Browsing by Subject "ethanol"
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item Conversion of sugarcane bagasse to carboxylic acids under thermophilic conditions(2009-05-15) Fu, ZhihongWith the inevitable depletion of the petroleum supply and increasing energy demands in the world, interest has been growing in bioconversion of lignocellulosic biomass (e.g., sugarcane bagasse). Lignocellulosic biomass is an abundant, inexpensive, and renewable resource. Most of current conversion technologies require expensive enzymes and sterility. In contrast, the patented MixAlco process requires no enzymes or sterility, making it attractive to convert lignocellulosic biomass to transportation fuels and valuable chemicals. This study focuses on pretreatment and thermophilic fermentation in the MixAlco process. Ammonium bicarbonate (NH4HCO3) was discovered to be a better pH buffer than previously widely used calcium carbonate (CaCO3) in anaerobic fermentations under thermophilic conditions (55?C). The desired pH should be controlled within 6.5 to 7.5. Over 85% acetate content in the product was found in paper fermentations and bagasse fermentations. Hot-lime-water-treated bagasse countercurrent fermentations buffered by ammonium bicarbonate achieved 50?60% higher total product concentrations than those using calcium carbonate. It was nearly double in paper batch fermentations if the pH was controlled around 7.0. Ammonium bicarbonate is a ?weak? methane inhibitor, so a strong methane inhibitor (e.g., iodoform) is still required in ammonium bicarbonate buffered fermentations. Residual calcium salts did not show significant effects on ammonium bicarbonate buffered fermentations. Lake inocula from the Great Salt Lake, Utah, proved to be feasible in ammonium bicarbonate buffered fermentations. Under mesophilic conditions (40?C), the inoculum from the Great Salt Lake increased the total product concentration about 30%, compared to the marine inoculum. No significant fermentation performance difference, however, was found under thermophilic conditions. The Continuum Particle Distribution Model (CPDM) is a powerful tool to predict product concentrations and conversions for long-term countercurrent fermentations, based on batch fermentation data. The experimental acid concentrations and conversions agree well with the CPDM predictions (average absolute error < 15%). Aqueous ammonia treatment proved feasible for bagasse. Air-lime-treated bagasse had the highest acid concentration among the three treated bagasse. Air-lime treatment coupled with ammonium bicarbonate buffered fermentations is preferred for a ?crop-tofuel? process. Aqueous ammonia treatment combined with ammonium bicarbonate buffered fermentations is a viable modification of the MixAlco process, if ?ammonia recycle? is deployed.Item Countercurrent Enzymatic Saccharification of Lignocellulosic Biomass and Improvements Over Batch Operation(2014-05-05) Zentay, Agustin NicholasTransportation fuels are the major driver for fossil fuel production, a burden that many countries have tried to ease by blending fossil fuels with biofuel substitutes such as ethanol. Current U.S. ethanol production relies on fermentation of starchy biomass (e.g., corn), which competes with food. Using lignocellulose avoids competition with food; however, it is difficult to digest using traditional batch saccharification. This work investigates countercurrent saccharification as an alternative that reduces enzyme requirements. Compared to baseline yields for standard batch saccharification, countercurrent saccharification reduces enzyme requirements by 5 to 37 times. Initial studies identified Solka-Floc as an acceptable substrate to represent treated biomass; it is readily available and reliably consistent from sample to sample. To measure yields, batch saccharifications were performed at various enzyme loadings and reaction times. Two relatively low enzyme concentrations were selected for further study: 2 and 5 mg protein/g biomass, or 2.6 and 6.4 mg protein/g glucan, respectively. Both of the selected loadings are below levels suggested for commercial use. For each enzyme loading tested, a multi-stage, semi-continuous countercurrent train was constructed. The first experiments used trains consisting of eight 1-L bottles loaded with ?-cellulose, using the same concentrations as the batch experiments. Liquid and solid phases were countercurrently contacted, with transfers of each phase occurring every second day for approximately 4?6 weeks, until steady-state operation was maintained for at least 10 days. At 2 and 5 mg/g enzyme loadings, total sugar yields reached 55.9% and 85.3%, respectively. A follow up study using 16 bottles and 2 mg/g loading produced total sugar yields of 73.4%. In the interest of future scale-up, alternatives to the cycloheximide and tetracycline antibiotic cocktail were investigated. Preliminary results suggest that chloroform or a volatile essential plant oil may be effective. Future work is needed to confirm the antimicrobial strength of these compounds at low concentrations, which is needed to limit enzyme inhibition.Item Impacts of Biofuel Production and Navigation Impediments on Agricultural Transportation and Markets(2013-08-22) Ahmedov, ZafarbekThis study investigated the impacts of U.S. biofuel production and barge navigation impediments on agricultural transportation and markets. Both past and future impacts of U.S. biofuel production levels mandated by the Renewable Fuel Standards of the Energy Policy Act of 2005 (RFS1) and the Energy Independence and Security Act of 2007 (RFS2) were examined. Examination of barge navigations impediments included analysis of the impact of lock failure and low water levels on rivers due to drought, on agricultural transportation, and on consumer welfare. All scenarios were simulated using the International Grain Transportation Model, a price endogenous mathematical programming model. The results showed that RFS-associated (RFS1 and RFS2) U.S. corn ethanol production increased the total corn supply and diverted corn from non-ethanol consumption, reduced regional grain transportation volumes, and contributed to a rise in corn prices. The results of the forward-looking scenarios indicated that grain exports and transport volumes were increased. Exports from Gulf ports increased by 41%, while grain movements by rail increased by 60%. Additional investments in the expansion of the grain handling capacities of Gulf ports and the railroad industry are needed in the near future unless a large increase in biofuel production occurs. The results of navigation impediment scenarios indicated that both lock failures and low water levels on rivers adversely affect U.S. grain exports. The Gulf ports were most negatively impacted, relative to Pacific Northwest and Atlantic ports. Truck and barge freight volume declined while rail freight volume increased. Because trucks deliver grain from grain elevators to barge locations, truck volume also decreased in response to the decline in barge volume. The scenarios imposed welfare losses on society with most accruing to consumers, while the barge industry lost $10-154 million in revenue. The low water levels were more expensive than the lock failures. Major rehabilitation of the locks is needed to avoid lock failures and more dredging of the shallow parts of the river system is required because of frequent droughts.Item Market penetration of biodiesel and ethanol(Texas A&M University, 2007-09-17) Szulczyk, Kenneth RayThis dissertation examines the influence that economic and technological factors have on the penetration of biodiesel and ethanol into the transportation fuels market. This dissertation focuses on four aspects. The first involves the influence of fossil fuel prices, because biofuels are substitutes and have to compete in price. The second involves biofuel manufacturing technology, principally the feedstock-to-biofuel conversion rates, and the biofuel manufacturing costs. The third involves prices for greenhouse gas offsets. The fourth involves the agricultural commodity markets for feedstocks, and biofuel byproducts. This dissertation uses the Forest and Agricultural Sector Optimization Model-Greenhouse Gas (FASOM-GHG) to quantitatively examine these issues and calculates equilibrium prices and quantities, given market interactions, fossil fuel prices, carbon dioxide equivalent prices, government biofuel subsidies, technological improvement, and crop yield gains. The results indicate that for the ranges studied, gasoline prices have a major impact on aggregate ethanol production but only at low prices. At higher prices, one runs into a capacity constraint that limits expansion on the capacity of ethanol production. Aggregate biodiesel production is highly responsive to gasoline prices and increases over time. (Diesel fuel price is proportional to the gasoline price). Carbon dioxide equivalent prices expand the biodiesel industry, but have no impact on ethanol aggregate production when gasoline prices are high again because of refinery capacity expansion. Improvement of crop yields shows a similar pattern, expanding ethanol production when the gasoline price is low and expanding biodiesel. Technological improvement, where biorefinery production costs decrease over time, had minimal impact on aggregate ethanol and biodiesel production. Finally, U.S. government subsidies have a large expansionary impact on aggregate biodiesel production, but only expand the ethanol industry at low gasoline prices. All of these factors increase agricultural welfare with most expanding producer surplus and mixed effects on consumers.Item Modeling and Optimization of a Bioethanol Production Facility(2011-10-21) Gabriel, Kerron JudeThe primary objective of this work is to identify the optimal bioethanol production plant capacity and configuration based on currently available technology for all the processing sections involved. To effect this study, a systematic method is utilized which involves the development of a superstructure for the overall technology selection, process simulation and model regression of each processing step as well as equipment costing and overall economic evaluation. The developed optimization model is also designed to incorporate various biomass feedstocks as well as realistic maximum equipment sizing thereby ensuring pragmatism of the work. For this study, the criterion for optimization is minimum ethanol price. The secondary and more interesting aim of this work was to develop a systematic method for evaluating the economics of biomass storage due to seasonal availabilities. In essence, a mathematical model was developed to link seasonal availabilities with plant capacity with subsequent integration into the original model developed. Similarly, the criterion for optimization is minimum ethanol price. The results of this work reveal that the optimal bioethanol production plant capacity is ~2800 MT biomass/day utilizing Ammonia Fiber Explosion pretreatment technology and corn stover as the preferred biomass feedstock. This configuration provides a minimum ethanol price of $1.96/gal. Results also show that this optimal pretreatment choice has a relatively high sensitivity to chemical cost thereby increasing the risk of implementation. Secondary to this optimal selection was lime pretreatment using switchgrass which showed a fairly stable sensitivity to market chemical cost. For the storage economics evaluation, results indicated that biomass storage is not economical beyond a plant capacity of ~98 MMgal/yr with an average biomass shortage period of 3 months. The study also showed that for storage to be economical at all plant capacities, the storage scheme employed should be general open air land use with a corresponding biomass loss rate as defined in the study of 0.5 percent per month.Item Regional Differences in Corn Ethanol Production: Profitability and Potential Water Demands(2010-07-14) Higgins, Lindsey M.Through the use of a stochastic simulation model this project analyzes both the impacts of the expanding biofuels sector on water demand in selected regions of the United States and variations in the profitability of ethanol production due to location differences. Changes in consumptive water use in the Texas High Plains, Southern Minnesota, and the Central Valley of California, as impacted by current and proposed grain-based ethanol plants were addressed. In addition, this research assesses the potential impacts of technologies to reduce consumptive water use in the production of ethanol in terms of water usage and the economic viability of each ethanol facility. This research quantifies the role of corn ethanol production on water resource availability and identifies the alternative water pricing schemes at which ethanol production is no longer profitable. The results of this research show that the expansion of regional ethanol production and the resulting changes in the regional agricultural landscapes do relatively little to change consumptive water usage in each location. The California Central Valley has the highest potential for increased water usage with annual water usage in 2017 at levels 15% higher than historical estimates, whereas Southern Minnesota and the Texas High Plains are predicted to have increases of less than 5% during the same time period. Although water use by ethanol plants is extremely minor relative to consumptive regional agricultural water usage, technological adaptations by ethanol facilities have the potential to slightly reduce water usage and prove to be economically beneficial adaptations to make. The sensitivity of net present value (NPV) with respect to changes in water price is shown to be extremely inelastic, indicating that ethanol producers have the ability to pay significantly more for their fresh water with little impact on their 10 year economic performance.Item Retrofitting analysis of integrated bio-refineries(Texas A&M University, 2007-04-25) Cormier, Benjamin R.A bio-refinery is a processing facility that produces liquid transportation fuels and/or value-added chemicals and other products. Because of the dwindling resources and escalating prices of fossil fuels, there are emerging situations in which the economic performance of fossil-based facilities can be enhanced by retrofitting and incorporation of bio-mass feedstocks. These systems can be regarded as bio-refineries or integrated fossilbio- refineries. This work presents a retrofitting analysis to integrated bio-refineries. Focus is given to the problem of process modification to an existing plant by considering capacity expansion and material substitution with biomass feedstocks. Process integration studies were conducted to determine cost-effective strategies for enhancing production and for incorporating biomass into the process. Energy and mass integration approaches were used to induce synergism and to reduce cost by exchanging heat, material utilities, and by sharing equipment. Cost-benefit analysis was used to guide the decision-making process and to compare various production routes. Ethanol production from two routes was used as a case study to illustrate the applicability of the proposed approach and the results were bio-refinery has become more attractive then fossil-refinery.Item The Renewable Fuel Standard and Ethanol Pricing: A Sensitivity Analysis(2014-04-18) McNair, RobertVolatile oil prices and political uncertainty surrounding uninterrupted oil supplies has pressured the U.S. Congress and economists to search for substitutes. In response, the U.S. has enacted policies to directly support the production and use of biofuel. The current Renewable Fuel Standard (RFS) requires 36 billion gallons of renewable fuel use by 2022. A large proportion of the mandate is to consist of corn-based ethanol. Most ethanol is consumed in the U.S. as a 10 percent blend of ethanol and gasoline. In 2014, it is projected oil refineries will hit the blend wall (BW). In short, oil refineries are required to blend more ethanol into gasoline than is allowed by the Environmental Protection Agency (EPA). As a consequence, the EPA will need to either reduce the Renewable Fuel Standard for 2014, or permit additional ethanol blends to be sold. Overall, the purpose of the study was to analyze the economic impact of changing energy policy on ethanol markets. A structural, supply and demand model was developed. Four equations were estimated, and residuals were simulated to estimate probability distributions for monthly ethanol prices and total demand. Alternative scenarios were developed to estimate how the RFS, the BW, and corn prices affect ethanol markets. The parameter estimates indicated the major determinants of ethanol demand were the RFS and the BW. The results showed the RFS and the BW positively affected the price of ethanol and demand. The base scenario estimated average ethanol price to be $1.89/gal. When the RFS was reduced by 10.59 percent, ethanol prices were estimated to decline $0.29/gal, compared to the base scenario. Total demand declined 600 million gallons. If the BW was increased to 15 percent, the price of ethanol increased approximately $1.10/gal from the base scenario. Total demand increased 1.4 billion gallons in response. Ethanol prices were found to be insensitive to corn prices.Item Transportation risk assessment for ethanol transport(2009-05-15) Shelton Davis, Anecia DelaineThis research is aimed at assessing the quantitative risks involved with an ethanol pipeline. Pipelines that run from the Midwest, where the vast majority of ethanol is produced, to the target areas where reformulated gasoline is required (California, Texas Gulf Coast, New England Atlantic Coast) will be of particular interest. The goal is to conduct a quantitative risk assessment on the pipeline, truck, and rail transportation modes to these areas. As a result of the quantitative risk assessment, we are able to compare the risk associated with the different modes of transportation for ethanol. In order to perform and compare the quantitative risk assessment, the following challenges are addressed: ? Identify target areas requiring reformulated gasoline ? Map detailed route for each transportation mode to all three target areas ? Perform a quantitative risk assessment for each transportation mode ? Compare quantitative risk assessment results for each route and transportation mode The focus is on California, Texas Gulf Coast, and New England Atlantic Coast because of the large volume. It is beneficial to look at these areas as opposed to the smaller areas because pipeline transportation requires very large volumes. In order to find a meaningful comparison between all three transportation modes, only the areas with the three large volumes were evaluated. Since the risk assessment is completed using historical data, each route is segmented in a way that is consistent with the data that is available. All of the curves support the hypothesis that pipeline transportation poses the least societal risk when transporting ethanol from the Midwest to target areas. Rail transportation poses the largest amount of societal risk. While overall rail incidents are not as frequent as road incidents, the frequency of a fatality is much higher when an incident does occur.