Lab Consumables: Scope for Biodegradable Plastics?

When selecting materials for the production of laboratory consumables, manufacturers look closely at the properties that users require and expect from their plates, tubes, and pipette tips. Although this list of requirements is extensive, the ones that normally top the list are purity, consistency, and stability. This means that these properties should be thoroughly studied when looking at potential new materials, such as biodegradable plastics.

What are biodegradable plastics?

Although most plastics degrade to some extent over decades, or in some cases centuries, the degradation rate of biodegradable plastics is higher due to the effect of microbes; as a result the environmental impact of these materials is lower. Degradation rate depends on the conditions the material is exposed to, but (unlike with organic matter) degradation typically still takes months or years depending on the exact composition^1. The reason for this faster degradation lies in the chemical bonds that hold the polymer’s building blocks (monomers) together. In most conventional plastics, these are highly stable and therefore hard to break, however biodegradable plastics are characterized by weaker (often hydrolysable) bonds that can be broken down by microbes² .

A common cause for confusion is the difference between bio-degradable plastics and bio-derived plastics (sometimes known as bioplastics or plastics from renewable biomass), which are made from plant-based materials but are not necessarily biodegradable. Conversely, some biodegradable plastics are bioderived – but not all. Examples of bioderived, biodegradable plastics include materials based on starch or cellulose, and polyesters such as polyhydroxyalkanoates (PHAs); non-bioderived examples of biodegradable plastics include poly(vinyl alcohol) (PVA), polyglycolic acid (PGA), and polycaprolactone (PCL)^3,4 .

In recent decades, biodegradable polymers have become common in a wide range of applications in daily life – in most cases replacing conventional plastics. Common uses include packaging, single-use carrier bags, and various food applications. However, due to their biodegradable nature, use is mostly limited to disposable applications.

Lab consumables and biodegradation

But what about lab consumables? Many plastics used in the lab are single-use, so is it possible to replace some existing lab consumables with biodegradable ones? To answer this question, we have to go back to the key requirements for these products: purity, consistency, and stability.

Biodegradable plastic products have the potential to fulfill the first two of these. Their use in the production of food-contact products, such as cutlery and meal boxes, demonstrates their consistency and safety3. The key issue, however, is the stability of biodegradable plastics. By definition, the structure of biodegradable plastics changes over time, which leads to changes in material properties. This effect is exacerbated by the conditions and entities to which consumables are exposed – including cells and bacteria, various chemicals such as acids and bases, and varying temperatures. These factors will inevitably have an effect on the structure and strength of biodegradable lab consumables over time2,5. More importantly, when biodegradable polymers are broken down, polymer fragments that can be detrimental to many lab applications might be released into a sample, causing contamination.

The underlying issue is that polymer degradation always occurs gradually. It is not yet possible to create a material that maintains its properties for the typical shelf life of a lab consumable, and only after reaching the expiry date, begins to degrade. Degradation will certainly be slower as long as consumables are stored in airtight packaging, but it would still be happening to some extent.

In addition, important concerns have been raised in recent years disputing the purely positive environmental impact of switching to biodegradable plastics. One of these concerns is that the production processes for many biodegradable plastics are complex and have a high energy consumption, in many cases higher than the energy consumption of conventional plastic production. Also disputed are the exact definitions of “biodegradable” and similar terms, as these have been used to promote products that do not actually degrade under the conditions of the places where they could end up (e.g. landfill sites or the ocean)^6,7 .

To degrade or not to degrade

When choosing materials for use in lab consumables, manufacturers need to consider many different properties in order to produce an optimized product – including quality, longevity, environmental impact, and cost. Currently available biodegradable plastics do not meet these requirements, particularly when it comes to performance over time and potential for sample contamination.

The use of biodegradable plastics also raises a broader question: is changing to biodegradable plastics really a more sustainable option? From a degradation perspective there are certainly important benefits, however the high energy consumption associated with biodegradable plastic production remains an environmental challenge. The search is continuing for a material for lab consumables that fulfills all criteria for both sustainability and user requirements.

References

[1] Napper, IE and Thompson RC, Environmental Deterioration of Biodegradable, Oxo-biodegradable, Compostable, and Conventional Plastic Carrier Bags in the Sea, Soil, and Open-Air Over a 3‑Year Period. Environmental Science and Technology 2019;53: 4775−4783.

[2] Lambert S and Wagner M, Environmental performance of bio-based and biodegradable plastics: the road ahead. Chemical Society Reviews 2017, 46(22), 6855–6871.

[3] https://greenliving.lovetoknow.com/Type_of_Biodegradable_Plastic

[4] Iwata, T, Biodegradable and Bio‐Based Polymers: Future Prospects of Eco‐Friendly Plastics. Angewante Chemie International Edition 2015;54(11): 3210–3215.

[5] https://library.wur.nl/WebQuery/wurpubs/fulltext/408350

[6] https://theconversation.com/when-biodegradable-plastic-is-not-biodegradable-116368

[7] https://www.youtube.com/watch?v=g9OqQ1PaACg

• Bioplastic in the Lab?