Subtopic 4: Rot – the problem with Bio-Plastics

Recently an alternative to conventional non-degradable plastics has emerged in consumer markets. Bio-plastics are polymers made from plants and other biological organisms like microbes that break down naturally. The cause for their biodegradability is not that they are made up of organic matter – fossil-based plastics are also fossilized biomass – but rather is a result of their molecular structure (Gibbens, 2018).

Figure 4. Classification of conventional and bioplastics (European Bioplastics)

Biodegradable plastics can be more environmentally friendly. Compared with fossil-based plastics, bio-based plastics can have a lower carbon footprint and exhibit advantageous materials properties; moreover, they can be compatible with existing recycling streams (Rosenboom et al., 2022). However, they also come with limitations like high manufacturing costs, low mechanical tendency, potential negative agricultural impacts, competition with food production, unclear end-of-life management, and higher costs.

When talking about bioplastics, we have to differentiate between three terms:

• Degradable – All plastic is degradable, even traditional plastic, but just because it can be broken down into tiny fragments or powder does not mean the materials will ever return to nature. Some additives to traditional plastics make them degrade more quickly. Photodegradable plastic breaks down more readily in sunlight; oxo-degradable plastic disintegrates more quickly when exposed to heat and light.
• Biodegradable – Biodegradable plastic can be broken down completely into water, carbon dioxide, and compost by microorganisms under the right conditions. “Biodegradable” implies that the decomposition happens in weeks to months. Bioplastics that do not biodegrade that quickly are called “durable,” and some bioplastics made from biomass that cannot easily be broken down by microorganisms are considered non-biodegradable.
• Compostable – Compostable plastic will biodegrade in a compost site. Microorganisms break it down into carbon dioxide, water, inorganic compounds, and biomass at the same rate as other organic materials in the compost pile, leaving no toxic residue.