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Recycling can be carried out on various raw materials. Recycling is an important part of creating more sustainable economies, reducing the cost and environmental impact of raw materials. Not all materials are easily recycled, and processing recyclable into the correct waste stream requires considerable energy. Some particular manufactured goods are not easily separated, unless specially process therefore have unique product-based recycling processes.


Main article: Asphalt concrete § Recycling

Asphalt concrete removed during road maintenance, resurfacing, and repair activities can be reclaimed and reused in new pavement mixtures, as an unbound aggregate base, or other civil engineering applications. Very little asphalt concrete — less than 1 percent, according to a survey by the Federal Highway Administration and the National Asphalt Pavement Association conducted annually since 2009 — is actually disposed of in landfills.[1] When asphalt pavement material is reclaimed for reuse, it is able to replace both virgin aggregates and virgin asphalt binder. Similarly, asphalt roof shingles can be recycled for use in new asphalt pavements.[2]


Concrete from a building being sent to a portable crusher. This is the first step in recycling concrete.
Crushing concrete from an airfield
Concrete recycling is the use of rubble from demolished concrete structures. Recycling is cheaper and more ecological than trucking rubble to a landfill.[3] Crushed rubble can be used for road gravel, revetments, retaining walls, landscaping gravel, or raw material for new concrete. Large pieces can be used as bricks or slabs, or incorporated with new concrete into structures, a material called urbanite.[4][5]


A Dutch public glass waste collection point for separating clear, green and amber glass
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Bottles in different colors
Mixed color glass cullet
Public glass waste collection point for different colors of containers

Glass recycling is the processing of waste glass into usable products.[6] Glass that is crushed or imploded and ready to be remelted is called cullet.[7] There are two types of cullet: internal and external. Internal cullet is composed of defective products detected and rejected by a quality control process during the industrial process of glass manufacturing, transition phases of product changes (such as thickness and color changes) and production offcuts. External cullet is waste glass that has been collected or reprocessed with the purpose of recycling. External cullet (which can be pre- or post-consumer) is classified as waste. The word "cullet", when used in the context of end-of-waste, will always refer to external cullet.

To be recycled, glass waste needs to be purified and cleaned of contamination. Then, depending on the end use and local processing capabilities, it might also have to be separated into different sizes and colours. Many recyclers collect different colors of glass separately since glass tends to retain its color after recycling. The most common colours used for consumer containers are clear (flint) glass, green glass, and brown (amber) glass. Glass is ideal for recycling since none of the material is degraded by normal use.

Many collection points have separate bins for clear (flint), green and brown (amber). Glass re-processors intending to make new glass containers require separation by color. If the recycled glass is not going to be made into more glass, or if the glass re-processor uses newer optical sorting equipment, separation by color at the collection point may not be required. Heat-resistant glass, such as Pyrex or borosilicate glass, must not be part of the glass recycling stream, because even a small piece of such material will alter the viscosity of the fluid in the furnace at remelt.




Main article: Aluminium recycling

Aluminium is one of the most efficient and widely recycled materials.[9][10] Aluminium is shredded and ground into small pieces or crushed into bales. These pieces or bales are melted in an aluminium smelter to produce molten aluminium. By this stage, the recycled aluminium is indistinguishable from virgin aluminium and further processing is identical for both. This process does not produce any change in the metal, so aluminium can be recycled indefinitely.

Recycling aluminium saves 96% of the energy cost of processing new aluminium, it also helps divert significant amounts of waste from landfills.[11] This is because the temperature necessary for melting recycled, nearly pure, aluminium is 600 °C, while to extract mined aluminium from its ore requires 900 °C. To reach this higher temperature, much more energy is needed, leading to the high environmental benefits of aluminium recycling. Americans throw away enough aluminium every year to rebuild their entire commercial air fleet. Also, the energy saved by recycling one aluminium can is enough to run a television for three hours.[12]


Like aluminium, copper is recyclable without any loss of quality, both from raw state and from manufactured products.[13] In volume, copper is the third most recycled metal after iron and aluminium.[14] An estimated 80% of all copper ever mined is still in use today.[15] According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of copper in use in society is 35–55 kg. Much of this is in more-developed countries (140–300 kg per capita) rather than less-developed countries (30–40 kg per capita).

The process of recycling copper is roughly the same as is used to extract copper but requires fewer steps. High-purity scrap copper is melted in a furnace and then reduced and cast into billets and ingots; lower-purity scrap is refined by electroplating in a bath of sulfuric acid.[16]

Iron and steel

Steel crushed and baled for recycling.

Main article: Ferrous metal recycling

Iron and steel are the world's most recycled materials, and among the easiest materials to reprocess, as they can be separated magnetically from the waste stream. Recycling is via a steelworks: scrap is either remelted in an electric arc furnace (90-100% scrap), or used as part of the charge in a Basic Oxygen Furnace (around 25% scrap).[17] Any grade of steel can be recycled to top quality new metal, with no 'downgrading' from prime to lower quality materials as steel is recycled repeatedly. 42% of crude steel produced is recycled material.[18]

Brass recycling

Brass recycling is a fascinating process that not only contributes to environmental sustainability but also showcases the remarkable properties of this alloy. Brass, a combination of copper and zinc, is highly prized for its durability, corrosion resistance, and aesthetic appeal.

Here are some interesting aspects of brass recycling:

Endless Recyclability: Brass is a non-ferrous metal, which means it doesn't lose its properties during the recycling process. Unlike some materials that degrade with each recycling cycle, brass can be recycled indefinitely without compromising its quality. This makes it a sustainable choice for various applications.

Energy Savings: Recycling brass requires significantly less energy compared to mining and refining raw materials. The extraction of copper and zinc, the primary components of brass, is an energy-intensive process. By recycling brass, we not only conserve valuable resources but also reduce the carbon footprint associated with metal production.

Other metals

For information about recycling other, less common metals, refer to:

This list is incomplete; you can help by adding missing items. (November 2014)


Plastic recycling
Clockwise from top left:
  • Sorting plastic waste at a single-stream recycling centre
  • Baled colour-sorted used bottles
  • Recovered HDPE ready for recycling
  • A watering can made from recycled bottles

Plastic recycling is the processing of plastic waste into other products.[19][20][21] Recycling can reduce dependence on landfill, conserve resources and protect the environment from plastic pollution and greenhouse gas emissions.[22][23] Recycling rates lag those of other recoverable materials, such as aluminium, glass and paper. From the start of production through to 2015, the world produced some 6.3 billion tonnes of plastic waste, only 9% of which has been recycled, and only ~1% has been recycled more than once.[24] Of the remaining waste, 12% was incinerated and 79% either sent to landfill or lost into the environment as pollution.[24]

Almost all plastic is non-biodegradable and without recycling, spreads across the environment[25][26] where it can cause harm. For example, as of 2015 approximately 8 million tons of waste plastic enter the oceans annually, damaging the ecosystem and forming ocean garbage patches.[27] Even the highest quality recycling processes lead to substantial plastic waste during the sorting and cleaning process, releasing large amounts of microplastics in waste water, and dust from the process.[28][29]

Almost all recycling is mechanical: melting and reforming plastic into other items. This can cause polymer degradation at a molecular level, and requires that waste be sorted by colour and polymer type before processing, which is complicated and expensive. Errors can lead to material with inconsistent properties, rendering it unappealing to industry.[30] In feedstock recycling, waste plastic is converted into its starting chemicals, which can then become fresh plastic. This involves higher energy and capital costs. Alternatively, plastic can be burned in place of fossil fuels, in energy recovery facilities or biochemically converted into other useful chemicals for industry. In some countries, burning is the dominant form of plastic waste disposal, particularly where landfill diversion policies are in place.

Plastic recycling is low in the waste hierarchy. It has been advocated since the early 1970s,[31] but due to economic and technical challenges, did not impact plastic waste to any significant extent until the late 1980s. The plastics industry has been criticised for lobbying for expansion of recycling programs, even while research showed that most plastic could not be economically recycled.[32][33][34]


A tidy stack of pallets awaits reuse or recycling.

Main article: Timber recycling

Recycling timber has become popular due to its image as an environmentally friendly product, with consumers commonly believing that by purchasing recycled wood the demand for green timber will fall and ultimately benefit the environment. Greenpeace also view recycled timber as an environmentally friendly product, citing it as the most preferable timber source on their website. The arrival of recycled timber as a construction product has been important in both raising industry and consumer awareness towards deforestation and promoting timber mills to adopt more environmentally friendly practices.

See also


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  2. ^ "Economics and Markets for Recycling Asphalt Shingles". Construction & Demolition Recycling Association. Retrieved January 14, 2020.
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