Biodegradable plastics - Two words that really shouldn’t go together

Influx of recycling bins seen in Upper Riccarton, a common student-central suburb. Source: Hariklia Nicola / Canta 

The term "biodegradable" is often slapped on packaging to boost business profits, but it creates more problems for recycling plants. To biodegrade means to break down over time, but there are no clear specifications on how long this process takes—it could be 500 years for all we know. Worse, these materials might degrade into microplastics—tiny, harmful bits of plastic that threaten aquatic life and could increase heart attack risk in humans. Labeling packaging as biodegradable is often a cover for deceptive claims. Your "biodegradable" coffee cup might take 372 years to break down, but for now, it’s mostly ending up in landfills or contaminating green bins. So, pay attention.  

Environmental science student and eco-warrior, Jess Lamb told Canta that “although both biodegradable and compostable packaging types have been advertised to be more sustainable and eco-friendly, that's all it is, advertising.”  

Jess Lamb interning at the Rotorua Lakes Council with the solid waste and sustainability team. Source: Supplied 

The excessive global consumption of plastic has increased immensely over the years due the fact it is lightweight, resilient, long lasting and relatively cheap. 300 million tons of plastic are made annually, for only 7% of it to be recycled and 8% to be incinerated - the rest goes straight to landfill. 

“A lot of people feel that we can recycle our way out of this crisis, but I don't think we can, because of the volumes that are being made, and it's just not practical,” said Environmental scientist and UC lecturer, Sally Gaw. 

Environmental Science and Chemistry Lecturer at the University of Canterbury, Sally Gaw. Source: Supplied / The Press.  

Though Gaw is interested in how everyday life leads to environmental contamination, as her career has gone on, she said she has become more interested in how we make sure that we're not releasing things into the environment that cause more problems.  

“We can keep documenting what we're finding in the environment, but I'd like to  

start taking more of that knowledge and actually trying to work how we stop things getting into the environment in the first place... otherwise, we're just going to keep playing this catch-up game forever,” Gaw said.  

Gaw's interest in environmental chemistry began during her childhood in developing countries, where she observed the direct impact of environmental issues on people's lives. She recalls seeing large yellow drums of DDT, labeled as made in the USA but not for sale there, highlighting discrepancies in environmental practices. The lack of regulatory around substances in some countries is a major issue, that indefinitely sparked a keen interest for chemistry and contaminants for Gaw. But what Gaw discussed in depth is the issue around plastic – the ugly, the bad, and the even uglier truth. 

Gaw notes one of the many challenges with compostable plastics, as they often require specific conditions to break down, which are not achievable in-home composting. Which unfortunately, I fear lots of student don’t even do anyway. But the important thing to know – is many of your ‘biodegradable packing’, is not going to compost in your green bin.  

"A lot of the compostable plastics need certain temperatures and conditions that you wouldn't get in your home compost," she explained. Instead of fully decomposing into harmless substances, these plastics can break down into microplastics, exacerbating environmental pollution.  

This issue is further complicated by the presence of other plastics added to improve the strength of compostable plastics, making them less compostable. The Christchurch City Council website says biodegradable or compostable bags, liners and packaging and cardboard and paper with food on it go in the red bin, including newspaper, dirty pizza boxes and many more things. So stop putting last night’s 2am dominoes in the green bin, if it is clean it goes in recycling, if it is dirty – bin it. And don’t chuck your ‘biodegrable’ plastics into your recycling either.  

Lamb takes it upon herself to enhance her education around everything eco-friendly, as well as spreading the word about what she knows. She is also co-organiser of the Compost club here at UC with her twin sister Kaitlyn. 

She echoed the intensity of this issue around biodegradable packaging still ending up in landfills, where it releases methane gas (CH4) due to the mix of plastic and plant-plastic materials - further contributing to the climate crisis. Lamb states that even compostable packaging often ends up in landfills because Aotearoa lacks facilities to break down these materials, leading to contamination if placed in green organics bins.  

Other countries such as China are saying “get lost, we don’t want your rubbish,” said Gaw.  With only ten facilities capable of breaking down bioplastic at the necessary temperature of 55 degrees, with only one facility in Christchurch, the country's waste management is further strained, leading to more significant environmental challenges.  

Lamb adds that "home compostable" packaging is an exception, but even then, it may contain chemicals unsuitable for soil, necessitating critical thinking about what goes into home composts. 

Gaw emphasised the classification of plastics and biodegradable plastics as inherently good or bad is complex. Instead, the focus should just be reducing plastic usage. Ultimately, Gaw believes the crucial question is, "When do we use plastic and when do we not use plastic?"  

Lamb echoes these sentiments, advocating for zero waste living and using reusable items instead of buying into unethical consumerism.  

“Companies that use marketing schemes saying that they're items are "biodegradable" or "eco-friendly" fire me up because they're only saying that so they can put a premium on their products and therefore make more profit,” Lamb said.  

During her internship with the Rotorua Lakes Council, her main role was focused on waste surveys of public litter bins. She discovered that a significant amount of the waste was "biodegradable" packaging, which still ended up in the bins.  

"Although consumers think that buying their food or drinks in biodegradable packaging is fine, it's actually not," she said, highlighting that this waste still goes to the landfill and harms the environment 

Jess Lamb doing mahi for WastewithoutwaterNZ as part of her PACE internship at the University of Canterbury. Source: Supplied. 

Her advice? Take reusable items out with you wherever you go, where nothing is thrown "away." 

“Use what you already have. Going out for a chai latte? Don't use a single use cup, bring a glass jar, put a piece of material around it, like a sock, [to prevent you from burning your hands] and use that for your drink.” 

As for Gaw, she’s advocating for stricter regulation of plastics, emphasising the need for more control over plastics to protect human health and the environment. 

“I think we don't fully yet know what the human health implications are, but we know that a lot of the additives that are used in plastics or made of chemicals used in the manufacture of plastics that are already on hazardous substance list, so we already know that they're a problem, yeah, but we're not necessarily regulating them.” 

So next time you see "biodegradable" on a package, remember: it's not as green as it seems. Think reusable, not disposable, and let's genuinely reduce our plastic footprint.