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Biodegradable Plastic Bag Myth - Are They Truly Eco-Friendly?

Updated: Dec 10, 2021

Biodegradable plastic bin liners and compostable garbage bags seem to be an eco-friendly alternative to conventional plastic bags. With consumers in Australia becoming more and more environmentally conscious even retail giants such as Coles and Woolworths are offering biodegradable plastic bags to their shoppers - oftentimes at very high prices. But are biodegradable bags eco-friendly and actually 100% degradable? And what are the problems with biodegradable plastics? In this post we gathered together some biodegradable plastic bag facts (all backed up by the science and reputable organisations of course) to dispel its myth - once and for all.

What are biodegradable plastic bags made of?

Biodegradable, compostable and bio-based plastic are all considered to be bioplastic.

Unlike plastic we are all used to, biodegradable plastic is not made from petroleum, but from plants or other biological material. There are two ways for producing biodegradable plastic: it can either be made by extracting sugar from plants like corn, cassava or sugarcane to convert into polylactic acids (PLAs), or else it can be made from polyhydroxyalkanoates (PHAs) derived from microorganisms. So far it sounds promising. But what’s the catch? It brings us to the following question.

How long does it take for a biodegradable bag to decompose?

The name biodegradable can be pretty misleading. You would think that such bags are degrading naturally and fully once they are disposed of, right? The truth is that biodegradable plastics require very high temperatures (at least 50C) and humid conditions to degrade which is very hard, if at all, to meet in the natural environment. In addition, same as petroleum-based plastic bags biodegradable plastic bin liners are never broken apart fully - instead, they become microplastics which stays in the environment forever.

If you think that compostable garbage bags are a better choice for the planet, you are wrong again. Although they do fully decompose, it happens so only under certain conditions - at either industrial composting facilities of which there are very few of in Australia, or in home composting systems. And if not gone through a managed composting process, compostable garbage bags pollute landfills, oceans and waterways the same way as regular, single-use plastic.

Is biodegradable plastic harmful to the environment?

You bet! Biodegradable bags are no good for the environment! Researchers from the University of Plymouth in the UK recently tested five different types of plastic carrier bag - two types of oxo-biodegradable bag, one biodegradable bag, one compostable bag, and a conventional high-density polyethylene plastic bag. They found no clear evidence that bioplastic bags including biodegradable bags and compostable bags offer an environmental advantage over conventional plastics since they were proven to stick around in the environment for a very long time. In addition, researchers raised a concern that biodegradable plastic bags specifically can be fragmented into microplastics, thus having the same environmental effect as traditional single-use plastic bags - partially degraded compostable or biodegradable bags can be ingested by animals and enter the food chain posing certain health risks.

In a recent report, Greenpeace and Environmental Investigation Agency (EIA) are strongly advising against usage of biodegradable and compostable plastics naming it a false solution.

They are pointing out that the majority of bioplastic is derived from agricultural feedstock, which competes with food crops. Thus as an effect, bioplastic threatens food security, as well as causes biodiversity loss and drives agricultural emissions. Rather than choosing a questionable solution, Greenpeace and EIA strongly recommend to focus on reduction and reuse.

So there you have it - the myth of biodegradable plastic bags busted! If you're passionate about reversing climate change, you know now that using biodegradable plastic bags or compostable garbage bags (any bioplastics) is definitely not good for the planet or people. If you use kitchen tidy bags (single-use or biodegradable) TOMbag reusable garbage bags might be exactly what you've been looking for.

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1 Comment

Richard Fine
Richard Fine
May 04, 2021

Compostable bags play an important role in reducing organic waste to landfill. They eliminate contamination of the organic recycling stream. Based on the content of this blog post it appears not to understand that the systemic role of compostable materials is to improve the treatment of compostable wastes, including food and garden waste, by ensuring their capture and clean return to soil without plastics. We have to ensure that we are not confusing the issue of generic claims for biodegradability with specified applications that have pass/fail criteria for biodegradability specified in standards, i.e. AS4736 or AS5810 There are also well-established organisations who

independently assess and certify an item’s conformance with one or more of these standards and other standards for…

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