Recycling is the process of turning waste materials into new materials and objects. This process often includes recovering energy from waste. How easily a material can be recycled depends on how well it can regain its original properties. Recycling is an alternative to traditional waste disposal methods. It helps save materials, reduce greenhouse gas emissions, and prevent the waste of useful resources. It also lowers the need for new raw materials, which reduces energy use, air pollution from burning waste, and water pollution from landfills.

Recycling is an important part of modern waste reduction and is the third step in the "Reduce, Reuse, and Recycle" waste hierarchy. It helps protect the environment and conserve natural resources by reducing the need for new raw materials and redirecting waste into the economy. Some international standards, like ISO 15270:2008 for plastic waste and ISO 14001:2015 for managing recycling practices, are related to recycling.

Materials that can be recycled include glass, paper, cardboard, metal, plastic, tires, textiles, batteries, and electronics. Composting and reusing biodegradable waste, such as food scraps and garden waste, is also a type of recycling. Recyclable materials are usually taken to a household recycling center or collected from curbside bins. After being sorted and cleaned, these materials are reprocessed into new materials used to make products.

In the best cases, recycling produces a new supply of the same material. For example, used office paper becomes new office paper, and used polystyrene foam becomes new polystyrene. Some materials, like metal cans, can be reused many times without losing their quality. Other materials are harder or more expensive to recycle, so they may be used to make different products, such as paperboard. Another type of recycling involves recovering valuable parts from complex items, such as lead from car batteries or gold from circuit boards, or removing hazardous materials like mercury from thermometers for safe reuse.

History

Reusing materials has been a common practice for most of human history. Ancient thinkers like Plato, who lived in the fourth century BC, supported this idea. When resources were limited, studies of ancient waste dumps show less household waste, such as broken tools and pottery, suggesting that people reused materials instead of throwing them away. However, recycled items made from materials like glass or metal might not look like the original objects, making it hard to see how much recycling happened in the past.

Before the industrial era, people in Europe collected scrap bronze and other metals to melt down and reuse. Paper recycling began in 1031 when Japanese shops sold repulped paper. In Britain, people collected dust and ash from fires to use in making bricks. These practices happened because recycled materials were cheaper than new ones, and cities needed ways to manage waste. In 1813, Benjamin Law in Yorkshire created a process to turn old cloth into wool called "shoddy" and "mungo." The shoddy industry in towns like Batley and Dewsbury lasted from the early 1800s until at least 1914.

Industrialization increased the need for affordable materials. Metals like iron were valuable because they were cheaper to get than raw ore. Railroads and industries like steel and automobile manufacturing bought scrap metal in the 1800s and early 1900s. People called "peddlers" collected scrap from dumps and streets to sell. By World War I, thousands of these workers collected materials in American cities to reuse in factories.

Beverage bottle makers, like Schweppes, offered refunds for bottles in Britain and Ireland around 1800. Sweden started a formal bottle recycling system in 1884, and a similar program for aluminum cans began in 1982. These systems helped recycle up to 99% of some materials.

New chemical industries in the late 1800s created materials like Bakelite and showed how waste could become valuable. A 1921 study by Arthur D. Little proved that chemistry could turn old materials into useful products.

During World War II, governments focused on recycling because of limited resources. People were encouraged to reuse materials to support the war effort. Campaigns like Britain’s "National Salvage Campaign" and the U.S. "Salvage for Victory" asked citizens to donate metals, paper, and other materials as a patriotic duty.

In the 1970s, recycling grew because of high energy costs. Recycling aluminum uses only 5% of the energy needed to make new aluminum. Recycling glass, paper, and other metals also saves energy.

Consumer electronics became popular in the 1920s, but recycling them was rare until 1991. Switzerland started the first program to collect old electronics, beginning with refrigerators. However, many countries struggled to handle e-waste, often sending it to developing nations with weak environmental rules. In the 2000s, demand for e-waste in Asia grew as people found valuable materials like gold and copper in discarded devices.

By 2014, the European Union had about half of the world’s recycling industry, with over 60,000 companies and €24 billion in revenue. EU countries must recycle at least 50% of waste, with some nations reaching 65%. In 2013, the EU recycled 39% of waste, a number that increased to 45% by 2015.

In 2015, the United Nations set 17 Sustainable Development Goals, including Goal 12, which focuses on reducing waste by 2030.

In 2018, the recycling industry faced a major change when China introduced the "National Sword" policy. This rule banned importing recyclable materials that were too dirty or hazardous, causing global recycling prices to drop and disrupting trade. Many countries shifted waste to Southeast Asia, raising concerns about environmental harm and the ethics of exporting waste to nations with weak regulations.

Health and environmental impact

According to the WHO (2023), "Every year, millions of electrical and electronic devices are thrown away. If these items are not handled, recycled, or disposed of properly, they can harm the environment and human health. Common items include computers. Many e-waste items are recycled using unsafe methods and may be stored in homes, warehouses, or dumped. Some are sent to other countries and recycled in poor conditions. When e-waste is treated improperly, it can release up to 1,000 different chemicals, including harmful substances like lead." A paper in the journal Sustainable Materials & Technologies explains that managing e-waste is difficult, especially from home automation products. These products become outdated quickly, creating more waste than recycling systems can handle.

Copper slag is created when copper and nickel are extracted from their ores through a type of industrial process. These ores often contain other elements, such as iron, cobalt, silica, and alumina. For every ton of copper produced, about 2.2 to 3 tons of copper slag are made. This results in roughly 24.6 tons of slag each year, which is considered waste.

Copper slag can harm the environment and humans. If swallowed, it can cause copper poisoning, leading to severe stomach bleeding and death. It may also cause skin irritation if touched. Toxic chemicals from slag can enter soil and be absorbed by plants, spreading to animals and food sources. This increases the risk of health problems like heart disease, cancer, brain damage, kidney issues, and harm to bones, the nervous system, and skin.

Using copper slag instead of gravel and grit in quarries is more cost-effective because slag is often closer to where it is needed. Trade between countries and the building of blast furnaces are helping to use more slag, which reduces waste and pollution.

Economist Steven Landsburg, who wrote a paper titled "Why I Am Not an Environmentalist," argued that recycling paper may actually reduce the number of trees. He claims that paper companies grow more trees when there is high demand for paper. If demand decreases, fewer trees are planted.

When companies cut down trees, they often plant new ones. However, these planted forests are not as good as natural forests. Planted forests do not fix soil as quickly, leading to soil erosion and the need for more fertilizer. They also have less biodiversity than natural forests. The new trees are smaller than the ones that were cut down, and the idea that "more trees" exist is not convincing to some experts when they count young trees.

Tropical rainforest wood is rarely used for paper because the trees are very different from each other. According to the United Nations Framework Convention on Climate Change, the main causes of deforestation are subsistence farming (48%) and commercial agriculture (32%). These activities are linked to food production, not paper.

Other recycling methods, like Waste-to-Energy (WTE) systems, have drawn attention recently because of debates about their emissions. While some see WTE as a way to generate energy from waste, others argue that the technology has not been widely used globally for various reasons.

Legislation

For a recycling program to be successful, a steady and large supply of materials that can be recycled is important. Three laws have been used to create this supply: laws that require cities to collect recyclables, laws that give money back for returning containers, and laws that stop certain materials from being thrown away. Laws requiring collection set goals for cities, such as needing to recycle a certain percentage of materials by a specific date. The city must work to reach this goal.

Laws about returning containers require people to get money back when they return certain items like glass, plastic, or metal bottles. When these items are bought, a small extra cost is added to the price. This cost can be returned when the container is brought back to a collection center. These programs have helped achieve an average recycling rate of 80%. However, some areas have resisted these laws because the cost of collecting recyclables has shifted from local governments to businesses and consumers. For example, in the European Union, the WEEE Directive requires companies that make electronics to pay for recycling their products.

Another way to increase the amount of recyclable materials is to stop people from throwing away certain items, such as used oil, old batteries, tires, and garden waste. This can create a system where these items are properly handled. However, it is important to make sure there are enough recycling services available, or else people might illegally dump these materials instead.

Four types of laws have also been used to increase the need for recycled materials: rules that require products to contain a certain amount of recycled material, rules that set recycling goals for industries, government policies that support buying recycled items, and rules that require labels showing how much recycled material is in products.

Rules that require products to include recycled material and rules that set recycling goals both increase demand by making companies use recycling in their work. Recycled content rules say that a certain percentage of a product must be made from recycled materials. Recycling goals are more flexible: companies can meet their targets at any stage of their operations or even hire others to recycle in exchange for credits. Some people disagree with these rules because they believe they increase the amount of paperwork needed and take away flexibility from industries.

Governments have used their power to buy goods to increase recycling by creating "procurement policies." These policies can mean setting aside money to buy recycled products or giving more money to companies that buy recycled items. Other rules can focus on specific situations, such as in the United States, where the Environmental Protection Agency requires government agencies to buy oil, paper, tires, and building insulation made from recycled or reprocessed materials whenever possible.

The last type of government rule that increases demand for recycled materials is requiring labels on products that show how much recycled material they contain. When companies must label their packaging with the amount of recycled material used, consumers can make better choices. When enough people choose products with recycled materials, companies may use more recycled materials in their products. Standardized labels can also help the supply of recyclable materials by explaining how and where the product can be recycled.

Types of recycling

Recycling is often grouped into different types based on the methods used and the results they produce:

• Mechanical recycling: Uses physical methods like shredding, melting, and reshaping materials (often used for plastics and metals).
• Chemical recycling: Uses chemicals to break materials into their basic parts, which can be used again to make new products.
• Closed-loop recycling: Materials are recycled into the same product without losing much quality.
• Open-loop recycling: Materials are made into different products, but the quality is usually lower (this is also called downcycling).

Closed-loop recycling is usually more sustainable because it helps keep resources from being wasted.

Recyclates

"Recyclate" is a type of material that is sent to a recycling plant or a materials-recovery facility to be processed and used to make new products. For example, plastic bottles can be turned into small plastic pieces called pellets or used to create synthetic fabrics.

The quality of recyclate is an important challenge for creating a green economy and achieving zero waste. Recyclate quality refers to how much of the material is the correct type of material compared to other materials that are not meant to be recycled. Metals like steel naturally have higher recyclate quality because about two-thirds of new steel is made from recycled steel. Only the correct type of material is usually recycled, so having too much of the wrong materials or materials that cannot be recycled can lower the amount of useful recycled products. If recyclate has too many unwanted materials, it may be turned into lower-quality products or, in some cases, sent to landfills. For example, colored glass is not allowed in the process to make clear glass products, and plastic food packaging is often turned into lower-quality items instead of being reused as the same type of packaging.

High-quality recyclate helps support better recycling and can reduce waste, reuse materials, and keep items out of landfills. It also helps the economy by increasing the value of waste materials. Selling high-quality recyclate can provide income to local governments, families, and businesses. Improving recyclate quality can also build trust in recycling programs and encourage more investment in waste management.

Many steps in the recycling process can affect recyclate quality. People who throw away the wrong materials in recycling bins can lower the quality of recyclate and require more work to remove those materials later. Different recycling systems can lead to different levels of contamination. When multiple materials are collected together, more effort is needed to sort them, which can lower the quality of the final products. Transporting and pressing materials together can also make sorting harder. Even with better technology, sorting facilities are not always completely effective at separating materials. Storing materials outside where they might get wet can also cause problems for recycling companies. Additional sorting steps may be needed to reduce the amount of unwanted materials in recyclate.

Recycling consumer waste

Many systems have been created to collect recyclable materials from general waste, each balancing the ease for the public and the cost for the government. The three main types of collection are drop-off centers, buy-back centers, and curbside collection. About two-thirds of the cost of recycling happens during the collection process.

Curbside collection includes many different systems, which mostly differ by where recyclables are sorted and cleaned. The main types are mixed waste collection, commingled recyclables, and source separation. A waste collection vehicle usually picks up the waste.

In mixed waste collection, recyclables are collected with the rest of the waste. Later, at a central sorting facility, the desired materials are sorted and cleaned. This method can result in some recyclable materials, like paper, becoming too dirty to reuse. However, it has benefits: the city does not need to pay for separate collection, no public education is required, and changes to recyclable materials can be made at the sorting facility.

In a commingled or single-stream system, recyclables are mixed but kept separate from non-recyclable waste. This reduces the need for cleaning after collection but requires teaching the public which materials can be recycled.

Source separation is the opposite approach, where each material is cleaned and sorted before collection. This method requires the least sorting after collection and produces the cleanest recyclables. However, it costs more to operate and needs a lot of public education to prevent contamination. In Oregon, USA, a survey found that about half of multi-family property managers had problems, including recyclable contamination from people who entered collection areas.

Source separation was once the preferred method because sorting mixed waste was expensive. However, new sorting technology has made this process cheaper, and many areas that used source separation have switched to commingled collection.

At buy-back centers, separated and cleaned recyclables are sold, giving people a reason to recycle and creating a steady supply. The processed material can then be sold. If profitable, this helps reduce greenhouse gas emissions; if not, it increases them. Buy-back centers usually need government support to operate. A 1993 report found that it costs about $50 to process a ton of material that can be sold for $30.

Drop-off centers require people to bring recyclables to a central location, such as a station or a reprocessing plant. These are the easiest to set up but often have low and unpredictable use.

For some materials, like plastic, new devices called recyclebots allow a type of recycling called DRAM (distributed recycling additive manufacturing). Studies show that using DRAM to make 3D printer filament from HDPE plastic in rural areas uses less energy than using new plastic or traditional recycling methods.

Another form of recycling mixes waste plastic with sand to make bricks in Africa. Studies have shown that these bricks can be sold for 100% profit and provide jobs. In West Africa, distributed recycling could create 19 million pavement tiles from 28,000 tons of plastic water bottles each year in Ghana, Nigeria, and Liberia. This method has also been used for recycling used masks from the COVID-19 pandemic.

Once commingled recyclables are collected, they are taken to a materials recovery facility where they are sorted. This process happens in several steps, many of which use automated systems. A truckload of material can be fully sorted in less than an hour. Some plants use automatic sorting, known as single-stream recycling. This may involve robotics and machine learning. Materials sorted include paper, different plastics, glass, metals, food scraps, and most batteries. Areas with these plants have seen a 30% increase in recycling rates. In the United States, there are over 300 materials recovery facilities.

At the start, commingled recyclables are removed from the collection vehicle and placed on a conveyor belt in a single layer. Large items like cardboard and plastic bags are removed by hand to avoid damaging later machines.

Next, machines like disk screens and air classifiers separate materials by weight, separating lighter items like paper and plastic from heavier items like glass and metal. Cardboard is separated from mixed paper, and common plastics like PET (#1) and HDPE (#2) are collected. This is usually done by hand, but some centers use special machines that use light to identify different materials. Plastics often do not mix well because of differences in their chemical makeup, similar to how oil and water separate.

Strong magnets are used to remove ferrous metals like iron, steel, and tin cans. Non-ferrous metals, like aluminum, are removed using magnetic eddy currents. A rotating magnetic field creates an electric current in aluminum cans, which is repelled by a strong magnetic field, pushing the cans out of the stream.

Finally, glass is sorted by color: brown, amber, green, or clear. This can be done by hand or by machines that use colored filters. Glass pieces smaller than 10 millimeters (0.39 inches) cannot be sorted automatically and are mixed as "glass fines."

In 2003, San Francisco’s Department of the Environment set a goal of zero waste by 2020. The city’s waste company, Recology, operates a highly effective sorting facility that has helped San Francisco achieve an 80% landfill diversion rate as of 2021. Other U.S. cities, like Los Angeles, have also reached similar rates.

Recycling industrial waste

Many government programs focus on recycling at home, but 64% of waste in the United Kingdom comes from industry. Recycling programs in industry often focus on how cost-effective they are. Cardboard is a common waste product because it is widely used in packaging. Companies that handle packaged goods, like retail stores, warehouses, and distributors, often recycle cardboard. Other industries work with specialized products based on the waste materials they handle.

Glass, lumber, wood pulp, and paper manufacturers deal with materials that are commonly recycled. However, independent tire dealers may collect and recycle rubber tires to make a profit.

The waste from burning coal in a coal-fired power station is called fuel ash or fly ash in the United States. It is a useful material used in concrete construction. It has a property called Pozzolanic activity.

Recycling levels for metals are generally low. In 2010, the International Resource Panel, hosted by the United Nations Environment Programme (UNEP), published reports about metal use and recycling rates. The reports noted that increased metal use in the 20th and 21st centuries has moved metal stocks from underground to above-ground uses in society. For example, in the United States, the amount of copper used per person grew from 73 to 238 kilograms between 1932 and 1999.

The report’s authors observed that metals can be recycled, so metal stocks in society act as large above-ground sources of materials, a concept called "urban mining." However, they found that many metals are not recycled at high rates. They warned that some rare metals used in devices like mobile phones, hybrid car batteries, and fuel cells are recycled so little that future recycling rates must increase significantly to avoid shortages of these materials.

The military recycles some metals. The U.S. Navy’s Ship Disposal Program breaks down old ships to reclaim steel. Ships may also be sunk to create artificial reefs. Uranium is a dense metal with properties better than lead and titanium for military and industrial uses. Uranium leftover from nuclear weapons and reactor fuel is called depleted uranium and is used by the U.S. military for items like armor-piercing shells and shielding.

The construction industry may recycle concrete and old road pavement, selling these materials for profit.

Some fast-growing industries, such as renewable energy and solar photovoltaic technology, are creating recycling policies before their waste streams become large, to prepare for future needs.

Recycling plastics is difficult because most programs cannot achieve the needed quality. Recycling PVC often results in downcycling, meaning only lower-quality products can be made from the material.

E-waste is a growing problem, with 20–50 million metric tons of global waste per year, according to the EPA. It is also the fastest-growing waste stream in the EU. Many recyclers do not handle e-waste responsibly. After the cargo barge Khian Sea dumped 14,000 metric tons of toxic ash in Haiti, the Basel Convention was formed to stop hazardous materials from reaching poorer countries. The e-Stewards certification was created to ensure recyclers follow strict environmental standards and help consumers find responsible recyclers. It works with other laws, like the EU’s Waste Electrical and Electronic Equipment Directive and the U.S. National Computer Recycling Act, to prevent harmful chemicals from entering water and air.

During recycling, items like televisions, monitors, cell phones, and computers are tested for reuse or repair. If broken, they may be taken apart for valuable parts if labor is cheap. Other e-waste is shredded into pieces about 10 centimeters (3.9 inches) in size and manually checked to remove toxic batteries and capacitors. Remaining pieces are further shredded to 10 millimeters (0.39 inches) and passed under a magnet to remove ferrous metals. An eddy current separates non-ferrous metals, which are sorted by density using a centrifuge or vibrating plates. Precious metals can be dissolved in acid, sorted, and melted into ingots. Glass and plastic are separated by density and sold for reprocessing. Televisions and monitors must be manually disassembled to remove lead from CRTs and mercury from LCDs.

Vehicles, solar panels, and wind turbines can also be recycled. They often contain rare-earth elements (REE) and other critical materials. Electric car production requires large amounts of REE.

While some critical materials can be recovered, environmental engineer Phillipe Bihouix reported that recycling elements like indium, gallium, germanium, selenium, and tantalum is still very difficult, and their recycling rates remain low.

Plastic recycling is the process of recovering scrap or waste plastic and reprocessing it into useful products, sometimes completely different from their original form. For example, soft drink bottles might be melted and turned into plastic chairs and tables. Some plastics can only be recycled 2–3 times before their quality drops too much to use again.

Some plastics are remelted to make new objects, like converting PET water bottles into polyester for clothing. A drawback is that the polymer’s molecular weight may change, and unwanted substances in the plastic may increase with each remelt.

A recycling facility was sent to the International Space Station in late 2019. It turns plastic waste and unused parts into feedstock for 3D printing.

For some polymers, it is possible to convert them back into monomers. For example, PET can be treated with alcohol and a catalyst to form a dialkyl terephthalate, which can be used with ethylene glycol to create new polyester. In 2019, Eastman Chemical Company announced methods to handle more types of used materials.

Another process converts mixed polymers into petroleum through thermal depolymerization. This method can accept almost any polymer, including thermoset materials like vulcanized rubber and biopolymers from agricultural waste. The chemicals produced can be used as fuels or feedstock. A RESEM Technology plant in Carthage, Missouri, uses turkey waste as input. Gasification is similar but not technically recycling since polymers are not likely to be the result. Plastic pyrolysis can convert petroleum-based waste like plastics into fuels and carbon. Suitable materials for pyrolysis include:

• Mixed plastic (HDPE, LDPE, PE, PP, Nylon, Teflon, PS, ABS, FRP, PET, etc.)
• Mixed waste plastic from paper mills
• Multi-layered plastic

Recycling codes

To help recyclers and manufacturers, a coding system was created. This system provides a consistent way to identify plastic types. The recycling code for plastics was introduced in 1988 by the plastics industry through the Society of the Plastics Industry. Because municipal recycling programs usually focus on packaging items like bottles and containers, the resin coding system offered a way to identify the plastic type in these common items found in household waste.

In the United States, plastic products are labeled with numbers 1–7 based on the type of plastic. Type 1 (polyethylene terephthalate) is used in soft drink and water bottles. Type 2 (high-density polyethylene) is found in hard plastics like milk jugs, laundry detergent bottles, and some dishware. Type 3 (polyvinyl chloride) includes items such as shampoo bottles, shower curtains, hula hoops, credit cards, wire covering, medical equipment, siding, and piping. Type 4 (low-density polyethylene) is used in shopping bags, squeezable bottles, tote bags, clothing, furniture, and carpet. Type 5 (polypropylene) is found in syrup bottles, straws, Tupperware, and some car parts. Type 6 (polystyrene) is used in meat trays, egg cartons, clamshell containers, and compact disc cases. Type 7 includes all other plastics, such as bulletproof materials, 3- and 5-gallon water bottles, phone and tablet frames, safety goggles, and sunglasses. A recycling code or the chasing arrows logo on a product does not automatically mean it is recyclable but explains the material’s type. Types 1 and 2 are the most commonly recycled.

Cost–benefit analysis

Fiscal efficiency refers to how well money is used. Sometimes cities find that recycling saves resources compared to other ways of handling waste. Two years after New York City said recycling would be "a drain on the city," leaders later saw that a good recycling system could save the city over $20 million. Many cities benefit financially from recycling because it lowers costs for landfills. A study by the Technical University of Denmark, as reported by The Economist, found that in 83 out of 100 cases, recycling is the most efficient way to handle household waste. However, a 2004 study by the Danish Environmental Assessment Institute found that burning waste (incineration) was the best method for disposing of drink containers, even aluminum ones.

Fiscal efficiency is different from economic efficiency. Economic studies of recycling often ignore "externalities," which are costs or benefits that affect people not directly involved in a transaction. For example, burning waste may reduce air pollution and greenhouse gases, while landfills may cause waste to leak into the environment. Without taxes or subsidies, businesses and consumers might ignore these effects even if they harm society. If pollution from landfills or incinerators is not properly controlled, these methods may seem cheaper than they are, because part of their cost is the harm to nearby people. Because of this, some people have pushed for laws that increase demand for recycled materials. The United States Environmental Protection Agency (EPA) said that recycling helped reduce the country’s carbon emissions by 49 million metric tonnes in 2005. In the United Kingdom, the Waste and Resources Action Programme reported that recycling efforts in Great Britain reduce CO₂ emissions by 10–15 million tonnes each year. The question for economic efficiency is whether these benefits are worth the extra cost of recycling and whether laws that create demand for recycled materials are helpful.

For recycling to be both economically and environmentally useful, certain conditions must be met. These include having enough recyclable materials, a system to collect them from waste, a nearby factory to reprocess them, and a market for the recycled products. The last two requirements are often overlooked. Without both an industrial market for products made from recycled materials and a consumer market for those products, recycling is incomplete and only "collection."

Free-market economist Julian Simon said there are three ways society can manage waste: (a) government control, (b) using taxes and subsidies to guide behavior, and (c) letting individuals and the market decide. These ideas divide economic thinkers today.

Frank Ackerman supports strong government involvement in recycling. He believes the benefits of recycling cannot be fully measured using traditional free-market economics. Allen Hershkowitz also supports government action, saying recycling is a public service like education or policing. He argues that manufacturers should take more responsibility for waste disposal.

Paul Calcott and Margaret Walls support using taxes and subsidies to encourage recycling without encouraging illegal dumping. Thomas C. Kinnaman believes a tax on landfills would push people, companies, and local governments to recycle more.

Most free-market thinkers oppose subsidies and government control, saying they waste resources. They argue that if cities charge the full cost of garbage collection, private companies would recycle materials only if the benefits of recycling are greater than the costs (e.g., aluminum) and would not recycle materials where the benefits are less than the costs (e.g., glass). Cities, however, often recycle even when they do not earn enough money from selling paper or plastic to cover the cost of collection and must pay private companies to take it. Terry Anderson and Donald Leal think all recycling programs should be run by private companies and would only operate if the money saved by recycling exceeds its costs. Daniel K. Benjamin argues that recycling can cost cities more than twice as much as landfills. He notes that landfills in the United States are heavily regulated, so their pollution effects are minimal, and that recycling also uses energy and may create pollution, which might not be less than using new materials.

Some countries trade unprocessed recyclable materials. Some people worry that recyclable materials sold to other countries may end up in landfills instead of being reused. One report said that in America, 50–80 percent of computers meant for recycling are not actually recycled. There are reports of illegal waste being sent to China for recycling, where workers’ health and the environment may be harmed. Although the Chinese government has banned these practices, they have not been completely stopped. In 2008, the prices of recyclable waste dropped sharply before rising again in 2009. Cardboard averaged about £53 per tonne from 2004 to 2008, then dropped to £19 per tonne and rose to £59 per tonne in May 2009. PET plastic averaged about £156 per tonne, dropped to £75 per tonne, and rose to £195 per tonne in May 2009.

Some regions struggle to use or sell all the recycled materials they collect. This is most common with glass: both Britain and the U.S. import large amounts of wine bottled in green glass. While much of this glass is recycled, outside the American Midwest, there is not enough wine production to use all the recycled glass. The extra must be used for less valuable purposes, like building materials, or sent back into the waste stream.

Similarly, the northwestern United States has trouble finding markets for recycled newspaper because of many pulp mills in the region and competition from Asian markets. In other parts of the U.S., demand for used newsprint has changed a lot over time.

In some U.S. states, a program called RecycleBank pays people to recycle. It receives money from local governments for reducing the need for landfill space. The program uses a system where all materials are automatically sorted.

Criticisms and responses

Recycling is difficult because many products are not made to be recycled. In the USA, about 6 to 7 percent of plastic is recycled. The idea of sustainable design aims to fix this problem. This idea was introduced in the 2002 book Cradle to Cradle: Remaking the Way We Make Things by architect William McDonough and chemist Michael Braungart. They suggest that every product and its packaging should have a full cycle planned. This means that each part of the product can either return to nature through biodegradation or be recycled forever.

Recycling keeps waste out of landfills, but it misses some parts of waste that are spread out. Critics say that recycling all waste is not possible because some waste becomes too diluted, making it too costly to recover.

Like environmental economics, it is important to look at all costs and benefits. For example, paperboard used for food packaging is easier to recycle than most plastics. However, it is heavier to transport and may cause more waste from spoiled food. Money spent on recycling can sometimes lead to dishonest practices.

Some people argue that recycling does not always save energy or money. They say that the energy used to collect and transport recyclables can outweigh the energy saved in making new products. They also say that jobs in the recycling industry may not replace jobs lost in industries like logging or mining. Additionally, materials like paper pulp can only be recycled a few times before they become too damaged for reuse.

The energy saved by recycling depends on the material and the method used to measure it. Scientists use life-cycle analysis and exergy, which measures useful energy, to study this. In general, making products from recycled materials uses much less energy than making them from raw materials.

Some researchers use a method called emergy (spelled with an m) to calculate energy. Emergy looks at how much energy is needed to create or change materials. Studies using emergy analysis show that materials with high refining costs can benefit most from recycling. Systems that recycle materials back into their original form are the most efficient, followed by systems that reuse materials for different purposes, and then systems that use parts of products to make new products.

The Energy Information Administration (EIA) says that paper mills use 40 percent less energy to make paper from recycled materials than from fresh wood. Some critics argue that recycling uses more energy than sending waste to landfills because it requires an extra truck to collect recyclables. However, recycling supporters say that using a second truck for logging is avoided, so the total energy used is the same. Emergy studies show that materials like fly ash, aluminum, recycled concrete, recycled plastic, and steel save more energy than recycling wood.

It is hard to measure the energy used in waste disposal because energy and material flows are complex. The energy saved by recycling depends on the material and the process used. Aluminum is widely agreed to use much less energy when recycled than when made from raw materials. The EPA says that recycling aluminum cans saves 95 percent of the energy needed to make the same amount from bauxite. In 2009, more than half of all aluminum cans produced came from recycled materials. Similarly, using recycled cans to make new steel reduces greenhouse gas emissions by 75 percent.

Some economists say that saving landfill space is not worth the energy and pollution from recycling. Others say that making recycled paper uses less energy and water than cutting down, processing, and transporting trees. If less recycled paper is used, more energy is needed to grow forests until they are as sustainable as natural forests.

Other studies say that recycling alone is not enough to stop using non-renewable resources. Recycling materials across countries can lead to different results because of how they are traded. As more natural resources are used, they will eventually run out. Recycling can only slow this process, not stop it. Completely reusing all materials is impossible because small amounts of materials can spread into the environment, harming ecosystems. This idea was first described by Karl Marx as the "metabolic rift," where resources from rural areas are taken to cities, creating waste that harms the environment. Improving energy efficiency can sometimes lead to more energy use, a concept called Jevon’s paradox.

Journalist John Tierney says that recycling is often more expensive for cities than sending waste to landfills. He calls recycling "the most wasteful activity in modern America."

The money saved by recycling depends on how well the recycling program works. The Institute for Local Self-Reliance says that costs depend on things like landfill fees and how much waste is recycled. Communities save money when they treat recycling as a replacement for traditional waste systems, not an extra step. This includes changing how waste is collected or using different trucks.

In some cases, recycled materials are more expensive than raw materials. Virgin plastic costs 40 percent less than recycled plastic. A study by the EPA found that the cost of clear glass ranged from $40 to $60 per ton between July and August 1991.

Public participation rates

Changes that have been shown to increase recycling rates include:

• Putting all recyclable materials into one bin (single-stream recycling)
• Charging people based on how much trash they throw away (pay as you throw fees)

A study by social psychologist Shawn Burn found that talking directly to neighbors in a community is the most effective way to increase recycling. In her study, 10 block leaders spoke with their neighbors to encourage recycling. A different group of people received flyers about recycling instead. The neighbors who were directly spoken to recycled more than those who only received flyers. Because of this, Shawn Burn believes that personal conversations within small groups help encourage recycling. Another study by Stuart Oskamp showed that people are more likely to recycle if their friends or neighbors also recycle.

Many schools have created recycling clubs to teach students about recycling. These clubs help students learn to recycle at school and at home.

Recycling rates for metals vary greatly. Titanium and lead are recycled more than 90% of the time. Copper and cobalt are recycled about 75% of the time. Only about half of aluminum is recycled. Most other metals are recycled less than 35%, and 34 types of metals are recycled less than 1%.

Between 1960 and 2000, the world made 25 times more plastic than it did in 1960, but less than 5% of that plastic was recovered for reuse. Many studies have looked at ways to encourage people to recycle. Some people think recycling is not natural because it needs planning for the future, while humans usually focus on short-term needs. They suggest using social pressure to help people recycle. However, recent studies say social pressure does not work well in large communities. One reason is that social pressure works better in small groups of 50 to 150 people, not in large communities. Another reason is that recycling is often done in private, not in public.

As recycling collection became more common, some people still placed recyclables in the same bins as trash, even though they were meant for separate collection.

Embracing a circular economy through advanced sorting technologies

A circular economy aims to help goods, parts, and materials last longer, which reduces waste and uses resources more efficiently. New sorting methods, such as optical and robotic sorting, can separate useful materials from waste, reducing the need for new raw materials and helping move toward a circular economy.

Teaching and informing people about recycling and reuse programs can help communities accept these practices and use more sustainable methods. Using a circular economy with modern sorting technology and community involvement can reduce environmental impact, save natural resources, and create job opportunities. According to Melati et al., to successfully move to a circular economy, laws and rules must support sustainable practices and address challenges that may arise when implementing these ideas.