Graduate Studies
First Advisor
Dr. Xu Li
Date of this Version
Fall 12-7-2022
Document Type
Article
Abstract
Plastics are widely used in modern society. How to handle plastic wastes presents a major environmental challenge. In this thesis we explored the potential of plastic biodegradation. The objectives of this research were to (1) examine the potential of cattle manure microbiome in anaerobically degrading various types of plastics; (2) characterize the surface modifications on plastics caused by pretreatment and biological treatment. Five types of plastics were included in this research, polypropylene (PP), polyethylene terephthalate (PET), low- and high-density polyethylene (LDPE and HDPE), and polyhydroxybutyrate (PHB). Results show that cattle manure microbiome could achieve specific surface degradation rates (SSDR) as high as 4.3 mm/year for PHB, a biodegradable plastic, with no obvious benefits from UV or thermal pretreatment. For the other plastic types, the microbiome could achieve SSDR as high as 22.0 μm per year for HDPE, 27.7 μm per year for LDPE, and 64.7 μm per year for PP. No mass reduction was observed for PET. For PP, LDPE, and HDPE, the UV and thermal pretreatment enhanced the biological treatment by cattle manure microbiome. In general, the SSDR rates achieved in this study are higher than those summarized in a recent review paper, demonstrating the superior ability of the microbiome in beef cattle manure in degrading complex molecules. According to gel permeation chromatography (GPC), the reductions in the molecular weights of molecules on plastic surfaces are commensurate to the SSDR results. Results from Fourier-Transform Infrared Spectroscopy (FTIR) further illustrate the functional groups on plastic surfaces that were altered by pretreatment and biological treatment. The overall findings demonstrate the potential of beef cattle manure as a source of microbes to biodegrade plastics.
Advisor: Xu Li
Comments
A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska Lincoln In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Civil Engineering, Under the Supervision of Professor Xu Li. Lincoln, Nebraska: December, 2022
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