Bioplastics – What are they?

Delving into the ever changing world of bioplastics is not for the faint-hearted. The confusing plethora of information (and misinformation) from competing sources ensures the waters are muddied at the best of times so understanding exactly what bioplastics are can be problematic.

The truth is that bioplastics are complicated. Complicated from the point of view of what they are, what they are derived from and what they can be used for. Because of that complexity people tend to conglomerate all the different properties of the varying materials into one single entity that will solve all the worlds problems when in fact bioplastics are a wide and diverse family of products each with widely different properties.

 

What Are The Two Main Types Of Bioplastics?

All bioplastics have one thing in common, that they are not derived from fossil fuel. Then there are two main types – bioplastics that mimic fossil based plastics, and bioplastics that have their own unique properties.

The first group - polypropylene, polyethylene, polyethylene terephthalate (PET) and other polymers - can be made from a bio based source and have all the properties associated with their fossil based counterparts. The difference is that the ethylene that is used in their production comes from a plant based source instead of gas and oil. They can also be recycled within the existing recycling streams, both mechanical and chemical, with no issues.

The second group is more diverse and complex and these include biodegradable and compostable plastics. To add to the confusion all compostable products are biodegradable but not all biodegradable products are compostable.

 

Biodegradable VS Compostable Plastics

Examples of biodegradable plastics include, Polyvinyl alcohol (PVA), and Cellulose acetate (CA). They are derived from corn starch, vegetable fats and oils, and other renewable biomass sources.

There are a bunch of recognised standards for biodegradability but the most helpful are ISO 14855 (method for determining the aerobic biodegradability of plastics) and ISO 17088 (standard for identifying and labelling plastics that can be composted aerobically) both of which specify that at least 90% of the material must biodegrade within six months. Therefore an item labelled “biodegradable” can still leave micro plastic particles.

Compostable plastics, on the other hand, will completely break down into soil conditioning material (i.e., compost) under a certain set of conditions within a given timeframe, and not leave any residue behind. Polylactic acid (PLA), Polybutylene adipate terephthalate (PBAT) and PLA compounds, and polybutylene succinate (PBS) and polyhydroxyalkanoates (PHAs) compounds are some of the more common compostable plastics.

And don’t get confused by oxo-degradable plastics, which are not biobased and are not related to either of the above. They contain an additive that breaks down polymers into micro plastics that then remain until broken down naturally. These have been banned in the European Union.

What About New Alternatives?

There are other “new” materials becoming available that are not strictly plastics - but are polymers - so are related (note – all plastics are polymers but not all polymers are plastics – does that sound familiar?). Materials based on seaweed, algae, or cornstarch can be used as substitutes for plastics and can have similar properties.

The difference is that these new materials are not chemically modified from their base material, where plastics are. Their main use at present is as waterproof coatings for boards and thin films, but some injection moulded products such as forks and spoons are beginning to become available.

A couple of things to remember are: just because something is labelled biodegradable it doesn’t mean it will decompose if you drop it as litter as both biodegradation and compostability rely on controlled conditions to be effective. Also, some biobased and compostable materials can disrupt existing mechanical recycling systems.

 

So, as you can see there is plenty of scope for confusion and misinformation caught up in the biodegradable plastics world. With companies using biobased, biodegradable, compostable, green, natural, and many other seemingly “eco-friendly” ways of describing their products it is no wonder people are confused. To help, just remember three things: always check the certifications and standards that a material conforms to, always check the exact claim that is being made (biodegradable, compostable etc.), and never take a claim at face value (always look for the evidence).

 

Like this article? Here's a few others to extend your knowedge further:

• The Case for Biobased Plastics
• How Is Plastic Made? A Simple Step-By-Step Explanation
• Bio-based plastics: Feedstocks, Production and the UK Market

 

Author:

Brian Lodge - Director of Packaging, British Plastics Federation

 

*Please note that this article is not a press release. Do not use on your own website unless given specific permission from the BPF.