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Biodegradable Teabags Fail Environmental Impact Test

New study finds that some "biodegradable" teabags don't fully degrade in soil

by University of Plymouth,Alan Williams
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Some teabags manufactured using plastic alternatives do not degrade in soil and have the potential to harm terrestrial species, a new study has shown.

The research, led by the University of Plymouth, looked at commonly available teabags made using three different compositions of polylactic acid (PLA), which is derived from sources such as corn starch or sugar cane.

The teabags were buried in soil for seven months, and a range of techniques were then used to assess whether – and to what extent – they had deteriorated.

The results showed that teabags made solely from PLA remained completely intact. However, the two types of teabags made from a combination of cellulose and PLA broke down into smaller pieces, losing between 60% and 80% of their overall mass and with the PLA component remaining.

The study also examined the impacts of the discs cut from the teabags on a species of earthworm, Eisenia fetida, which has a critical role in soil nutrient turnover as it consumes organic matter.

Researchers found that being exposed to three different concentrations of teabag discs – equivalent to the mass of half, one and two teabags – resulted in up to 15% greater mortality, while some concentrations of PLA had a detrimental effect on earthworm reproduction.

Writing in the journal Science of the Total Environment, the study’s authors highlight the need for accurate disposal information to be clearly displayed on product packaging.

Only one of the manufacturers whose products were chosen for the study indicated on the packaging that the teabags were not home compostable.

This could lead to them ending up in soil, while there is also high potential for consumer confusion about the meaning of terms such as plant-based or biodegradable, emphasising the need for clear guidance on appropriate disposal.

The research was designed to replicate the environmental conditions into which teabags might be discarded on account of a lack of clear labelling as to how they should be disposed. It used analytical techniques such as size exclusion chromatography, nuclear magnetic resonance, and scanning electron microscopy allowing scientists to examine not just how the teabags had changed visibly but also structurally.

Part of the BIO-PLASTIC-RISK project, it builds on previous research suggesting that some products labelled as biodegradable, including carrier bags, do not disintegrate after as much as three years in the environment. The study has also been published in the wake of the fourth session of the Intergovernmental Negotiating Committee (INC-4), where world leaders and scientists were among those to continue discussions towards the Global Plastics Treaty.

The full study – Courtene-Jones et al: “Deterioration of bio-based polylactic acid plastic teabags under environmental conditions and their associated effects on earthworms” – is published in Science of the Total Environment, DOI: 10.1016/j.scitotenv.2024.172806.

-Note: This news release was originally published on the University of Plymouth website. As it has been republished, it may deviate from our style guide.