Recycling is the reformation or reprocessing of a recovered material. The EPA defines recycling as "the series of activities, including collection, separation, and processing, by which products or other materials are recovered from or otherwise diverted from [the] solid waste stream for use in the form of raw materials in the manufacture of new products other than fuel" (U.S. EPA 1991a).
Recycled material can follow two major pathways: closed loop and open loop. In closed-loop systems, recovered material and products are suitable substitutes for virgin material. In theory a closed-loop model can operate for an extended period of time without virgin material. Of course, energy, and in some cases process material, is required for each recycling. Solvents and other industrial process ingredients are the most common materials recycled in a closed loop.
Open-loop recycling occurs when the recovered material is recycled one or more times before disposal. Most postconsumer material is recycled in an open loop. The slight variations or unknown composition of such material usually cause it to be downgraded to a less demanding use.
Some material also enters a cascade open-loop model in which it is degraded several times before the final discard. For example, used white paper can be recycled into additional ledger or computer paper. If this product is then dyed and not de-inked, it can be recycled as mixed grade after use. In this form, it can be used for paper board or packing, such as trays in produce boxes. Currently, the fiber in these products is not valuable enough to recover. Ledger paper also enters an open-loop system when it is recycled into facial tissue or other products that are disposed of after use.
Recycling can be an effective resource management tool. Under ideal circumstances, most material can be recovered many times until it becomes too degraded for further use. Even so, designing for recyclability is not the strategy for meeting all environmental requirements. As an example, studies show that refillable glass bottles use less life cycle energy than single-use recycled glass to deliver the same amount of beverages (Sellers and Sellers 1989).
When a suitable infrastructure is in place, recycling is enhanced by:
• Ease of disassembly
• Ease of material identification
• Simplification and parts consolidation
• Material selection and compatibility
In most projects, the material selection is not coordinated with environmental strategies. For instance, a passenger car currently uses 50 to 150 different materials. Separating this mixture from a used car is impossible. Designers can aid recycling by reducing the number of incompatible materials in a product. For example, a component containing parts of different materials could be designed with parts made from the same material.
Some polymers and other materials are broadly incompatible. If such materials are to be recycled for similar use, they must be meticulously separated for high purity.
Some new models in a personal system/2 product line are specifically designed with the environment in mind. These models use a single polymer for all plastic parts. The polymer has a molded-in finish, eliminating the need for additional finishes, and molded-in identification symbols. In addition, the parts snap together, avoiding the use of metal pieces such as hinges and brackets. These design features facilitate recycling, principally through easy disassembly, the elimination of costly plastic parts sorting, and the easy identification of polymer composition (Dillon 1993).
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