Closed-Loop Life Cycle Engineering of Biopolymer Composites: End-of-Life Degradation and ReuseEPA Grant Number: FP917498
Title: Closed-Loop Life Cycle Engineering of Biopolymer Composites: End-of-Life Degradation and Reuse
Investigators: Ryan, Cecily A
Institution: Stanford University
EPA Project Officer: Zambrana, Jose
Project Period: September 1, 2012 through August 31, 2015
Project Amount: $126,000
RFA: STAR Graduate Fellowships (2012) RFA Text | Recipients Lists
Research Category: Fellowship - Civil/Environmental Engineering , Academic Fellowships
The objective of this research is to further the development of biodegradable plastics and natural fiber composites by understanding and optimizing the relationship between processing, properties and end-oflife degradation. The key questions that will be addressed by this work include: How can anaerobic environments be optimized for rapid degradation of targeted polymers and composites? How does the crystallinity of the polymer component affect the degradability of the material? Will the composite and blend morphology create preferential pathways for microbial degradation?
To explore how the microbial environment affects the degradation process of biopolymer/natural fiber composites, anaerobic digesters will be operated on composite samples, optimizing the microbial community by natural selection to degrade the specific substrate. Two environments will be investigated: sludge adapted to the polymer substrate (simulated bioreactor for resource recovery) and anaerobic digester sludge (simulated landfill). For the second part of this study, how polymer crystallinity affects the overall properties of these composites will be understood, as well as how these properties affect microbial degradation of the polymer surfaces. To accomplish this, the study will undertake a series of experiments in thin biopolymer films, where diffraction and microscopy techniques will be used to characterize the morphology of the films during degradation. In the third part of this study, a novel application of X-ray micro-computed tomography (micro-CT) will be refined to observe how micro cracking and fiber/matrix interactions affect pathways for microbial ingress in composite samples and therefore impact the degradation process. Using this process, a time series of in situ three-dimensional images will be taken during the degradation of polymer and composite samples. Samples that have undergone simulated weathering via moisture absorption will be compared to un-weathered samples. The loss of material versus time as determined by micro-CT will be compared to biogas generation rate and methane/carbon dioxide composition.
The expected results of this research are a better understanding of how the fundamental properties of biopolymer-based composites affect its degradation in anaerobic environments. This research also will lead to a more optimized degradation environment for these materials, as indicated by an improved degradation rate and extent. This optimized anaerobic environment will be characterized, including the microbial community composition. Overall, this work will help lead to biocomposite materials that can be used in construction applications and then fully and completely degraded at the end of their useful life.
Potential to Further Environmental/Human Health Protection
There are significant global environmental and societal impacts of accumulating large volumes of waste, including the emissions from municipal solid waste and waste combustion facilities, which impact air quality and contribute to greenhouse gas emissions. By developing construction materials that rapidly and substantially degrade after use, these materials can be recycled rather than filling up space in a landfill. Anaerobic digestion of these materials leads to a useful methane-rich biogas that can be used in a gas-to-energy power plant or as a replacement for petrochemical feedstock used in materials manufacturing.