- Zakaria Ahmed
What happens to your household water bottle after you throw it in the recycling bin?
One thing we tend to not pay attention to is that almost all our daily life products are bought in containers and packaging such as household items. Bottled water is one simple example of a common consumable found in most houses. This product is made up of the potable water and the plastic container to deliver it to the consumer. We know quite well what happens to water when we consume it and its lifecycle; but what about the container? What is the life cycle of this container after we have consumed the water?
The fate and journey of this plastic container starts with the decision of the consumer after having used the water inside. Water bottles are made a valuable material for recycling companies which has the fancy chemical name of Polyethylene terephthalate (PET for short) because this material easy to recycle. The water bottles made of this material usually have the recycling sign (♲) imprinted on them with the number ‘1’ printed in the middle of the sign. The consumer most probably places the container in the recycling bin along with household recyclable items. Consumer decision to place the bottle in the correct recycling bin could determine whether the bottle goes through the journey described below or ending up in landfill or in the environment if placed elsewhere.
On the trash pick-up day this bottle starts its journey outside the consumer zone when it is loaded onto the back of a recycling truck after the consumer places it in the correct bin. The water bottle is now mixed with other types of products meant for recycling but not always. The dirty water bottle on the back of the truck has now reached the material recovery facility and their load is unloaded into piles of tonnes of trash in a storage area. This facility is mainly a sorting facility where plastics which are more valuable recycle material (including water bottle) are separated from less valuable materials. The recycling facility first picks up the bottle from the trash mixture. This is done by loading the trash mixture (from piled trash pick-up trucks) onto a moving mechanical belt where trash materials are sorted and separated by their type (glass, metal, plastic etc). This is done using technology that can recognise the bottle material and this sorting results in the collection of a stream of waste water bottles (clear and coloured bottles); and these valuable bottles are compressed in bales that are then sold to the recycling facilities.
Afterwards, the recycling facility take these bottle bales and start the recycling process. First, bales of dirty bottles are broken down and loaded onto a conveyor belt. The water bottle has become dirtier than when it was at the hand of the consumer having been mixed with other contaminating materials at three stops in its afterlife: in the household recycling bin, on the back of the truck, and in the sorting facility. Also, in these bales water bottles contain the caps, labels and adhesives which are made of materials different to the bottle material (PET). This requires that the water bottles in the stream are first cleaned to remove the contaminants from it. This is done in a washing step. Subsequent separations include separating bottles based on colour where clear bottles are separated from coloured ones. This is done using sorting technologies such as a laser machine that can differentiate between the colour of the bottles and this allows separation of clear bottles from coloured ones. Afterwards the caps, labels and adhesives are removed from the bottle in other separation steps which might include washing and heating to allow these components to come off the body of the bottle.
Then, the clean and pure bottle is shredded using specialised shredding machines in a similar manner to paper shredding. This process turns whole compressed bottles into small, shredded bits of plastic called flakes (centimetre size). These clean, pure and single-coloured flakes (named rPET for recycled PET) are then sold to other manufacturers which use them in different products such as carpets. This process is called downcycling - where the original bottle material after recycling is used for different application other than original application (water container). Usually, this new application requires material quality and purity that is less than that required in water bottle.
For these flakes to be used in making a new bottle, the recycled material must have high quality/purity that is necessary for its use for food-contact. Materials used in food packaging need to meet high standards of purity/quality to ensure safety of food and that harmful chemicals do not transfer into packaged food that is in contact with the packaging material. This means recycled bottle materials are subjected to more advanced processing by melting them, extruding into liquid and shaping them into pellets the size of a rice grain. These pellets are then sold to beverages manufacturers. In the bottle manufacturing facilities, these pellets are melted, injected into bottle-shaped moulds where they are blown to take the bottle shape. These bottles can then be filled with water or other beverages and sold again in the market.
This type of recycling of plastics is known as physical or mechanical recycling because the processes involved do not change the chemical structure of the water bottle material. This type of recycling is useful although it has drawback of producing low quality recycled material due to difficulty of eliminating impurities completely from the bottle material which is why the recycled bottle material mostly end up as a part of another product. Another form of recycling which changes the material structure is called chemical recycling. This recycling approach involves using processes which break down the bottle material into molecular bits (building blocks of the material) and other useful chemical compounds such as fuels (gases and liquids/oils) and solids. These building blocks of the bottle material (PET) can be further purified from impurities and later recombined chemically to make the original material of the bottle (PET); i.e., in other words this allows reproducing the water bottle.