Photos: Plastic by the numbers

The SPI plastic resin codes can help consumers to figure out what to toss in the trash versus a recycling bin, but they don't appear on much other packaging, such as clamshell packs for electronics, roll-on deodorant bottles, or many plastic bags.

Nor is there any easy way to recycle items with hidden plastic linings, such as these liquid containers. Recyclers tend to curse such containers when people toss them improperly into recycling bins. Another common recycling faux pas is caused by the lack of labeling on plastic caps, which often don't match the type of plastic used in the bottles or tubs they seal.