Bioplastic, what does this term mean?

Bioplastic compostable bag

A rise against single-use plastics. It’s happening! Did you know that the European Parliament recently approved a ban? A step in the right direction, if you ask me. Sadly, it’s too late for a lot of marine species. Last month, a whale washed up with more than 1000 pieces of plastic in its stomach – including 25 plastic bags.  No discussion needed: we need more sustainable options! Is ‘bioplastic’ the answer?

It turns out that the term ‘bioplastic’ is quite a confusing one…

An overheard conversation led to some personal research into so-called ‘bioplastics’. What makes bioplastic ‘bio’? Is it better than regular plastic? Can we trow bioplastic the ocean? Does it harm nature?

Let’s break down the differences!

1) The (non-)degradable plastic bag

Polyethylene (PE) is the ingredient of most plastic bags around us. The building blocks (monomers) of PE originate from fossil fuels. How to eventually end up with plastic? The monomers are chemically coupled to form long chains. These coupled monomers are called polymers.

So, why is this material non-degradable? Didn’t it originate from the decomposition of organic material – fossil fuel? Yes, it did. Sadly, due to the chemical manufacturing step (monomers to polymers), the new material becomes unrecognizable to the organisms that usually break down organic matter. In that way, a plastic bag almost takes forever to degrade by itself in the environment. In fact, a bag can outlive you multiple times easily! Time isn’t the only downside of the degradation process. Harmful microplastics will form as intermediates – damaging (marine) wildlife.

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2) The biobased plastic bag

To label a plastic ‘biobased’, the monomers need to derive (partially) from biomass. Corn, sugarcane, or cellulose provide biobased monomers. Next, these biobased monomers are also chemically bound to end up with polymers. Ultimately, plastic based on all natural materials!

This is where it gets tricky.

What if I told you that even polyethylene (PE) can originate from biobased monomers? We end up with the same product: A NON-DEGRADABLE (PE) plastic bag. Still, there’re some advantages. Lesser fossil fuels are wasted which leads to lower emissions of greenhouse gasses. Besides that, the starting materials originate from renewable resources. Is it a sustainable solution? Not really – these bags will also pollute our planet for a very long time.

bioplastic plastic ocean
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3) The biodegradable plastic bag

‘Biodegradable’ material has the ability to break down into natural substances – with the aid of microorganisms, such as bacteria, fungi, or algae. Yet, the term ‘biodegradation’ can be a misleading one as well. Doesn’t biodegradable plastic decompose quickly in a landfill or somewhere else in nature (e.g. the ocean?). Unfortunately, this is not the case. Time is not a definition in the biodegradation process. So, biodegradable plastic can still be around a long period of time.

Let’s take the most widespread biodegradable polymer as an example: polylactic acid (PLA). The monomers of PLA derive from biobased materials such as corn or sugar cane. The degradation process of PLA is not a fast nor cheap one. First, hydrolysis needs to take place. This breaks the polymer into smaller chains (oligomers, dimers, and monomers). In industrial settings, this happens after prolonged heating (45-60 days at 50-60°C). With the aid of microorganisms, these smaller particles can eventually break down to natural materials. Consequently, if PLA-plastic was discarded in the environment, it will NOT degrade quickly by itself. This article mentions it: no degradation observed after 6 weeks of soil burial tests (Ohkita and Lee, 2006).

In conclusion, biodegradable plastic breaks down into harmless compounds if treated under the right conditions!

4) The compostable plastic bag

The last term in the world of bioplastic: ‘compostable’. In order to call something compostable, the breakdown products have to be beneficial to nature. And the process needs to occur within a reasonable timescale. So, not every biodegradable type of plastic is called compostable.

Composting facilities don’t accept a plastic bag labeled as ‘biodegradable’. It simply takes too long to break down on its own. Or it will not decompose entirely. On the other hand, a plastic bag that meets standardized specifications will break down effectively in all composting systems!

Worldwide, the confusion of the terms ‘biodegradable’ and ‘compostable’ led to the formation of a clear set of standardized specifications. In order to label a plastic ‘compostable’, it needs to meet quite some criteria. The document ISO 17088 describes these specifications.

Bioplastic compostable bag earthlyiris
This bag is a certified compostable bag, according to the Europese specifications
A lot of information to take in. So, just to sum a few things up:
  • Long chains of polymers do not occur naturally. As a result, no microorganism can break it down. That’s why it (almost) lasts forever!
  • Biobased plastic does not guarantee a natural and safe degradation process. It can even have identical properties as plastic from fossil fuel.
  • Biodegradable plastic breaks down into harmless compounds. But it needs to be treated under the right conditions.
  • Compostable plastic is biodegradable, yet not all biodegradable plastic is compostable. Thanks to worldwide standardized specifications, clear differences are set.
Bioplastic diagram earthly iris
A schematic overview of ‘bioplastics’ © Earthly Iris

Next time you hear the term bioplastic, think twice! This term is quite confusing. Above all that, the easiest way to avoid all the confusion is to minimize your plastic use in the first place!


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