Policymakers need always to consider what happens to waste plastic products which escape collection and end up as litter. What supermarket director wants his grandchildren to find on a beach a plastic bag with his company's name on it, which has been floating around the oceans for 50 years
Discarded conventional plastics remain in the environment for many decades, and are often impossible or too expensive to collect, so recycling, landfill, composting, and incineration are not options for dealing with them. If collected, oxo- biodegradable plastics can be recycled or incinerated, and if not collected they will degrade and disappear, leaving no harmful residues.
Exposure to sunlight accelerates degradation, but the process of oxo-bio-degradation, once initiated, continues even in the absence of light, so long as air is present. The plastic will degrade much more quickly in the open than in a building, and in warm weather will disappear more quickly. Of course, if the product has been exposed to air for some time before being discarded it will disappear in an even shorter time thereafter.By contrast, hydro-biodegradable plastics will not readily degrade unless they are in a highly-microbial environment, and will instead merely fragment.
More Careless disposal? Degradable plastic bags have been dispensed by supermarkets for more than four years, but there is no evidence that people dispose more carelessly of them (whether oxo or hydro biodegradable) and they have not been encouraged to do so.
But suppose for the sake of argument that 10% more were discarded. If 1,000 conventional and 1,100 oxo-biodegradable bags were left uncollected in the environment, 1,000 conventional bags would remain in the rivers, streets and fields for decades, but none of the oxo-biodegradable bags would be left at the end of the short life programmed into them at manufacture.
There will always be people who will deliberately or accidentally discard their plastic waste. What will happen to all the plastic waste that will not be recycled or will not be incinerated, and instead will litter the countryside - would it not be better if the discarded plastic were all oxo-biodegradable?
To limit or discourage the availability of all types of plastic bags is not the answer, as there are so many purposes for which they are ideal.