Publication
Are biodegradable biobased plastics a green alternative?
| Summary: | Environmental sustainability is driving an intense search for “green materials”. Bio-based and biodegradable plastics have emerged as alternatives that aim to reduce the environmental pressure caused by conventional plastics. However, it remains doubtful whether these alternatives are environmentally friendly when we consider an in situ application without requiring their removal, such as mulch films applied in crops. Do these materials safely biodegrade in situ as expected? In the meantime, do they negatively impact the local fauna? A certified and commercially available biodegradable biofilm was selected as the object of study to answer these questions. Using microplastics from this biofilm, its potential biodegradation and ecotoxicity in agricultural soils were evaluated. For this purpose, the biodegradation tests occurred in the presence of the fungus Penicillium brevicompactum, and the ecotoxicity tests were performed with the earthworm Eisenia andrei, both key organisms (i.e., high ecological relevance and biomass) in these environments. In the biodegradation experiments in soil, the fungus P. brevicompactum interacted with the biofilm, although not so evident on its mass loss. Notwithstanding, the FTIR-ATR analysis suggests affinity between the fungi and the plastic material, with changes in fungi carbohydrate contents, and an apparent increase in low molecular weight esters in microplastics exposed to fungal material suggesting biodegradation. In the ecotoxicity tests, which involved pristine or UV aged microplastics, the results were distinct. The presence of pristine microplastics did not affect E. andrei survival but induced a significant decrease (from 28% to 44%) in the number of juveniles. Aged microplastics did not affect survival or reproduction. The analysis of FTIR-ATR spectra (prior bioassays) from weathered microplastics revealed some chemical changes that might be responsible for the lack of toxicity; whereas the FTIR-ATR spectra from earthworms exposed to pristine microplastics suggests a decline of energy reserves, reflected by a decrease in carbohydrates, lipids and proteins. The biodegradation and ecotoxicity tests required for the certification of bio-based and/or biodegradable plastics still lack ecological relevance since they occur under very different conditions than those found in the natural environment where they will be applied (e.g., high temperature, types of microorganisms). Similarly, the ecotoxicity tests applied aim at assessing preferentially acute effects (e.g., survival), neglecting their chronic effects (reproduction). This project brings new evidence regarding their biodegradation and ecotoxicity in agricultural soils considering ecologically relevant species. Although biodegradation tests with the fungus require further studies, ecotoxicity tests indicate that biofilm microplastics in environmentally relevant scenarios show an absence of acute and chronic toxicity for E. andrei. |
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| Main Authors: | Filipe, Diogo Alexandre Ferreira |
| Subject: | Penicillium brevicompactum Biodegradation Eisenia andrei Ecotoxicology Biobased mulch film |
| Year: | 2021 |
| Country: | Portugal |
| Document type: | master thesis |
| Access type: | open access |
| Associated institution: | Universidade de Aveiro |
| Language: | English |
| Origin: | RIA - Repositório Institucional da Universidade de Aveiro |
| Summary: | Environmental sustainability is driving an intense search for “green materials”. Bio-based and biodegradable plastics have emerged as alternatives that aim to reduce the environmental pressure caused by conventional plastics. However, it remains doubtful whether these alternatives are environmentally friendly when we consider an in situ application without requiring their removal, such as mulch films applied in crops. Do these materials safely biodegrade in situ as expected? In the meantime, do they negatively impact the local fauna? A certified and commercially available biodegradable biofilm was selected as the object of study to answer these questions. Using microplastics from this biofilm, its potential biodegradation and ecotoxicity in agricultural soils were evaluated. For this purpose, the biodegradation tests occurred in the presence of the fungus Penicillium brevicompactum, and the ecotoxicity tests were performed with the earthworm Eisenia andrei, both key organisms (i.e., high ecological relevance and biomass) in these environments. In the biodegradation experiments in soil, the fungus P. brevicompactum interacted with the biofilm, although not so evident on its mass loss. Notwithstanding, the FTIR-ATR analysis suggests affinity between the fungi and the plastic material, with changes in fungi carbohydrate contents, and an apparent increase in low molecular weight esters in microplastics exposed to fungal material suggesting biodegradation. In the ecotoxicity tests, which involved pristine or UV aged microplastics, the results were distinct. The presence of pristine microplastics did not affect E. andrei survival but induced a significant decrease (from 28% to 44%) in the number of juveniles. Aged microplastics did not affect survival or reproduction. The analysis of FTIR-ATR spectra (prior bioassays) from weathered microplastics revealed some chemical changes that might be responsible for the lack of toxicity; whereas the FTIR-ATR spectra from earthworms exposed to pristine microplastics suggests a decline of energy reserves, reflected by a decrease in carbohydrates, lipids and proteins. The biodegradation and ecotoxicity tests required for the certification of bio-based and/or biodegradable plastics still lack ecological relevance since they occur under very different conditions than those found in the natural environment where they will be applied (e.g., high temperature, types of microorganisms). Similarly, the ecotoxicity tests applied aim at assessing preferentially acute effects (e.g., survival), neglecting their chronic effects (reproduction). This project brings new evidence regarding their biodegradation and ecotoxicity in agricultural soils considering ecologically relevant species. Although biodegradation tests with the fungus require further studies, ecotoxicity tests indicate that biofilm microplastics in environmentally relevant scenarios show an absence of acute and chronic toxicity for E. andrei. |
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