The process of extracting resources or value from waste is generally referred to as recycling, meaning to recover or reuse the material. There are a number of different methods by which waste material is recycled: the raw materials might be extracted of the waste might be converted to electricity.
The meaning of ‘recycling’ in most developed countries refers to the widespread collection and reuse of everyday waste materials. These are collected and sorted so that the raw materials from which the items are made can be reprocessed into new products. Material for recycling may be collected separately from general waste dedicated bins and collection vehicles, or sorted directly from mixed waste streams.
The most common consumer products recycled include aluminium drink cans, steel can, plastic bottles, glass bottles and jars, paperboard cartons, newspapers, magazines and cardboard. These items are usually composed of a single material, making them relatively easy to recycle. Recycling more complex products (such as computers and other electronic equipment) is more difficult, due to the additional dismantling and separation required.
Waste materials that are organic in nature, such as plant material, food scraps, and paper products, can be recycled by composting. The resulting organic material is then recycled a mulch or compost for agricultural or landscaping purposes. In addition, waste gas from the processes (such as methane) can be captured and used for generating electricity. There is a large variety in complexity from simple home compost heaps to industrial-scale enclosed vessel digestion of mixed domestic waste.
The energy content of waste products can be harnessed directly by using them as a direct combustion fuel, or indirectly by processing them into another type of fuel. Recycling through thermal treatment rages from using waste as a fuel source for cooking or heating, to fuel for boilers to generate steam and electricity in a turbine.