Recycling is the process by which various materials — or anything resulting quickly from human activity that no longer serves as a useful good — are reused. In this process, waste is usually converted into raw materials from which new products are created.

Part of the recycling process also involves transforming environmentally harmful materials into less harmful or even harmless ones. In this way, their reintegration into the natural environment takes place more smoothly, with nature itself completing the recycling process in a natural way. An example of this is the treatment of domestic wastewater into a form that is less harmful, in contrast to its direct disposal, e.g., into the sea.