Recycling of PET Bottles is the activity whereby bottles made out of PET are collected, sorted and processed in order to reuse the material out of which they are made.
In many countries, PET plastics are coded with the number 1 which is found inside the universal recycling symbol, usually located on the bottom of the container.
PET is used as a raw material for making packaging materials such as bottles and containers for packaging a wide range of food products and other consumer goods. Examples include soft drinks, alcoholic beverages, detergents, cosmetics, pharmaceutical products and edible oils. PET is one of the most common consumer plastics used.
The empty PET packaging is discarded by the consumer after use and becomes PET waste. In the recycling industry, this is referred to as "post-consumer PET." Many local governments and waste collection agencies have started to collect post-consumer PET separately from other household waste. The collected post-consumer PET is taken to recycling centres known as materials recovery facilities (MRF) where it is sorted and separated from other materials such as metal, objects made out of other rigid plastics such as PVC, HDPE, polypropylene, flexible plastics such as those used for bags (generally low density polyethylene), drink cartons, and anything else which is not made out of PET.
Post-consumer PET is often sorted into different colour fractions: transparent or uncoloured PET, blue and green coloured PET, and the remainder into a mixed colours fraction. The emergence of new colours (such as amber for plastic beer bottles) further complicates the sorting process for the recycling industry.
This sorted post-consumer PET waste is crushed and pressed into bales, which are offered for sale to recycling companies. Transparent post-consumer PET attracts higher sales prices compared to the blue and green fractions. The mixed colour fraction is the least valuable. Recycling companies will further treat the post-consumer PET by shredding the material into small fragments. These fragments still contain residues of the original content, shredded paper labels and plastic caps. These are removed by different processes, resulting in pure PET fragments, or "PET flakes". PET flakes are used as the raw material for a range of products that would otherwise be made of polyester. Examples include polyester fibres, a base material for the production of clothing, pillows, carpets, etc., polyester sheet, strapping, or back into PET bottles.
PROCESS FLOW CHART
PET containers are identified by a resin identification code imprinted on the side or bottom of the container. PET bottles in the United States, which are usually clear or transparent green, carry the resin identification code " 1 " and the symbol "PETE." They may also be recognised by the dot, or circular gate, centrally located on the bottom.
For any collection program to succeed, consumers must become educated and motivated so that identification and collection of recyclable containers becomes a routine activity. Most consumers readily recognise PET soft drink bottles. However, the use of PET has expanded rapidly into other areas such as containers for water, sports drinks, food products, alcoholic beverages, household products, and cosmetics. Accordingly, it becomes vital that consumers understand and use the codes for proper identification of recyclable containers.
CLEANING AND SEPARATION
Once collected, containers are forwarded to recycling locations where they are run through grinders that reduce them to flake form. The flake then proceeds through a separation and cleaning process that removes all foreign particles such as paper, metal, and other plastic materials. Having been cleaned according to market specifications, the recovered PET is sold to manufacturers who convert t into a variety of useful products such as carpet fibre, strapping, moulding compounds, and non-food containers.
There are about three dozen recycling companies in operation, two-thirds of which are located in North America. These plants have the cleaning and separation technology to convert post-consumer bottles to flake for sale to end users. Their total capacity approaches together 436 thousand tonnes (960 million lb) on a three-shift basis - evidence that there is capacity available to handle the growing demand for recycled PET.The recycler is the vital link between the collection process and the end users having need of the recycled resin. Industry associations also play a valuable role by bringing communities and recycling outlets together.
SIMPLIFIED METHANOLYSIS PROCESS-SCHEMATIC
USES OF RECLAIMED PET
About three-fourhts of reclaimed PET is used to make products such as fibres for carpets, fibrefill, apparel and geotextiles. Much of the remainder is extruded into sheet for thermo-forming, stretch blow-moulded into non-food containers, or compounded for moulding applications. The chemical process for producing PET can be reversed by two commercially available depolymerisation methods - methanolysis and glycolosis.
These processes subject clean flake to a chemical reaction that reduces it to either a monomer or the original raw materials. These materials can then be purified and subsequently re-reacted into "new" PET for use in food-contact applications.
In some countries, reclaimed PET is used for food packaging by incorporating it into the core layer of a three-layer sandwich structure or by subjecting it to special cleaning processes.
Many communities send their trash to state-of-the-art, waste-to-energy incineration facilities, reducing the volume of waste going to landflls by as much as 90%. As stated earlier, incineration for energy recovery accounts for 17% of all solid waste disposal in the United States.
In Europe, the percentage is 30%, with Switzerland burning about 80%. As shown below, plastics have an inherent energy value higher than any other material commonly found in the waste stream.
While a growing number of PET containers are being recycled and others are being incinerated, some inevitably find their way into landfills. What happens to these containers? Virtually nothing. They contain no noxious components that might leach into underground water supplies, nor do they decompose. Landfill digs, conducted by noted professor of archeology Dr. William Rathje, indicate that many landfilled items, including some foods and paper, remain virtually unchanged for decades.
Since very little decomposition takes place in a modern landfill, such sites are, in effect, solid waste repositorios. Consequently, landfills simply fill up, with little or no decomposition taking place. Hopeftilly, fewer and fewer PET containers will go into landfills. However, those that do will be crushed to their minimum size, and their inert nature will not negatively impact the landfill.