Since introducing the 5p charge in the UK, plastic carrier bag sales have fallen by over 80%. Anecdotally this has translated into fewer bags being found as litter on our streets and a study concluded fewer were found in the seas around the UK. Though welcome, questions are being asked about the wider effects of plastic bag charges and bans, particularly with greater emphasis being placed on life-cycle costs.
The environmental quandry
Total life-cycle costs with shopping bags are largely carried from initial production and distribution. Once the bag reaches the consumer, it’s already taken on most of its environmental costs from energy and resource use. What happens at the end of its life has relatively little bearing on its total environmental cost.
A 2018 study by the Danish Environmental Protection Agency considered these impacts across a range of different bags. They looked at the total life-cycle costs, from raw material to eventual disposal, using a standard lightweight plastic carrier bag (LDPE) as their reference unit. In all 15 categories of measurable impacts, the LDPE bag was in lowest 3 impact bags, and had the lowest impact in 9.
Using the LDPE as a baseline they constructed a model that showed how many times a bag had to be reused to meet the same environmental performance.
Is cotton tote the new foe?
The analysis showed the Cotton Tote bag, often hailed as a “green alternative” performed the worst by some margin. Only accounting for climate change, a bag had to be used 150 or 52 times, depending on whether it was organic or non-organic cotton. Factoring in all environmental factors and an organic cotton bag would need 20,000 uses before it matched the lifetime performance of an LDPE. A non-organic bag would need to be used once a week for 11 years.
Other types of bags also fared badly. Except for recycled LDPE bags, all other types the Danes reviewed would need between 35 and 870 uses to match a single disposable carrier bag.
Behaviour is also to blame
Studies by economist Rebecca Taylor into California’s carrier bag bans showed another unintended consequence. The free bags handed out at stores often ended their lives being used as bin liners. When taken away, consumers bought bags created for the purpose. Sales of different size “trash bags” increased between 6% and 120%.
The effect, Taylor concluded, was more than a quarter of the claimed savings in carrier bag waste was offset by “trash bag” purchases.
Every human activity carries an environmental cost. It could be argued LDPE bags are the worst of a bad bunch and that removing them from our supermarkets has created environmental damage, not reduced it. However, the fact these bags were free created a mindset they were disposable, and they were discarded thoughtlessly. The benefits to our overall environment and wellbeing by feeling we’re taking action and seeing the effects immediately could speak to a much needed behavioural change.
It does leave the shopper with a quandary. Cotton tote bags are seen as fashionable and a visible statement of a personal commitment to reuse. Yet they appear to be significantly worse for the environment overall than the ones they replace.
The Danish research drew no direct conclusions, but working from their results the best compromise appears to be using a polyester bag at least 35 times and recycling it at the end of its life.
Reducing use of cheap, lightweight plastic bags has removed a visible blight from our landscape. Research suggests their overall impact is not as high as any of the alternatives looking to replace it, and that our behaviour may influence an overall increase in plastic bag use. As always, making changes to benefit the environment can have invisible and unintended consequences that only emerge much later.
Image credit: European Parliament. Used under Creative Commons licence.