Browsing by Subject "Bioenergy"
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Item Comparison of Biological and Thermal (Pyrolysis) Pathways for Conversion of Lignocellulose to Biofuels(2012-11-30) Imam, Tahmina 1983-Because of the limited supply of imported crude oil and environmental degradation, renewable energy is becoming commercially feasible and environmentally desirable. In this research, biological and thermal (pyrolysis) conversion pathways for biofuel production from lignocellulosic feedstocks were compared. For biological conversions of sorghum, ethanol yield was improved using M81-E variety (0.072 g/g juice) over Umbrella (0.065 g/g juice) for first-generation biomass (sorghum juice), and 0.042 g/g sorghum was obtained from the cellulosic portion of second-generation biomass. When ultrasonication was combined with hot water pretreatment, yields increased by 15% and 7% for cellulose to glucose, and hemicellulose to pentose, respectively. Ethanol yield was 10% higher when this pretreatment was combined with Accellerase 1500+XC for saccharification. Biological conversion yielded 1,600?2,300 L ethanol/ha for first-generation biomass, and 4,300?4,500 L ethanol/ha from lignocellulosic biomass. For thermal (pyrolysis) conversion of lignocellulosic switchgrass at 600 degrees C, product yield was 37% bio-oil, 26% syngas, and 25% bio-char. At 400 degrees C, product yield was 22% bio-oil, 8% syngas, and 56% bio-char. Bio-oil from pyrolysis was highly oxygenated (37 wt%). It required chemical transformation to increase its volatility and thermal stability, and to reduce its viscosity by removing objectionable oxygen, so the product could be used as transportation fuel (gasoline). As a consequence of upgrading bio-oil by catalytic hydrogenation, bio-oil oxygen decreased from 37?2 wt%, carbon increased from 50?83 wt%, hydrogen increased from 9?15 wt% and heating value increased from 36?46 MJ/kg, resulting in a fuel that was comparable to gasoline. The upgraded product passed the thermal stability test when kept under an oxygen-rich environment. The upgraded product consisted of 14.8% parrafins, 21.7% iso-parrafins, 3% napthene, 42.6% aromatics, 4.7% olefin, 4.7% DMF, 8% alcohol, and 0.6% ketone on a mass basis. Comparing the two pathways, biological conversion had 11 wt% ethanol yield from sorghum, and thermal conversion had 13 wt% gasoline yield from switchgrass. For process efficiency, thermal conversion had 35% energy loss versus 45% energy loss for biological conversions. For the biological pathway, ethanol cost was $2.5/gallon ($4/gallon, gasoline equivalent), whereas for the thermal pathway, switchgrass gasoline cost was $3.7/gallon, both with 15% before tax profit.Item Effect of Bioreactor Mode of Operation on Mixed-Acid Fermentations(2012-10-19) Golub, KristinaUsing mixed-culture fermentation, the carboxylate platform produces carboxylic acids, which are chemically converted into chemicals and fuels. To optimize the mixed-acid fermentation, different bioreactor configurations and operating modes were investigated. Intermittent air exposure did not affect fermentation performance and bacterial profiles, but reduced the high-molecular-weight carboxylic acids. The microbial flora contained strict and facultative microbes, suggesting the presence of a facultative anaerobic community existing in a biofilm. Compared to countercurrent trains, propagated fixed-bed fermentations have similar selectivity and acid distribution, but lower yield, conversion, productivity, and acid concentration. One- to six-stage countercurrent fermentations were operated with similar conditions. Fewer stages increased conversion, whereas more stages increased acid concentration and selectivity. One to four stages achieved similar yield, and four to six stages achieved similar maximum acid concentration. Maximum conversion was achieved with a single stage. Recycling residual biomass retained microorganisms and nutrients and increased yield and productivity. Relative to lower biomass reflux, higher reflux increased conversion, decreased selectivity, and did not affect yield. The recommended carbon-nitrogen ratio is ~24 g carbon/g nitrogen. In four-stage fermentations, recycle to the second fermentor and in parallel to the first three fermentors was optimal. Fermentations with excess or insufficient nitrogen had higher selectivity, but decreased yield and conversion. The glucose-utilization assay is a rapid and repeatable method for determining the amount of microbial activity in a sample. This method determined ~25% efficiency of a new cell separation method. In continuous fermentation, compared to no cell recycle, recycling cellular biomass increased selectivity and yield, but decreased conversion. Compared to lower cell reflux, higher reflux increased productivity, yield, and conversion, but decreased selectivity. Compared to residual biomass recycle, cell recycle had increased selectivity and yield, but decreased conversion. A new method to screen and rank inoculum sources from natural environments was successfully developed and tested.Item Essays on Economic and Environmental Analysis of Taiwanese Bioenergy Production on Set-Aside Land(2012-02-14) Kung, Chih-ChunDomestic production of bioenergy by utilizing set-aside land in Taiwan can reduce Taiwan?s reliance on expensive and politically insecure foreign fossil fuels while also reducing the combustion of fossil fuels, which emit substantial amounts of greenhouse gases. After joining the World Trade Organization, Taiwan?s agricultural sector idled about one-third of the national cropland, hereafter called ?set-aside land?. This potentially provides the land base for Taiwan to develop a bioenergy industry. This dissertation examines Taiwan?s potential for bioenergy production using feedstocks grown on set-aside land and discusses the consequent effects on Taiwan?s energy security plus benefits and greenhouse gas (GHG) emissions. The Taiwan Agricultural Sector Model (TASM) was used to simulate different agricultural policies related to bioenergy production. To do this simulation the TASM model was extended to include additional bioenergy production possibilities and GHG accounting. We find that Taiwan?s bioenergy production portfolio depends on prices of ethanol, electricity and GHG. When GHG prices go up, ethanol production decreases and electricity production increases because of the relatively stronger GHG offset power of biopower. Results from this pyrolysis study are then incorporated into the TASM model. Biochar from pyrolysis can be used in two ways: burn it or use it as a soil amendment. Considering both of these different uses of biochar, we examine bioenergy production and GHG offset to see to what extent Taiwan gets energy security benefits from the pyrolysis technology and how it contributes to climate change mitigation. Furthermore, by examining ethanol, electricity and pyrolysis together in the same framework, we are able to see how they affect each other under different GHG prices, coal prices and ethanol prices. Results show that ethanol is driven out by pyrolysis-based electricity when GHG price is high. We also find that when biochar is hauled back to the rice fields, GHG emission reduction is higher than that when biochar is burned for electricity; however, national electricity production is consequently higher when biochar is burned.Item Optimization and Simulation for Designing the Supply Chain of the Cellulosic Biofuel Industry(2012-02-14) An, HeungjoThe purpose of this dissertation is to provide an effective approach to design the supply chain (SC) of the cellulosic biofuel industry in order that it will support and accelerate the successful commercialization of the cellulosic biofuel industry. The methods of approach to this problem are (1) to assess the state-of-the-art biofuel SC studies, (2) to provide a decision support tool based on a mixed integer programming (MIP) model for the cellulosic biofuel supply chain design problem (BSCP), (3) to devise an exact solution method to solve large-scale instances of BSCP, (4) to evaluate a biomass logistics system based on biomass modules, by using new simulation elements for new machines, and (5) to compare several biomass logistics systems based on biomass module, bale, and silage, using simulation models. The first part of this dissertation broadly reviews the literature on biofuel SCs, analyzing the state-of-the-art biofuel and petroleum-based fuel SC studies as well as relating generic SC models that have been published over the last decade to the biofuel SC (An et al., 2010a). The resulting analysis proposes fertile opportunity for future research to contribute to improving biofuel SC. The second part of this dissertation formulates BSCP as a MIP model, which is a time-staged, multi-commodity flow, network design problem with an objective of maximizing profit (An et al., 2010b). The model prescribes strategic level decisions (i.e., facility locations, capacities, and technology types) as well as plans for transportation routes and material flows (i.e., quantities produced, stored, and transported) in each time period. A case study demonstrates managerial use in application to a region in Central Texas. The third part of this dissertation provides an exact solution method to solve BSCP. An embedded structure can be transformed to a generalized minimum cost flow problem, which is used as a sub-problem in a CG approach. This study proposes a dynamic programming algorithm to solve the sub-problem in O(m), generating improving path-flows. To accelerate branch-and-bound (B&B) search, it develops an inequality, called the partial objective constraint (POC), which is based on the portion of the objective function associated with binary variables. The fourth part of this dissertation evaluates a biomass module system, which is a conceptual logistics system based on large packages of chopped biomass with sufficient size and density to provide maximized legal highway loads and quick load/unload times. The last part of this dissertation evaluates economic benefits of the biomass module system, comparing it to bale and silage systems.Item QTLs for Energy Related Traits in a Sweet ? Grain RIL Sorghum [Sorghum bicolor (L.) Moench] Population(2012-10-19) Felderhoff, TerryRecent initiatives for biofuel production have increased research and development of sweet sorghum. Currently, the initial major limitation to integrating sweet sorghum into existing production systems is the lack of sweet sorghum hybrids adapted to industrial production systems. Hybrid development is now underway, and the application of genetic markers can be used to define the genetic basis of sugar yield and its components, as well as reduce the time required to deliver new sweet sorghum hybrids to market. The purpose of this research was to further characterize the genetic components that influence sweet sorghum productivity, agronomics, and composition. Specifically, a grain x sweet sorghum recombinant inbred line (RIL) population developed for quantitative trait locus (QTL) analysis related to sugar production was evaluated for 24 phenotypic traits including brix, percent moisture, and biomass yield across four environments. The 185 F4 RILs were derived from the parents 'BTx3197' and 'Rio', which are pithy stalk grain and juicy stalk sweet sorghums respectively. Following screening, two genetic maps were constructed with 372 and 381 single nucleotide polymorphisms (SNPs) evaluated using an Illumina GoldenGate assay. Analysis of the data in QTL Cartographer revealed a major and previously reported QTL for soluble solids on chromosome 3, but in contrast to previous studies, this QTL co-localized with other QTLs that have a negative influence on biomass and seed production. Therefore, selection for this QTL may not be advantageous. Because only a few QTLs for percent moisture were found, the results indicated that the pithy stalk phenotype does not have a major effect on percent moisture as measured in this study. Thus, breeding for high or low moisture content will be more challenging than previously expected. The absence of dominance effects indicated that brix must be high in both parents to produce high brix in the hybrid.Item Thin film nanoporous silica and graphene based biofuel cells (iBFCs) for low-power implantable medical device applications(2010-08) Sharma, Tushar; Zhang, Xiaojing, Ph. D.; Milner, Thomas E.This thesis describes the fabrication and characterization of an inorganic catalyst based glucose Biofuel cell using nanoporous (mesoporous) silica thin-film as a functional membrane. The desired use of nanoporous silica based biofuel cell is for a blood vessel implantable device. Blood vessel implantable Biofuel Cells (iBFCs) are subjected to higher glucose concentrations and blood flow rates. However, reduction in the implant thickness is critical for the intra-vascular implantable Biofuel cells. Platinum thin-film (thickness: 25 nm) deposited on Silicon substrate (500 [mu]m) served as the anode while Graphene pressed on Stainless steel mesh (175 [mu]m) was used as the cathode. Control experiments involved the use of surfactant-coated polypropylene membrane (50 [mu]m) and Activated Carbon (198 [mu]m) electrodes. Preliminary results show that nanoporous silica thin film (270 nm) is capable of replacing the conventional polymer based membranes with an increased power density output of as high as 10 [mu]W/cm2 under physiological conditions. in-vitro (5 [mu]W/cm2) and in-vivo (10 [mu]W/cm2) experiments demonstrate the potential of ultra-thin iBFCs towards powering future medical implants.Item Three Essays on Bioenergy Production in the United States(2013-12-02) Wlodarz, MartaThis dissertation examines future prospects of bioenergy production in the United States. The analysis examines three issues on liquid fuel and cellulosic ethanol. First, the amount that costs need to decrease in order to make cellulosic ethanol competitive, considering both production and market penetration costs. Second, the potential effect of mandate relaxations and carbon market related payments on liquid fuel production potential. Third, the effects of ignoring or considering asset fixity of refinery construction on liquid fuel production and market penetration. These analyses are framed using a theoretical graphical analysis then are empirically carried out using a version of the U.S. agricultural sector mathematical programming model FASOMGHG which is augmented and expanded to accommodate the issues examined. The main findings are: 1) processing costs of cellulosic ethanol need to be reduced by at least 70% to make cellulosic ethanol production fully cost competitive; 2) removal of market penetration barriers also are also a big contributor to the market presence of bioethanol; 3) carbon pricing and other market mechanisms provide incentives for more ethanol production; 4) greenhouse gas payments entail additional revenues flowing to the bioethanol industry and as a result, increase volumes of total ethanol produced and 5) asset fixity provides a major barrier to ethanol production increases. Furthermore under asset fixity: 1) cellulosic ethanol production is reduced when mandates hold; 2) cellulosic ethanol production is virtually eliminated when mandates are not in place; 3) asset fixity has a more significant impact on the amount of ethanol produced when no market penetration barriers are in place; 4) asset fixity influences the generation of biodiesel by changing its feedstock structure.