or a two-level design with the tipping floor on the upper level and the baler and bale discharge on the lower level.

The baler building doors should allow extra height for packer trucks to pull out with the tail gate up or roll-offs (and other boxes that dump by tipping) to exit raised.

The baler building will cost about 211/42 times more than a simple equipment building. Other landfill costs should include construction of the cell, roads, drainages, buildings and utility preparation.

The cell's construction costs for both disposal methods is based on its life expectancy. (In this example, loose-waste cells are 15 years, and baled waste cells average 17 and 18 years.)

The buildings' and utilities' financing is uniformly set at 20 years. A sinking fund, which parallels the cell construction schedule, also is established to close the cells. Since a baled waste cell includes an extra two to three years of life, the construction costs can be financed over an a longer period, reducing annual payments.

The sinking fund also has an additional two to three years of interest to accrue, allowing the annual payments to be reduced.

Equipment Costs Equipment expenses - including capital, operating and maintenance (O&M) costs - can vary greatly, depending on the type and number of pieces needed.

The O&M costs depend on how often the equipment is used and how well it is handled and maintained. Replacement costs also will depend on these factors.

Costs associated with a baling operation includes a conveyor, the baler and the cost of the baler's overhaul about every 10 years (in our site, approximately $20,000). The baler's cost will depend on the desired bale density and its manufacturer.

When developing costs for a loose-waste operation, don't overlook the cost associated with the time spent collecting blowing trash, which can be as high as six to eight hours a day.

Additional benefits to a baler operation include improved aesthetics and the ability to dump inside a building. Since baler buildings have concrete floors, vehicles won't get stuck as they could in a landfill cell, and loads are more easily inspected.

Also, since virtually all waste brought to the landfill would be processed through the baler, materials can be separated prior to baling, and the unit can be used to bale recyclable materials.

Landfilling baled waste should be considered by communities with lower generation rates. A baler can be incorporated into the disposal operation at any time. It can become part of a transfer station, be placed into an existing landfill or be added into a proposed new landfill.

Compared to traditional loose waste landfills, baling waste could result in reduced disposal costs and should improve operation efficiency. Regardless of any other benefits, baling waste will greatly improve site aesthetics.