The Environment Agency of the UK Government published a Life Cycle Assessment of Supermarket Carrier Bags. The Report shows that the global-warming potential (GWP) of the lightweight oxo-bio carrier bag is much lower than that of starch-polyester blend bags. This report is good news for oxo-biodegradable bags, and is actually even better news for the reasons mentioned below.
1. However, when describing oxobio bags at the Report misses the fundamental point about oxo-biodegradable technology. This is that the prodegradant additive included at manufacture turns ordinary plastic at the end of its useful life into a material with a completely different molecular structure. At that stage it is no longer a plastic and has become a material which is inherently biodegradable in the open environment in the same way as a leaf. Approximate timescale for degradation can be set at manufacture as required.
2. By contrast starch-polyster bags are designed for industrial composting and will not readily biodegrade in the open environment.
3. The Report does not consider the effects of littering, and therefore no credit has been given for the main purpose for which oxobio plastics have been developed - so that they will harmlessly degrade then biodegrade in the presence of oxygen if they escape the collection processes and find their way into the open environment.
4. There is no evidence in the Report, nor anywhere else, that degradable plastics of any kind encourage littering. A litter-lout would not know that oxo-bio products were biodegradable unless they were so labeled, because they look and feel the same as normal plastic. It is absurd to imagine that such a person would examine a label before deciding to discard as litter. In any event a lot of litter is accidentally discarded, without any conscious decision.
5. The Report found that 76% of these lightweight plastic bags were re-used, and that 53% of households re-used them as kitchen bin-liners. Other uses were as bin-liners in other rooms, as garbage sacks, and for a variety of other uses. The Report found that 18% were re-used for shopping, but the Report gives no credit for this type of use (known as primary use). If they had, the oxo-bio and conventional lightweight bags would have been rated even higher.
6. The Report makes an important point about terminology. It says “We have avoided calling lightweight bags “single use” or “disposable”, because consumers are increasingly reusing lightweight carriers for shopping.
Additionally a high proportion were used as a genuine replacement for another product and the secondary reuse of these bags plays an important part in reducing their global warming potential.” Indeed “The reuse of conventional HDPE and other lightweight carrier bags for shopping and/or as bin-liners is pivotal to their environmental performance and reuse as bin liners produces greater benefits than recycling the bags.
