The light bulk density of expanded polystyrene (EPS) provides outstanding insulation and cushioning and is frequently used in applications requiring these properties. EPS is most often collected and recycled in a dedicated, source selected system outside the scope of the APR Design Guide for Plastics Recyclability such as a distribution center stream.
EPS is a very recyclable material once the product arrives at the reclaimer. Collection and transportation challenges should not be confused with processibility and reusability of this material. A limited number of curbside EPS collection systems exist in North America so this material does not currently meet the collection accessibility criteria established in “APR’s definition of recyclable” or by the FTC. Anticipating the development and growth of future EPS recycling programs, the APR recommends the following guidelines:
- BARRIER LAYERS, COATINGS & ADDITIVES
- CLOSURES & DISPENSERS
- LABELS, INKS AND ADHESIVES
- POSTCONSUMER CONTENT
- RESIN IDENTIFICATION CODE, RIC
Degradable additives (photo, oxo, or bio) require testing to determine the appropriate APR recyclability category.
Recycled EPS is intended to be used in new products. The new products are engineered to meet particular quality and durability standards given properties of typical recycled EPS. Additives designed to degrade the polymer diminish the life of the material in the primary use. If not removed in the recycling process, these additives shorten the useful life of the product made from the RPS as well, possibly compromising quality and durability.
Degradable additives should not be used without testing to demonstrate that their inclusion will not materially impair the full service life and properties of any product made from the EPS that includes the additive. These additives must either separate and be removed from the EPS in the recycling process or have no adverse effects on future uses. When used, their content should be minimized to the greatest extent possible to maximize yield, limit potential contamination, and reduce separation costs.
Unpigmented or white polymer is preferred.
This material has the highest value as a recycled stream since it has the widest variety of end-use applications.
Light pink or light blue color is preferred.
These colors are common and dilute enough that they don’t significantly affect the color of the recycled product.
Black color renders the package non-recyclable per APR definition.
NIR sorting is critical to establishing an EPS stream in a MRF. This technology is not capable of identifying a black polymer and manual sorting cannot distinguish one black polymer from another. Therefore, black packaging is considered a contaminant for nearly all reclaimers.
Size and shape are critical parameters in MRF sorting, and this must be considered in designing packages for recycling.
The MRF process separates items by size and shape first, then by material. Screens direct paper, and similar two-dimensional lightweight items, into one stream; containers and similar three-dimensional heavier items into another steam; while broken glass and smaller but heavy items are allowed to drop by gravity to yet another stream, which may or may not be further sorted. Large, bulky items are typically manually sorted on the front of the MRF process.
Items more two-dimensional than three-dimensional render the package non-recyclable per APR definition.
Aside from not being captured in the plastic stream, they cause contamination in the paper stream. Items should have a minimum depth of two inches in order to create a three-dimensional shape for proper sorting. This issue is unrelated to the polymer type. The APR encourages and anticipates developments in MRF design and technology to improve capture and recovery of thin plastics; however, at the current time this technology either does not exist or is uninstalled in the majority of MRFs.
Items smaller than 3 inches in all dimensions render the package non-recyclable per APR.
The industry standard screen size loses materials less than three inches to a non-plastics stream, causing contamination in that stream, or directly to waste. These small packages are lost to the plastic recycling stream. It is possible that some small containers travel with larger ones when either the screens wrap with film or they are operated above their design capacity. Film wrapping reduces the effective size of the screen and over-running provides a cushion of large items on which the smaller items travel. The design guidelines use clean screens operating at their design capacity for the determination of the recyclability category. The APR anticipates and encourages technology development to improve the process of small package recovery but currently these items are not recovered.
Items greater than two gallons in volume are detrimental to recycling.
RRecycling machinery, particularly automatic sorting equipment, is not large enough to accept items larger than two gallons. Because larger containers jam the systems, most MRFs employ manual sortation before the automatic line to remove the large items. These items are recovered in a stream of bulky rigid containers that are sold and processed as polyethylene since the vast majority of bulky rigid items are comprised of this polymer. Other polymers either negatively effect or are lost by the polyethylene processing.
Polypropylene and polyethylene closures are detrimental to recycling.
Although the polymer is heavier than water EPS floats in water due to the air entrapped in the structure. PE and PP float as well so they are not separated by conventional density separation methods. PE and PP therefore, remain with the EPS until the extrusion process. Contaminates that remain until the extrusion process are filtered from the PS if they remain solid at PS processing temperatures. PE and PP are liquid at these temperatures and are not removed.
The use of PVC closures renders the package non-recyclable per APR.
Float sinks tanks are not perfect machines. Even though PVC sinks and the EPS floats small amounts of PVC travel with the EPS. The recycled EPS stream is very intolerable to even minute amounts of PVC since it degrades quickly at EPS processing temperatures, erodes machinery and creates a safety risk. Small pieces of PVC render large amounts of the finished product unusable.
Some EPS recycling processes do not remove adhesive. The adhesive travels through the process with the PS and is blended in the final product. The most recyclable packages use the lowest quantity of adhesive that is compatible with PS. Lower adhesive usage reduces processing cost and potential contamination risk.
Polystyrene labels are preferred.
PS is the same material as the package so the label will behave like the package and be recycled along with it creating no added contamination or yield loss.
Direct printing on EPS is preferred.
Most direct print inks withstand the standard EPS recycling process and remain on the package. Since no adhesive is used and the weight percent of label is extremely low compared to alternative labeling, they add little contamination to the final product.
High melting temperature plastic labels such as PET are preferred.
These labels sink in the float sink tank if one is employed and remain solid in the PS extruder so they can be removed through filtering.
Metal foil labels are detrimental to recycling.
Metal detectors are employed in the recycling process to protect machinery. Even thin metal foil labels may be identified by detectors and can cause the entire package to be rejected as waste, thereby creating yield loss. If not detected, they pass through the process with the PS and cause contamination in the extrusion process. Since they remain solid in the extrusion process they can be filtered from the melted polymer, which is advantageous over other materials that melt.
Paper labels are detrimental to recycling.
Most paper labels remain on the package during the washing phase of the recycling process and enter the extruder with the PS. Paper degrades in the extruder emitting a burnt smell into the plastic that cannot be removed. Most of the paper can be filtered from melted PS but the smell and small individual fibers remain.
Polypropylene or polyethylene labels are detrimental to recycling.
Like most labels, PP and PE labels remain on the package during the washing phase of the recycling process and enter the extruder with the PS. Both PE and PP are liquid at the operating temperatures of the PS extruder and cannot be removed by a filter. They contaminate the final PS.
PVC labels render the package unrecyclable per APR.
This material is extremely difficult to remove in the recycling process due to its similarity in density to PS. Furthermore, it degrades in the extruder rendering large sections of PS unusable.
Adhesives require testing to determine the appropriate APR recyclability category.
Most adhesives will remain on the package during the EPS washing process and enter the extruder with the PS. Adhesives should either remain solid so they can be melt filtered from the PS or be compatible with PS.
Clear PS attachments affixed to EPS containers are preferred.
Attachments made of the base polymer cause no contamination.
Non-PS attachments such as handles require testing to determine the appropriate APR recyclability category.
These should not be adhesively bonded to the package and should readily separate from the package when ground. They should be made from materials that sink in water such as filled PP/HDPE, or PET. If adhesives are used to affix attachments, their selection should consider the adhesive criteria within this document.
One test protocol for PP is available that can be used for EPS:
Screening Test: Float test - TBD
Metal and metal containing attachments are detrimental to recycling.
Metal attachments to EPS are either detected by metal detectors at the beginning of the recycling process and cause the entire section to be rejected or they enter the process with the EPS where they wear and damage machinery before being separated in the float-sink tank. If they stay attached to the material they can be floated into downstream equipment with the EPS and damage the machinery.
Welded attachments are detrimental to recycling.
A certain amount of a welded attachment cannot be separated from the main polymer in the recycling process. These attachments, even when ground and made of floatable materials, cause contamination and yield loss issues in both cases: when the EPS they are attached to causes the ground section containing both polymers to float, or when the ground section floats.
RFID’s (radio frequency identification devices) on packages, labels or closures are detrimental to recycling).
Unless they are compatible with EPS recycling and are demonstrated not to create any disposal issues based on their material content, the use of RFID’s is discouraged as it limits yield, introduces potential contamination, and increases separation costs.
PVC attachments of any kind render the package non-recyclable per APR.
The use of PVC attachments of any kind on EPS packaging is undesirable and should be avoided. Even though PVC sinks, the recycled EPS stream is very intolerable to even minute amounts of PVC since it degrades quite easily and renders large sections of the finished product unusable.
The use of postconsumer PS in all packages is encouraged to the maximum amount technically and economically feasible.
Use of the correct Resin Identification Code symbol of the proper size as detailed in ASTM D7611 is encouraged.