A new report from Europe has found issues with testing on biodegradable plastic bags and urges caution when considering whether they should be exempt from plastic bag bans and levies.
Jesse Harrison and co-authors argue in the report that existing industry standards and test methods are insufficient when it comes to predicting how biodegradable plastic bags break down in lakes, rivers and marine environments.
The Biodegradability standards for carrier bags and plastic films in aquatic environments report was commissioned by the UK Department for Environment, Food and Rural Affairs and involved the University of Edinburgh, the University of Vienna, and the University of Helsinki.
said the data obtained by current standards, test methods and specifications can significantly underestimate how long it takes for polymer biodegradation in natural ecosystems.
“Existing biodegradability standards and test methods for aquatic environments do not involve toxicity testing or account for potentially adverse ecological impacts of carrier bags, plastic additives, polymer degradation products or small plastic particles that arise via fragmentation,” the report said.
Auckland University of Technology Professor Thomas Neitzert said this research helps destroy the current thinking a plastic bag with a biodegradable label is safe for the environment.
“The co-existence of conventional plastic bags and so-called biodegradable plastic bags of compostable materials is also upsetting current recycling operations and is confusing the general public,” Dr Neitzert said.
“The current standards are not taking properly into account real-life conditions and are therefore underestimating the break-down times of plastic materials.
“The standards are also not accounting for the damage of break-down particles on marine life when they are digested. A biodegradable plastic bag is potentially dangerous to marine life from the moment it enters the water until it dissolves into micro- or nanoparticles over many years,” he said.
University of Waikato Professor Kim Pickering said the review provided an excellent overview of the current assessment of biodegradability, including its shortfalls.
“It is important to assess how long things take to degrade in real situations and also what they break into and the consequences of that and we need to address such shortfalls,” Dr Pickering said.
“If it is to be assumed that we cannot prevent some plastic products getting into the environment, then biodegradable plastics could be a step in the right direction (depending on the product),” she said.
“It shows that there are great uncertainties regarding the impact these could have on the environment and so we should still assume responsibility of waste and consider its disposal, whether biodegradable or not.”