Why Are Laboratory Consumables Not Made of Recycled Plastic?

Scientists use plastic consumables in a wide range of products in and around the lab – including tubes, plates, pipette tips, petri dishes, and more. To get accurate and reliable results, the materials used in consumables need to be of the highest standards when it comes to quality, consistency, and purity. The consequences of using substandard materials can be severe: data from an entire experiment, or series of experiments, can become worthless with just one consumable failing or causing contamination. So, is it possible to achieve these high standards using recycled plastics? To answer this question, we need to first understand how this is done.

How are plastics recycled?

Worldwide, the recycling of plastics is a growing industry, driven by increased awareness of the impact that plastic waste has on the global environment. However, there are large variations in the recycling schemes operating in different countries, both in terms of scale and execution. In Germany, for example, the Green Point scheme, where manufacturers pay towards the cost of recycling the plastic in their products, was implemented as early as 1990 and has since expanded to other parts of Europe¹ . However, in many countries the scale of plastics recycling is smaller, partially due to the many challenges associated with effective recycling. The key challenge in plastic recycling is that plastics are a much more chemically diverse group of materials than, for example, glass. This means that to get a useful recycled material, plastic waste needs to be sorted into categories² . Different countries and regions have their own standardized systems for categorizing recyclable waste, but many have the same classification for plastics^3,4 :

1. Polyethylene terephthalate (PET)
2. High-density polyethylene (HDPE)
3. Polyvinyl chloride (PVC)
4. Low-density polyethylene (LDPE)
5. Polypropylene (PP)
6. Polystyrene (PS)
7. Other

There are large differences in the ease of the recycling of these different categories. For example, groups 1 and 2 are relatively easy to recycle, whereas the ‘other’ category (group 7) is not usually recycled⁵ . Regardless of group number, recycled plastics can differ significantly from their virgin counterparts in terms or purity and mechanical properties. The reason for this is that even after cleaning and sorting, impurities, either from different types of plastics or from substances relating to the previous use of the materials, remain. Therefore, most plastics (unlike glass) are only recycled once and the recycled materials have different applications than their virgin counterparts.

Which products can be made from recycled plastics?

The question for lab users is: What about lab consumables? Are there possibilities to produce lab-grade plastics from recycled materials? To determine this, it’s necessary to look closely at the properties users expect from lab consumables and the consequences of using substandard materials. The most important of these properties is purity. It is essential that impurities in the plastic used for lab consumables are minimized as they can leach out of the polymer and into a sample. These so-called leachables can have a range of highly unpredictable effects on, for example, cultures of live cells, while also influencing analytical techniques6. For this reason, manufacturers of lab consumables always select materials with minimal additives. When it comes to recycled plastics, it is impossible for producers to determine the precise origin of their materials and therefore the contaminants that may be present. And even though producers put a lot of effort into purifying plastics during the recycling process, the purity of the recycled material is much lower than virgin plastics² . For this reason, recycled plastics are well suited for products whose use is not affected by low amounts of leachables. Examples include materials for construction of houses and roads (HDPE), clothing (PET), and cushioning materials for packaging (PS)⁵ . However, for lab consumables, as well as other sensitive applications such as many food-contact materials⁷ , the purity levels of current recycling processes are not sufficient to guarantee reliable, reproducible results in the lab. In addition, high optical clarity and consistent mechanical properties are essential in most applications of lab consumables, and these demands are also not satisfied when using recycled plastics. Therefore, using these materials could lead to false positives or negatives in research, errors in forensic investigations, and incorrect medical diagnoses⁸ .

Conclusion

Plastic recycling is an established and growing trend worldwide that will have a positive, lasting impact on the environment by reducing plastic waste. In the lab environment, recycled plastic can be used in applications which are not so dependent on purity, for example packaging. However, the requirements for lab consumables in terms of purity and consistency cannot be met by current recycling practices, and therefore these items still have to be made from virgin plastics.

References
1. https://www.howtogermany.com/pages/recycling.html
2. Singh, N. Recycling of plastic solid waste: A state of art review and future applications. Composites Part B: Engineering 2017;115: 409–422.
3. https://plastics.americanchemistry.com/Plastic-Resin-Codes-PDF/
4. https://www.thisiseco.co.uk/news_and_blog/recycling-symbols-explained.html
5. http://www.polymer-search.com/recycling-polymer-plastics.html
6. Morrow, KJ. Addressing Challenges Posed by the Adoption of Single-Use Systems: Developing effective strategies to deal with accumulated plastic waste and cross-contamination issues. Genetic Engineering News 2019. https://www.genengnews.com/topics/bioprocessing/how-should-companies-deal-with-single-use-accumulated-plastic-waste/
7. https://www.efsa.europa.eu/en/topics/topic/plastics-and-plastic-recycling
8. Grigore, ME. Methods of Recycling, Properties and Applications of Recycled Thermoplastic Polymers. Recycling 2017;2(24).

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