Got an old down feather comforter or pillow and not sure what to do with it? Since old feather-filled home products can also be filled with dust, mold, mildew and bacteria, it's best not to donate them to charity. Instead, rip 'em open. Since feathers for these products are just washed (not chemically treated), they break down pretty quickly in a garden setting. Feathers are full of nitrogen, so if you sprinkle them in your garden and till them, they'll biodegrade in a few weeks or months.