Many alternatives to single use plastic bags have huge environmental footprints – some for instance, need to be used 131 times. The worst bags being paper bags – sure, they break down after use but the energy consumption and materials used to produce them are off the scale.
Taking all this into account, the report was able to work out how many times you needed to use an alternative to a single use plastic bag for it to have a lesser impact on the environment.
“The benefits of a reusable bag are highly sensitive to the number of times each bag is used during its life,” said the report. “For example, if a reusable PP green bag is only used 52 times (weekly for a year) instead of the assumed 104 times (weekly for two years) then its impact on global warming is higher than the impact of each of the single-use bags except the paper bag.”
Other reports confirm plastic bag replacements are far worse environmentally if they are only used a handful of times and then loiter, unloved, in a corner.
A 2016 report by the NSW Environmental Protection Agency (EPA) found a cotton bag had to be used 131 times to equal the environmental impact of an HDPE bag used just once. A 2006 UK Government report came to a similar conclusion.
A paper bag has to be used three times and a thicker LDPE bag four times. The EPA’s report doesn’t concur with Woolworths on how many times a green bag has to be used, but it does have to be reused on multiple occasions. They suggest a green bag has to be reused 11 times for it to equal one current bag.
SINGLE USE BAGS ARE USED MORE THAN ONCE
However, “single-use” plastic bags aren’t really used once at all.
“Most shopping bags are used twice because people take them home and use them as rubbish bags or for picking up dog poop and that further reduces their environmental impact,” said Dr Thornton.
Every time an HDPE bag is reused, the environmental hurdle other bags have to jump over to better them increases. Paper bags, which aren’t all that strong, have to be used six times; green bags 20+ times and a cotton bag more than 260 times.
If you use a plastic bag to carry your shopping home, take your lunch to work and then pick up your pet’s waste then, according to Woolies figures at least, you might have to use your green bag hundreds of times for it to be truly green in comparison.
“When we talk about banning single use plastic bags we’re talking about littering. When people see plastic bags it bothers them and that’s why society decided to act on it. But plastic bag littering is the tip of the iceberg; what is underneath is even more scary.”
What scares Prof Karma is that as the globe’s population grows and becomes increasingly affluent, demand for products that contain plastics will only increase. The rubbish produced will far outweigh the gains made by a plastic bag ban.
“We have replaced lots of traditional materials with plastics — even clothing which is full of synthetic fibres. A recent study in Europe found when we wash these clothes just once we release 700,000 plastic particles into environment,” he said.
“Of course, in the short term, this ban will affect littering but the plastic bag ban gives the misperception to society that it’s problem solved. But have we resolved the problem? Not really. We’re still polluting the environment with plastic.”
Like Dr Thornton, Prof Sami said the key was not recycling and it wasn’t finding nifty end-of-life solutions. That’s because every product created has an environmental impact. Only using less stuff will do the trick.
But, making sure you use your green bags at least 25 times or more would be a start.