Waste is any substance which is discarded after primary use, or is worthless, defective and of no use.Disposing of waste has huge environmental impacts and can cause serious problems. Some waste will eventually rot, but not all, and in the process it may smell, or generate methane gas, which is explosive and contributes to the greenhouse effect. Leachate produced as waste decomposes may cause pollutionSo, we use recycling process for converting waste materials into new materials and objects. It is an alternative to "conventional" waste disposal that can save material and help lower greenhouse gas emissions. The composting or other reuse of biodegradable waste such as food or garden waste is also a form of recycling.