Recycling is the processing of used materials into new products usually by using energy inputs to reduce the material to its more basic constituents for the same or another use. e.g. to melt and remould a used glass bottle into a new one.

Ideally the recycled product would produce a fresh supply of the same material, however in practice this is rarely the case. e.g. office paper is more likely to become cardboard than more office paper. The benefits of recycling may have been overemphasised as it is unclear whether the net economic and environmental benefits outweigh the costs in terms of energy and other resource use. The composting of food and garden waste is another form of recycling, as decomposer organisms such as earthworms, recycle organic matter to make it available for plant growth and health.