Weed blocker material
Most retail stores have those big heavy plastic/canvas banners that they use outside their store to advertise with. Usually within 3 years they just toss them away!! I have a source where I just ask and they give them to me. These are about 4 feet long and about 3 feet wide. I lay them down in the bottom of any raise beds I'm making, and they outlast even the weed blocker stuff in keeping weeds and grass from coming into your beds. Plus, they keep mositure in your beds longer. And I'm keeping something that won't break down in trash out of the trash heap. Check with your local stores and see if they will let you recycle too.