PET bottle recycling

PET and rPET are both used in the creation of bottled water (still and carbonated). Bottled water companies have been voluntarily using rPET in the production and many companies are producing bottles using 100% rPET nowadays. Such companies include Dasani, Fiji and Nestlé Pure Life. Other goods bottled in PET include oil, vinegar, milk, and shampoo. These bottles are closed with polyolefin screw closure with antitamper ring, and have a label which may be printed on paper or plastic and may be glued on. The resin may be colourless or tinted blue, green or brown, or pigmented white. When manufacturing these water bottles, the energy used to mold the resin into its shape varies based on the bottle shape and its thickness. Some bottles have complex shapes such as Dasani while other bottles have a very simple form such as Smartwater. Therefore, the energy used to create these bottles can range from 8.33 - 20 MJ/kg where the units "MJ" represent megajoules, a unit for energy. The emissions associated with the production range from 0.034 – 0.046 kg C02-eq per 500mL. == Collection and sorting ==

The empty PET packaging is discarded by the consumer after its use and becomes PET waste. In the recycling industry, this is referred to as "post-consumer PET". All types of PET packaging, including bottles are usually marked with the recycle symbol 1. The bottles are sent to trash centers (materials recovery facilities) and get sorted out from the other disposable items. There are times when the recyclables are taken to a transfer station first. At this facility, the materials are stored, sorted, and compacted before being transported to a true recycling facility where they are further processed. This step is especially common in areas where MRFs are located far from collection points Here the PET bottles are sorted and separated from other objects and bottles made of other materials Collection and sorting process in Switzerland Source: For material recovery facilities, colored PET bottles are therefore a cause for concern as they can impact the financial viability of recycling such materials. The Plastics Recyclers Europe (PRE, Brussels, Belgium), that an upsurge in a variety of PET colors would be a problem because no market exists for them in the current recycling climate. From there, there are two types of recycling; chemical or mechanical. Types of collections • Deposit: some countries have legislated a deposit for packaging including PET bottles. In the EU, deposit schemes average an 86% recovery rate. • Collect: waste collectors pick up PET bottles mixed into some other stream (54% recovery in EU). • Bring: consumers take PET bottles and place them into a container (43% recovery in EU). Different countries have opted for different systems. • France: public voluntarily puts PET bottles into containers for plastic bottles and metal packaging. The stream in which PET bottles are collected comprises metallic packaging, plastic bottles, and unwanted contaminants. • Germany: PET bottles carry a deposit, so PET bottles are collected by retailers. The collected stream consists almost entirely of PET bottles. • Singapore: plastic bottles are collected with glass bottles. The stream in which PET bottles are collected comprises PET bottles, other plastic bottles and glass bottles, and contamination. • Switzerland: Retailers contribute a fee to a national operator (PRS) who manages collection bins, sorting and production of rPET flake. The stream in which PET bottles are collected is intended to be PET bottles, but contains other PET packaging and other contamination. The stream in which PET bottles are collected varies by municipality, but always require further sorting. • United States: curbside recycling to which most consumers have access. The waste hauler brings the recycled material to a material recovery facilities (MRFs) where it is further separated. The PET is then baled and sent on to a PET reclaimer. The PET reclaimer processes the bale, grinding the PET into flakes. Some do additional processing to make ready for food grade packaging. == Chemical recycling ==

This method of recycling is not very common anymore since it is a more intensive and expensive process. Chemical recycling involves breaking down the plastic into its monomers which can be used as building blocks for new materials. Because of the use of more energy for the chemical reactions to take place, chemical recycling produces more emissions than mechanical recycling. This process is also known as "Tertiary" or "Advanced" recycling. Polyethylene terephthalate can be depolymerized partially or completely to yield the constituent oligomers or the monomers, MEG and PTA or DMT. The main processes are glycolysis, methanolysis or hydrolysis. After purification, the oligomers or monomers can be used to prepare new recycled polyethylene terephthalate ("r-PET"). The ester bonds in polyethylene terephthalate may be cleaved by hydrolysis, or by transesterification. The reactions are simply the reverse of those used in production. Partial glycolysis Partial glycolysis (transesterification with ethylene glycol) converts the rigid polymer into short-chained oligomers that can be melt-filtered at low temperature. Once freed of the impurities, the oligomers can be fed back into the production process for polymerization. The task consists in feeding 10–25% bottle flakes while maintaining the quality of the bottle pellets that are manufactured on the line. This aim is solved by degrading the PET bottle flakes—already during their first plasticization, which can be carried out in a single- or multi-screw extruder—to an intrinsic viscosity of about 0.30 dℓ/g by adding small quantities of ethylene glycol and by subjecting the low-viscosity melt stream to an efficient filtration directly after plasticization. Furthermore, temperature is brought to the lowest possible limit. In addition, with this way of processing, the possibility of a chemical decomposition of the hydro peroxides is possible by adding a corresponding P-stabilizer directly when plasticizing. The destruction of the hydro peroxide groups is, with other processes, already carried out during the last step of flake treatment for instance by adding H3PO3. The partially glycolyzed and finely filtered recycled material is continuously fed to the esterification or prepolycondensation reactor, the dosing quantities of the raw materials are being adjusted accordingly. Total glycolysis The treatment of polyester waste through total glycolysis to fully convert the polyester to bis(2-hydroxyethyl) terephthalate (C6H4(CO2CH2CH2OH)2). This compound is purified by vacuum distillation, and is one of the intermediates used in polyester manufacture (see production). The reaction involved is as follows: investments were announced in 2021 and 2022 into methanolysis plants. Hydrolysis Hydrolysis can be done in a neutral, alkaline or acidic environment. Neutral hydrolysis Polyethylene terephthalate can be hydrolyzed to terephthalic acid and ethylene glycol under high temperature (200-300 °C) and pressure. The resultant crude terephthalic acid can be purified by recrystallization to yield material suitable for re-polymerization: : [(CO)C6H4(CO2CH2CH2O)]n + 2n H2O → n C6H4(CO2H)2 + n HOCH2CH2OH Avoiding a neutralization step consumes less resource than alkaline or acidic hydrolysis, but there is no opportunity to filter a solution, so mechanical impurities remain with the terephthalic acid. Enzymatic recycle may require size reduction and amorphisation prior to the depolymerization reaction. Chemical recycle to molecules other than PET monomers The chemical recycling where transesterification takes place and other glycols/polyols or glycerol are added to make a polyol which may be used in other ways such as polyurethane production or PU foam production ==Mechanical recycling==

The bales consisting mostly of PET mostly of a single colour are delivered to plants where the bottles may be treated by a variety of processes to convert them into usable feedstocks. The preferred method for recycling this stream is mechanical recycle, a process in which the resin is remelted, filtered and extruded or molded into new PET articles, such as bottles, strapping or fibers.(Bottles or flakes may be exported from one country to another) If the PET feedstock is not pure enough for mechanical recycle, then chemical recycling back to monomers or oligomers is used. Terephthalic acid (PTA) or dimethyl terephthalate (DMT) and ethylene glycol (EG), or bis(2-hydroxyethyl) terephthalate (BHET) are popular reaction products. However, chemical recycling to other products is also done. Physical recycling For physical recycling, especially for recycle to food contact applications, rigorous sorting and cleaning is required. In Switzerland, for example, the steps that the bottles follow are the following • metal separation (to protect the granulator) • granulation to "flake" • washing in hot water • flotation (which separates materials with density 6000 m/min, microfilaments, and micro-fibers are produced from virgin polyester only. Simple re-pelletizing of bottle flakes This process consists of transforming bottle waste into flakes, by drying and crystallizing the flakes, by plasticizing and filtering, as well as by pelletizing. Product is an amorphous re-granulate of an intrinsic viscosity in the range of 0.55–0.7, depending on how complete pre-drying of PET flakes has been done. Special feature are: Acetaldehyde and oligomers are contained in the pellets at lower level; the viscosity is reduced somehow, the pellets are amorphous and have to be crystallized and dried before further processing. Processing to: • A-PET film for thermoforming • Addition to PET virgin production • BoPET packaging film • PET Bottle resin by SSP • Carpet yarn • Engineering plastic • Filaments • Non-woven • Packaging stripes • Staple fibre. Choosing the re-pelletizing way means having an additional conversion process that is, at the one side, energy-intensive and cost-consuming, and causes thermal destruction. At the other side, the pelletizing step is providing the following advantages: • Intensive melt filtration • Intermediate quality control • Modification by additives • Product selection and separation by quality • Processing flexibility increased • Quality uniformization. Manufacture of PET-pellets or flakes for bottles (bottle to bottle) and A-PET This process is, in principle, similar to the one described above; however, the pellets produced are directly (continuously or discontinuously) crystallized and then subjected to a solid-state polycondensation (SSP) in a tumbling drier or a vertical tube reactor. During this processing step, the corresponding intrinsic viscosity of 0.80–0.085 dℓ/g is rebuilt again and, at the same time, the acetaldehyde content is reduced to 2 is necessary for full dull or semi dull yarn. In order to protect the spinnerets, an efficient filtration of the melt is, in any case is necessary. For the time-being, the amount of POY made of 100% recycling polyester is rather low because this process requires high purity of spinning melt. Most of the time, a blend of virgin and recycled pellets is used. Staple fibers are spun in an intrinsic viscosity range that lies rather somewhat lower and that should be between 0.58 and 0.62 dℓ/g. In this case, too, the required viscosity can be adjusted via drying or vacuum adjustment in case of vacuum extrusion. For adjusting the viscosity, however, an addition of chain length modifier like ethylene glycol or diethylene glycol can also be used. Spinning non-woven—in the fine titer field for textile applications as well as heavy spinning non-woven as basic materials, e.g. for roof covers or in road building—can be manufactured by spinning bottle flakes. The spinning viscosity is again within a range of 0.58–0.65 dℓ/g. One field of increasing interest where recycled materials are used is the manufacture of high-tenacity packaging stripes, and monofilaments. In both cases, the initial raw material is a mainly recycled material of higher intrinsic viscosity. High-tenacity packaging stripes as well as monofilament are then manufactured in the melt spinning process. Drying PET polymer is very sensitive to hydrolytic degradation, resulting in severe reduction in its molecular weight, thereby adversely affecting its subsequent melt processability. Therefore, it is essential to dry the PET flakes or granules to a very low moisture level prior to melt extrusion. PET must be dried to <100 parts per million (ppm) moisture and maintained at this moisture level to minimize hydrolysis during melt processing. Dehumidifying Drying – These types of dryers circulate hot and de-humidified dry air onto the resin, suck the air back, dry it and then pump again in a closed loop operation. This process reduces moisture level in the PET down to 50ppm or lower. The efficiency of moisture removal depends on the air dew point. If the air dew point is not good, then some moisture remains in the chips and cause IV loss during processing. Infrared Drying polyester pellets and flakes – A new type of dryer has been introduced in recent years, using Infrared drying (IRD). Due to the high rate of energy transfer with IR heating in combination with the specific wavelength used, the energy costs involved with these systems can be greatly reduced, along with the size. Polyester can be dried and amorphous flake crystallized and dried within only about 15 minutes down to a moisture level of approx. 300ppm in one step, and down to <50 ppm using a buffer hopper to complete the drying in typically under 1 hour == Global statistics ==

fabric. Worldwide, approximately 7.5 million tons of PET were collected in 2011. This gave 5.9 million tons of flake. In 2009 3.4 million tons were used to produce fibre, 500,000 tons to produce bottles, 500,000 tons to produce APET sheet for thermoforming, 200,000 tons to produce strapping tape and 100,000 tons for miscellaneous applications. Thus only approximately 15% of collected PET bottles were actually recycled into new bottles, the rest being used in generally non-recyclable products. Petcore, the European trade association that fosters the collection and recycling of PET, reported that in the EU 28+2,) • 28% bottles (half for food contact). (2010: 25%) • 24% fibres (2010: 38%) • 10% strapping (2010: 10%) • 8% other NAPCOR reported that for the US and Canada in 2018: out of 3 Mt bottles sold, 900kt of PET bottles (up from 600kt in 2008) were collected in 2018 (so around 1/3). 700kt of r-PET were produced for which the end uses were: • 15% sheets & films • 35% bottles (1/5 for food contact). • 40% fibres • 8% strapping • 1% other In 2019, 81% of the PET bottles sold in Switzerland were recycled, as in 2012. In 2018, 90% of the PET bottles sold in Finland were recycled. The high rate of recycling is mostly result of the deposit system in use. The law demands a tax of €0,51 /l for bottles and cans that are not part of a refund system. Thus encouraged by the law, products are included to have a 10¢ to 40¢ deposit that is paid to the recycler of the can or bottle. rPET end use in 2020 (total of 1,805 million pounds) • 38% fiber • 34% beverage bottles • 14% sheet & film • 7% non-food bottles • 5% strapping • 2% other PET bottles recycle-rate globally ==Uses==

Re-use of PET bottles In 2019, 2 billion PET bottles were refilled with mineral water in Germany. There is a plan to make these refillable bottles from rPET. PET bottles are also repurposed for various uses, including for use in school projects, and for use in solar water disinfection in developing nations, in which empty PET bottles are filled with water and left in the sun to allow disinfection by ultraviolet radiation. PET is useful for this purpose because many other materials (including window glass) that are transparent to visible light are opaque to ultraviolet radiation. According to online sources, the bottles, in a labor-intensive process, are filled with sand, then stacked and either mudded or cemented together to form a wall. Some of the bottles can be filled instead with air or water, to admit light into the structure. Fibres Most recycled PET is used as apparel fiber. However rPET has also been sold in the form of carpet fiber. Mohawk Industries released everSTRAND in 1999, a 100% post-consumer recycled content PET fiber. Since that time, more than 17 billion bottles have been recycled into carpet fiber. Pharr Yarns, a supplier to numerous carpet manufacturers including Looptex, Dobbs Mills, and Berkshire Flooring, produces a BCF (bulk continuous filament) PET carpet fiber containing a minimum of 25% post-consumer recycled content. Energy recovery If it not possible to recycle PET bottles for whatever reason, PET works well as a fuel in waste to energy plants, composed as it is of carbon, hydrogen, and oxygen, with only trace amounts of catalyst elements (but no sulfur). PET has the energy content of soft coal. ==Life cycle analysis==

Studies have shown that mechanical recycle has a lower environmental impact than incineration, due to avoided new raw material production. One study for the USA territory in 2018 concluded that recycle PET vs virgin gave reductions in environmental footprint (all forms are covered but bottles dominate the PET stream). Assuming that virgin PET will be used regardless of the existence of recycling: • Energy 70 → 15 MJ/kg • Water 9.9 → 10.3 L/kg (this increase due to the intense washing required for mechanical recycle) • Greenhouse gas emissions 2.8 → 0.9 kgCO2 /kg ==See also==