New research from the University of Auckland reveals that not all compostable products are as eco-friendly as they claim.

University of Auckland researchers have been investigating how compostable products like paper cups and food trays can affect soil health.

In 2023, the Ministry of Environment of New Zealand commissioned researchers at the University to investigate how compostable products affect soil health.

Three new reports have been published in detail, with findings, potential consequences and recommendations for regulating these products, aiming to improve compostable product practices in New Zealand with a focus on soil health and cultural relevance.

Packaging products contain harmful substances

As part of the study, researchers tested ten products, including paper cups, bin liners, pizza boxes and food trays, for harmful substances such as plastics, heavy metals, endocrine disrupting chemicals and PFAS.

Analysis revealed that many products contained these contaminants, which threaten soil and groundwater if composted in large quantities. Food safety concern is also raised when a cardboard pizza box with all chemical classes tested.

Compostable packaging may not be green

One of the concerning findings is that an unlined fiber tray labelled “compost me” contains high levels of total fluorine and PFOA, a banned chemical listed on the Stockholm Convention.

Associate Professor Lokesh Padhye, one of the researchers, explained that chemical additives, such as contaminants like PFAS and plastic polymers can persist in the environment for decades, posing long-term risks to soil and groundwater health.

Lokesh Padhye, Associate Professor and one of the researchers.

Although additives are often used to maintain functionality of compostable products, such as preventing soggy and crumbling packaging, products with these additives might prove equally or more harmful in the longer term than single-use plastics.

Actions to be taken

These findings reflect a need for greater transparency and stricter regulations regarding the use of additives in compostable products.

Labelling also pose another challenge in New Zealand as the country lacks clear guidelines on how terms such as “green” and “sustainable” can be used.

Furthermore, the reports will help shape future regulations for compostable products in New Zealand. As there is distinction between home and industrial composting, public misconception can result in improper disposal practices, where products may not decompose as intended.

Furthering the research

The researchers developed a guide, which is the country’s first attempt to create guidelines, to help stakeholders in New Zealand navigate decision-making processes across the different stages of the life cycle of compostable products.

They also aimed to include a diverse range of products to gain a clearer understanding of the issue.