TEN COMMANDMENTS OF WOOL
Wool is a protein composed of amino acids, very much like our skin and hair. Amino acids are the building blocks of life. When you bury a wool product in soil under the right conditions, it will naturally biodegrade.
Fossil fuel-based fibers such as nylon, polyester, acrylic, and spandex do not biodegrade. Ever. They get smaller and smaller until they become microplastics. Microplastics act as magnets for other nasty contaminants in the environment. A single microplastic can be up to a million times more toxic than the water around it. 
 Chelsea M. Rochman, Eunha Hoh, Tomofumi Kurobe & Swee J. Teh, Ingested plastic transfers hazardous chemicals to fish and induces hepatic stress.