Plastic recycling is the process of turning plastic waste into new products. Recycling helps reduce the need for landfills, saves natural resources, and protects the environment from plastic pollution and harmful gases. Recycling rates for plastic are lower than for other materials like aluminum, glass, and paper. Between the start of plastic production and 2015, the world created about 6.3 billion tons of plastic waste. Only 9% of this waste was recycled, and less than 1% was recycled more than once. Of the remaining waste, 12% was burned, and 79% was either placed in landfills or released into the environment as pollution.
Most plastic does not break down naturally and, if not recycled, spreads throughout the environment, causing pollution. For example, by 2015, about 8 million tons of plastic waste entered the oceans each year, harming ocean life and creating large areas of floating trash.
Most plastic recycling today uses a mechanical process, which involves melting and reshaping plastic into new items. This method can weaken plastic molecules over time and requires sorting waste by color and type before processing, which is often difficult and costly. Mistakes during this process can create materials with uneven qualities, making them less useful for industries. While filters in mechanical recycling help reduce tiny plastic pieces, even the best filters cannot stop all tiny plastic particles from entering water systems.
In feedstock recycling, plastic waste is broken down into its original chemical components, which can be used to make new plastic. This method requires more energy and money. Alternatively, plastic can be burned to produce energy instead of using fossil fuels, or it can be chemically changed into other useful materials. In some countries, burning plastic is the main way waste is handled, especially in places where landfills are not allowed.
Plastic recycling is near the bottom of the waste management hierarchy, meaning that reducing plastic use and reusing items are better long-term solutions for protecting the environment. Recycling has been promoted since the 1970s, but due to economic and technical challenges, it did not significantly change how plastic waste was managed until the late 1980s.
History
Plastics were discovered before the 20th century, but large-scale production began during World War II. Nylon was used instead of silk in parachutes, and Perspex was used as a lightweight replacement for glass in airplanes. After the war, these materials were sold widely. The plastic age started around 1950, during the post-war economic growth.
In the 1960s and 1970s, global environmental movements led to the creation of environmental agencies in the United States (EPA, 1970), the European Union (DG ENV, 1973), Australia (EPA, 1971), and Japan (JEA, 1971). People became more aware of environmental issues, and plastic waste was examined closely. The first major effort to reduce plastic pollution was the MARPOL agreements in 1973 and 1978, which banned dumping plastics into the ocean.
As rules about the environment grew, the plastics industry tried to protect its business by influencing lawmakers. In the United States, the 1970 Resource Recovery Act encouraged recycling and using waste for energy. By 1976, over 1,000 attempts were made to pass laws banning or taxing plastic packaging. The plastics industry responded by promoting recycling and launching a $50 million annual campaign, led by groups like Keep America Beautiful, to encourage recycling and support curbside recycling programs.
However, recycling plastic was not economically possible with the technology available at the time. A report from April 1973 by industry scientists said, "There is no recovery from obsolete products" and that "plastic properties degrade during use and reclamation." The report also said sorting plastic was "infeasible." Other scientific reports also pointed out many technical challenges.
Until the 1980s, most plastic waste was sent to landfills. After that, burning plastic waste increased. Early incinerators often lacked advanced systems to control pollution, leading to the release of harmful chemicals like dioxins.
In the late 1980s, recycling efforts for plastic began seriously. In 1988, the U.S. Society of the Plastics Industry formed the Council for Solid Waste Solutions to promote recycling. This group encouraged cities to start or expand plastic waste collection and pushed states to label plastic products with recycling symbols.
In 1988, the industry introduced resin identification codes to help identify different types of plastic at recycling centers.
During the 1990s, globalization led to the export of plastic waste from wealthy countries to developing and middle-income nations, where sorting and recycling was cheaper. Plastic waste trade grew rapidly after 1993.
Some governments count waste as recycled if it is exported, even if it ends up in landfills. This practice, called environmental dumping, occurs because environmental laws are weaker in poorer countries. By 2016, about 14 million tons of plastic waste were exported, with China receiving 7.35 million tons. Much of this was low-quality mixed plastic that ended up in landfills. However, China used recycled plastic in manufacturing, and most imported waste was processed with basic technology. High-income countries like Germany, Japan, the United Kingdom, and the United States were the top exporters.
In 2017, China limited imports of waste plastics through Operation National Sword. Exporters then sent waste to countries in Southeast Asia, such as Vietnam and Malaysia, as well as Turkey and India. Indonesia, Malaysia, and Thailand strengthened border controls to stop illegal imports. Illegally imported waste was returned or refused entry, causing plastic waste to pile up in ports.
With fewer export options, attention shifted to local solutions. One idea was to tax plastic producers to support recyclers.
In 2019, the Basel Convention regulated international trade in plastic waste. Under the convention, any country can ban imports of hazardous plastic waste and, since January 2021, some mixed plastic waste. Countries must manage their waste responsibly through alternative importers or by improving recycling capacity.
The COVID-19 pandemic temporarily reduced plastic waste trade due to slower waste management operations, shipping delays, and low oil prices, which made recycling less profitable.
In 2015, the European Commission’s "Action Plan" for a circular economy identified plastics as a key area for reducing waste. In 2017, the Commission focused on making all plastic packaging recyclable by 2030. In 2018, the Commission released a plan outlining goals for global plastic recycling efforts.
Production and recycling rates
The total amount of plastic made worldwide up to 2015 is believed to be 8.3 billion tonnes. About 6.3 billion tonnes of this became waste. Of this waste, 79% ended up in landfills or the environment, 12% was burned, and 9% was recycled. Only about 1% of all plastic was recycled more than once. By 2017, 9% of the 9 billion tonnes of plastic produced was recycled.
By 2015, the world produced about 381 million tonnes of plastic each year. That year, 19.5% was recycled, 25.5% was burned, and 55% was disposed of, mostly in landfills. These numbers are lower than recycling rates for materials like paper, metal, and glass. Even though more plastic is being recycled or burned each year, the amount of plastic waste left behind is still increasing. Plastic production may reach about 800 million tonnes per year by 2040. However, using all possible solutions could reduce plastic pollution by 40% compared to 2016 levels.
Recycling rates depend on the type of plastic. Common plastics have different chemical and physical properties, which affects how easy they are to sort and process. This influences the value and market size of recycled materials. PET and HDPE have the highest recycling rates, while polystyrene and polyurethane are rarely recycled.
One reason for low plastic recycling is weak demand, as plastic materials often have poor or inconsistent qualities. The amount of plastic that can be fully recycled, instead of being downcycled or wasted, can increase if manufacturers avoid mixing different packaging materials and remove contaminants. The Association of Plastics Recyclers has created a "Design Guide for Recyclability" to help with this.
The most common plastic products include packaging made from LDPE (such as bags, containers, and food wrap), containers made from HDPE (like milk bottles, shampoo bottles, and ice cream tubs), and PET (such as water and drink bottles). These products make up about 36% of all plastic production. Plastics are also widely used in construction, textiles, transportation, and electrical equipment, which account for a large share of the plastics market.
Plastic use varies by country and community, but it is found nearly everywhere. In 2022, North American countries (NAFTA) used 21% of the world’s plastic, followed closely by China (20%) and Western Europe (18%). In North America and Europe, people used about 94 kg and 85 kg of plastic per person each year, respectively. In China, the average was 58 kg per person each year.
In 2012, the European Union collected 25.2 million tonnes of post-consumer plastic waste. Of this, more than 60% (15.6 million tonnes) was recovered, and 40% (9.6 million tonnes) was thrown away as household waste. Of the 15.6 million tonnes recovered, about 6.6 million tonnes was recycled, while the rest was likely used as fuel or burned to produce energy. Europe recycles about 26% of its plastic waste, the highest rate globally.
The recycling efforts of the largest plastic waste producers have the biggest impact on global recycling averages. These producers include both developed and developing countries. Some share official recycling data, while others only provide partial information, usually from urban areas. This makes it hard to compare recycling rates accurately, as reported numbers vary widely.
Although the European Union is not a country, recycling rules are often set at the EU level.
Identification codes
Many plastic items have symbols that show the type of material they are made from. These symbols are called resin identification codes (RICs) and are used worldwide. They were created in 1988 by the Society of the Plastics Industry (now called the Plastics Industry Association) in the United States. Since 2008, a group called ASTM International has managed these codes.
RICs are not required in all countries, but many companies choose to include them on their products. More than half of U.S. states have laws that require plastic items to be labeled. There are seven RICs: six for the most common types of plastic and one for other materials. The European Union uses a similar system with nine codes, including ones for ABS and polyamides.
RICs are not very important for single-stream recycling because these systems use machines that sort materials automatically. However, in some countries, people must separate their plastic waste by type before it is collected. For example, in Japan, PET bottles are collected separately for recycling.
Waste composition
Plastic waste is made up of different types of polymers. Polyolefins make up almost half of all plastic waste. Over 90% of this waste is made of thermosoftening polymers, which can be melted again.
Collecting and sorting
Recycling starts with collecting and separating waste. Many countries use curbside collection, where waste is picked up from homes. This waste is sent to a recycling center or a materials recovery facility. At these places, plastic is separated, cleaned, and sorted for sale. Materials that cannot be recycled are sent to landfills or burned. These steps cost a lot of money and use a lot of energy.
Sorting plastic is harder than sorting other materials because there are many different types. For example, glass is divided into three groups: clear, green, and amber. Metals are usually steel or aluminum and can be separated using magnets or special machines. Paper is often sorted into one group.
About 75% of plastic waste comes from six common types of plastic. The rest includes many other types, such as polyurethanes and synthetic fibers. Items made from the same type of plastic may not work well together if they have different additives. Additives are chemicals added to improve plastic’s strength or color, such as stabilizers, fillers, and dyes. Clear plastic is more valuable because it can be colored after recycling, while black or strongly colored plastic is less valuable because it affects the final product’s color. Plastic is usually sorted by both type and color.
Many methods and tools are used to sort plastic. These methods can be combined, but none are perfect. Sorting accuracy varies between recycling centers, leading to inconsistent quality of recycled products. This inconsistency makes recycling more difficult.
Hand sorting is the oldest and simplest method. In some countries, waste pickers do this manually, while in recycling centers, workers pick items off a conveyor belt. This method requires little technology and money but uses a lot of labor. Even though plastic items have codes, workers often don’t have time to check them, causing errors. Advanced facilities still use manual workers to fix mistakes. These jobs can be unsanitary.
Plastic can be sorted by its density. First, plastic is broken into small pieces, washed, and separated using gravity. This can be done with air-based systems, water-based systems, or a method called the float-sink test. These methods work best for plastics with different densities, but some plastics have similar densities. For example, polypropylene (PP) and polyethylene (PE) are similar, as are polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC). If plastic has fillers, its density might change. The lighter PP and PE group is called mixed polyolefin (MPO) and is sold as a low-value product. The heavier group is usually not recyclable.
In electrostatic sorting, plastic is charged using friction, causing it to have an electric charge. Different plastics are charged differently. Then, the charged plastic is passed through an electric field, which directs it into collectors. This method works best with dry, uniform plastic pieces. It can be used with density sorting to fully separate plastics, even if they are different colors.
Automated sorting uses sensors connected to computers. The sensors identify items and send them to the correct place. Near-infrared light can help identify plastic types, but it may not work well for black or strongly colored plastics or materials like plastic-coated paper. Optical sorting, such as color sorters or advanced imaging, can separate plastics by color. Sensor-based sorting is expensive but produces high-quality recycled materials.
Plastic waste comes from two main sources: industrial scrap and consumer waste. Industrial scrap, also called post-industrial resin, is created during manufacturing. It includes materials like trimmings, sprues, and rejected pieces. This scrap is clean, known, and valuable. It is often sold privately and not included in official statistics. Consumer waste is plastic used by people and is usually more difficult to recycle.
Mechanical recycling
Most plastic waste is made from thermoplastic materials, which can be melted and reshaped into new items through mechanical recycling. This is the most widely used recycling method worldwide and is the only type used in many countries. It is simple and cost-effective. It also has a smaller environmental impact compared to other recycling methods. However, the quality of recycled products can sometimes be lower, which limits how useful the recycled plastic can be.
Thermoplastic materials are melted at temperatures between 150–320 °C (300–610 °F), depending on the type of plastic. This process can cause unwanted chemical changes that weaken the plastic. These changes may create harmful gases, change the color of the plastic, or make it smell bad. Certain additives, like those designed to help plastic break down, can speed up this damage. Flame retardants, which are used to reduce fire risk, can also cause problems. The quality of the final product also depends on how well the plastic was sorted before recycling. Some plastics do not mix well when melted and separate into layers, which weakens the material. In extreme cases, certain plastics, like PVC, can release harmful chemicals that damage other types of plastic, such as PET.
Many of these issues can be solved with special technologies, though these solutions may cost more money. Stabilizers can help protect plastic from damage during recycling. Harmful gases can be removed using specific techniques. Flame retardants can be removed through chemical treatments, and harmful metal additives can be neutralized with special chemicals. Mixed plastics can be improved by using compatibilizers, which are small molecules that help different plastics mix better. These molecules act like tiny "nails" to hold the plastics together. However, compatibilizers work best with mixtures of only two types of plastic and are not cost-effective for mixtures with many different plastics. Even with these solutions, it is difficult to recycle plastic to a quality that is safe for food contact.
In closed-loop recycling, used plastic is recycled into new items of the same quality and type. For example, used drink bottles can be turned back into new drink bottles. This is an example of a circular economy, where materials are reused repeatedly. However, keeping plastic quality the same during repeated recycling is difficult because the plastic breaks down over time and may become contaminated. In 2013, only 2% of plastic packaging was recycled in this way. So far, the only successful industrial example of closed-loop recycling is with PET bottles. This is because PET can often be repaired after breaking down. Chemicals called chain extenders can help rejoin broken plastic chains. One such chemical is pyromellitic dianhydride.
In open-loop recycling, also called secondary recycling or downcycling, the quality of the plastic decreases each time it is recycled. Eventually, the material becomes too damaged to be reused. This is the most common type of recycling. For example, PET bottles are often recycled into products like clothing fabric, which is a major use for recycled PET. Studies show this process helps the environment by reducing the need for new plastic. However, if recycled plastic is used to make products that would not have been made otherwise, it does not help the environment.
Lower-quality recycled plastic can sometimes be mixed with new plastic to improve its strength. Compatibilized plastics can replace new plastic if they have the right properties for manufacturing. Low-quality mixed plastics are often used in open-loop recycling, but these products are usually dark in color and have limited uses, such as outdoor furniture or plastic lumber. These materials are weak but inexpensive, so they are made into thick planks to increase strength.
Although thermoset plastics do not melt, methods exist to recycle them. These methods usually involve crushing the material into small pieces and mixing them with a binding agent to create a new composite material. For example, polyurethane can be recycled into a type of foam used in products like cushions.
Feedstock recycling
Feedstock recycling, also called chemical recycling or tertiary recycling, breaks down polymers into their basic chemical parts, called monomers. These monomers can then be used to make new plastics. In theory, this process allows plastics to be recycled many times because impurities, additives, dyes, and chemical defects are completely removed during each cycle. However, in practice, chemical recycling is much less common than mechanical recycling. This is because current technology cannot reliably break down all types of polymers on a large scale, and the equipment and costs for chemical recycling are much higher. In 2018, Japan had one of the highest feedstock recycling rates globally at about 4%, compared to 23% for mechanical recycling. At the same time, Germany reported a feedstock recycling rate of only 0.2%. Breaking down, purifying, and re-making plastics through chemical recycling often uses a lot of energy, which usually results in a higher carbon footprint than mechanical recycling. Some plastics, like PET, PU, and PS, are broken down commercially to some extent, but feedstock recycling of polyolefins, which make up nearly half of all plastics, is limited.
Certain polymers, such as PTFE, polystyrene, nylon 6, and polymethylmethacrylate (PMMA), can be broken down through a process called thermal depolymerisation when heated to very high temperatures. These reactions require clean and well-sorted waste to produce quality results, but even with clean materials, not all breakdown reactions are fully efficient. Some competing chemical reactions may occur, so the resulting monomers must be purified before they can be reused. Feedstock recycling of polystyrene has been developed commercially, but global production capacity remains limited.
Condensation polymers that have specific chemical groups, such as esters and amides, can be completely broken down through processes like hydrolysis or solvolysis. These are chemical processes that may also be helped by enzymes like PETase. These methods use less energy than thermal depolymerisation but are not available for all types of polymers. Polyethylene terephthalate (PET) has been the most studied polymer in this area and has reached commercial use.
Energy recovery
Energy recovery, also called energy recycling or quaternary recycling, is a process where waste plastic is burned to produce energy instead of using fossil fuels. This method is included in recycling data reported by many countries, though the European Union does not classify it as recycling. It is different from incineration without energy recovery, which has been more common historically but does not reduce plastic production or fossil fuel use.
Energy recovery is often used as the final option for managing waste, a role once held by landfills. In cities, limited space for new landfills and regulations, such as the EU's Landfill Directive, encourage this method. Compared to other recycling options, energy recovery is mainly chosen for its economic benefits. When proper technology is used, plastics do not need to be separated from other waste, which lowers costs. Electricity demand is more predictable than the market for recyclable materials, making energy recovery seem less risky financially. As a waste management method, it is very effective, reducing waste volume by about 90%. The leftover material is either sent to landfills or used to make cinder blocks. While energy recovery produces high levels of carbon dioxide, comparing its environmental impact to other recycling methods is complicated. For example, recycling reduces greenhouse gas emissions more than incineration but is more expensive than investing in renewable energy.
Plastic waste can be burned directly as refuse-derived fuel (RDF) or converted into synthetic fuel through chemical processes. In both cases, polyvinyl chloride (PVC) must be avoided or handled with special equipment to prevent the release of hydrogen chloride (HCl), which can damage equipment and contaminate fuel. Burning waste has long been linked to harmful dioxins, but advanced technology can reduce these risks. Incineration with energy recovery is the most common method, while newer technologies like pyrolysis face challenges related to cost and technical limitations.
Mixed plastic waste can be broken down into synthetic fuel through a process called depolymerization. This fuel has a higher heating value than the original plastic and burns more efficiently, though it is still less efficient than fossil fuels. Pyrolysis is the most common conversion method, often used in incineration cycles or to produce fuel for sale. This process creates a range of chemical products, including gases and liquids. Using catalysts can improve the quality and value of these products. Liquid fuels made from plastic can be used as synthetic diesel, with commercial production in some countries. Studies show that converting plastic to fuel can reduce fossil fuel use and lower greenhouse gas emissions by about 15%.
Compared to the widespread use of incineration, plastic-to-fuel technologies have faced challenges in becoming economically practical.
Other uses
In Japan, about 200,000 tonnes of waste plastic are processed each year. This plastic is sometimes used as a source of carbon in the recycling of scrap steel, replacing a material called coke.
Recycled plastic is increasingly used in building materials. Crushed plastic can act as a filler or support material in some construction projects. While it is not typically used in strong concrete structures, plastic can be added to asphalt used for roads, creating rubberized asphalt. It may also be used in the base layer of roads and in insulation made from recycled materials. An example is the creation of roads made mostly or partly of plastic. This practice is common in India, where by 2021, over 700 kilometers of highways had been built using this method. However, this process might cause harmful chemicals from the plastic to leak into the environment.
Scientists are studying ways to use plastic in materials like concrete. Methods include making plastic materials such as PET bottles and plastic bags denser to use as part of concrete, or breaking down PET into smaller parts to use as a binding material in concrete. These experiments aim to improve the strength and usefulness of concrete.
Criticism
Research on plastic recycling shows that most plastic cannot be recycled in a cost-effective way at this time. This has led to some cases where plastic waste placed in recycling bins was not recycled and was instead treated as regular trash. Resin identification codes use the recycling symbol, but they have been criticized because they suggest that items with these codes can always be recycled, but this isn't always the case.