When packages and package systems are being designed or modified, relatively small changes can sometimes make the difference in whether the package will be recyclable at the end of its life or whether it will not. (It should be noted that the term recyclable means different things to different people — it is used here in its practical sense, of being capable of fitting into existing or developing recycling programs and, hence, likely to be recycled at the end of its useful life.)

First, in the United States, for the most part only plastic bottles are accepted by recycling collection programs accessible to consumers. Therefore, if a consumer package is not a bottle (or jar), there is little likelihood that it will be recycled. Further, the vast majority of recycling programs collect only HDPE and PET bottles. Any other type of bottle is also unlikely to be recycled. Adding new materials to recycling programs generally faces a "which came first—the chicken or the egg" problem. Community organizations understandably do not want to collect materials that have no market. From an environmental perspective, there is no value in using additional resources, including energy, to segregate, collect, and process materials if they are ultimately headed for disposal. On the other side, potential users of the recycled material do not want to invest in developing the knowledge base and process changes necessary if they will not have a reliable source of recycled material that is available at a reasonable price. In the past, legislation has often been utilized to "jump-start" the system, either by mandating collection of materials for recycling, mandating use of recycled material, or creating financial incentives for the establishment of recycling systems and markets for recycled materials.

It is not uncommon for there to be a trade-off between recyclability and source reduction. For example, ground coffee can be effectively packaged in either a steel can, or a multilayer vacuum pouch containing several layers of plastic, including a metallized film. The steel can is recyclable in most locations and has a relatively high recycling rate, 58.4% in 2000 in the United States [19]. The pouch is essentially unrecyclable since virtually all recycling programs will not accept it. However, the pouch represents considerable reduction in the amount of material used, as well as in energy requirements for distribution. Similarly, the LLDPE milk pouches described above are not recyclable in most cases, while the HDPE bottles they replace are recyclable. For this particular case, DuPont claimed that a 90% recycling rate for the bottles would be required to match the reduction in waste volume achieved by use of pouches [17].

When new packages are introduced, proper attention to package design can make the difference in whether the package will be a valued addition to the recycling stream, nonrecyclable and essentially neutral, or a problem for existing recycling systems. In 1995, recommendations for plastic bottle design for recycling were released from the Plastic Redesign Project, funded by the U.S. EPA and the states of Wisconsin and New York (and later California) and involving representatives from industry, government, and plastic bottle recyclers [20]. An updated list of recommendations was released in late 1998 [21]. Among the recommendations are the following:

• Do not pigment natural HDPE bottles such as those for water and milk; do not pigment or tint PET bottles any color other than green.

• Do not use pigmented caps on natural HDPE bottles; make caps and fitments on HDPE bottles compatible with HDPE (except living hinge applications).

• Do not use aluminum caps; do not use aluminum seals unless the consumer can pull the seal completely off.

• Use only water-dispersible adhesives on labels; use labels that have a specific gravity less than 1 on PET bottles; do not use metallized labels on bottles with a specific gravity greater than 1; use PVC and PVDC labels only on PVC containers; ensure that pigments do not bleed from the label during recycling.

• Do not print directly on unpigmented bottles, except date coding.

• Make all layers in multilayer bottles sufficiently compatible so that the material can be sold into high-value end markets.

• Do not use PVC bottles for products that are also packaging in bottles such as PET that look like PVC.

The Association of Postconsumer Plastic Recyclers (APR), a U.S. trade association representing plastics recycling companies, also publishes a list of design guidelines for plastic bottles. Specific sets of guidelines are presented for PET, natural HDPE, pigmented HDPE, PP, and PVC bottles [22]. Guidelines include:

• No paper attachments of any kind; no PVC attachments of any kind except on PVC bottles; no PET attachments on PVC bottles.

• No metal closures; PP or HDPE/EVA closures and closure liners preferred on PET bottles; HDPE, LDPE or PP closures preferred on HDPE, PP, and PVC bottles.

• Sleeves and safety seals should be completely detachable and easily removed in conventional separation systems; shrink sleeves preferred if sleeves are necessary.

• Unpigmented or green preferred for PET; unpigmented preferred for homopolymer HDPE; pigmented preferred for copolymer HDPE; unpigmented preferred for PP.

• Nonbleeding inks and water-soluble or dispersible adhesives preferred.

The APR also operates the Champions for Change program that "invites consumer product companies, technology companies, suppliers, converters and others to test new bottle compositions directly with commercial plastics recyclers" in order to [22]:

• "Help ensure that new materials and designs are compatible with the existing plastics recycling infrastructure;

• Help promote technology transfer so that the recovery of plastic materials keeps pace with new packaging designs; and

• Help sustain the economics of an industry supplying valuable post-consumer recovered material to markets worldwide."

As mentioned, when PET beer bottles were introduced in the United States, recyclers voiced concern, on several grounds, over the effect these bottles would have on PET recycling systems. First, existing processes were set up to handle green and clear bottles, and many of the new bottles were amber. That meant, in many cases, that processes would have to be modified to segregate an additional color, or else the existing product streams would be contaminated and therefore decrease in value. If pure streams of amber PET were produced, the processors were concerned that there would be no market for the material. Second, the bottles contained an aluminum cap. Most soft drink bottles are collected for recycling with the cap in place, and the same would be true for beer bottles. When PET soft drink bottle recycling systems were initiated, all the bottles also had aluminum caps. High-quality recycled PET requires that aluminum contamination be kept extremely low. Separating the aluminum from the PET turned out to be one of the most difficult aspects of recycling system operation. A change in design to PP caps, although not done with the aim of improving recyclability, greatly facilitated PET recycling. Now the processors faced reintroduction of this highly problematic material. Further, the initial bottle design incorporated a metallized label, which added to the threat of unacceptable levels of aluminum contamination. An additional concern, for some container designs being introduced, was the presence of novel barrier materials and their unknown effect on the recycling process. This combination of factors drew criticism, calls for boycott, and even resolutions from local governments to prohibit introduction of the container, before the industry committed to design changes.

In contrast, when Heinz introduced PET ketchup bottles, the company paid explicit attention to ensuring that the bottles were compatible with existing PET

soft drink bottle recycling systems. The bottle is manufactured with a five layer structure: PET/EVOH/PET/EVOH/PET. The EVOH is required to obtain sufficient oxygen barrier for the product. The absence of a tie (adhesive) layer between the PET and EVOH causes the material to delaminate when the bottles are ground and the material washed during recycling. The EVOH material is mostly removed during the wash and rinse processes. The small amount that remains is not detrimental to PET properties.

In December, 2000, a new report from the Plastic Redesign Project examined the effect of new plastic packaging innovations on plastic bottle recycling, with a specific focus on whether trends in bottle design could further erode the prices paid to local recycling programs for plastic bottles because of the expense in handling new structures [23]. Mentioned as design changes that have facilitated plastics recycling are elimination of the base cup in 2-liter soft drink bottles, substitution of PET for PVC bottles, substitution of EVOH for PVC liners in closures for carbonated beverages, and development of LDPE shrink labels to substitute for glued-on labels on milk bottles.

The major concerns identified are the increasing use of colors other than green in PET bottles and the growth in use of PET bottles that contain non-PET components to enhance barrier properties. Both of these developments increase the cost of processing recovered plastic bottles and also affect the value of the recovered material. The study estimates that the intermediate processor's cost to manually separate another color from clear and green PET bottles would be about 6 cents per pound, and if mechanical sorting is available, it would be about 1.5 cents per pound. The value of green PET flake currently averages 18.9% lower than clear PET flake. The value of new colors, such as amber from beer bottles and blue from water bottles, would be lower, averaging perhaps 1.1 cents per pound less than clear.

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