Is there a perfect solution to the plastic bag?


The single use plastic bag has been a priority issue for many environment groups and some individuals and businesses around New Zealand and globally for many years. Denmark was the first country to ban single use plastic bags back in 1994, and over 40 countries around the world have followed, either imposing complete bans or charging a tax of some kind.

Many Kiwis are asking why New Zealand is so far behind on this issue, especially when many third world countries have already made more progress than us. We keep hearing that biodegradable and compostable bags are a more environmentally friendly alternative, however, are they really a viable solution? Here’s what we know…

What is a plastic bag?

A single use plastic carry bag is defined by its purpose to transport, segregate or hold food or merchandise, and is given to a customer upon point of sale. These single use plastic bags are made from crude oil, natural gas or other petrochemical derivatives, which are transformed into polymers or polymer resin. A very small amount of oil goes a very long way, and the making of plastic bags contributes to 0.2% of Earth’s oil consumption each year[1].

What are the problems identified with plastic bags?BlogImage-RubbishDump.jpg

Although many people tend to reuse plastic bags for other purposes, there is still a significant number of plastic bags that eventually end up in landfill. This number is shrinking now in New Zealand, with the average consumer growing more environmentally conscious, and the growing use of the soft plastics recycling programme. The main concern with plastic bags are the impact that they have on the marine environment. It is reported that most plastic waste that ends up in the ocean is coming from other countries[2]. Nonetheless, New Zealanders are committed to limiting their impact and doing their part to continue protecting marine life from harmful plastic waste.

What is a degradable bag?

 A degradable bag means that is breaks down. Technically speaking, all plastic is degradable plastic because you can break it down by several different methods, therefore “degrading” the plastic. This creates confusion because it is common for plastics to have added chemicals that will accelerate the break down process under certain conditions. However, this breaking down of larger plastics will still result in very small pieces of plastic[3], which can continue to linger in the environment dependant on their composition.

What is a biodegradable or compostable bag?

 A biodegradable plastic indicates that it must break down over time by natural processes and micro-organisms, giving off CO2 and eventually becoming carbon molecules in the ecology of the Earth[4]. Many plastic bags in the current market place are biodegradable, however it is not clear how long it really takes before they break down. To be clear, there is no time requirement that defines a plastic a biodegradable, making it difficult to put standards in place. This is the current debate that is sparking various research on the breaking down of biodegradable plastic products, including bags.

 On the other hand, compostable products are defined by three things: 60-90% of the product will break down into organic elements within 180 days; 90% of the product is going to disintegrate into 2mm pieces or smaller; and the eco-toxicity levels will not leave harmful chemicals in the soil. Compostable plastics are mostly made from the raw material such as corn starch, which is then converted into a polymer with similar properties as normal plastic.

It is important to note that plastic bags made from renewable resources are often processed in ways that result in a non-biodegradable finished product, as they cannot be processed by microorganisms.  Additionally, some biodegradable plastics can only be composted in industrial composting sites. If placed in landfills, these biodegradable plastics either break down, or produce the harmful greenhouse gas known as methane. These results in confusion for consumers, who therefore wont compost or recycle these plastics appropriately. A compostable plastic will break down into only organic molecules, therefore are less harmful to soil and the marine environment.

BlogImage-CarryingAPlasticBagOne concern to many Kiwi consumers who are participating in the soft plastic recycling scheme is that degradable, biodegradable or compostable plastic bags cannot be accepted by The Packaging Forum under this scheme. That is because such “biodegradable” or “compostable” bags have been specifically manufactured to break down in the general waste stream, meaning that they would start to degrade before they are processed for recycling[5]. This potentially renders the output of the soft plastics recycling programme unusable.

Which is better?

Degradable, biodegradable and compostable plastics are easily confused among consumers.

There are two significant difference between degradable and biodegradable plastics. Firstly, the break down of a degradable plastic is a result of heat, moisture and exposure to light or UV rays, whereas microorganisms are responsible for the break down of a biodegradable product. Secondly, degradable products tend to take much longer to break down into carbon dioxide, biomass and water.

There is misconception that these alternatives are better for the environment because natural processes allow them to break down over time, resulting in less waste in landfills and inflicting less harm on sea life. However, there are a few flaws with this argument. Firstly, Kiwis contribute very little to the littering of plastic bags in both landfills and oceans. Second, the definition of these various alternatives and their makeup have blended together and become misleading to consumers. Lastly, the variations between the three alternatives have a few differences in environmental impact: a turtle can suffer if it eats a “biodegradable” or “compostable” bag as much as if it eats an oil-based plastic bag; and the use of “biodegradable” or “compostable” bags threaten to contaminate batches of recycled plastic, rendering it unfit for use again.

There is debate around the use and environmental impact of biodegradable, degradable, or compostable plastic bags as an alternative to single use plastic bags. However, Retail NZ believes that the solution of biodegradable bags is no better a solution than plastic bags, and recommends that retailers are cautious about exploring these alternatives.

By Emily Duncan – Advisor






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