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Published on: May 10, 2013
The fate of post-use biodegradable PBAT-based mulch films buried in agricultural soil
Fabiana Convertino1, Sabrina Carola Carroccio2, Maria Cristina Cocca3
1Department of Soil, Plant and Food Science, University of Bari, Bari, Italy.
Abstract:
The fate of black biodegradable mulch film (MF) based on starch and poly(butylene-adipate-co-terephthalate) (PBAT) in agricultural soil is investigated herein. Pristine (BIO-0) and UV-aged film samples (BIO-A192) were buried for 16 months at an experimental field in southern Italy. Visual, physical, chemical, morphological, and mechanical analyses were carried out before and after samples burial. Film residues in the form of macro- and microplastics in soil were analyzed at the end of the trial. Progressive deterioration of both pristine and UV-aged samples, with surface loss and alterations in mechanical properties, occurred from 42 days of burial. After 478 days, the apparent surface of BIO-0 and BIO-A192 films decreased by 57 % and 66 %, respectively. Burial determined a rapid depletion of starch from the polymeric blend, especially for the BIO-A192, while the degradation of the polyester phase was slower. Upon burial, an enrichment of aromatic moieties of PBAT in the film residues was observed, as well as microplastics release to soil. The analysis of the MF degradation products extracted from soil (0.006-0.008 % by mass in the soil samples) revealed the predominant presence of adipate moieties. After 478 days of burial, about 23 % and 17 % of the initial amount of BIO-0 and BIO-A192, respectively, were extracted from the soil. This comprehensive study underscores the complexity of biodegradation phenomena that involve the new generation of mulch films in the field. The different biodegradability of the polymeric components, the climate, and the soil conditions that did not strictly meet the parameters required for the standard test method devised for MFs, have significantly influenced their degradation rate. This finding further emphasizes the importance of implementing field experiments to accurately assess the real effects of biodegradable MFs on soil health and overall agroecosystem sustainability.
Insights
Biodegradable mulch films (MFs) made of starch and PBAT break down in soil, releasing microplastics and altering soil composition over 16 months. Field conditions significantly impact degradation rates, highlighting the need for real-world assessments of agricultural film sustainability.
Area of Science:
- Agricultural Science
- Polymer Science
- Environmental Science
Background:
- Biodegradable mulch films (MFs) are increasingly used in agriculture to improve soil conditions and crop yields.
- Understanding the environmental fate of these MFs, particularly their degradation in soil, is crucial for sustainable agriculture.
- Starch and poly(butylene-adipate-co-terephthalate) (PBAT) are common components in these next-generation MFs.
Purpose of the Study:
- To investigate the degradation behavior of black biodegradable mulch films (starch/PBAT) in agricultural soil over 16 months.
- To analyze the physical, chemical, and mechanical changes in the films and their residues (macro- and microplastics) in soil.
- To assess the release of degradation products and the overall impact on soil following film burial.
Main Methods:
- Burial of pristine (BIO-0) and UV-aged (BIO-A192) starch/PBAT mulch films in southern Italian agricultural soil for 478 days.
- Comprehensive analyses including visual, physical, chemical, morphological, and mechanical testing before and after burial.
- Quantification of film residues, microplastics, and degradation products (e.g., adipate moieties) in soil samples.
Main Results:
- Significant deterioration of both film types observed, with surface area reduction of 57% (BIO-0) and 66% (BIO-A192) after 478 days.
- Rapid starch depletion and slower PBAT degradation occurred, leading to the release of microplastics and enrichment of aromatic PBAT moieties in soil.
- Approximately 23% (BIO-0) and 17% (BIO-A192) of the initial film mass was extracted from soil, with adipate as the predominant degradation product.
Conclusions:
- Biodegradation of starch/PBAT mulch films in field conditions is complex, influenced by varying component biodegradability and environmental factors.
- Real-world soil conditions deviate from standard test methods, significantly affecting degradation rates and outcomes.
- Field experiments are essential for accurately evaluating the soil health and agroecosystem sustainability impacts of biodegradable mulch films.
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