In the near future, biomass-derived energy is predicted to substantially complement that generated from petroleum. However, certain types of biomass employed as substrates in the microorganism-mediated production of renewable fuelethanol contain significant amounts of the recalcitrant hexose sugar galactose. The consumption of galactose in hexose sugar-fermenting yeasts is often delayed with respect to other sugars, such as glucose and mannose, because of an intrinsic preference for carbon sources requiring less energy in the preparatory reactions preceding glycolysis. This work comprised the search for, and characterization of anethanologenic yeast capable of efficiently assimilating galactose. Screening experiments conducted with wild-type Saccharomyces cerevisiae strains identified one isolate (Y-1528) exhibiting exceptionally fast galactose fermentation. The absence of conventional glucose repression, including a preference for galactose as carbon source and notable delays in the utilization of glucose and mannose, was demonstrated in mixed sugar fermentations. Endogenous extracellular glucose was observed during double sugar fermentations of galactose and mannose. This glucose was traced to supplied galactose by radioisotope labeling, suggesting involvement of UDP-galactose 4-epimerase in the responsible reaction mechanism(s).Sub-cellular fractionation was employed in an attempt to ascertain enzyme localization in Y-1528. Fermentations of lignocellulosic substrate mixtures by Y-1528 illustrated better performance than that accomplished by a reference yeast strain, and again showed a preference for galactose. Mixed cultures of Y-1528 and the same reference strain demonstrated accelerated hexose sugar consumption, and no detrimental effects from competition, during synthetic and lignocellulosic substrate fermentations. Glucose repression was absent in mixed culture fermentations. Fermentations of synthetic sugar mixtures augmented with lignocellulosic inhibitory compounds showed Y-1528 to have better performance than a reference yeast strain, despite a global detrimental effect relative to inhibitor-free fermentations. Cell recycle batch fermentations of spent sulfite liquor illustrated the toxic effect of the hardwood variant, as well as a net loss of performance from all strains tested. Y-1528 was taxonomically confirmed as S. cerevisiae. UDP-galactose 4-epimerase chromatographic purification was unsuccessful, but a partial sequence of the enzyme, showing complete identity with type sequence, was obtained by electrophoretic separation, liquid chromatography, and mass spectrometry. A significantly mutated UDP-galactose 4-epimerase gene was successfully sequenced.

In the near future, biomass-derived energy is predicted to substantially complement that generated from petroleum. However, certain types of biomass employed as substrates in the microorganism-mediated production of renewable fuelethanol contain significant amounts of the recalcitrant hexose sugar galactose. The consumption of galactose in hexose sugar-fermenting yeasts is often delayed with respect to other sugars, such as glucose and mannose, because of an intrinsic preference for carbon sources requiring less energy in the preparatory reactions preceding glycolysis. This work comprised the search for, and characterization of anethanologenic yeast capable of efficiently assimilating galactose. Screening experiments conducted with wild-type Saccharomyces cerevisiae strains identified one isolate (Y-1528) exhibiting exceptionally fast galactose fermentation. The absence of conventional glucose repression, including a preference for galactose as carbon source and notable delays in the utilization of glucose and mannose, was demonstrated in mixed sugar fermentations. Endogenous extracellular glucose was observed during double sugar fermentations of galactose and mannose. This glucose was traced to supplied galactose by radioisotope labeling, suggesting involvement of UDP-galactose 4-epimerase in the responsible reaction mechanism(s).Sub-cellular fractionation was employed in an attempt to ascertain enzyme localization in Y-1528. Fermentations of lignocellulosic substrate mixtures by Y-1528 illustrated better performance than that accomplished by a reference yeast strain, and again showed a preference for galactose. Mixed cultures of Y-1528 and the same reference strain demonstrated accelerated hexose sugar consumption, and no detrimental effects from competition, during synthetic and lignocellulosic substrate fermentations. Glucose repression was absent in mixed culture fermentations. Fermentations of synthetic sugar mixtures augmented with lignocellulosic inhibitory compounds showed Y-1528 to have better performance than a reference yeast strain, despite a global detrimental effect relative to inhibitor-free fermentations. Cell recycle batch fermentations of spent sulfite liquor illustrated the toxic effect of the hardwood variant, as well as a net loss of performance from all strains tested. Y-1528 was taxonomically confirmed as S. cerevisiae. UDP-galactose 4-epimerase chromatographic purification was unsuccessful, but a partial sequence of the enzyme, showing complete identity with type sequence, was obtained by electrophoretic separation, liquid chromatography, and mass spectrometry. A significantly mutated UDP-galactose 4-epimerase gene was successfully sequenced.

In the near future, biomass-derived energy is predicted to substantially complement that generated from petroleum. However, certain types of biomass employed as substrates in the microorganism-mediated production of renewable fuelethanol contain significant amounts of the recalcitrant hexose sugar galactose. The consumption of galactose in hexose sugar-fermenting yeasts is often delayed with respect to other sugars, such as glucose and mannose, because of an intrinsic preference for carbon sources requiring less energy in the preparatory reactions preceding glycolysis. This work comprised the search for, and characterization of anethanologenic yeast capable of efficiently assimilating galactose. Screening experiments conducted with wild-type Saccharomyces cerevisiae strains identified one isolate (Y-1528) exhibiting exceptionally fast galactose fermentation. The absence of conventional glucose repression, including a preference for galactose as carbon source and notable delays in the utilization of glucose and mannose, was demonstrated in mixed sugar fermentations. Endogenous extracellular glucose was observed during double sugar fermentations of galactose and mannose. This glucose was traced to supplied galactose by radioisotope labeling, suggesting involvement of UDP-galactose 4-epimerase in the responsible reaction mechanism(s).Sub-cellular fractionation was employed in an attempt to ascertain enzyme localization in Y-1528. Fermentations of lignocellulosic substrate mixtures by Y-1528 illustrated better performance than that accomplished by a reference yeast strain, and again showed a preference for galactose. Mixed cultures of Y-1528 and the same reference strain demonstrated accelerated hexose sugar consumption, and no detrimental effects from competition, during synthetic and lignocellulosic substrate fermentations. Glucose repression was absent in mixed culture fermentations. Fermentations of synthetic sugar mixtures augmented with lignocellulosic inhibitory compounds showed Y-1528 to have better performance than a reference yeast strain, despite a global detrimental effect relative to inhibitor-free fermentations. Cell recycle batch fermentations of spent sulfite liquor illustrated the toxic effect of the hardwood variant, as well as a net loss of performance from all strains tested. Y-1528 was taxonomically confirmed as S. cerevisiae. UDP-galactose 4-epimerase chromatographic purification was unsuccessful, but a partial sequence of the enzyme, showing complete identity with type sequence, was obtained by electrophoretic separation, liquid chromatography, and mass spectrometry. A significantly mutated UDP-galactose 4-epimerase gene was successfully sequenced. / Forestry, Faculty of / Graduate

The utilization of activated sludge as feedstock for biofuel and oleochemical production was investigated. Initial studies included optimization of biodiesel production from this feedstock through in situ transesterification. Results of these studies indicated that activated sludge biodiesel is not economically viable. This was primarily due to relatively low yields and the high economics of feedstock dewatering. Strategies to increase biofuel yield from activated sludge were then evaluated. Bacterial species present in activated sludge are known to produce a wide variety of lipidic compounds as carbon and energy storage material and as components of their cellular structures. In addition to lipidic compounds, activated sludge bacteria might also contain other compounds depending on wastewater characteristics. Among these bacterial compounds, only the saponifiable ones can be converted to biodiesel. The unsaponifiable compounds present in the activated sludge are also important, not only for biofuel production, but also for a wide variety of applications. Characterization of lipids in activated sludge revealed that it contains significant amount of polyhydroxyalkanoates, wax esters, acylglycerides and fatty acids. It also contains Template Created By: James Nail 2010 sterols, steryl esters and phospholipids as well as small but detectable amounts of hydrocarbons. This indicated that activated sludge could be also an inexpensive source of oleochemicals. Another strategy that was evaluated was lipid-enhancement by fermentation of activated sludge. Since the majority of products from petroleum oil are used as transportation fuel, the aim here was to increase the saponifiable lipids in activated sludge bacteria by applying a biochemical stimulus (i.e. high C:N ratio). Results showed that application of this stimulus increased the amount of saponifiable lipids, particularly triacyglycerides, in the activated sludge. Furthermore, fermentation homogenized the lipids in the sludge regardless of its source. This solidified the concept of utilizing wastewater treatment facilities as biorefineries. To support the utilization of other compounds in raw activated sludge for biofuel production, a model compound was chosen for catalytic cracking experiments. Results indicated that catalytic cracking of 1-octadecanol over H+ZSM5 proceeds via dehydration, producing octadecene. The octadecene then undergoes a series of reactions including β-C─C bond scission, alkylation, oligomerization, dehydrocyclization and aromatization producing aromatics, paraffins and olefins suitable for fuel applications.

No description available.

The curing of flue-cured tobacco (Nicotiana tabacum L.) is an energy intensive process and represents a significant portion of the overall cost of production. Given the goal of the industry to reduce the environmental footprint of tobacco production and the energy demand of curing, attention has been directed to explore options for the use of renewable fuels for heating tobacco barns. A two-year study conducted at the Virginia Tech Southern Piedmont Center evaluated the effectiveness and cost of curing flue-cured tobacco with a wood pellet burner. Additionally, field studies were conducted to evaluate the feasibility of on-farm production of biomass fuel crops as well as on-farm manufacture of biomass fuel pellets. The first time use of a wood pellet burner with an air-to-air heat exchanger in a bulk curing barn proved to be a viable alternative to a conventional propane fueled burner. Curing cost averaged $0.05 with the pellet burner compared to $0.04 per kilogram of tobacco with the propane burner. The increase in cost was offset by a 90 percent reduction of CO2 emissions with the use of wood pellets. The use of low lignin grass varieties did have an impact on biomass pellet properties. Pellet testing revealed high ash and chloride levels which could be problematic using a high efficiency wood pellet burner. Full maturity harvest of annual grasses fertilized with 112 kg per ha N resulted in higher yields. However, fertilizing for maximum yield would increase the CO2 footprint for biomass fuel pellet production. / Master of Science

Biomass is the world’s largest renewable energy source, accounting for approximately 10% of global primary energy supply, and 5% of energy consumed in the United States. Prominent national programs like the U.S. Renewable Fuel Standard incentivize increased use of biomass, primarily as a transportation fuel. There has been comparatively little government support for using biomass as a renewable feedstock for the chemical sector. Such asymmetry in incentives can lead to sub-optimal outcomes in the allocation of biomass toward different uses. Greenhouse gas reduction is among the most cited benefits of bioenergy and bio-based products, however, there is increasing controversy about whether increased use of biomass can actually contribute to greenhouse gas emission targets. If biomass is to play a role in current and future greenhouse gas mitigation efforts its use should be guided by efficient use of natural and economic resources. This thesis addresses these questions through a series of case studies, designed to highlight important tradeoffs in the use of biomass for greenhouse gas mitigation. Should biomass be used as a fuel, a chemical feedstock, or neither? The first case study in this thesis focuses on the ‘fuel vs feedstock’ question, examining the greenhouse gas implications of expanding the scope of the U.S. Renewable Fuel Standard to include credits for bioethylene, an important organic chemical readily produced from bioethanol. Results suggest that an expanded policy that includes bioethylene as an approved use for ethanol would provide added flexibility without compromising greenhouse gas targets – a clear win scenario. Having established that bioethylene based plastics can achieve similar greenhouse gas reductions to bioethanol used as fuel, this thesis expands the analysis by considering how the greenhouse gas emissions from a wider range of bio-based plastics compare to each of the main commodity thermoplastics produced in the U.S. The analysis demonstrates that there are large uncertainties involved in the life cycle greenhouse gas emissions from bio-based plastics, and that only a subset of pathways are likely to be preferable to conventional plastics. The following chapter then builds on the existing model to compare the greenhouse gas mitigation potential of bio-based plastics to the potential for reducing emissions by adopting low carbon energy for plastics production. That chapter concludes that switching to renewable energy across the supply chain for conventional plastics energy cuts greenhouse gas emissions by 50-75%, achieving a greater reduction, with less uncertainty and lower cost, than switching to corn-based biopolymers – the most likely near-term biopolymer option. In the long run, producing bio-based plastics from advanced feedstocks (e.g. switchgrass) and/or with renewable energy likely offers greater emission reductions. Finally, this thesis returns to the dominant form of policy surrounding biomass use: biofuel mandates. That study takes a consequential approach to the ‘fuel or neither’ question. Specifically, this work examines how petroleum refineries are likely to adjust their production in response to biofuel policies, and what this implies for the success of these policies. The research demonstrates that biofuel policies induce a shift toward greater diesel production at the expense of both gasoline and non-combustion petroleum products. This has the potential to result in an increase in greenhouse gas emissions, even before accounting for the emissions from producing the biofuels themselves.

For many decades, demand for agricultural commodities has remained stagnant and its growth has been limited. In contrast, agricultural production continues to become ever more efficient by increasing output for stable or decreased inputs. Long-run profits have historically been near zero due to an ongoing relative equilibrium. But recent U.S. energy policy has changed to include a Renewable Fuels Standard (RFS), the goal of which is to boost domestic energy independence in an environmentally sound way. Most of the RFS in the near-term relies on the production of 15 billion gallons of ethanol made from corn. This has the effect of creating a new sector of demand for grain corn and subsequently supports rural economies. The RFS creates a new demand for 5.5 billion bushels of corn by 2015. At the corn-ethanol conversion ratio of 2.7 gallons per bushel, this will sustain the production of 15 billion gallons of ethanol. The RFS is a blending floor imposed on gasoline refiners. Ethanol producers, on the other hand, are not forced to supply ethanol. While the Environmental Protection Agency (EPA) has the authority to implement the RFS, it does not have the ability to expand ethanol supplies. The U.S. government has therefore supported the use of ethanol through a current 45 cent tax credit for each gallon of ethanol blended into gasoline. Other financial support programs such as grants and loan guarantees are in place for ethanol refiners. Ethanol in the U.S.is primarily made from the starchy molecules in corn. One bushel of corn in a dry mill ethanol plant will produce approximately 2.7 gallons of ethanol and 17 pounds of dried distillers grains with solubles (DDGS) which can be used in livestock rations. A wet mill plant will produce other by-products. Ethanol can be used directly in the nation's fuel supply at limited levels of blending. Most cars in the United States can withstand the corrosive nature of ethanol in blends of up to 10% or more. But flex-fuel vehicles, which are able to operate on 85% ethanol are increasingly becoming available for sale and their use continues to grow. Corn ethanol is a very complex issue when implemented on such a large scale as the RFS dictates. The amount of transportation fuel actually displaced by its use is a hotly debated topic. In any case, the large scale production of corn ethanol has created a firm link between agricultural markets and the energy sector. Ethanol is also an environmental issue. One of the primary goals of the RFS is to combat global warming and whether or not this is achieved it currently in debate. Aside from the climate change issue, there are other environmental ramifications tied directly to ethanol such as contamination, water use and land-use change. Since the inception of the RFS, price volatility and uncertainty has never been greater. In the first half of 2008, prices for all commodities reached historically high levels. This raises the concern of the impacts with the RFS has on markets other than corn. The livestock industry and other grain markets have been affected to some degree by the RFS. This is in part due to the changing profile of the major trading participants in the commodity trading centers. All of this is related to a structural change which has taken place in the agricultural markets as a result of the RFS. Historical relationships between price, supply and demand have adjusted and currently continue to adjust. The reasons for the adjustments are founded in economic theory regarding system-wide demand shocks. In this case, the demand shock is roughly a net 50% increase in the demand for corn by 2015 compared to the most recent decade. The adjustments which take place can be summarized by three periods. In period 1, the demand curve shifts outward, equilibrium is lost and higher corn prices are observed. In period 2, the market struggles to find a new equilibrium by increasing output. This period is marked by increased volatility and market participants over and under react to price signals until the new equilibrium is discovered. Period three is represented by the discovery of a relative market equilibrium at price higher than previously, but not as high as the initial demand shock. Results from, a fundamental analysis of the grain markets show that the expected market behavior has begun to take place and agriculture finds itself in period 2 of the changes described above. While most of the price changes and acreage shifts can be explained, the degree to which prices have increased are not fully explained. A change in trading center activities (Boards of Trade, etc.) may help to further account for the new prices. A survey of brokers shows that the behavior of commercial traders has significantly changed since RFS implementation. Volatility and uncertainty have ensued. The consequences of the RFS to the farmer have also been significant. Farm income has increased significantly sufficiently to overcome the riding costs of fuel and fertilizer. The risk exposure of farmers has also changed; the data indicates that exposure to risk has increased greatly. However, the farm gate prices have been more than enough to compensate for the changes in risk.

The Renewable Fuel Standard requires US oil refineries to blend biofuels into domestic transportation fuels. To ensure that compliance costs under this mandate don’t disproportionately affect any subset of refiners, the regulation includes a compliance credit program, whereby refiners blending excess biofuels can sell their excess compliance to refiners that do not blend enough. The price of these credits can be interpreted as the marginal cost of compliance with the mandate. I measure how changes in the prices of these compliance credits affect the stock prices of oil refining firms. There are a number of ways one might expect these compliance credits to affect firms. Much economic research finds that oil refiners are able to pass the costs of RFS compliance to consumers quite easily, suggesting that changes in the compliance cost should not affect firms’ value at all. Large refiners tend to claim that the RFS imposes a large cost and drags down their profits. Perhaps the most interesting claim is that of the “merchant refiners”—generally small refiners who do not own the infrastructure to blend biofuels on their own and are thus forced to comply with the mandate completely with compliance credits. They claim that larger refiners are able to hoard the credits and sell them for windfall profits at the expense of the merchant refiners. My results indicate that positive shocks in compliance credit prices are associated with stock losses only among large, non-merchant refiners, and that even this association is small. This discredits the claims of merchant refiners, but opens a new puzzle: why are large, integrated refiners the only ones affected? I conclude my paper with a number of potential explanations, though I am not able to test between them using my data.

This paper studies castor oil’s potential as a biodiesel feedstock. Base-catalyzed transesterification batch reactions were conducted at various experimental conditions while measuring the concentration of the reaction components over time. A gas chromatograph with a flame-ionization detector analyzed these samples. A factorial design of experiments was used to determine how conversion was affected by reaction temperature, sodium methoxide concentration, and ratio of methanol to oil. Conversion was maximized (0.9964) at 30 °C, 0.5% catalyst, and 9:1 molar ratio. The concentration data were used to study the reaction kinetics. Modeling the reaction as three equilibria yielded six rate constants. These values indicate that castor oil transesterifies faster than soybean oil. The fuel properties were determined by ASTM D 6751. Viscosity was excessively high, but specifications were met for the remaining tests. Despite the promising yield and kinetics of the reaction, the fuel viscosity limits castor oil’s viability as a biodiesel feedstock.