Biodegradation of plastics at home composting conditions

Abstract

Plastics have become an ever-increasing environmental pollution problem since high amounts of them are dumped every year into the environment. To remediate this problem, many proposals attempt to produce new plastics with the same sound characteristics as the old ones, but with an increased biodegradability to remain only a few months in the environment before they can be turned into safe non-polluting natural products by microbes. One example of these materials is the polylactic acid-based plastic (PLA), which is presented as a biodegradable-compostable material but usually with a warning that they perform in this way under particular conditions. In this work, we evaluate the biodegradability of PLA and other plastics in a composting system under normal atmospheric conditions with an average temperature around 24 ºC in order to establish its compostability in typical conditions of tropical countries. Results obtained by monitoring the integrity and weight of plastic pieces and NMR over time reveal that none of the materials was biodegraded after 31 weeks (∼7 months) under the studied conditions. On the other hand, amplicon sequencing of the 16S rRNA showed the presence of bacterial groups identified previously on the degradation of biodegradable plastics (e.g., Methylotrophs and Actinobacteria) and are aligned with previous studies that conclude that plastics considered as biodegradable influence the soil microbiota. This work contributes to establishing which plastic materials should be classified as biodegradable in prevailing conditions in tropical countries.

Keywords

• Polylactide plastic (PLA)
• Oxobiodegradable plastic
• Compost
• Methylotrophs
• Actinobacteria