Carpet underlay comes in three main types: fibre, rubber, and foam. The first two may be a combination of various materials, while the latter is entirely composed of polyurethane. If your underlay is made of jute fibre, it will naturally break down in the landfill, but if it's any other material, consider options to divert the material elsewhere. Recycled foam underlay can be used toward the production of new underlay 8-10 times, greatly reducing the need to use new materials.