Digital Commons Network^™

Switchgrass (Panicum Virgatum L.) Pollen-Mediated Gene Flow And Transgene Bioconfinement Strategies, Reginald Millwood

Doctoral Dissertations

Switchgrass (Panicum virgatum L.) is a native North American grass under development as a bioenergy feedstock. Genetic engineering has been employed to introduce transgenic traits for economical biofuel production. However, potential transgene movement from switchgrass raises regulatory and environmental concerns. Experimental studies are needed to determine the potential for transgene flow from switchgrass. The aims of this research are to estimate pollen dispersal and pollination distances for transgenic switchgrass, and evaluate genetically engineered male sterility as a transgene bioconfinement strategy. A three-year field experiment was performed to estimate switchgrass pollen dispersal and pollination distances using a modified Nelder wheel design. …

Proteome Characterizations Of Microbial Systems Using Ms-Based Experimental And Informatics Approaches To Examine Key Metabolic Pathways, Proteins Of Unknown Function, And Phenotypic Adaptation, Suresh Poudel

Doctoral Dissertations

Microbes express complex phenotypes and coordinate activities to build microbial communities. Recent work has focused on understanding the ability of microbial systems to efficiently utilize cellulosic biomass to produce bioenergy-related products. In order to maximize the yield of these bioenergy-related products from a microbial system, it is necessary to understand the molecular mechanisms.The ability of mass spectrometry to precisely identify thousands of proteins from a bacterial source has established mass spectrometry-based proteomics as an indispensable tool for various biological disciplines. This dissertation developed and optimized various proteomics experimental and informatic protocols, and integrated the resulting data with metabolomics, transcriptomics, and …

Genetic Diversity, Genetic Variation And Identification Of Quantitative Trait Loci (Qtl) Associated With Biomass Yield And Establishment-Related Traits In Lowland Switchgrass (Panicum Virgatum L.), Cheryl Ontolan Dalid

Doctoral Dissertations

Switchgrass is a warm-season C4 grass used for biofuel production. The primary goal of this study is biomass yield improvement for use as a bioenergy feedstock. The research plan was partitioned into three main objectives: (i) evaluate the genetic diversity among lowland switchgrass populations using microsatellite markers; (ii) assess genetic variation in an Alamo half-sib (AHS) population developed through phenotypic selection; (iii) and identify quantitative trait loci (QTL) associated with biomass yield and establishment related seed traits using a Nested Association Mapping (NAM) population. The genetic diversity study on lowland switchgrass showed significant phenotypic variations (P<0.05) among and within germplasm accessions. The Analysis of Molecular Variance (AMOVA) revealed that among genotypes within populations and among populations explained 84 and 16% of molecular genetic variations. The Principal Coordinate Analysis (PCoA) and cluster analysis separated switchgrass populations according to the ancestral background. The study on genetic variation showed significant variation (P<0.05) among AHS for biomass yield, tillering ability, and spring vigor, suggesting the importance of additive genetic variation in these traits. Results also showed great potential for biomass yield improvement through selection based on family performance. Using 10% selection intensity, parental control of two, and a narrow-sense heritability estimate of 0.11, gain per cycle selection from half-sib family selection is estimated to be 23%. The study on identification of QTLs associated with biomass yield and establishment related traits showed significant variation among NAM families and genotypes within families for biomass yield, seed weight, and germination (P<0.05). A total of 785 significant markers for biomass yield were detected (P<0.05) of which 176 were for seed weight and 131 for germination. Composite interval mapping revealed 21 QTLs for biomass yield across locations in 2 years the highest LOD score of 7.6 detected in chromosome Ia that explained a 12.5% of the phenotypic variation. Two QTLs located in chromosome VIIIb for seed weight explained 5.2% and 4.6% phenotypic variation. One QTL for germination located in chromosome IXa explained 5.2% of the phenotypic variation. The results of these studies will be useful for future breeding efforts in switchgrass and other perennial grasses.

Identification, Characterization, And Genetic Comparison Of Fusarium Species Isolated From Switchgrass (Panicum Virgatum L.), Tamara Annette Collins

Masters Theses

Fusarium spp. are ubiquitous, soilborne and seedborne pathogens that affect over 100 economically important plant hosts annually, resulting in billions of dollars in economic losses. They cause a variety of plant disease symptoms including, crown, root, and stem rots, wilts, and foliar necrosis. Furthermore, they produce harmful mycotoxins that are detrimental to the health of animals and humans. Members of this genus have been isolated from diseased tissues of switchgrass. The objective is to correctly identify and classify Fusarium isolates to species using both classic phenotypic characterization and current genetic technologies of DNA extraction and polymerase chain reaction and create …

Characterization Of Fusarium Species And Alternaria Alternata, And Their Effects On Switchgrass Health And Chemical Components, Sara Beth Collins

Masters Theses

Panicum virgatum L., readily referred to as Switchgrass, is a perennial warm-season bunch grass, used as an alternative energy source for biofuel production. There is insufficient research on switchgrass pathogens, and is expected that an increase in disease pressure will result as more land is reserved for this perennial crop. The purpose of this research was to identify and characterize pathogenic Alternaria alternata and Fusarium species on Switchgrass (Panicum virgatum L.), and to evaluate their impact on stand establishment and plant health. Molecular identifications of fungal isolates obtained from infected commercial switchgrass seed yielded eight species (A. alternata, …

Switchgrass Extractives Have Potential As A Value-Added Antimicrobial Against Plant Pathogens And Foodborne Pathogens, Alexander Ian Bruce

Masters Theses

Panicum virgatum (switchgrass), a perennial grass native to North America, is a leading biomass feedstock candidate for the manufacture of cellulosic ethanol. Switchgrass is considered a viable option for biofuel production due to its cheap production cost and ability to grow on marginal land. Biofuel derived from switchgrass has been shown to be very energy efficient, producing 540% more renewable energy versus nonrenewable energy expended. Switchgrass-derived biofuel is also estimated to have greenhouse gas emissions that are 94% lower than emissions from gasoline (Schmer et al 2008). Biofuels are created through biochemical processes that utilize various enzymes and microorganisms for …

Modification Of Carbohydrate Active Enzymes In Switchgrass (Panicum Virgatum L.) To Improve Saccharification And Biomass Yields For Biofuels, Jonathan Duran Willis

Doctoral Dissertations

The natural recalcitrance of plant cell walls is a major commercial hurdle for plant biomass to be converted into a viable energy source as alternative to fossil fuels. To circumvent this hurdle manipulation of carbohydrate enzymes active in the cellulose and hemicellulose portions of the plant cell wall can be utilized to improve feedstocks. Production of cellulolytic enzymes by plants have been evaluated for reducing the cost associated with lignocellulosic biofuels. Plants have successfully served as bioreactors producing bacterial and fungal glycosyl hydrolases, which have altered plant growth to improve saccharification. A bioprospecting opportunity lies with the utilization of insect …

A Simulation Model Of The “Bio-Depot” Concept In The Context Of Components Of Variance And The “Taguchi Loss Function”, Maximilian Platzer

Masters Theses

The research focuses on the simulation, statistical evaluation, costs, and continuous improvement of supply chains for bio-based materials. A significant challenge of using cellulosic feedstocks for biofuel or bioenergy production is the high per unit costs of final products, e.g., biofuels. The goal of the research is to provide practitioners with useful statistical methods and a simulation Excel template for evaluating the variance and costs associated with the supply chain of bio-based products. Statistical Process Control (SPC), components of variance, Taguchi Loss Function, and reliability block diagrams (RBD) are used in this thesis for the evaluation of the supply chain …

Genetic Modification Of Switchgrass (Panicum Virgatum L.) For Improvement Of Plant Architecture, Biomass Productivity And Sugar Release Efficiency For Biofuel, Wegi Aberra Wuddineh

Doctoral Dissertations

Switchgrass (Panicum virgatum L.) is a leading candidate bioenergy crop for sustainable biofuel production. To ensure its economic viability, tremendous improvements in switchgrass biomass productivity and recalcitrance to enzymatic saccharification are needed. Genetic manipulation of lignin biosynthesis by targeting transcriptional regulators of higher level domains of lignin biosynthesis and other complex traits could alter several bioenergy-desirable traits at once. A three-pronged approach was made in the dissertation research to target one plant growth regulator and transcription factors to alter plant architecture and cell wall biosynthesis.

Gibberellin (GA) catabolic enzymes, GA 2-oxidases (GA2oxs), were utilized to alternatively modify the lignin …

Economic And Environmental Optimization In The Supply Of Switchgrass In Tennessee, Jia Zhong

Masters Theses

The low efficiency of collection, storage and transportation in the switchgrass supply chain has hindered the commercialization of a switchgrass-based biofuel industry, even given its ecological and environmental advantages in carbon sequestrate, soil quality, water use, and pollution pressure. Thus, designing a switchgrass-based supply chain balancing both environmental and economic performance is important to expedite the development of the cellulosic biofuel industry to meet the national energy plan.

The objectives of this study are to 1) determine economic cost and multiple environmental outcomes in feedstock supply chains and 2) identify the relation between the economic and environmental performances. The first …

Modeling Water Quality For Switchgrass Crop Production: Implications For Bioenergy Sustainability In East Tennessee, Zachariah Tzvi Seiden

Masters Theses

With passing of the US Energy Independence and Security Act (EISA) of 2007, there has been considerable research conducted on the sustainability of bioenergy crop production in the United States; switchgrass has shown particular potential for bioenergy production in East Tennessee. Many studies evaluating the environmental impact switchgrass has on runoff and water quality use the Soil and Water Assessment Tool (SWAT) for watershed modeling. Because SWAT is a lumped watershed model, it evaluates the result of hydrological processes for each hydrologic response unit (HRU), without accounting for the physical interactions between these HRUs. The Water Erosion Prediction Project (WEPP) …

Enhancing The Sustainability Of Integrated Biofuel Feedstock Production Systems, Amanda Joy Ashworth

Doctoral Dissertations

As use of second-generation biofuel crops increases, so do questions about sustainability, particularly their potential to affect fossil energy consumption and greenhouse gas emissions. Nitrogen (N)-fixing legumes interseeded into switchgrass (Panicum virgatum L.) may be an alternative to inorganic fertilizer in forage-feedstock systems. Research herein is divided into four general experiments: I). N replacement and feedstock impacts from legume intercrops and biochar in switchgrass; II). N-fixation rates in intercrop systems; III). impacts of biofuel systems under enhanced climate change; and, IV). projected sustainability of regional switchgrass production. Approaches included: characterization of feedstock/forage quality traits based on legume, biochar and …

Diallel Analysis Of Biomass And Ethanol Yield In Leaves Versus Stems Of Lowland Switchgrass, Alexandria Christina Desantis

Masters Theses

Switchgrass (Panicum virgatum L.) is a warm season perennial grass used widely as a forage crop. This research seeks to address improving biomass yield and predicted ethanol yield through certain traits by the following objectives: (1) differences in average biomass and predicted ethanol yields from leaves versus stems, (2) genetic variance and heritability estimates of biomass and ethanol yield traits (3) general (GCA) and specific combining ability (SCA) among the five parents for biomass and ethanol yield, and (4) correlations between agronomic and morphological traits. Five parents with varying morphological traits were crossed in a diallel design, excluding selfs. …

Performance Of Beef Cattle Grazing Native Warm-Season Grasses In An Integrated Forage/Biofuels System In The Mid-South, William Matthew Backus

Masters Theses

Early season (ES) and full season (FS) grazing strategies were used to evaluate performance of stocker steers grazing native warm-season grasses (NWSG) in 2010, 2011 and 2012 in two experiments. Experiment one was conducted at the Research and Education Center (REC) at Ames Plantation near Grand Junction and experiment two was conducted at Highland Rim REC near Springfield in which Angus and Angus cross steers (268±25kg) were used in completely randomized design with three forage treatments: 1) switchgrass (Panicum virgatum L.); 2) a combination of big bluestem (Andropogon gerardii Vitman) and indiangrass (Sorghastrum nutans); and 3) …

Evaluation Of The Over-Expression Of A Miscanthus X Giganteus Ppdk (C4ppdk1) In Switchgrass (Panicum Virgatum) For Improved Cold Temperature C4 Photosynthesis, Mathew Christian Halter

Masters Theses

Switchgrass (Panicum virgatum) has been proposed as a potential biofuel feedstock to aid in the displacement of petroleum-based combustible fuels over the course of the next several decades. Improving the yield potential of this perennial grass is therefore of economic interest. Increased net ethanol yields can be achieved in cellulosic feedstocks via two means: 1. Improved sugar release from digestible cell wall materials, 2. Increased overall biomass yield. The latter is the subject of this study.

As a C4 photosynthetic plant, switchgrass is highly productive in the hot, humid climate of the southeastern United States. By bypassing the …

Optimal Location Of Cellulosic Ethanol Facilities And Their Impacts On Surface Water Quality In The Southeastern United States, Kevin Eric Cavasos

Masters Theses

Research suggests that by 2022, 10.5 billion of the 21 billion gallon annual production target for advanced biofuels mandated by the expanded 2007 Renewable Fuel Standard (RFS2) could originate in the Southeastern United States (US) (USDA 2010). This study applied a biorefinery siting and feedstock optimization model and a water quality model to examine the ex-ante impact of biorefinery locations on agricultural input use and nitrogen (N) loading into the region’s hydrological system. The objective of this research is to understand the potential implications of this level of cellulosic ethanol production and concomitant changes in land use on surface water …

Exploring The Potential To Penetrate The Energy Market For Tennessee-Produced Switchgrass, Fnu Shikha

Masters Theses

The need for alternative sources of energy which are renewable and environmentally friendly has focused attention on the development of biomass-based energy sector. Lignocellulosic energy crops such as switchgrass are considered potential feedstock for biomass-based energy because of wide range adaptability in conjunction with lower input requirements. However, the costs of the collection, storage, and transportation of the low density feedstock from farm to conversion facilities in the switchgrass supply chain pose a major barrier to the development of bioenergy sector.

The objective of the present study is to determine the optimal logistics configuration for Tennessee-produced switchgrass to penetrate the …

A Hydrological Analysis Of Switchgrass Land Cover In East Tennessee, Jordan Avery Hayes

Masters Theses

Energy needs and the recent installation of a cellulosic biofuel plant in Vonore, TN have created a demand for switchgrass in East Tennessee. Switchgrass has many strengths such as erosion protection, nutrient removal, and runoff mitigation. The Soil and Water Assessment Tool (SWAT) was selected to model the impact of transitioning traditional crops into switchgrass land cover. Field data was needed to properly calibrate the SWAT model for East Tennessee. The National Resources Conservation Service (NRCS) curve number (CN) was needed for runoff calibrations. This value was determined by both standard NRCS methods as well as an asymptotic method. The …

Genetic Variability For Biomass Yield, Yield Components, And Ethanol Yield Among Half-Sibs Of Switchgrass, Eifion Wyn Hughes

Masters Theses

For bioenergy crops to be an economical alternative to fossil fuels, rapid biological and technological advancements will need to occur. Some advancements can be accomplished by producing new switchgrass (Panicum virgatum L.) varieties with higher biomass and ethanol yields. The objective of this research was to quantify biomass and ethanol yield potential of four F₁ [F1] half-sib populations for future variety development as a bioenergy crop.

The four parental lines were PI 421999 (AR), PI 607837 (TX), PI 421552 (Cimarron), and Exp. # NSL-2001-1 (OK). Seed for one hundred and forty F₁ [F1] half-sib progeny were produced …

Reducing Cell Wall Recalcitrance And Increasing Biomass For Enhanced Ethanol Production In Switchgrass (Panicum Virgatum L.), Charleson Rajendran Poovaiah

Doctoral Dissertations

Lignocellulosic biomass is a potential large-scale biofuel feedstock for conversion to ethanol through saccharification and fermentation. The presence of lignin in lignocellulosic biomass impedes its degradation and subsequent fermentation. The removal of lignin by pretreatment is the most expensive step in the production of lignocellulosic biofuels. Manipulation of monolignol pathway is needed to reduce lignin and for the rational design of engineered cell walls of lignocellulosic feedstocks.

PvMYB4, a transcriptional repressor of lignin gene expression was identified and evaluated for its potential for improving switchgrass as a lignocellulosic feedstock. Ectopic overexpression of PvMYB4 in transgenic switchgrass reduced lignin content and …

Preservation Of Nutrients In Cool- And Warm-Season Forages At Different Stages Of Maturity And Management, Jason Allen Shultz

Masters Theses

The overall goals of the studies described in this thesis were to investigate management practices of tall fescue and native warm-season grasses (NWSG) and find the best time to harvest and method to preserve forage quality. Study one investigated the effects of maturity on tall fescue and switchgrass and the effects of preservation method on forage quality. This study confirmed that maturity reduced forage quality in both tall fescue and switchgrass. Both tall fescue and switchgrass were successfully preserved as haylage or hay and did not differ in forage quality. Forages harvested before mid-May met the TDN and CP requirements …

Selected Costs And Benefits Of Protecting Vital Wildlife Habitats While Producing Biofuel, Benjamin Lewis Totty

Masters Theses

The objective of this study is to estimate selected costs and benefits of meeting the 2022 biofuel production mandates using switchgrass as the feedstock. This study involves the simulation of three scenarios to evaluate the cost of protecting and promoting biodiversity while producing switchgrass for biofuel. Two models are used in this study. The first, the Biofuels Facility Location Analysis Modeling Endeavor (BioFLAME), was developed at the University of Tennessee to study biorefinery location, feed stock source areas and costs associated with biofuel production. The second model was developed by the Nature Conservancy as part of Tennessee’s State Wildlife Action …

Factors Influencing The Feasibility Of Switchgrass Feedstocks: From A Biorefinery’S Perspective, Elizabeth Ann Humphreys

Masters Theses

Research suggests that biomass with high cellulose content like switchgrass is more efficient for producing ethanol than corn grain. The objective of this study is to evaluate factors influencing the economic feasibility of ethanol production from a biorefinery’s perspective using switchgrass as the only feedstock. The research conducted utilizes a model which considers switchgrass procurement costs, transportation costs, storage costs, dry matter loss, biorefinery construction costs, operating and maintenance costs, and ethanol production in determining the break-even price of ethanol. The break-even prices of ethanol estimated range from $2.02 to $2.45 per gallon. The sensitivity analysis demonstrated that when the …

Life-Cycle Assessment In Government Policy In The United States, Daniel L. Reed

Doctoral Dissertations

The United States government, both at the Federal and state levels, are continuously relying on emerging technological and methodological tools in order to provide essential information to decision and policy-makers. Life-cycle assessment (LCA) is a rapidly emerging tool for both the private and public sectors. Governments around the world are aggressively looking towards life-cycle information to guide policy and promote environmental issues. LCA’s beginning in the United States dates back to 1969 at the Coca-Cola Company as a innovative way at looking at their beverage container’s impact on the environment. Since then life-cycle concepts have been slowly adapted and accepted …

The Epidemiology Of Puccinia Emaculata (Rust) In Switchgrass And Evaluation Of The Mycoparasite Sphaerellopsis Filum As A Potential Biological Control Organism For Switchgrass Rust., Jonathan Allen Black

Masters Theses

Switchgrass (Panicum virgatum L.) is a warm-season, perennial grass, whose native range includes the entire United States and north into Canada, excluding areas along the pacific coast. Recently, symptoms and signs of rust disease (Puccinia emaculata) have been observed on agronomic switchgrass, which include chlorosis of leaf tissue, necrosis, lodging, and plant death.

To evaluate disease progress of switchgrass rust, in four fields, individual leaves of twenty-five switchgrass plants were rated once per week for fifteen weeks over two growing seasons for disease severity. Rust was first observed on Julian day 166 and 152 in 2010 and …

Optimal Draw Area And Feedstock Delivery Schedule Of Biorefineries In The Southeast U.S. Based On Least Cost And Producers’ Willingness To Plant A Dedicated Energy Crop, Wen Tu

Doctoral Dissertations

To overcome the limitations of starch-based and sugar-based ethanol, scientists propose to expand the use of cellulosic ethanol. Cellulosic ethanol is a biofuel produced from wood, grasses, or the non-edible parts of plants. As the U.S. has a large cellulosic biomass production base (Perlack et al., 2006), production of ethanol from cellulosic feedstock and use of ethanol as a substitute for gasoline could help promote rural development, reduce green house gases emissions, and increase energy independence. This study focuses on the cost of producing cellulosic ethanol along with the amount of carbon sequestered and emitted using switchgrass as a feedstock. …

Impact Of Switchgrass Bioenergy Feedstock Production On Soil Carbon Dioxide Flux And Below Ground Soil Organic Carbon Storage In East Tennessee, Leah Denise Soro

Masters Theses

Bioenergy production from switchgrass has shown promise in restoring degraded soils and helping to mitigate greenhouse gas (GHG) emissions. CO₂ loss and C-sequestration in soils are important topics for research to better understand the environmental impacts of bioenergy crops. The need for more thorough research of the carbon cycle in soils used for bioenergy production precipitated the primary interest of this study. The specific objectives of this study were 1) to measure SOC under switchgrass production in order to predict storage of carbon in soils based on previous cropping history, land management, soil physical characteristics, and time; and to …

Evaluation Of Capital Investment And Cash Flows For Alternative Switchgrass Feedstock Supply Chain Configurations, Jie Chen

Masters Theses

Biofuels have been widely recognized as a potential renewable energy source, and the United States’ government has been interested in producing ethanol from lignocellulosic biomass such as switchgrass. To evaluate whether lignocellulosic biomass based biofuels production is economically feasible, this paper estimated the capital investment outlays, operation costs, and net present value for investment in alternative switchgrass feedstock supply chain configurations in East Tennessee a 25 million gallon per year ethanol biorefinery. Two scenarios are analyzed in the study. The conventional hay harvest scenario includes the production, harvest, storage and transportation of biomass feedstocks from the fields to the biorefinery. …

Evaluation Of Pre-Processing And Storage Options In Biomass Supply Logistics: A Case Study In East Tennessee, Yuan Gao

Masters Theses

Biofuels have been widely recognized as a potential renewable energy source that can lessen the United States’ dependence on imported petroleum and enhance the domestic economy. Particularly, biofuels derived from lignocellulosic biomass (LCB) have been the focus in the development of a sustainable biofuels industry. However, technical barriers in the LCB feedstock supply chain have been one of the major challenges impeding the economic viability of this industry. To expedite the commercialization process of LCB-based biofuels production, this paper employed a spatial mixed-integer mathematical model to explore the optimal biomass logistic system for a switchgrass-based biofuels biorefinery in East Tennessee. …

Establishment And Persistence Of Legumes In Switchgrass Biomass And Forage/Biomass Production Systems, Kara Spivey Warwick

Masters Theses

Switchgrass, Panicum virgatum, is being developed as an economically and ecologically sustainable biomass crop. Nitrogen is considered one of the most limiting inputs of switchgrass. Alternatives to synthetic nitrogen fertilization may be nitrogen-fixing legumes interseeded into switchgrass. The objectives of this research were: (1) develop efficient legume management strategies for switchgrass production systems, (2) evaluate and identify cool and warm-season legumes that can be grown compatibly with switchgrass, (3) determine whether switchgrass yields are increased by legume N-fixation, and (4) determine N-fixation of common (Vicia sativa) and hairy vetch (Vicia villosa).

This study examined the …