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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1977. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Mohamad Metghalchi. / M.S.

Potential thermophiles for ethanol production at elevated temperature were compared based on their kinetic performances. T. thermophilus HB27 demonstrated superior kinetics and its growth was not greatly affected when containing the recombinant plasmid pTEV231. Detailed kinetic studies demonstrated that it could utilize glucose and xylose in medium containing 0.5 % (w/v) yeast extract, and could produce low levels of L-lactate, acetate and ethanol. Kinetic evaluation of the newly isolated G. thermoglucosidasius M10EXG showed it could grow on fully defined media and coferment glucose and xylose. G. thermoglucosidasius M10EXG produced higher levels of products (acetate, and L-lactate) at about 2 g/l each, compared to T. thermophilus HB27 although ethanol levels were only 0.1-0.2 g/l in shake flask fermentations under partially aerobic conditions. Improved conditions for natural transformation of T. thermophilus HB27 were determined. Optimal conditions for electroporation of were: Milli-Q water washing of cells rather than with 10% (v/v) glycerol; an electrical field of 5 kV/cm; cell concentration of 1.4x1010 cells/ml; and a DNA concentration of 500 ng in 40 Fl (125 Fg/ml) which achieved a transformation efficiency of 3x103 transformants /Fg DNA. The chloramphenicol resistance (cat) and green fluorescence protein (gfp) genes from pCJS10 were cloned into an E. coli -- T. thermophilus shuttle vector (pMK18) as possible selection markers at elevated temperatures. Both genes were expressed in E. coli DH5H and it was demonstrated that gfp expression in E. coli DH5H decreased as temperature increased to 45oC. However following transformation of T. thermophilus HB27, no evidence of expression were found. The pet operon containing adhT (with its promoter) from G.thermoglucosidasius M10EXG and pdc from Z. mobilis Zm4, was cloned into pMK18 and low level expression in E. coli JM109 occurred with some increase in ethanol production. However the pet operon was not expressed in T. thermophilus with pMK18. For further gene expression studies, a new shuttle vector, pPOPTE (4-5 kb), based on the T. thermophilus plasmid pTEV231 (containing thermostable kanamycin resistance gene) was constructed. pPOPTE was capable of multiplying in both E. coli and T. thermophilus HB27 and demonstrated higher stability and transformation efficiency compared to pMK18.

Environmental concerns about urban air quality, global climate change, energy security and economic considerations motivate a growing interest in alternative fuels for the transportation sector. Ethanol, a fermentation-derived fuel, can be produced by bioconversion of renewable materials, such as wood, grass, and waste. Combustion of ethanol fuel, in both neat and blended form, can improve the engine efficiency, and lower the emission of CO, NO[subscript x], and volatile organic compounds (VOC), hence reducing the urban ozone level. Moreover, enhanced agricultural activities for production and collection of lignocellulosic feedstocks and industrial developments for production of ethanol will help the economic growth by creating new jobs and new income sources. Bioconversion of lignocellulosic feedstocks into ethanol requires a pretreatment process to increase the digestibility of cellulose by cellulolytic enzymes. The dilute-sulfuric acid pretreatment can hydrolyze hemicelluloses (xylan), disrupt lignin structure, and increase the yield of ethanol production from fermentation of monomeric units of cellulose (glucose). In this study, herbaceous (corn stover and switchgrass) and woody (poplar chips) feedstocks were pretreated with dilute sulfuric acid (0.6, 0.9, and 1.2% w/w) in a batch reactor at relatively high temperatures (140, 160 and 180��C). A unifying kinetic model including reaction time, temperature and acid concentration was developed, and pertinent kinetic parameters were determined. This model can predict the percentages of xylan remaining in the pretreated solids, net xylose yield in the liquid prehydrolysate, and xylose loss after pretreatment of a feedstock at a certain set of reaction conditions. Using this model, four optimum reaction conditions for obtaining maximum net xylose yield in the liquid prehydrolysate were identified. The yield and rate of ethanol production from the optimum prehydrolysates by the pentose fermenting yeast, Pichia stipitis, were determined. It was found that pretreating the selected feedstocks at 170-180��C with 1.0-1.2% sulfuric acid for 1-3 min resulted in the recovery of 80-85% of the original xylan in the liquid prehyrolysate. It was also found that feedstocks with higher neutralizing capacity (e.g., corn stover) produced lower sugar yields as a result of acid neutralization. Pretreatment of feedstocks at conditions beyond the optimum reaction conditions would increase the extent of xylose degradation, and lower the yield and rate of ethanol production due to loss of fermentable sugars and formation of toxic byproducts. The optimum prehydrolysates of corn stover produced the highest yields of ethanol (0.39-0.47 g ethanol/g xylose) followed by switchgrass (0.36-0.45) and poplar (0.26-0.44). The inhibitory effects of byproducts (e.g., acetate) was more pronounced in poplar prehydrolysates. / Graduation date: 1997

This study outlines the development of an emissions modeling process in which tractive power based emissions functions are applied to microscopic traffic simulation data. The model enables transportation planners to evaluate the effects of transportation infrastructure projects on emissions and fuel consumption to aid in selecting the projects providing the greatest environmental return on investment. Using the developed model, the performance of a set of simplified macroscopic velocity profiles used in an existing emissions model has been evaluated. The profiles were found to under predict the vehicle emissions due to the low acceleration rates used. To illustrate the use of the model in evaluating transportation infrastructure projects, the benefits of two potential development scenarios in a major transportation corridor were evaluated. Weighing the benefits provided by each scenario against their associated costs revealed that greenhouse gas emissions would be reduced at a cost an order of magnitude greater than the value of a carbon credit suggesting that neither option is economical solely as a greenhouse gas emissions reduction tool.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2004. / Includes bibliographical references.

The purpose of this work is to investigate the implementation of nitride fuels containing little or no uranium in a fast-spectrum nuclear reactor to reduce the amount of plutonium and minor actinides in spent nuclear fuel destined for the Yucca Mountain Repository. A two tier recycling strategy is proposed. Thermal spectrum transmutation systems converted from the existing LWR fleet were modeled for the first tier, and the Japanese fast reactor MONJU was used for the fast-spectrum transmutation. The modeling was performed with the Monteburns code. Transmutation performance was investigated as well as delayed neutron fraction, heat generation rates, and radioactivity of the spent material in the short and long term for the different transmutation fuel cycles. A two-tier recycling strategy incorporating fast and thermal transmutation with uranium-free nitride fuel was shown to reduce the long-term heat generation rates and radioactivity of the spent nuclear fuel inventory.

<p>The main objective of this work it to produce membrane electrode assemblies (MEAs) that have improved performance over MEAs produced by the conventional manner, by producing highly efficient, electroactive, uniform catalyst layers with lower quantities of platinum electrocatalyst. The catalyst coated membrane (CCM) method was used to prepare the MEAs for the PEM fuel cell as it has been reported that this method of MEA fabrication can improve the performance of PEM fuel cells. The MEAs performances were evaluated using polarisation studies on a single cell. A comparison of polarisation curves between CCM MEAs and MEAs produced in the conventional manner illustrated that CCM MEAs have improved performance at high current densities (&gt / 800 mA/cm2).</p>

Flax shives are a source of abundant biomass from renewable sources. They are considered to be environmentally benign and have a high-energy content for heating and generation of electricity, but only after being processed into pellets. Pelleting of the shives was done by using the single-pelleter and pilot-scale mill. The effect of grinding with screens of 2.4, 3.2, and 6.4 mm on unit density and durability was conducted with a completely randomized design using shives from Biofibre Industries Inc., Canora, SK. The central composite face-centered design with 3 levels of lower grade canola meal used as a binder (18, 21, and 24%), moisture content (8, 11, and 14% (w.b)), and hammer mill screen size (3.2, 4.8, and 6.4 mm) was used to determine the effects of these three factors on the properties of fuel pellets made from shives obtained from Biolin Research Inc., Saskatoon, SK. The initial moisture content of coarse flax shives from both sources was about 10.5% wet basis (w.b.). The moisture content of flax shive grinds ranged from 9.6 to 10.5% (w.b.) after grinding, using the smaller screens for the Biofibre material, while the moisture content ranged from 7.9 to 8.6% (w.b.) for shives from Biolin. Also, smaller screen size reduced the geometric mean particle size for shives from both sources. The use of the smaller hammer mill screen resulted in an increase in both bulk and particle density of shives. There was a decrease in coefficient of the internal friction of shives from 0.20 to 0.14 and an increase in a cohesion of shives from 2.18 to 3.83 kPa when the screen size decreased from 6.4 to 3.2 mm. The flax shives contained cellulose (53.27%), hemicelluloses (13.62%), and lignin (20.53%) at a moisture content of 7.9% (w.b). Specific heat capacity of flax shives changed from 1.5 to 2.7 kJ/ (kg °C) when the moisture content was increased from 8 to14% (w.b.) and temperature from 15 to 80°C. The shives had the combustion energy of 17.67 MJ/kg at a moisture content of 8.1% (w.b.).<p> The smallest screen size (2.4 mm) resulted in the highest unit density (1010 kg/m3) and the highest durability (88%) in the pellets produced by the single-pelleting equipment. The change in length of pellets produced by the pilot-scale mill increased as canola meal increased from 18 to 24% at the highest moisture content (%). The pellets were more stable at the highest moisture content when the lowest canola meal used. The addition of 18% canola meal and grinds from a screen size of 6.4 mm produced the highest unit density in the pellets at all moisture levels. The highest bulk density (682 kg/m3) was obtained from shive mixtures with 18% canola meal and a moisture content of 8%. The highest hardness and durability were found for the shive pellets that were produced with 18% canola meal at a moisture content of 14% (w.b). Pellets that were produced at a moisture content of 14% (w.b) resulted in the lowest percentage of moisture absorption. The inclusion of the canola meal in the shive mixture resulted in an increase in the combustion energy of the pellets because of the fat content in the binder. The two levels of canola meal for shive pellets had essentially the same level of emissions. However, there were significant differences between shive pellets and commercial wood pellets in the level of the emissions. Lower amounts of methane (1.29 ppm) and oxygen (164.3 ppt) were found for flax shive pellets than of methane (1.63 ppm) and oxygen (176.6 ppt) in commercial wood pellets.<p> In short, pelleting of flax shives into fuel pellets improved the handling characteristics, increased bulk density and energy content. Fuel pellets made from flax shives had less emission of methane and oxygen from combustion when compared to commercial wood pellets.

Due to concerns about energy security, rising oil prices, and adverse effects of internal combustion engine vehicles on the environment, the automotive industry is quickly moving towards developing efficient “green” vehicles. Fuel cell-powered vehicles offer high efficiency and practically zero emissions. The main obstacles for widespread commercial production of fuel cell vehicles are high cost and short lifetime of fuel cell stacks, lack of a hydrogen infrastructure, and generation of hydrogen in an environmentally-friendly manner and its storage. Using actual fuel cells and actual vehicular loads in the study of fuel cell vehicular systems can be prohibitive due to cost (initial and running) and safety issues. It is very desirable to have a test station that emulates a vehicle with a high degree of accuracy and flexibility to alleviate cost and safety issues. This thesis proposes a design for a test station that emulates the drive train of a typical fuel cell-powered vehicle that is equipped with regenerative braking capability. As part of the test station, a fuel cell emulator is designed and validated through simulation based on the Nexa Fuel Cell power module manufactured by Ballard Power Systems. As another building block for the test station, a bi-directional controllable DC load is developed that can realize a given drive cycle for the scaled-down version of a given vehicle. The load allows simulation of regenerative braking capability. The performance of the load is validated through simulation. A DC-DC boost converter for controlling the fuel cell power, as well as an energy storage system for assisting the fuel cell in providing the required power during high-demand periods, are incorporated into the proposed test station. Simulation results are used to show that the test station is capable of simulating the real-life conditions experienced by actual fuel cell vehicles on the road. The test station, when realized by hardware, can be used for performing a wide range of studies on the drive train architecture and power management of fuel cell vehicles.