HOW FAST DO ORGANIC AND INORGANIC MATERIALS DECOMPOSE?

We bury a banana (organic) and a piece of plastic bag (inorganic).

 After 1 week: we can't find the banana. The plastic bag is still there, with holes.

 After 2 weeks: we can't find the banana agin. It's decomposed

. The plastic bag is still there, with more holes and thinner.