Is PLA biodegradable? (a debate over its use) 

In this short report we will discuss the topic “Is PLA biodegradable?”. We will look at its material compossibility over plastic, its biodegradability, its recyclability and what research is being carried out for its potential use as an eco-friendly material. 

Is PLA biodegradable? 

There is no straight answer to this question as some research debates on whether there are enough biodegradable enzymes produced by natural means that can biodegrade polylactic acid. Most of the known microorganisms do not produce the enzyme required for biodegradation of PLA. 

Is the PLA degraded or bio-degraded

Reviews on PLA biodegradation have described that biodegradation of PLA occurs only after its hydrolysis process, which is breakdown of polymer chain backbone through chemical or physical methods. However, these processes are independent of all biological agents. 

The only way polylactic acid can self-hydrolyse is by treating it at a temperature of 104°F which cannot be carried out through natural process. Hence, it is important to treat them in an industrial set up and convert it into a compostable material for further biodegradation. 

In addition, it is also known that certain proteinase K enzyme hydrolyse PLA, but it’s so rare that it does not produce any beneficial effects to the environment. 

For the biodegradation process to happen, the polylactic acid has to be degraded first followed by enzymatic treatment. Thus, a variety of chemical physical and biological processes are required for complete biodegradation of polylactic acid. 

What are the potential uses of PLA? 

Polylactic acid is also called as bioplastic because many of their properties are like plastic, but PLAs are much more eco-friendly. Hence, they are a better source for replacing plastics products such as plastic films, bottles and medical devices. However, with the development of 3D printers the use of PLA has skyrocketed. 

They are used as a 3D printing feedstock for many fabrications. Polylactic acid provides better rheological properties for printing and their filament is more sustainable and safer than other materials used for 3D printing. The following properties of PLA allow for its wider applications:

• Rheological properties

• Biocompatible nature 

• Modifications of PLA 

The rheological property allows for better printability of the PLA filament. They tend to behave like liquid under pressure and hence PLA like material show less resistance to flow like other shear thinning fluids. Thus, PLAs are used widely for 3D printing applications including making biocompatible medical parts. 

PLA is a thermoplastic with high-strength and high-modulus like traditional polymeric materials and hence finds applications in the industrial packaging field and bioabsorbable medical devices. Further, the mechanical, thermal property of PLA can be varied as per the requirement by changing their molecular weight. 

Scientists have incorporated carbon nanotubes to increase the mechanical strength and electrical conductivity of PLA thermoplastic thus maximizing its application. In another study, PLA has been modified with lignocellulose to significantly improve the properties of PLA such as mechanical strength, thermal stability and bioactivity. 

Biocompatibility is one of the most attractive features of PLA. The FDA approved PLA is non-toxic to humans and due to its biocompatible nature, it has found many applications in the clinical field for making screws, plates for bone fixation and for surgical structures and meshes. 

What are the environmental benefits of polylactic acid? 

Compared to plastic, the production of PLA is most economical and eco-friendly. The following points can highlight the advantages of PLA. 

• Utilizing renewable raw material 

• Lowers greenhouse effect 

• Recyclable 

• Energy efficient 

• Can replace plastic in many application 

Though biodegradation of polylactic acid is a debate for the future, the current production and use of PLA has some environmental benefits over conventional plastics. Polylactic acid is made from repeating units of the monomer lactic acid which is obtained by the fermentation of sugars from sources such as sugarcane or corn starch or other carbohydrates unlike most plastics which utilizes non-renewable petroleum reserves. 

Hence PLA is eco-friendly and being non-toxic or non-carcinogenic, finds wide application in medical devices. Besides, during its production it consumes CO2 and thus provides a carbon-free and cost-effective method of production as well as a better source of carbon capture for a much greener environment. The production of PLA required 25-55% less energy compared to the production of petroleum-based polymers. 

Another advantage is its recyclability. Since PLA is a thermoplastic, it melts at a lower temperature thereby making it an energy efficient method of recycling. The use of bioplastic is another advantage of PLA, where single use traditional plastics can be replaced with PLA plastic and provide a better alternative to much widely used plastic products. 

Even more, most cities do not have facilities for segregating PLA from plastic waste and they end up in landfill. What are the issues with PLA? Like any other material, PLA is also not 100% efficient material and lacks some of the key features thereby limiting its application. One such factor is its low melting temperature which limits its use for a tougher daily use material. 

Making PLA needs a lot of raw material and production of these carbohydrates require fertilizers and pesticides that contribute to greenhouse gasses more potent than carbon dioxide. This also adds up the requirement of land enough to produce PLA to meet the global demand. PLA is too fragile and hence has limited use in the packaging manufacturing process. They are too brittle for rigorous processes particularly compared to other plastic materials. 

Hence it should be strengthened with additives or strengthening compounds which is going to add up the difficulty in processing. Recyclability is another issue where most PLA plastics end up with normal plastic and if not sorted out properly, they will end up with other toxic- contaminants. Thus, their reuse is questionable because after recycling most of the product will have the toxic plastic waste. 

Conclusion 

Through this discussion we have attempted to communicate the biodegradability aspects of polylactic acid and its related products including its potential uses and what research is being done to make PLA more biodegradable. 

We have further highlighted the difference between PLA degradability and biodegradability and how PLA can be a better choice over traditional plastic if it is treated properly through recycling and composting. 

Frequently asked question (FAQs): “Is PLA biodegradable?” 

Is PLA environmentally friendly? 

PLA is degradable but not biodegradable because microorganisms lack the required enzymes to break down the polymer. They require high temperatures to first hydrolyse the PLAs and they are susceptible to biodegradation. Hence, hydrolysis can be carried out only in an industry setup which is not a cost-effective method. Further, incineration of PLA plastics does not emit toxic fumes making its hydrolytic process both safe and environmentally friendly. 

Is polylactic biodegradable? 

PLAs are not completely biodegradable. Though they are made from naturally occurring raw materials, the final product needs much stringent conditions for initial breakdown. At first hydrolysis of PLA needs to happen and at present the enzymes that can process PLA are very rare. However, once the hydrolysis step is completed, the compound breaks down naturally and becomes biodegradable. 

Will PLA biodegrade in landfill? 

In a landfill, the temperature and humidity are not sufficient for the complete breakdown of PLA. PLA needs to be treated in industrial composting facilities where it is heated up to 140 degrees Fahrenheit and further exposed to microbial enzymes for complete biodegradation. However, It may take between 100 to 1000 years for PLAs to decompose in a landfill. What does PLA biodegrade into? Polylactic acid is a polymer lactic acid, and its biodegradation is influenced by high temperature and humidity with further treatment with microorganisms. With these conditions, PLA breaks down to carbon dioxide and water. 

What are the uses of PLA? 

Due to its inert and biocompatible nature, PLA has found wider applications in the clinical field including cardiovascular implants, dental niches, orthopedic interventions etc. However, with modification of PLAs by changing its molecular weight or integration with other materials, its application can be maximized. Another use of PLA is in 3D printing applications. Due to its good rheological property PLAs have been used in tissue engineering, drug delivery, a platform for tissue growth and many medical procedures. 

Is PLA recyclable?

PLAs can be effectively recycled due to its lower melting point. However, much of the PLA waste get mixed with normal plastics, since both resemble the same, it becomes difficult to segregate them in an industrial setup. 

References

Muniyasamy, Sudhakar & Ofosu, Osei & John, Maya & Anandjiwala, Rajesh. (2016). Mineralization of Poly (lactic acid)(PLA), Poly (3-hydroxybutyrate-co-valerate)(PHBV) and PLA/PHBV Blend in Compost and Soil Environments. Journal of Renewable Materials. 4. 133-145. 

https://www.creativemechanisms.com/blog/learn-about-polylactic-acid-pla-prototypes

Shady Farah, Daniel G. Anderson, Robert Langer, Physical and mechanical properties of PLA, and their functions in widespread applications — A comprehensive review. 2016, Advanced Drug Delivery Reviews, 107 (367-392). https://doi.org/10.1016/j.addr.2016.06.012 

Zhai S, Liu Q, Zhao Y, Sun H, Yang B, Weng Y. A Review: Research Progress in Modification of Poly (Lactic Acid) by Lignin and Cellulose. Polymers (Basel). 2021;13(5):776. https://doi.org/10.3390/polym13050776 

Vincent DeStefano, Salaar Khan, Alonzo Tabada, Applications of PLA in modern medicine. 2020. Engineered Regeneration, 1 (76-87). https://doi.org/10.1016/j.engreg.2020.08.002.

K. Madhavan Nampoothiri, Nimisha Rajendran Nair, Rojan Pappy John, An overview of the recent developments in polylactide (PLA) research. 2010, Bioresource Technology, 101, 22 (8493-8501)

https://doi.org/10.1016/j.biortech.2010.05.092.

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