Key Takeaways from this newsletter:

• Bioplastics can reduce the carbon footprint compared to conventional plastics.
• In some cases unique properties make them the plastic of choice.
• Further research and development are needed for broader acceptance.

A friend of mine recently had some steering issues with his car and took it to the shop. It turned out that rodents had chewed through the soy-based wiring insulation. The technician explained that rodents are attracted to the soy, seeing it as food. My friend was furious and decided that the absence of soy-protected wiring would be the main criterion for his next vehicle purchase.

This practice isn't new. Automobiles started using soy-based wiring in the early 2000s to make them more environmentally friendly. My friend's complaint isn't new either. In 2016, a class action lawsuit was filed against Toyota, claiming the company should cover damage from rodents chewing through soy-based wiring.(1)At the time, Toyota stated, "Rodent damage to vehicle wiring occurs across the industry and is not brand- or model-specific. We are currently not aware of any scientific evidence that shows rodents are attracted to automotive wiring because of alleged soy-based content." The lawsuit was dismissed in 2018 and partially resurrected on appeal in 2020.(2) Regardless of the lawsuit and its outcome, car technicians today still believe that rodent damage is due to soy content. The original reason for using soy was sustainability, as soy is a more sustainable solution than petroleum-based plastics. A plastic like soy-based plastic, which is based on renewable resources, is referred to as a bioplastic. Renewability is one of the main benefits touted for bioplastics.

A more well-known bioplastic is poly(lactic acid) or PLA, which is the most abundant bioplastic, accounting for 26% of all bioplastics in 2024. It can be derived from lactic acid or lactide, both of which originate from fermented carbohydrates. PLA is used in disposable tableware, cutlery, and housings for appliances and electronics. It is also used in compost bags and food packaging and is the most widely used plastic in FDM 3D printing processes, which use a continuous filament of plastic material.(3) PLA is biodegradable but needs to be composted under certain conditions to degrade. Like soy-based plastics, the main benefit of PLA is that it is based on natural products and not petroleum.

Another well-known class of bioplastics is polyhydroxyalkanoates (PHAs). These polymers are used in numerous biomedical applications, most notably as absorbable sutures.(4)

Bioplastics have their pros and cons.(5,6)  Besides reducing dependence on petroleum, the benefits of bioplastics include:

- Potential biodegradability or compostability.

- Non-toxicity, as they are made from natural materials.

- Unique properties in certain cases that make them the plastic of choice.

The downsides are:

- They can be more expensive.

- Land use issues—should the land be used for food or bioplastics?

- They may need composting in an industrial facility.

- Increased pollution from fertilizers.

- They are usually not biodegradable on their own.

- As seen with soy-based bioplastics, they may not be suitable for certain plastic applications.

Bioplastics can reduce the carbon footprint compared to conventional plastics by sequestering carbon dioxide during their lifecycle. Additionally, certain bioplastics possess unique properties that set them apart from traditional plastics. As research continues to address the current limitations, bioplastics are expected to capture a larger share of the plastics market. 

(1) Newer cars' soy-based wire insulation may be 'delicious' to rodents, Christina Hall, “Rats Can’t Resist the Wiring in Newer Cars:  Here’s Why,” USA Today, online edition, May 8, 2018. (https://www.usatoday.com/story/money/nation-now/2018/05/07/rats-love-car-wiring-soy-based-insulation/588638002/)   

(2) Toyota Soy Wiring Class Action Lawsuit Resurrected | CarComplaints.com, David A. Wood, “Toyota Soy Wiring Class Action Lawsuit Resurrected,” Carcompliants.com, September 20. (2020https://www.carcomplaints.com/news/2020/toyota-soy-wiring-class-action-lawsuit.shtml )

(3) Polylactic acid - Wikipedia, Polylactic acid Wikipedia entry as of January 14 2025. 

(4) Biomedical Applications of Polyhydroxyalkanoate in Tissue Engineering Thiruchelvi Pulingam et al., “Biomedical Applications of Polyhydroxyalkanoate in Tissue Engineering,” Polymers 2022, 14(11), 214, May, 24 2022. (https://www.mdpi.com/2073-4360/14/11/2141)

(5) Bioplastics: Pros & Cons and are they the Future?  Ben Hardman, “Bioplastics: Pros and Cons and Are They the Future?” Green Living Blog, April 6, 2022. (https://www.greenlivingblog.org.uk/advantages-and-disadvantages-of-bioplastics/)

(6)  Bioplastics—are they truly better for the environment?, Sarah Gibbens, “What you need to know about plant-based plastics,” nationalgeographic.com,  November 15, 2018.  (https://www.nationalgeographic.com/environment/article/are-bioplastics-made-from-plants-better-for-environment-ocean-plastic)  

(photo credit:  Ron Lach, pexels.com)