The international recycling symbol. Recycling is the reprocessing of old materials into new products, with the aims of preventing the waste of potentially useful materials, reducing the consumption of fresh raw materials, reducing energy usage, reducing air (from incineration) and water (from landfilling) pollution by reducing the need for "conventional" waste disposal, and lowering greenhouse gas emissions as compared to virgin production.[1][2] Recycling is a key concept of modern waste management and is the third component of the "Reduce, Reuse, Recycle" waste hierarchy, though colloquial usage of "recycling" can also include "reuse". "Recyclable materials" or "recyclables", may originate from home, business or industry. They include glass, paper, metal, textiles and plastics. Though analogus, the composting of biodegradable waste—such as food or garden waste—is not typically considered recycling.[2] These materials are either brought to a collection centre or picked-up from the curbside; and sorted , cleaned and reprocessed into new products bound for manufacturing. To judge the environmental benefits of recycling, the cost of this entire process must be compared to the cost of virgin extraction. In order for recycling to be economically viable, there usually must be a steady supply of recyclates and constant demand for the reprocessed goods; both of which can be stimulated through government legislation.[2] Meanwhile, critics claim that government mandated recycling wastes more resources than it saves. These critics claim that free market prices, and not politicians, are the most accurate way to determine whether or not any particular type of garbage should be recycled. According to these critics, whenever recycling truly does save resources, the private sector will voluntary offer people money for their garbage. [3], [4]