Biodegradability of PLA

Recently, We can easily find a product made in Polylactic acid (PLA), not only in the 3D printing industry but also in various final consumable products. Since we realised the negative effects of wasted plastic products on our planet, many major companies replaced synthetic plastic with PLA which is well known for its biodegradability. When I visited South Korea in September 2021, I saw the below poster in Starbuck Korea (Figure 1). The poster says the provided plastic cups that are made in PLA can be treated as general waste due to their biodegradability. When I saw this information, I was curious about the truth.

 

Is PLA biodegradable?

 

Figure 1. The poster shows the provided PLA products by Starbuck Korea can be binned as general waste.

'Biodegradability' is defined as below;

Biodegradability is the capacity for biological degradation of organic materials by living organisms down to the base substances such as water, carbon dioxide, methane, basic elements and biomass [1]. 

 

Pure PLA is sourced from the lactic acids of natural plants such as corn and it is categorised as a plant-based hydro biodegradable plastic. PLA can partly be decomposed into water and carbon dioxide within 47 to 90 days in controlled conditions such as correct temperature, UV exposure and hydrolysis [2]. However, many final PLA products are produced with blended PLA and processed with chemicals that reduce their biodegradability. As the materials' degree of crystallinity strongly affects the rate of decomposition [3], in result, the biodegradability of PLA is vary depending on the chemical purity of PLA and also the correct decomposing conditions. Therefore, in reality, it is hard to treat PLA as general waste and believe it will be decomposed under the natural environment.    

 

Currently, the SPI resin identification classifies PLA as code 7, 'others'. There is no specific recycling guideline for PLA at a moment, therefore, end of life, PLA products follow regular plastic waste processes like the below [4]. 

 

1. Recycling
2. Composting
3. Incineration
4. Landfill

 

PLA is indeed more eco-friendly than any other synthetic polymers, however, to maximise its biodegradable capacity, we need a proper recycling guideline. Otherwise, the waste of PLA products will harm the environment like other plastics.

 

PLA in 3D printing

There are positive movements to make the 3D printing market more sustainable. Some companies developed recyclers that grind used PLA plastics and reproduce either pellets or filaments that can be reused. Recycled PLA spools are also available in the market at competitive prices. I've attached possible sustainable options for 3D printing enthusiasts to minimise the footprint on our planet, but still enjoy 3D printing.        

 

[Recycled PLA]

1. Filamentive: https://www.filamentive.com/

Filamentive | Leading 3D Printer Filament Brand in UK

2. Formfutura: https://www.formfutura.com/shop/product/reform-rpla-2838?category=450 

ReForm rPLA

3. 3DJAKE: https://www.3djake.uk/3djake/rpla-blue

rPLA Blue 1,75 mm / 1000 g

[Filament Recycler/Maker]
1. 3devo: https://3devo.com/filament-makers/

Meet The Composer And Precision - Desktop Filament Makers | 3devo

2. ProtoCycler+: https://redetec.com/products/protocycler?variant=39805373743152 

ProtoCycler+

 

 

 

 

References

 

[1] Goswami, P. and O'Haire, T., 2016. Developments in the use of green (biodegradable), recycled and biopolymer materials in technical nonwovens. Advances in Technical Nonwovens, pp.97-114.

[2] Harris, W., 2010. How long does it take for plastics to biodegrade?. HowStuffWorks. Np.

[3] Pantani, R. and Sorrentino, A., 2013. Influence of crystallinity on the biodegradation rate of injection-moulded poly (lactic acid) samples in controlled composting conditions. Polymer Degradation and Stability, 98(5), pp.1089-1096.

[4] En.wikipedia.org. 2021. Polylactic acid - Wikipedia. [online] Available at: <https://en.wikipedia.org/wiki/Polylactic_acid#cite_note-Pantini2013-53> [Accessed 13 December 2021].