How long does an average supermarket plastic carrier bag take to decompose?
Plastic bags in generally usually don’t decompose, like uranium. It takes about an average of 300-500 years to decompose plastic. Best way the decompose plastic is to melt it, and then make it into something else.
Left on the surface of the earth, with sun, air, water attacking it it can decompose in months. Buried it can take a long long time, centuries. But I would not try to use it after a decade.