Bioplastics or organic plastics are derivied from renewable sources such as starch, vegetable oil and even chicken feathers.
They are also derived from ethane got from plants
Some bioplastics, like the one made from chicken feathers, do biodegrade.
Others, like the plant derived ethane used to make PET used by Coke, do not.
In fact it shares the same long lasting, non biodegradable qualities as petroleum derived PET.
YET The term bio-plastics is used to describe both types of plant derived plastic ie biodegradable and biomass derived.
This has led to CONFUSION
In short, just because a plastic has been made from plants does not mean it is biodegradable.While not all plant based plastics are biodegradable, these are
Polyhydroxyalkanoates or PHAs ( taken from Wikipedia) : are linear polyesters produced in nature by bacterial fermentation of sugar or lipids. They are produced by the bacteria to store carbon and energy.
Biodegradable, degradable and compostable plastics.
Some conventional plastics are labeled biodegradable which may lead you to think they are, well, biodegradable! They are not. They have a an additive that makes the plastic fall apart, degrade, more quickly. And only in certain conditions. You can read more here