Instead of cotton being inside a coat or mattress there could be bits of fabric that have come out of the production of clothes. It is an environmentally friendly way to not use as much cotton in stuffing.
Another way that is eco is pom pom cut offs. Pom pom cut offs are bits of wool that come off the pom pom when it is finished. Buckwheat hulls, ground walnut shells and flaxseeds are another good option instead of cotton or polyester. You could also fill a pillow with bits of lavender with natural latex, it would feel and smell wonderful!