Most of us have understood for years that plastic is an environmental no-no. It's fuel based, requires lots of energy to produce and it clogs up landfills for what might as well be forever. It's difficult to imagine a plastic we can buy without guilt. And whether eco-plastics fit that bill depends on how "green" you want to be.
Eco-plastics come in several different flavors: recycled petroleum-based plastics, plant-derived (bio) plastics and miscellaneous. Each boasts different "green" properties.
Recycled traditional plastic is composed of varying percentages of "virgin" (nonrecycled), traditional plastic. The eco draw here is that all that virgin plastic is reused to make your lawn furniture instead of being tossed into a landfill. This type is no more biodegradable than the original, though.
Bioplastic is made from plant material and it should degrade relatively quickly in landfills and, in some cases, compost bins. The most common forms are starch-based (often corn starch), like polyactide (PLA) plastic, which is the most common form. You'll find PLA in things like biodegradable food-service trays and disposable cups. Polyhydroxyalkanoate (PHA) plastic uses starch also, typically from corn or sugarcane or beetroot, and it shows up in things like cosmetics bottles. Cellulose-based plastics are made of cellulose, the main component in plant tissues. You'll also find bioplastics made from soy protein or lactic acid.
Finally, there are several recent plastics innovations that make up the "miscellaneous" category. ECM Biofilms has come up with a way to add microbe-attracting pellets during the manufacturing process for traditional plastics, causing the end product to degrade faster in landfills [source: ACF]. The company Novomer plans to create biodegradable plastic using carbon dioxide and carbon monoxide (reacted with liquid metal), which would offer the double "green" whammy of biodegradability and removing harmful gasses from the air [source: CNET].
While all of these eco-plastics offer some type of environmental benefit over traditional plastics, the issue ultimately comes down to theory versus practice. In theory, these plastics are biodegradable. But since they're pretty new, at least in industrial terms, the long-term research is a bit lacking.