Matching Items (4)
Description
Lipids and free fatty acids (FFA) from cyanobacterium Synechocystis can be used for biofuel (e.g. biodiesel or renewable diesel) production. In order to utilize and scale up this technique, downstream processes including culturing and harvest, cell disruption, and extraction were studied. Several solvents/solvent systems were screened for lipid extraction from Synechocystis. Chloroform + methanol-based Folch and Bligh & Dyer methods were proved to be "gold standard" for small-scale analysis due to their highest lipid recoveries that were confirmed by their penetration of the cell membranes, higher polarity, and stronger interaction with hydrogen bonds. Less toxic solvents, such as methanol and MTBE, or direct transesterification of biomass (without pre-extraction step) gave only slightly lower lipid-extraction yields and can be considered for large-scale application. Sustained exposure to high and low temperature extremes severely lowered the biomass and lipid productivity. Temperature stress also triggered changes of lipid quality such as the degree of unsaturation; thus, it affected the productivities and quality of Synechocystis-derived biofuel. Pulsed electric field (PEF) was evaluated for cell disruption prior to lipid extraction. A treatment intensity > 35 kWh/m3 caused significant damage to the plasma membrane, cell wall, and thylakoid membrane, and it even led to complete disruption of some cells into fragments. Treatment by PEF enhanced the potential for the low-toxicity solvent isopropanol to access lipid molecules during subsequent solvent extraction, leading to lower usage of isopropanol for the same extraction efficiency. Other cell-disruption methods also were tested. Distinct disruption effects to the cell envelope, plasma membrane, and thylakoid membranes were observed that were related to extraction efficiency. Microwave and ultrasound had significant enhancement of lipid extraction. Autoclaving, ultrasound, and French press caused significant release of lipid into the medium, which may increase solvent usage and make medium recycling difficult. Production of excreted FFA by mutant Synechocystis has the potential of reducing the complexity of downstream processing. Major problems, such as FFA precipitation and biodegradation by scavengers, account for FFA loss in operation. Even a low concentration of FFA scavengers could consume FFA at a high rate that outpaced FFA production rate. Potential strategies to overcome FFA loss include high pH, adsorptive resin, and sterilization techniques.
ContributorsSheng, Chieh (Author) / Rittmann, Bruce E. (Thesis advisor) / Westerhoff, Paul (Committee member) / Vermaas, Willem (Committee member) / Arizona State University (Publisher)
Created2011
Description
This work focuses on a novel approach to combine electrical current with cyanobacterial technology, called microbial electrophotosynthesis (MEPS). It involves using genetically modified PSII-less Synechocystis PCC 6803 cells to avoid photoinhibition, a problem that hinders green energy. In the work, a cathodic electron delivery system is employed for growth and synthesis. Photoinhibition leads to the dissipation energy and lower yield, and is a major obstacle to preventing green energy from competing with fossil fuels. However, the urgent need for alternative energy sources is driven by soaring energy consumption and rising atmospheric carbon dioxide levels. When developed, MEPS can contribute to a carbon capture technology while helping with energy demands. It is thought that if PSII electron flux can be replaced with an alternative source photosynthesis could be enhanced for more effective production. MEPS has the potential to address these challenges by serving as a carbon capture technology while meeting energy demands. The idea is to replace PSII electron flux with an alternative source, which can be enhanced for higher yields in light intensities not tolerated with PSII. This research specifically focuses on creating the initiation of electron flux between the cathode and the MEPS cells while controlling and measuring the system in real time.
The successful proof-of-concept work shows that MEPS can indeed generate high-light-dependent current at intensities up to 2050 µmol photons m^‒2 s^‒1, delivering 113 µmol electrons h^‒1 mg-chl^‒1. The results were further developed to characterize redox tuning for electron delivery of flux to the photosynthetic electron transport chain and redox-based kinetic analysis to model the limitations of the MEPS system.
ContributorsLewis, Christine Michelle (Author) / Torres, César I (Thesis advisor) / Fromme, Petra (Thesis advisor) / Woodbury, Neal (Committee member) / Hayes, Mark (Committee member) / Arizona State University (Publisher)
Created2023
Description
A Study of the gasification of municipal solid waste (MSW) for hydrogen production was completed through research and statistical design of experiment. The study was done for general syngas production with conditions of high temperature and pressure. Waste samples from kitchen waste including rice, avocado, and egg shells were used. Dry orange blossom tree leaves were included and a very minimal fraction of used paper and Styrofoam. One of the components of the syngas predicted was hydrogen, but this study does not discuss techniques for the separation of the hydrogen from the syngas. A few suggestions, however, such as the use of gas chromatography and membranes are made for the study of the syngas and separation of the hydrogen from the syngas. A three level, three factors-half factorial design was used to analyze the impact of pressure, residence time and temperature on the gasification of MSW through a hydrothermal gasification approach. A series 4590 micro stirred reactor of 100mL was used to gasify MSW, but first, it was established through a TGA approach that the waste was about 5% moisture content and 55% organic content (OC). The TGA device used was the TG 209 F1 Libra. Results of the gasification indicated that the most important factor in the gasification of MSW is temperature, followed by residence time and that the syngas yield increases with a decreasing pressure of the system. A thermodynamic model relating the three factors and the syngas yield was developed.
ContributorsBuyinza, Allan Smith (Author) / Deng, Shuguang (Thesis director) / Nannenga, Brent (Committee member) / Chemical Engineering Program (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Extensive literature exists examining the maximum mitigation potential of
biochar. This research has found biochar to hold massive potential as a means of stabilizing current levels of atmospheric carbon. Furthermore, the research and resources to massively expand biochar production exist, yet one could easily argue the industry is not expanding quickly enough given its known potential benefits. This paper serves to address this lack of growth, and identified a lack of formalized networks for knowledge and innovation exchanges amongst biochar production firms as a leading obstacle to quick expansion. I focus on two particular biochar production firms operating in vastly different contexts and analyze both through a conceptual framework known as “knowledge networks”. In depth literature on the topic of knowledge networks highlight the dynamics of exchange, including the obstacles in establishing such a network. I applied the findings from a multitude of case studies centered around knowledge networks to biochar production, asserting that exchange networks centered around reciprocity would serve as a catalyst to the growth of the biochar industry. I also assert that public research institutions such as Arizona State University would play a critical role in such a network, as they would serve as a mutual party connecting two private entities. Private biochar production firms around the world would be exposed to new knowledge and information that would serve to maximize the energy value of their product while reducing the environmental externalities associated with their process.
biochar. This research has found biochar to hold massive potential as a means of stabilizing current levels of atmospheric carbon. Furthermore, the research and resources to massively expand biochar production exist, yet one could easily argue the industry is not expanding quickly enough given its known potential benefits. This paper serves to address this lack of growth, and identified a lack of formalized networks for knowledge and innovation exchanges amongst biochar production firms as a leading obstacle to quick expansion. I focus on two particular biochar production firms operating in vastly different contexts and analyze both through a conceptual framework known as “knowledge networks”. In depth literature on the topic of knowledge networks highlight the dynamics of exchange, including the obstacles in establishing such a network. I applied the findings from a multitude of case studies centered around knowledge networks to biochar production, asserting that exchange networks centered around reciprocity would serve as a catalyst to the growth of the biochar industry. I also assert that public research institutions such as Arizona State University would play a critical role in such a network, as they would serve as a mutual party connecting two private entities. Private biochar production firms around the world would be exposed to new knowledge and information that would serve to maximize the energy value of their product while reducing the environmental externalities associated with their process.
ContributorsChernak, Jarod Ross (Author) / Chhetri, Netra (Thesis director) / Henderson, Mark (Committee member) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05