I recently found Green Genius biodegradable plastic double zip storage bags in the one gallon size. According to the label, the bags should break down through anaerobic composting in a landfill within 15 years. Their website states that after the bags break down, the final products will be water, carbon dioxide, methane, and humus. This sounds much better than little tiny bits of plastic, which I've heard is the final product of some bags marketed as degradable.
I plan to use these instead of the ordinary plastic zipper bags I've been using for my handspinning projects, once those are worn out.
A one gallon bag is a good size for an ounce of wool and a drop spindle. The wool comes out of the bag intact more easily than it does with a cloth bag, and the project is also more visible than it is when mewed up in a cloth bag.
Environmentally, I would probably do better to use an upcycled cloth bag, like this one that I made. There are also cellophane bags made from true cellulose that breaks down through aerobic composting, the kind made to line kitchen composting bins. I might switch in the future, but for now I'm going to try this.