Bale Density: What's It Worth?

The whole purpose behind baling any material is to densify it -- to squeeze more material into less space. Webster's Dictionary defines density as the "quality or state of being dense." Others may describe density as the amount of something per unit measure, or per unit length, area, or volume. The North American Recycling industry normally refers to density in terms of pounds per cubic foot. In many parts of the world, kilograms per cubic meter are the standard measurement.

No matter the measurement nomenclature, density achievement should be an important consideration when selecting baling equipment. The density of a bale is actually more important than its weight, even though the weight of a bale is usually the focus of Recycling processors. Maximizing density can save a processor a tremendous amount of money in reduced wire use, storage, shipping, handling and maintenance costs.

Wire is the most expensive consumable in a scrap paper baling operation. For example, consider a processor who bales 200 tons a day of product with one machine that densifies material at 26 pounds per cubic foot and another baler that densifies at 31 pounds per cubic foot. The increased density produced by the second baler could reduce his wire cost by more than 40 cents per ton of material baled. That amounts to savings in excess of $20,000 a year in wire cost alone. Using the same example, consider the processor's storage space, a 20 feet x 50 feet area. Increasing bale density by five pounds more per cubic foot, could create space for 25 tons of additional baled paper.

Higher densities will also allow the processor to stack bales at greater heights without reducing staff safety. More dense bales will result in fewer trips by forklifts from the baler to storage, and from storage to the shipping conveyance. This in turn can lower forklift maintenance, operating and fuel costs. Producing more dense bales also requires fewer bales to be tied by the automatic tying device on the baler. Reducing auto-tier use ultimately will lower baler maintenance costs.

Bale density also plays a big part in lowering the most expensive cost to a scrap paper processor — the cost of transportation. When shipping bulk or on conveyances that do not have a maximum load restriction, you can save as much as $20 per ton and ship more tons of product to long distance markets. For instance, compare two 50-foot rail cars, each loaded with the same number of bales. One is loaded with 140,000 pounds of more dense OCC bales, the other payload is only 110,000 pounds. The more dense bales allow 15 tons of additional material to ship at little or no additional cost. With a typical shipping cost of $20 per ton, that is a $300 savings per car, or over $4 per ton on the 70 loaded tons.

Generally speaking, greater density is achieved by the use of higher forces when compacting the material. However, there are a lot of other factors that play a part. For instance, if you are loading a baler with a 100-cubic-foot charge box and load a light commodity weighing one and a half to two pounds per cubic foot, the density of that charge will be significantly higher than if the material in the box weighed four pounds per cubic foot. The only explanation for this is that the amount of force being applied to the bale has more impact when trying to bale a small charge versus a large one.

There are examples of balers with eight-inch diameter cylinders that can densify old corrugated containers to 34 pounds per cubic foot, yet 12-inch compressing cylinders might have trouble achieving 30 pounds per cubic foot. Many of these differences are related to with the weight and size of the charge, as well as the penetration of the compressing ram.

Fixed box, two-ram balers and balers with pre-pressing devices tend to achieve densities lower than channel presses baling low-density materials with maximum pressure on every charge.

Maximizing density can come at a cost as well. It is very difficult, or maybe even impossible, to achieve maximum density as well as maximum throughput at the same time. Usually one has to be sacrificed to some degree to achieve the other. While it might be thought that achieving higher densities will cause your capital cost to go up on the equipment, this may not necessarily be so. While there are $300,000 baling machines that will produce incredible densities, there are also machines selling for a little over $100,000 that will do the same thing. On the flip side, there are models selling for over $300,000 that do not maximize density.

Many times when buying a baler, the customer focus is on the purchase price of the baler. Experience clearly shows that purchase price is only part of the picture to baler economics - the cost of owning and operating the baler over its life has a far greater impact to the bottom line.

If you have thoughts about upgrading your baling system, think about increasing the bale density. The savings will more than pay for your baler over the life cycle cost of your machine. Remember the 200 tons a day example stated earlier. That $20,000 per year savings becomes $200,000 when looked at over the life of the equipment. That extra $4 per ton in shipping cost savings can be another $20,000 per year. When considering these savings, you will realize that the price of the baler is not the single major cost in the end. An efficient, durable, long-lasting baler that produces more dense bales will more than make up for its price tag in lower transportation, handling, storage and maintenance costs. Major cost savings are possible when bale density is given its fair attention.