What’s The Deal With Compostable Plastic?

Walking past my local salad joint the other month, I stumbled across something interesting. The piles of plastic containers which have always plagued the salad bar window were sporting a brand new look. At the bottom of each container was the bold green writing: 'This plastic is compostable'.

My first thought was "Great! Finally local businesses are taking responsibility for our growing plastic epidemic", but then I thought a little deeper into the issue. What does compostable plastic even mean? What's it made of? Can I throw it in my household compost? After all, these containers looked exactly like traditional plastic. So, I did some investigating.

It turns out that all plastics on the market can be placed into three categories: degradable, biodegradable and compostable. To understand how compostable plastic breaks down, it's helpful to understand the difference between degradable and biodegradable plastics.

Degradable simply refers to the ability of something to break down. All types of plastic, including petroleum based plastics and plastics made from natural materials are degradable. They can be crushed and shredded into little pieces and will eventually break down completely.

Biodegradable plastic is degradable. But what sets biodegradable plastic apart is that it can be ingested by bacteria and other micro-organisms, which facilitate a process called biodegradation. Biodegradable plastic can take any time between months and several years to break down depending on the conditions it is exposed to. Moisture, light and heat are some of the factors that can increase the speed it takes for a biodegradable piece of plastic to degrade. Although some biodegradable plastics are made from corn and can integrate into the environment once biodegraded, many are made from petroleum and leave toxic residue once they have broken down.

What is compostable plastic?

Compostable plastic is both degradable and biodegradable. According to Australian standards, for plastic to be labelled compostable, 90% of it must biodegrade within 180 days of being in compost, it must be made up of at least 50% of organic materials and it mustn't leave behind toxic residue once it has broken down.

Can I compost it at home?

Despite the friendly sounding label, compostable plastic will only biodegrade under special circumstances. Heat is a major factor in the ability for compostable plastic to biodegrade, therefore it is not suitable for your household compost. It needs to be taken to an industrial composting facility where it can be placed under the right heat conditions to undergo biodegradation.

Is compostable plastic good for the environment?

If disposed of correctly, compostable plastic can have a minimal impact on the planet and can be re-integrated into soil within weeks or months. That said, there are dangers involved with looking to compostable plastic as a one-stop solution to our plastic epidemic. With widespread confusion over compostable plastic and how it should be disposed of, the rollout of this plastic as an 'environmentally friendly' alternative to traditional plastic may do more harm than good. In order for compostable plastic to be a sustainable solution, it relies entirely on the consumer to be informed and dispose of it responsibly. Consumers have three options when disposing of compostable plastic: recycle, place in the garbage or compost.

Depending on what the plastic is made of and your local recycling requirements, compostable plastic can be tricky to recycle. Although some recyclers accept compostable plastic for recycling, many consider it a contaminant.

If placed in the garbage, compostable plastic can have a harmful impact on the planet and contribute to global warming. In landfill there is minimal oxygen and therefore insufficient micro-organisms to induce the process of biodegradation. So when a piece of compostable plastic breaks down in landfill, it emits methane, a harmful greenhouse gas 23 times the potency of carbon dioxide.

The low impact option of disposal is to send the plastic to your local industrial composting facility (if you have one!), where it can undergo biodegradation.

Regardless of whether a piece of plastic takes 300 days or 300 years to break down, it is polluting our planet. When it comes to compostable plastic, the safest option for the earth is to avoid it altogether. Living plastic free doesn't have to be a hard as you might think. Check out our guide for making the transition.

Read this next: How to Freeze Food Without Using Plastic

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