Browsing by Subject "microalgae"
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Item Determining an Appropriate Method to Simulate Pump Shear on the Diatom Nitzschia sp. and a Methodology to Quantify the Effects(2012-12-13) Lassig, JarrettWhen cultivated properly in bioreactors, microalgae have been found to produce vast amounts of biomass. In the case of diatom cultivation where the organisms will fall out of suspension quite easily, paddle wheels or pumps are the primary means to maintain the necessary velocity in the raceway. This study will focus on the potentially harmful shear stress these devices may impart onto the organisms. The system used to impart shear stress to a diatom culture was a cone and plate viscometer. Cells were counted using a fluorescein diacetate staining method with a fluorescent and brightfield microscope. Under the white light all cells were visible while only the healthy cells were visible under fluorescent light. The sample was exposed to shear stress with the cone and plate viscometer at 6 Pascals for 10 minutes and compared against a non-sheared sample. For each sample, 5 pairs of white and fluorescent light images were captured, counted, and averaged. A non-sheared sample was paired with a sheared sample to calculate the decrease in cell viability. The slope was calculated from the plot of shear stress and cell viability for 9 strains. In each case shear stress resulted in a significant decrease in cell viability; however, there was no statistical difference between strains. While effective, this method would be impractical for a commercial algae cultivation facility as the viscometer in this study costs approximately $100,000. Therefore, tests were performed to determine if a rotary mixer could be substituted for the viscometer. The hypothesis was that the cell damage was a product of shear stress and exposure time. For the viscometer test, the shear exposure was 3600 Pa s. Two rotational mixer tests were performed, one at 1250 RPM for 7 hours and one at 313 RPM for 28 hours, providing the same 3600 Pa s shear exposure. After staining, cell viability decreased 35.62% and 11.07% in the 1250 RPM and 313 RPM test, respectively. This difference was significant compared to the 6.04% decrease in the viscometer test. The increased cell damage was attributed to turbulence in the mixer tests and the basis for further study.Item Improving the Methane Production in the Co-Digestion of Microalgae and Cattle Manure(2014-04-28) Cantu, Matthew ScottThe objective of this thesis is to evaluate the effects from various treatments in the anaerobic digestion of cattle manure when mixed with microalgae. The analysis would focus on two primary subjects: the effects of different treatments on the microalgae sludge, and the balancing of the carbon-to-nitrogen ratio. The results of this experiment would give a viable estimate on the possible methane production from co-digestion of these resources. At the conclusion of the experiment, it was found that biogas production increased when algae was added to the digester. The highest methane production in the control groups, containing only manure, digestion sludge, and newsprint was 48120 L, while the highest in the mixtures containing algae and pretreated algae were 71170 L and 87715 L, respectively. Based on volatile solids, the highest production in the control groups was0.36 (L CH_(4))/(g VS), while the production rates in the algae and pretreated algae mixtures were 0.22 (L CH_(4))/(g VS) and 0.44 (L CH_(4))/(g VS), respectively. This shows that the presence of algae increases the overall methane production, but is hindered by inhibitory factors contributing to ineffectiveness in the overall digestion process. The effects of carbon balancing for the carbon-to-nitrogen ratio also showed that overall, mixtures balanced at 25:1 carbon-to-nitrogen yielded more biogas. The exception is the normal algae mixture, in which the optimal ratio was 20:1. In conclusion, the anaerobic co-digestion of cattle manure with pretreated algae, when balanced for carbon and nitrogen, can severely increase methane production rates.Item Low Cost, Low Energy, Method of Dewatering Cultures of the Green Microalgae Nannochloris oculata: Electrocoagulation(2014-05-01) Murdock, JaredMicroalgae have received a substantial amount of attention as an alternative fuel feedstock due to their ability to produce large quantities of lipids. The goal of this research was to determine the ideal operating parameters for electrocoagulation; a low cost, low energy method of dewatering cultures of microalgae. The objectives of this research focus on recognizing parameters that influence the overall efficiency of the process, effective electrode materials, and finally directional improvements in operating parameters contributing to a high reduction in optical density. Variables found to have a statistically significant effect on the efficiency of electrocoagulation were the electrode material, current, and duration. With no adjustment of the algae culture prior to electrocoagulation, iron and nickel were identified as the best performing electrode materials, in terms of optical density reduction. Of the materials tested, iron was found to achieve the greatest recovery of microalgae at the lowest power consumption, while staying below the threshold for animal feed tolerance. The most desirable operating parameters for electrocoagulation, within the confines of the experimental apparatus and using iron electrodes, were found to be a current of 0.3 amps and a 15 min reaction time. Increases in current and duration were found to provide the highest levels of optical density reduction. However, the average voltage, and therefore, power consumption are the highest when current and duration are maximized. Additional testing should be performed at higher currents and longer durations, in an attempt to find a peak in the optical density reduction.Item The Future of Biofuels: An Economic Analysis of the Design and Operation of a Microalgae Facility in Texas and the Southwestern United States(2011-10-21) Allison, Marc S.The world of energy is changing. With rising energy costs and concerns over the supply of energy materials, more research is being conducted into alternative sources of fuel and microalgae is one of the sources being researched, although much research had been conducted on it as a part of the Aquatic Species Program from the 1970s to the early 1990s. With the emergence of microalgae as a source of alternative energy, the need for an economic analysis of microalgae has arisen. This research studies the economic feasibility of the design and operation of a microalgae production facility in two Texas locations (Pecos and Corpus Christi) and in southeastern New Mexico using a stochastic simulation model. It examines the production levels needed for the facility to be profitable and also some facility designs necessary for that profitability. It also measures several annual financial indicators so that potential investors have some estimates of the future profitability of the microalgae industry. The results show that for microalgae to become a viable commercial operation, production must be improved beyond the current levels and the levels suggested by the literature. Production needs to be at least 0.8 g/L/day with 40 percent oil content and 24 inches of water depth. Production must be improved through increasing growth rates and oil contents at greater water depths. Production can be improved through nutrient and carbon dioxide usage, two elements that are being heavily researched. Water usage will become a major focus because of the limited resources and the quantities necessary to operate a commercial-scale facility. With the necessary improvements in technology and research, microalgae could prove to be a viable source of alternative energy.