All types of carrier bag, whether made from plastic, paper or jute, will have some impact on the environment during the manufacturing process, transportation and ultimate disposal. The best way to reduce their carbon footprint is to simply re-use them as many times as possible and then recycle them at the end of their useful life.
Plastic carrier bags
While plastic carrier bags are efficient and use 70% less plastic than they did 20 years ago, they are still made from polyethylene (PE) which is derived from non-renewable oil and require energy to manufacture.
Plastic bags are recyclable and are increasingly being recycled, but the majority still end up in landfill where they may take hundreds of years to break down. Increasing the recycled content of new plastic bags is a way of using fewer natural resources and reduces their impact on the environment.
Degradable PE carrier bags
There are a number of retailers who provide ‘degradable’ PE carrier bags, (also known as ‘oxy-degradable’ or ‘UV degradable’). Degradable bags are made from oil-derived PE but also contain a special additive that causes the plastic to degrade by oxidation and exposure to light and heat.
The bags initially fragment then undergo biodegradation which reduces the material to water, CO2, biomass and trace elements. The bags may take between 18 months to four years to disappear depending on conditions and are unlikely to fully degrade in landfill sites, but will not release methane either.
It is unknown what the full impact of mixing degradable and conventional plastic carrier bags will have if they enter the plastic recycling system in large numbers. Degradable bags do not conform to the recognised standard for biodegradable plastics EN 13432.
Biodegradable carrier bags
These bags are not so commonly used by retailers as they are less strong for the same gauge of material. They are made from renewable crop-derived sources (e.g. corn starch). They are usually designed to biodegrade in aerobic industrial composting conditions and may conform to EN 13432. They may be compostable in home composting conditions but there is no UK standard for home compostability at present.
The bags are not designed to degrade in anaerobic landfill conditions (i.e. without oxygen) and they may release methane in such conditions. Methane is a greenhouse gas 25 times more powerful than CO2.
While paper carrier bags are from a renewable source and are biodegradable, compostable and recyclable, they require significantly more energy to manufacture and transport than plastic bags and normally have limited re-use ability. If disposed of in landfill, they are likely to degrade and release methane.
Jute and cotton are made from plants which need a lot of water and fertiliser to grow and energy to harvest and process into bags. They encourage re-use, and can be reprocessed at the end of their useful life as, for example, blankets used by removal companies. If disposed of in landfill, they are likely to degrade and release methane.