UK research calls for clear labeling on tea bags amid vague compostability claims

29 May 2024 --- Tea bags manufactured using plastic alternatives might not biodegrade and could harm terrestrial species, according to a new study. The study’s authors highlight the need for accurate disposal information to be displayed on product packaging, differentiating between industrial and home compostability.

The research looked at commonly available tea bags from three different compositions of polylactic acid (PLA), which is derived from sources such as cornstarch or sugar cane. 

The tea bags were buried in soil for seven months and a range of techniques were then used to assess if they had deteriorated. 

The results showed that tea bags made solely from PLA remained completely intact. However, the two types of tea bags 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.

Study co-author professor Antoine Buchard, formerly of the University of Bath, UK, and now professor for Sustainable Polymer Chemistry at the University of York, UK, explains: “Using a number of chemical analysis techniques, we’ve shown that when it [PLA] is not properly disposed of, for example after seven months in the soil, its molecular structure remains intact.” 

“Labels such as biodegradable and compostable have the potential to mislead the public. Therefore, it is important that scientists, policymakers and manufacturers work together to ensure clear standards are followed and that the public has easy access to information on where to dispose of those new plastics.”

Avoiding consumer confusion 
The study examined the impacts of the discs cut from the tea bags on a species of earthworm, Eisenia fetida, which the researchers say has a critical role in soil nutrient turnover as it consumes organic matter. 

The scientists found that exposure to three different concentrations of tea bag discs — equivalent to the mass of half, one and two tea bags — resulted in up to 15% greater mortality. In contrast, some PLA concentrations had a detrimental effect on earthworm reproduction.

Researchers are calling for clear on-pack labeling for tea bag compostability features.“In this study PLA-based tea bags did not fully deteriorate, and it seems that composting worms may be harmed by them. The lack of clear labeling can lead to consumers disposing of tea bags in their compost, where any limit to complete degradation of the material raises the potential for plastics to enter the soil when compost is added to the garden, with potential impacts on garden wildlife and uptake by food plants,” asserts Dr. Mick Hanley, associate professor in Plant-Animal Interactions at the University of Plymouth and senior author on the study.

The study was published in Science of the Total Environment. 

The study’s authors highlight that only one of the manufacturers whose products were chosen for the study indicated on the packaging that the tea bags 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, emphasizing the need for clear guidance on appropriate disposal.

Avoiding mistakes in plastic treaty
The study has been published in the wake of the UN’s Global Plastics Treaty.

Study co-author professor Richard Thompson, head of the University of Plymouth’s International Marine Litter Research Unit and lead of the Bio-plastic-risk project, is a co-coordinator for the Scientists’ Coalition for an Effective Plastics Treaty. 

“After 30 years of research on plastic pollution, I am delighted there is now a global consensus, as evidenced by the UN Plastics Treaty, that current production use and disposal of plastic is unsustainable,” he says.  

“But it is with immense frustration that I see alternative and substitute materials entering the market without clear guidance on how their benefits might be realized. Even if consumers understand how to dispose of these products, only around half of households in the UK currently have access to the necessary waste streams for the type of composting required.”

“It is essential we learn from the mistakes we made with plastic materials by testing and labeling these novel materials in relation to the prevailing waste management infrastructure.”

Calls for degradation evidence
The study was designed to replicate the environmental conditions into which tea bags might be discarded on account of a lack of clear labeling 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 tea bags had changed visibly but also structurally.

The research was carried out as part of Bio-plastic-risk, a four-year £2.6 million (US$3.3 million) project led by the University of Plymouth and funded by the Natural Environment Research Council. The project assesses how biodegradable packaging and products break down and, in turn, whether the plastics or their breakdown products affect species both on land and in the marine environment.

Dr. Winnie Courtene-Jones, a post-doctoral research fellow at the University of Plymouth, UK, and the study’s lead author, comments: “In response to the plastic waste crisis, biodegradable plastics such as PLA are being used in an increasing range of products. This study highlights the need for more evidence on the degradation and possible effects of such materials before their use becomes even more widespread and to prevent the generation of alternative problems if they are not properly disposed of.”

By Natalie Schwertheim