Recycling

Recycling is the process of converting waste materials into new materials and objects. This concept often includes the recovery of energy from waste materials. The recyclability of a material depends on its ability to reacquire the properties it had in its original state. It is an alternative to "conventional" waste disposal that can save material and help lower greenhouse gas emissions. It can also prevent the waste of potentially useful materials and reduce the consumption of fresh raw materials, reducing energy use, air pollution (from incineration) and water pollution (from landfilling).

Recycling is a key component of modern waste reduction and represents the third step in the "Reduce, Reuse, and Recycle" waste hierarchy, contributing to environmental sustainability and resource conservation. It promotes environmental sustainability by removing raw material input and redirecting waste output in the economic system. There are some ISO standards related to recycling, such as ISO 15270:2008 for plastics waste and ISO 14001:2015 for environmental management control of recycling practice.

Recyclable materials include many kinds of glass, paper, cardboard, metal, plastic, tires, textiles, batteries, and electronics. The composting and other reuse of biodegradable waste—such as food and garden waste—is also a form of recycling. Materials for recycling are either delivered to a household recycling center or picked up from curbside bins, then sorted, cleaned, and reprocessed into new materials for manufacturing new products.

In ideal implementations, recycling a material produces a fresh supply of the same material—for example, used office paper would be converted into new office paper, and used polystyrene foam into new polystyrene. Some types of materials, such as metal cans, can be remanufactured repeatedly without losing their purity. With other materials, this is often difficult or too expensive (compared with producing the same product from raw materials or other sources), so "recycling" of many products and materials involves their reuse in producing different materials (for example, paperboard). Another form of recycling is the salvage of constituent materials from complex products, due to either their intrinsic value (such as lead from car batteries and gold from printed circuit boards), or their hazardous nature (e.g. removal and reuse of mercury from thermometers and thermostats).

Reusing materials has been a common practice for most of human history with recorded advocates as far back as Plato in the fourth century BC. During periods when resources were scarce, archaeological studies of ancient waste dumps show less household waste (such as ash, broken tools, and pottery), implying that more waste was recycled in place of new material. However, archaeological artefacts made from recyclable material, such as glass or metal, may neither be the original object nor resemble it, with the consequence that a successful ancient recycling economy can become invisible when recycling is synonymous with re-melting rather than reuse.

In pre-industrial times, there is evidence of scrap bronze and other metals being collected in Europe and melted down for continuous reuse. Paper recycling was first recorded in 1031 when Japanese shops sold repulped paper. In Britain dust and ash from wood and coal fires was collected by "dustmen" and downcycled as a base material for brick making. These forms of recycling were driven by the economic advantage of obtaining recycled materials instead of virgin material, and the need for waste removal in ever-more-densely populated areas. In 1813, Benjamin Law developed the process of turning rags into "shoddy" and "mungo" wool in Batley, Yorkshire, which combined recycled fibers with virgin wool. The West Yorkshire shoddy industry in towns such as Batley and Dewsbury lasted from the early 19th century to at least 1914.

Industrialization spurred demand for affordable materials. In addition to rags, ferrous scrap metals were coveted as they were cheaper to acquire than virgin ore. Railroads purchased and sold scrap metal in the 19th century, and the growing steel and automobile industries purchased scrap in the early 20th century. Many secondary goods were collected, processed and sold by peddlers who scoured dumps and city streets for discarded machinery, pots, pans, and other sources of metal. By World War I, thousands of such peddlers roamed the streets of American cities, taking advantage of market forces to recycle post-consumer materials into industrial production.

Manufacturers of beverage bottles, including Schweppes, began offering refundable recycling deposits in Great Britain and Ireland around 1800. An official recycling system with refundable deposits for bottles was established in Sweden in 1884, and for aluminum beverage cans in 1982; it led to recycling rates of 84–99%, depending on type (glass bottles can be refilled around 20 times).