Number 7 plastics include a hodge podge of resiny materials that don't really fit into any of the other categories. In fact, the abbreviations for #7 plastics range from MISC to OTHER. The hard plastic polycarbonate falls into this polymeric catch-all, which contains Bisphenol-A (BPA), a chemical compound that it has become trendy to fear in recent years, after studies have suggested that-- when leached-- it acts as a hormone disruptor in animals and humans.
The best "plastic" in this bunch, in my humble opinion, is polyactide (PLA). While at first glance it may seem that these letters are an obvious abbreviation for "plastic", it actually gives savvy recyclers a hint as to what it is really made of... plants! Remember back in Plastics 101 when we learned that cellulose (plant material) is a naturally occurring polymer? Well, some innovative scientists are using the power of nature to create compostable plastic packaging! The only catch is that, because it is biodegradable, it is not recyclable.
Because of the variety of items that fall under the category of #7 plastics, they weren't traditionally recycled. However, more curbside programs (Chicago's included) now accept this type of packaging. In addition to the now-recyclable three- and five-gallon water bottles and food containers, (which can be turned into plastic lumber and other custom-made products) miscellaneous plastics are used in bullet-proof materials, DVDs, nylon, signs, and computer cases.