Biodegradable seems like the better option. But how sure are we that it truly breaks down when it is out of our sight?
Biodegradable plastic is currently one of the most popular and well-known alternatives to the conventional plastic that fails to break down over time.
However, how much do we know about the effectiveness of biodegradable plastic and its ability to prevent chemicals from polluting our environment?
In this article, we explain what it means when plastic is labelled as ‘biodegradable’, what it is usually made of, and why disposal methods play an important role in ensuring these biodegradable are truly a beneficial replacement for traditional plastics.
Chemically speaking, what is plastic?
One of the main characteristics with conventional plastics is that it sticks around for a long time in our environment without breaking down.
This is the case because all plastics are made of long molecules called polymers. A polymer is a substance consisting of many repeating units (i.e., think of a chain of paper clips).
Natural polymers exist, of course – examples of naturally occurring polymers include things such as our DNA, silk, wool, cellulose, to name a few.
On the other hand, synthetic polymers are derived from petroleum oil. Examples of these include nylon, polyethylene, polyester, Teflon, and epoxy.
To manufacture plastic, the raw material used is called a resin, and some of the most common resins include polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS). Plastics are produced by the conversion of natural products or by the synthesis from primary chemicals generally coming from oil, natural gas, or coal.
Synthetic polymers in the form of plastic are widely used today for its favorable properties, such as being resistant to chemicals, insulators of heat and electricity, and they can be proceed in ways to produce varying products.
What is biodegradable plastic?
According to PlasticsEurope, biodegradable plastics are plastics degraded by microorganisms into water, carbon dioxide (or methane) and biomass under specified conditions.
Some of them are also compostable, meaning that they can be turned into compost along with food and other organic waste as well.
What is it made of?
According to the Earth Institute, there are two main types of bioplastics – PLA and PHA.
Polyactic acid (PLA)
PLA is made from sugars in corn starch, cassava, or sugarcane, and it is biodegradable, carbon-neutral and edible.
It can come across as polyethylene (which is used to make plastic film and bottles), polystyrene or polypropylene, and they are commonly used in food packaging.
PLA does break down, but only in industrial composting facilities, meaning that you cannot compost PLA products at home.
PHA is made by microorganisms that produce plastic from organic materials, where the microbes are deprived of nutrients (such as nitrogen, oxygen and phosphorus) but given high levels of carbon.
As a result, they produce PHA as carbon reserves, which has a chemical structure similar to that of traditional plastics, and these are harvested. PHAs are commonly used in medical devices such as sutures and cardiovascular patches.
In comparison to PLAs, PHAs are able to biodegrade in ambient environments, even in the ocean.
Disposal methods matter for biodegradability
The truth is, the biodegradability of a bioplastic is largely based on disposal methods.
In other words, a compostable or biodegradable product can be just as harmful for the environment as traditional plastic if it is not disposed of properly.
Why is this the case?
Typically, there are two kinds of disposal – one in managed environments (i.e., industrial composting facilities, anaerobic digestion and home composting) and the other in unmanaged environments (i.e., where plastic litter ends up – the ocean, soil).
In a study investigating several biodegradable plastic blends and its consequent waste management, Narancic et al. (2018) emphasized the importance of understanding biodegradability as consumers, and for product designers to take this into account.
This is because they found that while PLA is one of the best-selling biodegradable plastics, it is not home compostable – meaning that it needs special equipment to be broken down safely and properly.
Thus, if a PLA-based biodegradable plastic ends up as litter in the ocean chances are it is not breaking down like we expect it to.
This is crucial for us to remember.
Similar to wishcycling, just because it says that it is biodegradable does not mean that it will break down over time. Without proper facilities and the appropriate conditions most of these biodegradable products will not break down.
Blends of biodegradable products make it more possible for home composting
The study also uncovered interesting insights. For instance, if the biodegradable plastic was blended.
The researchers found that by adding 20% of PCL (polycaprolactone) to PLA the plastic becomes home-compostable and more flexible. This greatly improves its end-of-life and also its in-use properties – which is great!
Other types of biodegradable plastic investigated in the study – TPS (thermoplastic starch), PHB (polyhydroxybutyrate), PBS (poly(butylene succinate)), PHO (polyhydroxyoctanoate) – displayed varying levels of biodegradation.
In this case, TPS and PHB were the only bioplastics tested in this study to satisfy the criteria for biodegradation proposed by international standards across all seven tested environments, while PBS and PHO reached standards criteria only in industrial composting.
Biodegradable plastic should not be recycled
An important note here is that biodegradable plastic should not be recycled at all – it will only wound up as contamination in the stream of recyclables.
What does this mean for us?
This knowledge of biodegradability and how blends can affect it will come in handy to inform the design and application of materials so that they will not continue harming the environment.
Many biodegradable materials require industrial composting facilities to degrade properly, only few of these materials can do so in unmanaged environments.
As consumers, reading labels on these biodegradable plastic will help us in determining how to handle it after using the product.
For a guide on what labels to look for, please refer here.
Is biodegradable plastic better than traditional plastic?
While biodegradable plastic seems like a better option to eventually replace conventional plastic, it remains important to reduce our overall plastic consumption and to consider proper disposal methods for biodegradable products.
Again, to reinforce our point – proper waste disposal goes a long way in making sure both our plastic and biodegradable plastic end up where they should be.
Biodegradability only works when it is properly disposed of after use.
It will also be worthwhile to ask manufacturers for the truth on biodegradable products – “Can these biodegradables be composted in my home, or will it require an industrial composting facility?”
“What should I do with my biodegradables if there isn’t an accessible industrial composting facility?”
(We hate to say this, but the actual answer would be the landfill bin since we want to avoid contaminating the recycling steam and leaching chemicals into the environment if it is tossed in an unmanaged environment).
Many times we will find that caring for the environment turns out to be choosing between the lesser of two evils.
The choices are difficult.
We continue to emphasize, though, that every small consideration, effort and mindfulness will count. It’s for our planet, after all.