The environmental benefit of degradable supermarket bags has been questioned by the UK Compostable Packaging Group (CPG) who suggests the best environmental option is to encourage people to use fewer bags.
Following Tesco’s announcement that from September 2006 all of its plastic bags will be degradable, the UK CPG wants to clarify any confusion between biodegradable bags and degradable bags.
The informal group represents the biodegradable polymer supply chain from manufacture to waste disposal. It says that degradable bags, to be introduced by Tesco, are made from polythene into which a chemical catalyst has been introduced to trigger the earlier breakdown of the polymer. The complete breakdown of the bag will take some time.
The Co-op, that already uses such bags, advises that its bags will start to break down about 18 months from manufacture, with the whole process taking about three years.
According to UK CPG degradable bags are unsuitable for composting or anaerobic digestion and offer no advantage over conventional plastic in terms of waste management. It says that if degradable bags are sent to landfill, the most likely waste disposal route, the lack of sunlight and oxygen which are both needed to stimulate the breakdown of degradable materials, will mean the degradable bags are unlikely to break down much more rapidly than conventional plastic bags.
Biodegradable materials break down via a biological process into CO2 and water. And in the UK plastics that claim to be compostable need to ensure the resultant compost meets the quality standards set out by the British Standards Institution’s Publicly Available Specification for Composted Materials (PAS100:2005).