Metals, glass, building materials, clay ceramics and most plastics are made from limited raw materials. Much of the energy used to make them also comes from limited resources. Getting raw materials out of the Earth by quarrying and mining harms the environment, for example by destroying habitats and making dust and noise.
End users can cut these impacts by using less, by reusing products and by recycling. This saves limited resources and energy sources, and it reduces waste and environmental damage.
Some products can be reused as they are. A glass bottle can be washed and filled again. Glass bottles can also be crushed and melted to make different glass products. Products that cannot be reused are recycled for a different use. Metals are recycled by melting and recasting, or by reforming into different products.
How much separation recycling needs depends on the material and on the properties the final product must have. For example, some scrap steel can be added to iron from a blast furnace. This reduces the amount of iron that has to be extracted from iron ore.
When asked to evaluate a way of reducing resource use, use the information given to weigh the benefits, such as less energy and less waste, against costs such as collecting and sorting.