Defining compostable and biodegradable packaging

Packaging is under the spotlight, and rightly so as we progress towards achieving Australian National Packaging Targets, whereby all packaging, by 2025 should be recyclable, reusable or compostable.

So let’s have a closer look at what is meant by compostable, why it is so often confused with biodegradable and, in a packaging context, what does the consumer do with the empty package?

For compostable packaging to be utilised to its full potential, what needs to change in our waste collection steams? Now that renewable packaging is starting to gain momentum, what does bio-based add to the supply chain and why are bio-based raw materials not necessarily biodegradable?

What is compostable?
Although not many consumers have access to one, we are familiar with compost heaps. The composting process allows us to dispose of leftover foods for example to decompose and creates fertiliser for your soil. When it comes to compostable packaging however, we need to understand that backyard composts have a completely different set of physical conditions than industrial composting facilities – an important distinction.

Industrial composting can cope with a wider range of compostable products as it involves pre-processing – where materials are ground and chipped down into smaller pieces, and in addition, industrial composting provides the higher temperatures needed for more efficient break down. Home composting takes place at much lower temperatures and over an extended time frame, which can typically go up to a year, compared to a matter of weeks for industrial composting.

Compostable packaging will likely not break down in a landfill, as they lack the right conditions, especially in a modern landfill where there will be no oxygen. The only desirable waste stream for compostable packaging is an industrial compost facility.

And while not currently available in all regions of Australia, industrial composting facilities are becoming increasingly widespread with many more councils and private companies providing bins, where food scraps and garden waste can be disposed of together.

However, with a significant amount of education required to advise consumers about what can go into such bins, many council schemes do not permit packaging of any type, in case it results in a negative impact due to the wrong packaging ending up at an industrial composting facility. As the volumes of compostable packaging on the market are relatively small, the impetus to study its compatibility with council schemes is low.

What is Biodegradable?
Everything will degrade over time, but true biodegradation occurs through a biochemical process, with the aid of enzymes produced by naturally occurring microorganisms, both in the presence and absence of oxygen i.e. aerobic or anaerobic, without leaving behind any toxins, yielding only carbon dioxide, water and humus or biomass. Biodegradation is just a natural process taking its course and breaking down materials to their component parts.

Biodegradable packaging can be derived from several sources, including renewable sources – like paper or bioplastics, as well as petroleum-based plastics, which are specifically engineered, to decompose in the natural environment, which is significant at the end of life. A biodegradable plastic will be considered a contaminant in the plastics recycling stream, as on being exposed to moisture and appropriate microorganisms, the biodegradation process will commence.

So, we are clear on what is compostable and what is biodegradable, subtle but important differences when it comes to disposing of the package in the right waste stream. Now let’s not allow ‘bio-based’ to add any confusion. A package derived from a ‘bio’ source, can be designed to be compostable or biodegradable, however it is equally possible that it is not – meaning the package can be disposed of with like-packaging in a recycling stream for example.

Many different renewable ‘bio-based’ ingredients are now used as packaging inputs. Some enable compostable and biodegradable packages, whereas others produce packaging that is identical to that from fossil-based sources hence, the bio-based packaging can be recycled with like polymers. Examples are bio-polyethylene and polypropylene derived from plant based renewable feed stocks, that have properties that cannot be distinguished by the equivalent polymers derived from petrochemicals. The following summarises the two sources of plastic – fossil based and renewable, with their corresponding four attributes:

All these packaging formats are desirable – as long as the consumer has the right information and the right facilities for proper disposal. Currently whilst there are standards and guidelines from organisations such as the Australian Industrial Composting Standard (AS4736) and the Australian Organics Recycling Association, there is no universally recognised symbol for labelling consumer packaging. With the uptake of the Australasian Recycling Label (ARL), this problem could be addressed down the track.

Compostable and biodegradable packaging comes into its own where it enables food waste to be captured in the organics waste sector and this is predominantly at public events where the inputs to the waste stream can be controlled. This is likely to be the area in which we see the most growth in compostable and biodegradable packaging and provided that growth mirrors the capacity of the organics collections to handle it, that’s a positive outcome on all fronts.


  Biodegradable Non-biodegradable
Fossil Based Some fossil-based plastics, whilst not common in packaging, are biodegradable.  Examples are polybutyrate adipate terephthalate (PBAT) and Polycaprolactone (PCL) Conventional Plastics like HDPE, PP and PET are derived from fossil sources and whilst not biodegradable, they are recyclable.
Bio-based Polylactic Acid (PLA) is an example of a Bioplastic which made from renewable sources. It is also biodegradable. Plastics like PE, PP and PET can also be derived from renewable sources and hence are known as Bioplastics. This does not mean that they are biodegradable. However, they are recyclable with conventional plastics
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