Saturday, 28 August 2010

Effects of Plastic Bags on the Environment

The world's annual consumption of plastic materials has increased from around 5 million tonnes in the 1950s to nearly 100 million tonnes today.

Uses of plastic

Packaging represents the largest single sector of plastics use in the UK. The sector accounts for 35% of UK plastics consumption and plastic is the material of choice in nearly half of all packaged goods.

Plastic consumption is growing by about 4% every year in western Europe

Types of Plastic

There are about 50 different groups of plastics, with hundreds of different varieties. All types of plastic are recyclable. To make sorting and thus recycling easier, the American Society of Plastics Industry developed a standard marking code to help consumers identify and sort the main types of plastic.

A report on the production of carrier bags made from recycled rather than virgin polythene concluded that the use of recycled plastic resulted in the following environmental benefits:

  • Reduction of energy consumption by two-thirds
  • Production of only a third of sulphur dioxide and half of the nitrous oxide
  • Reduction of water by nearly 90%
  • Reduction of carbon dioxide generation by two and a half times.

Plastic bags are made from low density polyethylene (LDPE)

One tonne of plastics is equivalent to 120,000 carrier bags.

In addition, plastics manufacture requires other resources such as land and water and produces waste and emissions. The overall environmental impact varies according to the type of plastic and the production method employed.

Plastics production also involves the use of potentially harmful chemicals, which are added as stabilisers or colorants. Many of these have not undergone environmental risk assessment and their impact on human health and the environment is currently uncertain. An example of this is phthalates, which are used in the manufacture of PVC. PVC has in the past been used in toys for young children and there has been concern that phthalates may be released when these toys are sucked (come into contact with saliva). Risk assessments of the effects of phthalates on the environment are currently being carried out.

The disposal of plastics products also contributes significantly to their environmental impact. Because most plastics are non-degradable, they take a long time to break down, possibly up to hundreds of years - although no-one knows for certain as plastics haven't existed for long enough - when they are landfilled. With more and more plastics products, particularly plastics packaging, being disposed of soon after their purchase, the landfill space required by plastics waste is a growing concern.

Plastic waste, such as plastic bags, often becomes litter. For example, nearly 57% of litter found on beaches in 2003 was plastic.

Hows, whats and wheres of recycling plastic

Plastics are used in a wide range of applications and some plastics items, such as food packaging, become waste only a short time after purchase. Other plastic items lend themselves to be reused many times over.

Reusing plastic is preferable to recycling as it uses less energy and fewer resources. Long life, multi-trip plastics packaging has become more widespread in recent years, replacing less durable and single-trip alternatives, so reducing waste. For example, the major supermarkets have increased their use of returnable plastic crates for transport and display purposes four-fold from 8.5 million in 1992 to an estimated 35.8 million in 2002. They usually last up to 20 years and can be recycled at the end of their useful life.

According to a 2001 Environment Agency report, 80% of post-consumer plastic waste is sent to landfill, 8% is incinerated and only 7% is recycled. In addition to reducing the amount of plastics waste requiring disposal, recycling plastic can have several other advantages:

  • Conservation of non-renewable fossil fuels - Plastic production uses 8% of the world's oil production, 4% as feedstock and 4% during manufacture.
  • Reduced consumption of energy.
  • Reduced amounts of solid waste going to landfill.
  • Reduced emissions of carbon-dioxide (CO2), nitrogen-oxide (NO) and sulphur-dioxide (SO2).

Plastic process scrap recycling

Currently most plastic recycling in the UK is of 'process scrap' from industry, i.e. polymers left over from the production of plastics. This is relatively simple and economical to recycle, as there is a regular and reliable source and the material is relatively uncontaminated. Process scrap represents some 250,000 tonnes of the plastic waste arisings in the UK and approximately 95% of this is recycled. This is usually described as reprocessing rather than recycling.

Post-use plastic recycling

Post-use plastic can be described as plastic material arising from products that have undergone a first full service life prior to being recovered. Households are the biggest source of plastic waste, but recycling household plastics presents a number of challenges. One of these relates to collection. With over 20 million UK households, kerbside recycling systems are required to regularly collect relatively small quantities of mixed plastics from a large number of sources. Currently, just over half of local authorities offer some form of plastic bottle collection service, and only an estimated 15% of UK households are served by kerbside collections that include plastic bottles. The densest network of plastic bottle collection schemes is found in the South and East of England and the Midlands. East Anglia, Wales, Scotland and Northern Ireland have the least coverage. There are approximately 4,000 plastic bottle collection banks in the UK.

RECOUP (RECycling Of Used Plastics Limited) undertakes an annual survey of plastic bottle recycling activity in the UK. Results of the most recent survey indicate that an estimated 24,000 tonnes of plastic bottles were collected in 2003. However, this still only amounts to approximately 5.5% of all plastic bottles sold.

Mechanical recycling

Mechanical recycling of plastics refers to processes which involve the melting, shredding or granulation of waste plastics. Plastics must be sorted prior to mechanical recycling. At the moment in the UK most sorting for mechanical recycling is done by trained staff who manually sort the plastics into polymer type and/or colour. Technology is being introduced to sort plastics automatically, using various techniques such as X-ray fluorescence, infrared and near infrared spectroscopy, electrostatics and flotation. Following sorting, the plastic is either melted down directly and moulded into a new shape, or melted down after being shredded into flakes and than processed into granules called regranulate.

Chemical or feedstock recycling

Feedstock recycling describes a range of plastic recovery techniques to make plastics, which break down polymers into their constituent monomers, which in turn can be used again in refineries, or petrochemical and chemical production. A range of feedstock recycling technologies is currently being explored. These include: pyrolysis, hydrogenation, gasification and thermal cracking. Feedstock recycling has a greater flexibility over composition and is more tolerant to impurities than mechanical recycling, although it is capital intensive and requires very large quantities of used plastic for reprocessing to be economically viable (e.g. 50,000 tonnes per year).

Plastics recycling in the UK

In 1998, a pilot feedstock recycling plant went operational at BP's Grangemouth site in Scotland, with a capacity to process 400 tonnes of mixed plastic waste per annum. A feasibility study into its viability concluded that a 25,000 tonnes per annum plant could be supported from the area's municipal waste sources alone.

In 1991, LINPAC Plastics Recycling opened a unique plant with the ability to recycle post-consumer polystyrene products. The plant, based in Allerton Bywater, West Yorkshire, has a capacity of over 14,000 tones per year, which is set to increase to 25,000 tonnes per year by 2005. The plant is able to process fast food boxes, meat trays, egg cartons, yoghurt pots, vending cups, and a range of other polystyrene products. In addition, the plant processes a range of polyethylene and polypropylene goods, such as bottles, crates, sheets, caps, pipes and fibres.

Degradable and bio-plastics

Degradable plastics

A number of UK retailers have recently introduced degradable carrier bags. These bags are made from plastic which degrades under certain conditions or after a predetermined length of time. There are two types of degradable plastic: bio-degradable plastics, which contain a small percentage of non oil-based material, such as corn starch; and photodegradable plastics, which will break down when exposed to sunlight.

Degradable plastics are already being used successfully in Austria and Sweden, where McDonalds has been using bio-degradable cutlery for three years. This enables all catering waste to be composted without segregation. Carriers for packs of beer cans are now being manufactured in a plastic which photo-degrades in six weeks. There is also potential to use such plastics in non-packaging applications such as computer or car components.

There are a number of concerns over the use of degradable plastics. First, these plastics will only degrade if disposed of in appropriate conditions. For example, a photodegradable plastic product will not degrade if it is buried in a landfill site where there is no light. Second, they may cause an increase in emissions of the greenhouse gas methane, as methane is released when materials biodegrade anaerobically. Third, the mixture of degradable and non-degradable plastics may complicate plastics sorting systems. Last but not least, the use of these materials may lead to an increase in plastics waste and litter if people believe that discarded plastics will simply disappear.


A number of manufacturers have been exploring alternatives to plastics made from non-renewable fossil-fuels. Such alternative 'bio-plastics' include polymers made from plants sugars and plastics grown inside genetically modified plants or micro-organisms.

Health and safety concerns have arisen over potentially hazardous chemical additives to plastics and consumer pressure has contributed to manufacturers switching to plant-based plastics in such cases. For example, the world's largest toy manufacturer Mattel announced in 1999 that PVC would be replaced with plant-based plastics in new products from 2001 onwards. A range of other companies, including LEGO, IKEA, Nike and The Bodyshop have made similar pledges.

Use of recycled plastic

There is a wide range of products made from recycled plastic.This includes polyethylene bin liners and carrier bags; PVC sewer pipes, flooring and window frames; building insulation board; video and compact disc cassette cases; fencing and garden furniture; water butts, garden sheds and composters; seed trays; anoraks and fleeces; fibre filling for sleeping bags and duvets; and a variety of office accessories.

The Recycled Products Guide (RPG) is a listing of products made from recycled. Buying recycled products is a practical way of supporting markets for recycled products and 'closing the loop'. In addition, a list of suppliers of goods made from recycled plastic is available on RECOUP's website

Here are some facts about plastic bags helping to highlight the importance of reusable bags to the consumer and the environment.
  • Plastic bags aren't biodegradable. They go through a process called photo-degradation which means the plastic is being broken down into smaller and smaller toxic particles that contaminate soil and water and then enter the food chain therefore being eaten accidentally by animals.
  • According to various estimates, Taiwan consumes 20 billion plastic bags annually thats 900 per person. Japan consumes 300 billion bags each year that's 300 per person.
  • Hundreds of thousands of whales, dolphins, sea turtles and other marine mammals die every year after eating discarded plastic bags they mistake for food.

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