Not all biodegradable teabags biodegrade, UCC study reveals

The UCC study showed that teabags made entirely of PLA, which were marketed as completely biodegradable, were found completely intact.

Tea is akin to water in Ireland, one of the top tea-drinking nations in the world. We brew throughout the day, building mounds of two or 12 spent teabags, and smile proudly as we unload them into our compost bins once we’ve had our fill, doing our bit for the environment, or so we thought.

However, putting certain teabags into the compost bin may not be the environmentally friendly thing to do, according to a study carried out by UCC.

In response to some brands opting to switch to alternative plant-made materials such as cellulose or 'bioplastics' including polylactic acid (PLA), UCC compared the degradation of teabags from eight brands commonly found on Irish shelves.

For the study, teabags were individually buried outdoors in garden soil in Cork City during 2020 and 2021 and checked periodically for one year.

After a year, all teabags and their fragments were measured and visualised using a powerful microscope to look for signs of degradation.

The study found that teabags made of both cellulose and a plastic used as a sealant called polypropylene, which is the most common teabag, had produced the highest numbers of microplastic fragments.

Marketed as biodegradable

Most surprising, however, was that teabags made entirely of PLA, which were marketed as completely biodegradable, were found completely intact.

The teabags made entirely of cellulose biodegraded within three weeks, while those made from a blend of mostly cellulose and small amounts of PLA biodegraded in 3.5 months.

“Alternative materials are being placed into the market with little research behind their impact in terms of degradation potential, which has mostly been tested under laboratory conditions that do not resemble the real environment,” said study leader Alicia Mateos-Cárdenas.

Although preferring coffee, Ms Mateos-Cárdenas drinks tea and, in a perfect world, would advise using loose-leaf tea.

“Obviously, I know it’s more convenient to buy teabags,” she said, before advising consumers to seek out cellulose-based teabags that do not have any plastic.

However, she said that teabags in one box marked 'biodegradable' did not break down at all during the study.