Blilly
I recycle carpet and am also an organic gardener. Many of the carpet fibers decay in sunlight but can last for 100s of years in a landfill where they are kept in the dark. Therefore a layer of pea gravel would prevent the sunlight from degrading the carpet. Carpet in general is made of 60 % inert (polypropylene, nylon, and polyester) fiber with 40 % backing (CaCO3, latex plus some organics if post consumer).
I plan to use carpet/gravel for the walking paths in an urban garden between raised beds.
