Microplastic Pollution in Organic Waste: Shocking Findings from NZ Study

Photo supplied by UC PhD candidate Helena Ruffell.

A new study has revealed significant contamination of organic waste from microplastics, raising alarms about the long-term effects of the persistent pollutant.

Between 2006 and 2021, only 7% of microplastics-related research addressed land-based contamination, underscoring the need for further investigation into how these pollutants affect soil and agricultural processes.

Released in January by the University of Canterbury (UC) and the Institute of Environmental Science and Research (ESR), the study highlights the urgent need for better waste management strategies, and the reduction of plastic use to prevent further pollution.

Since the 1950’s, mass production and use of plastic has contributed to a global crisis, with microplastics – defined as plastic particles smaller than 5mm – entering ecosystems worldwide.

The study was lead by Helena Ruffell, a UC PhD candidate, as part of her thesis, and took around three years and “a lot of sweat and tears.”

Photo supplied by Helena Ruffell: Types of Microplastics: a) polyester glitter, b) polyurethane kitchen sponge, c) polyethylene microbead, d-f) acrylic films from packaging, patterns on mugs/drink bottles, credit cards.

Helena was initially inspired to investigate the microplastics issue from the environmental chemistry and contaminants lectures at UC as a biochemistry undergrad, before the environmental science major existed.

The tiny plastic particles originate from two primary sources: those designed for specific purposes, such as microbeads, commonly found in face washes, glitter and resin pellets, and those resulting from the breakdown of larger plastic products.

Organic waste, biodegradable materials derived from plant and animal sources, such as food scraps, garden waste and compostable materials, is supposed to decompose naturally. These materials are commonly recycled into compost or biofertilizers to enrich soil health as a sustainable method of waste management.

Alarmingly, biodegradable plastics such as polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) were detected in mature compost samples, indicating the current composting processes fail to fully degrade these materials.

This finding raises concerns about the effectiveness of biodegradable plastics in reducing long term pollution.

The study cites previous research showing microplastics can remain in soil for decades, with evidence of contamination from 12 years after compost application, and even 34 years in North America and Germany

Christchurch City Council Resource Recovery Manager Dr Alec McNeil said the council operates an extensive audit program supporting the community to reduce the potential contamination in the kerbside system.

“Since the introduction of the kerbside organics wheelie bin in 2009, the council has provided ongoing education to support residents in what goes in the organics bin,” Dr McNeil said.

In February 2024, Christchurch City Council began following the new Kerbside Standardization which was introduced by the Ministry for the Environment to “improve the quality and consistency of materials collected”.

Dr McNeil, who was aware of Ruffell's study added the council contractor, who produces compost from the kerbside organics, adhers to New Zealand composting standards

“Whilst the standard does not address microplastics directly, it does confirm the quality of the compost through a batch testing regime”.

Ruffell told Canta microplastics are notoriously difficult to isolate from solid samples, comparing it to trying to remove a needle from a haystack.

“I had to manually identify [the microplastics] under the microscope, pick them out individually with tweezers, and analyse each particle... to confirm it was made of plastic,” Ruffell said.

Findings from the study identified 3,798 suspected microplastics particles, 86% of which were confirmed to be plastic polymers.

Among the most distinguishable microplastics found in biowaste samples were plastic fragments such as plastic kitchen utensils, microbeads, glitter, polyurenthane foam sponge fragments, and multi-coloured films from packaging and decorative materials, many of which had not been widely reported in biowastes.

Canta asked Ruffell how students can do better to assist in reducing the amount of microplastics.

“Just be aware of the plastic products you use and in the flat,” Ruffell said.

Finding non-plastic, good quality kitchen products, purchasing clothing made from natural fibers like cotton, linen and wool from Op shops and being aware only food scraps and garden waste can go in your green bin are all ways to make a difference.

Ruffell stressed the pressure needs to be pushed onto the plastics industry, big corporations, and local and central government to reduce our reliance on plastic products and “promote reusable, sustainable and real solutions, not false ones like ‘made from plants not oil’ or ‘compostable’ plastics’ that support the circular economy.”