What are the points against plastics?
1) they're made out of gasoline (well, hydrocarbons) - thus less gas for you.
2) they are very stable - they don't degrade, so plastic junk will still be around long after everything else (except maybe ceramics).
Biodegradable plastics are plastic materials that degrade through the natural process of living organisms into humus, gas, water or other basic elemental materials. Non-biodegradable plastics are any plastics that either do not break down at all or plastics that require mechanical or chemical breakdown. PLA and oxodegradable plastics are examples of non-biodegradable plastics. PHA and ENSO plastics are examples of biodegradable plastics.