What can I put in an Ecobrick?
Any type of plastic! We want to maximize the volume of your bottle to trap the materials that are going to be poisonous for the environment. Specifically: Styrofoam, cellophane, plastic bags, wrappers, packaging, foam, bubble wrap, silver lined plastics, etc. You want to make sure that these plastics are clean and dry (otherwise the biological material on them will root and create gas inside the bottle).
There is no need to put paper, cardboard, glass or metal inside an ecobrick. These materials are not poisonous to the environment and will naturally break down. Be especially careful not put to glass or metal inside your ecobrick. These can cut the bottle plastic, protrude, and make your ecobrick dangerous to handle.