I'm researching this because of the 3D printing I am doing.
I use PLA plastic which is considered fairly eco friendly as its made from plant starch and is compostable.
I was wondering how long my new 3D printed bird feeders would last outside in the elements all year, and how well it would break down once in a compost heap.
Here is a video of an interesting experiment on how well PLA and other "compostable" plastics biodegrade:
I also found this interesting experiment someone had done with his 3D printed items outside for a year: