Recycling is the process by which various materials or anything that results rapidly from human activity—and which, in its current form, is no longer a good for humans—are reused. In this process, waste is usually converted into raw materials from which new products are produced.

Part of the recycling process is also the transformation of materials harmful to the environment into materials that are less or not at all harmful. In this way, their reintegration into the natural environment occurs more smoothly, essentially completing the recycling process naturally. An example of such a case is the transformation of household wastewater into a form that is less harmful, in contrast to its direct disposal, for example, into the sea.