Science

60% Of Compostable Plastics Not Breaking Down In Home Compost Bins

Plastic pollution in our marine and land environments is one of the greatest challenges facing attempts to clean up our planet. Could compostable plastics help to solve this issue? For the next in our series in the run up to COP27 we look at new research on compostable plastic.

The world is producing twice as much plastic waste as two decades ago, with the bulk of it ending up in landfill, incinerated or leaking into the environment, and only 9% successfully recycled, according to a new OECD report.

The 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.

Many countries, including Scotland, have produced measures to reduce single use plastic and to encourage people to recycle. Scotland Takes Action on Single Use Plastics

There has been an increase in use by manufacturers of compostable plastics but many people remain confused about the various labels on products.

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.

Compostable plastic that has not fully disintegrated in compost bin Image credit: Citizen scientist image from http://www.bigcompostexperiment.org.uk

The research project ‘The Big Compost Experiment‘, showed that people were keen to use compostable plastics but were often unable to make an informed choice because of poor labelling.

More worrying, however, was that the research also found that 60% of the ‘compostable’ plastics were not disintegrating in home designed compost bins.

Researcher  Danielle Purkiss explained:

“Compostable packaging does not break down effectively in the range of UK home composting conditions, creating plastic pollution. Even packaging that has been certified as home compostable is not breaking down effectively.

“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

“We have shown that home composting, being uncontrolled, is largely ineffective and is not a good method of disposal for compostable packaging.”

The researchers concluded that, in this case, the better solution is to send compostable plastics to industrial composting facilities, where composting conditions are regulated.

Click on this link to access the full report: The Big Compost Experiment: Using citizen science to assess the impact and effectiveness of biodegradable and compostable plastics in UK home composting, published in Frontiers in Sustainability.

World Statistics on Plastic (via OECD)

  • Plastic consumption has quadrupled over the past 30 years, driven by growth in emerging markets. Global plastics production doubled from 2000 to 2019 to reach 460 million tonnes. Plastics account for 3.4% of global greenhouse gas emissions.
  • Global plastic waste generation more than doubled from 2000 to 2019 to 353 million tonnes. Nearly two-thirds of plastic waste comes from plastics with lifetimes of under five years, with 40% coming from packaging, 12% from consumer goods and 11% from clothing and textiles.
  • Only 9% of plastic waste is recycled (15% is collected for recycling but 40% of that is disposed of as residues). Another 19% is incinerated, 50% ends up in landfill and 22% evades waste management systems and goes into uncontrolled dumpsites, is burned in open pits or ends up in terrestrial or aquatic environments, especially in poorer countries. 
  • In 2019, 6.1 million tonnes (Mt) of plastic waste leaked into aquatic environments and 1.7 Mt flowed into oceans. There is now an estimated 30 Mt of plastic waste in seas and oceans, and a further 109 Mt has accumulated in rivers. The build-up of plastics in rivers implies that leakage into the ocean will continue for decades to come, even if mismanaged plastic waste could be significantly reduced.
  • Considering global value chains and trade in plastics, aligning design approaches and the regulation of chemicals will be key to improving the circularity of plastics. An international approach to waste management should lead to all available sources of financing, including development aid, being mobilised to help low and middle-income countries meet estimated costs of EUR 25 billion a year to improve waste management infrastructure.

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