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Best Practices in PET Recycling Click here for printable PDF version Post-Consumer
PET Bale Specifications
Issue: The lack of
standardization and the resulting variability
of the quality and content of baled post-consumer
PET bottles and containers adds economic
cost to and limits the efficiency of the
PET recycling process.
Introduction: The
proposed post-consumer PET bale specifications
that follow are not intended to meet any
one company’s individual specifications,
but to represent a standard that will be
acceptable to most
PET purchasers and ensure a quality
standard that can reduce the cost of the
PET recycling process.
While the proposed specifications
may represent a standard which is acceptable
to most of the PET recycling industry, every
PET processor has specific requirements
based on their particular processing system
and the end-use application for which the
recycled PET is intended.
Therefore,
suppliers must always determine the
exact levels of contamination that a particular
purchaser accepts as well as other unique
purchasing specifications they might have.
Bale specifications include a number of factors.
They include both physical and quality
characteristics such as bale size, bale
density, levels and types of contamination,
etc. The
physical properties can improve operating,
handling, and safety factors such as ease
and efficiency of truck loading and unloading,
and in-plant storage. Physical bale characteristics can also impact
the efficiency and throughput of some “auto-sort”
technologies which are used by intermediate
processors, plastic recycling facilities
(PRF), reclaimers and end-users who process
baled PET plastic bottles and containers
(see Sorting Best Practices). Finally, the quality of the bale impacts the
technical and economic ability to reclaim
PET resin from the post-consumer waste stream
and remanufacture it into new products.
There are essentially three generic types of post-consumer
PET bales that are purchased in the PET
recycling industry. These are: 1) bales consisting solely of PET
carbonated beverage bottles -- referred
to throughout the industry as “soda bales”;
2) those that consist of a mixture of soda
bottles and “custom” PET containers and
referred to in the industry as “curbside
bales”; and, 3) bales composed solely of
custom-PET bottles -- referred to as “custom
bales.” The increase of curbside recycling programs
around the United States has made curbside
bales the most prevalent form of PET offered
for sale. (In cases where curbside bales
are offered for sale, it is imperative to
confirm with a particular purchaser if they
have restrictions on the percentage of custom-PET
containers that they allow relative to PET
carbonated beverage containers.)
Best Practice: To ensure the marketability of post-consumer
PET plastic bottles and containers collected
through your local recycling program, a
best practice is to design a baling system
that can achieve the following specifications: POST-CONSUMER
PET BALE SPECIFICATIONS
ALLOWABLE LEVELS
OF CONTAMINANTS
THE
TOTAL MAXIMUM LEVEL OF CONTAMINATION SHALL
NOT EXCEED 4% BY WEIGHT. ADDITIONALLY, NO MORE THAN 2% BY WEIGHT OF
ANY OF THE FOLLOWING INDIVIDUAL CONTAMINANTS
ALLOWED:
· HDPE Rigid Plastic Containers (#2) · LDPE Rigid Plastic Containers (#4) · PP Rigid Plastic Containers (#5) · Aluminum · Tin Food Cans or Beverage Containers · Paper/Cardboard · Transparent Amber PET Containers
NO MORE THAN
1% BY WEIGHT IN TOTAL OF ANY TYPE OF PVC
(#3) CONTAINERS, TAMPER PROOF SEALS, CAP
LINERS AND LABELS, OR OTHER PVC ALLOWED.
PROHIBITED CONTAMINANTS
THE FOLLOWING
CONTAMINANTS ARE NOT ALLOWED AT ANY LEVEL:
·
Plastic
microwave trays, dishes, bakery trays, covers,
deli containers, drink cups, and “clamshells”
·
Polystyrene
(PS) (#6) plastic - rigid or foam
·
Plastic
bags and plastic film
·
Wood
·
Glass
·
Motor
Oils and Grease
·
Rocks,
Stones, Mud, Dirt
·
Medical
and Hazardous Waste
BALE SIZE:30" x 42" x 48" BALE DENSITY: 15-18 lbs/ft3 BALE WIRE: Bales should be held together with 10-12 gauge, non-corrosive galvanized metal wire, with all bale wires wrapped in one direction. A minimum number of bale wires should be used that maintains bale integrity.This number will vary with bale size. BALE INTEGRITY:Bale integrity should be maintained throughout loading, shipping, unloading and storage. MINIMUM SHIPPING WEIGHT:35,000 lbs
Other Considerations: Some PET purchasers offer differing price structures for the bales they purchase based on the actual composition of the bales in terms of the types and color of PET plastics they contain. In some cases, this may require that bale suppliers meet more stringent specifications. Once again, suppliers should check with their particular purchaser to match these differing prices with their production capacity and the costs necessary to meet these specifications. While many of the prohibited materials identified in these bale specifications account for the major sources of contamination to the PET recycling process, a supplier must always confirm a buyer’s specifications as some may have different requirements for specific plastic resin contaminants unique to their process and end-use application.
Discussion: The levels and type of contaminants allowed by baled PET purchasers will depend on the end-use application the recycled PET is intended for as well as the specific processing equipment and system design used by a particular processor. The levels of allowable contamination proposed in these specifications should yield bales that are acceptable to most PET purchasers. The common sense criteria to preparing a high-quality PET bale is that PET purchasers are purchasing exactly that, PET plastic resin from bottles and containers. And, nothing should be added to a bale that is not a PET bottle or screw-neck container.
However, most PET purchasers understand the difficulty for baling operations to produce bales that are 100% free of contaminants, particularly from curbside programs where different recyclable materials are commingled, and therefore allow for some flexibility in the types and levels of contaminants that are acceptable. While contaminants may be allowable, every reasonable effort should be made to remove contaminants prior to baling.
The allowable levels of PVC are based on the rationale that the relative percentage of PVC containers to PET containers is shrinking in the packaging waste stream. Estimates of bottle-grade vinyl resin sales for 1996 provided in the January 1997 issue of Plastics Recycling Update indicate monthly sales of approximately 14 million pounds/month or about 170 million pounds in total for 1996. This compares to 1996 sale figures of approximately 2.2 billion pounds of bottle-grade PET resin. Therefore, the natural incidence of PVC to PET bottles in the post-consumer waste stream is no more than 8% by weight. If every reasonable effort to remove PVC containers is made, a 1% or less level is achievable, while providing a realistic tolerance for plastic bale suppliers. In addition, most reclaimers and end-users have sortation capacity to handle this level of contamination, particularly with the increased use of auto-sort technologies.
Many PET markets prohibit all glycol-modified PET (PET-G) and other extrusion-blown PET (E-PET) containers, most commonly used in containers with built-in handles. These containers have a lower melting point than bottle grade PET resin and can cause of number of technical and operating problems to PET reclaimers. These specifications prohibit the most common E-PET handleware containers, however, there are some PET-G and other E-PET containers without handles in the post-consumer waste stream that are difficult to distinguish with current sorting technology. The incidence of these containers in the post-consumer waste stream relative to bottle-grade PET is on the order of only 1%. Like multi-layer PET containers, identifying PET-G and other E-PET bottles or containers that do not contain handles is difficult via manual or automated sorting techniques. While some reclaimers specifically prohibit all E-PET containers, others maintain they have developed systems to deal with E-PET to the extent that it occurs in incoming bales. Once again, the concern is in balancing the general quality of baled PET bottles and containers with the costs to the bale suppliers in meeting these specifications.
The proposed PET bale size will allow for the most efficient truck loading and unloading. Standard 48-foot trailers, probably the most popular means of over-the-road transport, have interior loading dimensions of 47.5' long, 101.5" wide and 96"-108" high. With these bale dimensions and these truck dimensions it is possible to stack a truck “row” with six bales, that is, 2 bales wide (with the 48" side stacked in the horizontal direction), and three bales high (the 30" dimension in the vertical direction). This will result in a total of thirteen rows of bales, for a total of 78 bales/truck (47.5'/42"= 13.6 rows, therefore 13 rows).
At a bale density of 15-18 lbs/ ft3, this will yield bales weighing between approximately 525 and 630 lbs., yielding a truckload shipping weight of 40,000 to 49,000 lbs. This should satisfy any purchaser’s minimum shipping weight requirements. While the latter weight is possible with these bale characteristics, it would exceed the maximum legal shipping weight for most 48' tractor trailers, requiring that less than 78 bales be loaded.
While other bale sizes with the same density range can be packed to obtain the desired minimum shipping weights of most purchasers, it will usually require that bales be stacked on end, or some other deviation from the packing structure proposed above. While a trained forklift driver is capable of this type of truck packing, it takes far more time than the configuration proposed.
These bale dimensions should allow for sufficient clearances of the truck walls and ceiling, particularly for those facilities that use forklifts with a two-stage hydraulic system, and therefore facilitate ease and efficiency of loading and unloading. These bale dimensions also allow for meeting minimum shipping weight requirements without packing the truck so tightly that it will be difficult to unload.
The proposed bale densities pose several industry advantages. First is that these bale densities are not high enough to cause significant “sandwiching,” that is, two or more bottles becoming inseparable without pulling them apart by hand. Bottles that become stuck together can lessen the efficiency of some auto-sort technologies, particularly those that rely on surface scanning techniques, where one bottle can “hide” another from the auto-sort detector. In addition, these densities should yield material volumes to achieve the throughputs that most auto-sort technologies are designed for.
Second, higher density bales can cause PVC bottles to shatter under pressure, yielding PVC pieces that can migrate into the opening of PET containers, or create pieces so small that they cannot be recognized by manual or automated sortation systems. Even these small amounts of PVC entering a grinder could yield a box of regrind that exceeds acceptable levels of PVC contamination for many end-use applications.
Third, this bale density will yield the required minimum shipping weights required by most processors (30,000 lbs. - 40,000 lbs/truckload). This bale configuration will also satisfy most export shipping weight requirements.
The bale wire configuration proposed should limit the amount of metal that a processor needs to handle as a by-product. Using a non-corrosive galvanized metal wire prevents bale wires from “popping” due to corrosion if stored for prolonged periods of time. Single direction wire wrapping makes it easier and safer for debaling. All in all, these bale wire specifications should lead to bales that maintain their integrity throughout loading, shipping, unloading and storage. Bales that break open during shipment are a tremendous cost burden to purchasers, and most will apply price penalties for any bales that do break, particularly if it occurs repeatedly by the same supplier.
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