Biodegradable plastic is coming up as an alternative to plastic. It is popularly being cited as the answer to the ‘plastic problem’ – the fact that plastic does not degrade quickly enough and is harmful to the environment. But is biodegradable plastic the solution we have been looking for? Or is it simply too good to be true?
PBSA, or polybutylene succinate-co-adipate, is a biodegradable plastic option made partly from plants. It is said to be the alternative to plastic, suitable for use in fishing nets and lines, food packaging, plant pots, and mulch film. The bio-based mulch film is known to biodegrade under regular agricultural field circumstances. However, biodegradable plastic options are relatively new and not all is known about their degradation process and the impact it has on the ecosystem.
When learning more about the behaviour of PBSA, its degradation process, and its impact on the other living organisms in the ecosystem, two studies conducted in Germany found two results that can help start constructing a picture. The first experiment observed the behaviour of this film under the climate circumstances of today, as well as the predicted climate change of Germany in the year 2070.
It found that PBSA in soil degraded well. “We were able to show that after just under a year, around 30% of the PBSA had already degraded. This is quite a lot under the climatic conditions that currently prevail in Germany. The main actors are fungi, which are supported by a diverse bacterial community and several other micro-organisms. These include bacteria that supply the fungi with nitrogen, which is rare in plastic, or bacteria and archaea that utilise toxic degradation products. An intelligent degradation and recycling community is forming on and around the plastic – even with a similar degradation rate under the simulated future climate conditions. The changed climate apparently does not harm the PBSA-degrading fungi. The microbial community around them is slightly different – but the degradation result is similar,” said Dr. Witoon Purahong, a soil ecologist at the UFZ, and lead author of the study.
The second experiment observed the behaviour of microorganisms involved under more stringent conditions. This included larger quantities of PBSA in the soil as well as more amounts of nitrogenous fertilisers. They found that the increased amounts of these elements in the soil affected the microbial community. It not only decreased the presence of microorganisms that helped the degradation process but also increased the ones that would cause harm to the plant life. It gave way to the proliferation of the plant damaging fungus Fusarium solani.
Based on the results of these two experiments, it is arguable that moderation is the way ahead, even with environment-friendly options. While biodegradable plastic options are relatively better in some ways, they will not serve as an excuse to continue rampant and unchecked use of plastic or plastic alternatives.
The studies were also limited to the behaviour of PBSA in soil, and under weather conditions in Germany. Plastic alternatives, like plastic, are likely to end up in a number of environments if their use is made commonplace. Their behaviour under such conditions remains to be seen.
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