Bio-based teabags do not readily degrade in environment, study shows

A new study by University of Plymouth and University of Bath shows that some teabags manufactured using plastic alternatives do not degrade in soil and have the potential to harm terrestrial species.

A new study shows that some bio-based teabags do not degrade in soil. (Source: University of Bath)

The research was conducted as part of BIO-PLASTIC-RISK, a project funded by the Natural Environment Research Council which is assessing how biodegradable packaging and products break down in the environment.

Research methodology

The researchers looked at commonly available teabags made with three different compositions of polylactic acid (PLA), which is derived from sources such as corn starch or sugar cane.

The study was designed to replicate the environmental conditions into which teabags might be discarded. The teabags were buried in soil for seven months and a range of analytical techniques were used to access whether, and to what extent, they had deteriorated.

The analytical techniques used include size exclusion chromatography, nuclear magnetic resonance, and scanning electron microscopy, which help examine the visual and structural change of teabags.

Result

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

Visual and structural change of tested teabags. (Source: Science Direct)

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% higher mortality, while some concentrations of PLA had a detrimental effect on earthworm reproduction.

Implications

Only one of the teabag sellers whose products were chosen for the study indicated on the packaging that the teabags were not home compostable. The study’s authors highlight the need for clear and accurate disposal guidance on product packaging.

“Current labels on packaging such as biodegradable or compostable can be misleading for the public. Therefore, it is imperative that scientists, policy makers and manufacturers work together so that the public has an easy access to information and learn how to dispose of those new types of plastic,” said Dr Fannie Burgevin from the University of Bath’s Department of Chemistry.