Making sense of plastics and biodegradability…
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The understanding of the detriment of plastic waste to us and our environment has increased over the past few decades. As a consequence, there have been significant advancements in the development of plastics that biodegrade and hence do not create the same waste issues as traditional plastics. However, questions are now being raised as to whether these new ‘biodegradable’ plastics actually do biodegrade, what the best ways to dispose of them are and whether they are actually better for us and the environment. These questions are still being debated, but it is worth us having a look at plastics and their biodegradability, so that we can make better choices for ourselves and our environment.
Traditional plastics are made from non-renewable fossil fuels, such as oil and gas. These plastics are what we are most familiar with in our daily lives. These are the plastics responsible for accumulating in and polluting our environment and the usage of these plastics are associated with a variety of health issues. A number of these traditional plastics are reusable or recyclable but they are definitely not biodegradable. Eventually all of these traditional plastics end up in landfill or as waste in the environment.
There is also another group of plastics known as bioplastics. These are plastics generally made from renewable, plant based materials such as cornstarch, soy or potato. A number of these bioplastics can be made to have similar properties to traditional plastics, whilst other bioplastics can be made to biodegrade. So depending on the bioplastic, it may be recyclable or compostable, but not both. To know which is which, we do have to rely on the symbols the plastic product carries.
When it comes to plastics that are classified as biodegradable, there are two main groups. The first are the biodegradable plant based bioplastics. These bioplastics are compostable, the majority of which require large scale industrial composting conditions in order to break down within a reasonable time frame. In Australia, these plastics can be identified by having either AS4736-2006 printed on them, or sometimes EN13432. We can dispose of these plastics in our council green waste bin, provided food waste is acceptable in the bin and that the collection goes to a commercial composting facility. It is best to check this with your local council first. If disposed of in landfill, these types of plastics will still biodegrade but at a much slower rate due to the lack of correct conditions required for composting. It is not recommended to throw these plastics in your recycling bin as they don’t suit standard recycling processes. So, to get the benefit of their biodegradability, it is best to ensure these bioplastics are disposed of correctly.
A small number of biodegradable bioplastics are home compostable. In Australia, these should have AS 5810-2010 printed on the product or its label. These plastics can go in your home compost bin and will biodegrade into compost that you can use to feed your garden.
The second category of biodegradable plastics are the oxo-degradable plastics. These are traditional plastics made from non-renewable fossil fuels which have had a chemical added to them that will help them break down on exposure to oxygen in air. Oxo-degradable plastics break down into smaller and smaller pieces of plastic. They were some of the first biodegradable plastics created to address plastic waste and their usage uptake has been quite popular. They are commonly used in plastic bags, like shopping bags, bin liners and dog waste bags. In certain instances, oxo-degradable plastic breakdown is accelerated by heat and light but the breakdown is inhibited by water. So those dog waste bags that get left on the beach and wash out to sea remain as plastic bags in the ocean. It is still to be proven whether oxo-degradable plastics fully biodegrade or whether they just form plastic dust and so calling them biodegradable is a contentious issue.
Because oxo-degradable plastics break down into smaller and smaller pieces, their negative impact in our environment can be much greater than traditional plastics. This is because one discarded plastic bottle cap can impact one animal, but if made from oxo-degradable plastic, it can break down into thousands of smaller pieces impacting many animals and entering our food chain.
Another problem with oxo-degradable plastics is that they are detrimental to current recycling streams. The chemicals added to make plastics oxo-degrade contaminate recycled plastic, weakening it and making it less suitable for its intended purpose. Additionally, oxo-degradable plastic is not suitable for composting because it contaminates the generated compost with microplastics.
Overall, biodegradable plant based plastics are a good choice in comparison to traditional plastics, particularly if they are home compostable. However, oxo-degradable plastic is best avoided because it doesn’t appear to truly biodegrade. In Europe there are calls to ban this type of plastic completely and in Australia, it is not supposed to be referred to as biodegradable but rather degradable.
So when trying to choose a more environmentally friendly plastic, look for plastics that state they are compostable and avoid plastics claiming to be degradable.
Written by Jo Seater for Simply Organic Mag.
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