The amount of plastic produced in the world has consistently increased since 1950. Since it was invented, the amount of plastic has increased to 311 billion kilos in 2014. This amount will double in the next 20 years to 622 billion kilos. There are also many different types of plastic. This page goes more deeply into the types of plastic.

What is plastic?

Plastics are polymers. These are large molecules that are formed by chains of smaller molecules called monomers. The properties of plastic depend on the length of the polymers. For example Polyethylene (PE) has long chains of polymers and is hard and rigid. The chemical industry produces different types of plastic. There are seven primary groups.

In 1988 The Society of the Plastics Industry (SPI) created a coding system that assists recyclers with the recycling of plastics. Virtually all plastic products have the recycling symbol (a triangle of arrows). The number inside the triangle indicates the type of synthetic:

Recyclingcode

PET 1

i.e. PET bottles for soft drinks.
Is relatively safe. You should not refill PET bottles as the risk of additives leakage increases.

HDPE 2

i.e. plastic containers and pipes.
Is considered safe and is easy to recycle.

PVC 3

i.e. sewage pipes and synthetic window frames.
Is to be avoided. In the manufacturing process the toxic dioxin is released and softeners are often added.

LDPE 4

i.e. soft plastics such as cling film, plastic drycleaner covers, carry bags.
Is considered safe.

PP 5

i.e. plastic furniture, jerry cans, car parts, bottle tops.
Is considered safe.

PS 6

i.e. disposable cups, meat trays, packaging for electronics.
is to be avoided because of possible leakage of styrene.

Other and mixed plastics 7

Code 7 is a miscellaneous category that nobody can do anything with.

Notes on the Recycling Code

  • The number in the triangle suggests that plastic is been recycled by category of product. In reality this is not the case (yet).
  • Whereas the number indicates the type of synthetic, it does not tell its durability, form or consistency. For example the same type of synthetic can be used for plastic bags or bottles.
  • Not every type of plastic can be adequately recycled and only a low percentage of plastic is in fact recycled.
  • The regulations that reflect the symbols leave much to be desired. Often the symbols are punched in too small, are hard to find and difficult to read (especially when the plastic is transparent).
  • Code 7 is a miscellaneous category that nobody can do anything with.

Recycling code and plastic soup

On 14 February 2013 an article was published in the science magazine Nature in which it was suggested to classify as harmful substances those types of plastics that are made of toxic materials and which are the most difficult to recycle. Named were PVC (code 3), polystyrene (code 6), polyurethane and polycarbonate (both code 7). In the United States a number of cities have banned polystyrene (mostly known as styrofoam). This insulating plastic is used especially in the fast food industry for packaging. Much ends up as litter and breaks up quickly.

As long as certain plastics and/or additives are not prohibited, it is for consumers to use the recycling codes to decide what types of plastic they want to purchase or not.

For plastics fished out of the ocean (as by fishing for litter) the codes are of no use. In the ocean plastic breaks up into smaller fragments, is subject to fouling deposits and the code becomes quickly unreadable.

Bioplastics and biodegradable plastics

Organic vegetables and fruit in supermarkets are often packaged in biodegradable plastic. Plant pots and magazine wrappers are also often biodegradable. The logo of a sprouting leaf on the packaging shows that this plastic is compostable. The definition of the logo is that the material should disappear completely within seven weeks in an industrial composting unit which runs at up to 65 degrees Celsius. The material is broken down into natural resources by bacteria. But if you add this biodegradable plastic to your own compost, the natural biodegrading process can take two years.

The term bioplastic is used for plastic that partly consists of natural materials such as sugar cane or starch. This means that these bioplastics ultimately have the same characteristics as regular plastic and, despite their name, are not biodegradable.

Biodegradable plastic – so not bioplastic – that can be put into the vegetable/fruit/garden bin for collection can also be put in the compost. If biodegradable plastics are mixed with conventional oil-based plastics, they will negatively affect the quality of recycled plastic.

Composting at sea – is that possible?

The conditions required at sea for ‘composting’ barely exist. The temperature is lower so no heating takes place, and there are no bacteria of the type needed to break down the plastic. This means that the animals that swallow the biodegradable plastics or get entangled in them face the same fate as they would with ordinary plastics. Simply put, the breaking down process in animals’ stomachs takes so long that they do not have a higher chance of survival swallowing biodegradable plastic as they would ordinary plastic. This has been proven by research into sea turtles.

Sea turtles are the victims

While manufacturers assume that biodegradable plastic bags are 100% compostable in industrial composting units within 49 days, it appears that if these bags remain in the stomachs and intestines of sea turtles for 49 days, they would only disintegrate by between three and nine percent. Ordinary plastic bags even remain completely intact. The researchers then concluded that, while the speed of breaking down of biodegradable polymers may be higher than ordinary plastic bags in the stomach and intestines of sea turtles, it is still not fast enough to prevent the animals dying from ingesting plastic. Sea turtles unfortunately do not see the difference between a jellyfish and a plastic bag floating in the sea, whatever it is made of.

Click here (pdf) for the sea turtle research.

Be critical about packaging

The Plastic Soup Foundation believes that we should always look critically at which potential uses of biodegradable plastics are desirable and which are not. Some uses are preferable, such as making fishing nets from biodegradable plastic instead of from nylon or plastic as they will eventually break down. They are also heavier and will therefore sink to the seabed more quickly.

Much packaging is completely unnecessary. Why should vegetables and fruit that have a natural protective layer such as pumpkins and bananas still need to be wrapped in plastic? Even packaging them using biodegradable materials is redundant.

There is much confusion about biodegradable plastic and bioplastics. For example, Coca Cola’s Plant Bottle is presented as sustainable because 30 percent of its components are natural resources (sugar cane). The production of the bottles may need less energy, but the bottles themselves are not biodegradable. Another objection is that the resources used to produce bioplastics could also be used for food instead and the clearing of land to make room for plantations for the bioplastics industry could lead to further deforestation.