Waste is unwanted material. It may include components of a product that are obsolete by themselves, unusable byproducts of processes, or once-usable items that have expired. Waste also refers to substances that people must discard due to their hazardous properties.

The practice of waste management involves properly collecting, transporting, processing and/or disposing of waste. Different strategies exist for different categories of waste. Environmentally harmful strategies such as building landfills and incinerating waste are now generally discouraged in favor of more sustainable methods, such as recycling and composting. (Photo: Shutterstock)