In another study published in Environmental Science Europe, the UFZ researchers examined the community of micro-organisms under more stringent conditions. They investigated how the community changes when large amounts of PBSA enter the soil as well as what happens when high concentration of nitrogenous fertiliser is applied. "Large amounts of PBSA actually make the microbial community in the soil quite different", says doctoral candidate Benjawan Tanunchai and lead author of the study. With a 6% increase of PBSA in the soil, the diversity of fungal species decreased by 45% and that of archaea by 13%. On the other hand, the high load of PBSA in combination with the fertilisation of the area led to the proliferation of Fusarium solani, a widespread plant-damaging fungus.
The two UFZ studies thus yield one piece of good news and one piece of not-so-good news: PBSA in the soil can be degraded comparatively quickly and efficiently – even under future climate conditions. However, if PBSA is present in large quantities together with high concentrations of nitrogenous fertiliser, PBSA degradation can have a negative impact on agricultural production as a result of a disturbed microbial community and the increased presence of pests.
"When large amounts of plastic end up in the environment, it is never good – even if it is a biodegradable plastic", says Buscot. "The best thing would be to avoid plastic altogether. However, because this is currently an unrealistic goal, we should at least rely on biodegradable plastics everywhere possible and know as much as possible in advance about their degradation properties and consequences."