Not all “biodegradable” tea bags live up to their name, a new Irish study shows

The Irish are among the best tea drinkers in the world, but a new study has found that not all tea bags are biodegradable.

We might think that our tea bags are made entirely of paper and can be thrown in the compost, but surprisingly most tea bags on the market contain a plastic called Polypropylene (PP) as a seal.

Recently, some major Irish tea brands have started to switch to alternative plant-based materials such as cellulose or so-called ‘bioplastics’ such as polylactic acid (PLA).

A newly published University College Cork (UCC) study compared the degradation of eight different brands of tea bags commonly found on Irish shelves.

For the study, tea bags were individually buried outdoors in garden soil in the city of Cork in 2020 and 2021 and checked regularly for a year.

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

The main results of the study show that tea bags made from a mixture of cellulose and PP (common plastic), the most common tea bags found in supermarkets, had produced the most fragments after 12 months in the ground.

This was to be expected since plastics are known to break down into smaller fragments called microplastics, but tea bags made entirely of PLA (“bioplastic”) and marketed as fully biodegradable have been found still fully intact in the ground.

However, not all tea bags behaved the same and some biodegraded in the soil. Made entirely from cellulose, the tea bags biodegraded in three weeks, while those made from a mixture of cellulose and PLA (bioplastic) biodegraded in three and a half months.

The results show that this is because the blend only contains PLA at a very low level, meaning that the tea bag is mostly composed of cellulose, which is known to degrade very quickly.

The study leader and postdoctoral fellow at the UCC School of Biological, Earth and Environmental Sciences said studies like these provide industries and policymakers with “factual and timely” results.

dr Alicia Mateos-Cárdenas said: “Alternative materials are being brought to market with little research into their impact on degradation potential, which has largely been tested under laboratory conditions that resemble the real environment.”

“It is very important to understand the real fate of bioplastics and to continue to understand the spread of plastic pollution,” she said.

“Studies like these can provide industries and policymakers with factual and timely results, especially for the upcoming international meetings on a UN plastics treaty that will regulate the production and pollution of plastics.” Not all “biodegradable” tea bags live up to their name, a new Irish study shows

Fry Electronics Team

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