60% of Home “Compostable” Plastic Doesn’t Fully Decompose, Contaminating Our Soil
By FRONTIERS
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| Compostable plastic that has not fully disintegrated in compost bin. Credit: Citizen scientist image from www.bigcompostexperiment.org.uk |
In a UK-wide study, researchers found that 60% of home-compostable plastics do not fully disintegrate in home compost bins, and inevitably end up in our soil. The study also found that citizens are confused about the labels of compostable and biodegradable plastics, leading to incorrect plastic waste disposal. These results highlight the need to revise and redesign this supposedly sustainable plastic waste management system.
Global
plastic pollution remains one of the biggest environmental challenges of our
time. A new OECD report shows that plastic consumption has
quadrupled over the past 30 years. Globally, only 9% of plastic waste is
recycled, while 50% ends up in landfills, 22% evades waste management systems,
and 19% is incinerated.
In
response to this pollution crisis, several countries have set targets to
eliminate all single-use plastics and to make plastic packaging 100%
recyclable, reusable, or compostable by 2025.
Compostable
plastics are becoming more common as the demand for sustainable products grows.
The main applications of compostable plastics include food packaging, bags;
cups and plates, cutlery, and bio-waste bags. But there are some fundamental
problems with these types of plastics. They are largely unregulated and claims
around their environmental benefits are often exaggerated.
Now, in a new study published in Frontiers in Sustainability, researchers at University College London found that consumers are often confused about the meaning of the labels of compostable plastics, and that a large portion of compostable plastics do not fully disintegrate under home composting conditions.
(Un)compostable plastics
‘Compostable
plastic’ describes a material that can undergo biological degradation in a
compost site at a rate consistent with other known compostable materials,
leaving no visible (toxic) residues.
However,
compostable plastics are currently incompatible with most waste management
systems. There exists no harmonized international standard for home compostable
plastics. The fate of these plastics, when thrown away or sorted for recycling,
is therefore either incineration or landfill.
“The
typical fate of landfill or incineration is not usually communicated to
customers so the environmental claims made for compostable packaging can be
misleading,” said corresponding author Danielle Purkiss.
The Big Compost Experiment
Purkiss
and her colleagues designed a three-part citizen science study, The
Big Compost Experiment, to investigate what the public thinks
about home compostable plastics, how we deal with them, and whether they fully
disintegrate in our compost.
First,
participants from across the UK completed an online survey about opinions and
behavior surrounding compostable plastics and food waste. Then, participants
were invited to take part in a home composting experiment. Lastly, those who
participated in part two were sent a request to search for traces of their
chosen compostable plastic items in their composter. The researchers collected
the data over a period of 24 months.
“Our
study was created in response to feedback from the public and stakeholders from
industry, policy, and third sector organizations, which highlighted many
systemic issues in the manufacturing, use, and disposal of compostable plastic
packaging,” explained Purkiss.
The
results show a general willingness to make sustainable choices by buying
compostable plastics. However, participants showed confusion about the labeling
and identification of these plastics. Out of a randomized sample of 50 item
images, the researchers found that 46% showed no identifiable home composting
certification or standards labeling and 14% showed industrial composting
certification.
“This
shows that there is a current lack of clear labeling and communication to
ensure that the public can identify what is industrially compostable or home
compostable packaging, and how to dispose of it correctly,” said Purkiss.
But
a more shocking result is that 60% of plastic certified as home compostable did
not fully disintegrate in home compost bins.
“Compostable
packaging does not break down effectively in the range of UK home composting
conditions, creating plastic pollution,” Purkiss added. “Even packaging that
has been certified as home compostable is not breaking down effectively.”
The
participants indicated that they use their compost in their flower and
vegetable gardens. As the results of the experiment show that the compost
contains plastic that has not fully disintegrated, plastic inevitably ends up
in soil of UK citizens.
The
experiment also showed that compost bins are important sites for biodiversity,
with pictures sent in by the participants showing 14 different categories of
organisms such as fungi, mites, and worms.
Revising the system
The
question remains whether compostable plastics serve as a solution to our
widespread plastic pollution problem.
“Compostable
plastics are potentially useful for products that are not suited to recycling
due to contamination such as tea bags, fruit labels, take-away food packaging,
and certain hygiene products. These products typically end up in landfill,”
explained Purkiss.
But
the research shows that, in this case, the better solution is to send
compostable plastics to industrial composting facilities, where composting
conditions are regulated.
“We
have shown that home composting, being uncontrolled, is largely ineffective and
is not a good method of disposal for compostable packaging,” said Purkiss.
Overall,
there is a need for the revision and improvement of home compostable plastics.
“The idea that a material can be sustainable is a widespread misconception.
Only a system of production, collection, and reprocessing of a material can be
sustainable,” concluded Purkiss.
Reference:
“The Big Compost Experiment: Using citizen science to assess the impact and
effectiveness of biodegradable and compostable plastics in UK home composting”
by Danielle Purkiss, Ayşe Lisa Allison, Fabiana Lorencatto, Susan Michie and
Mark Miodownik, 3 November 2022, Frontiers in Sustainability.
DOI:
10.3389/frsus.2022.942724
