VTechWorks Repository :: Browsing by Author "Cundiff, John S."

Browsing by Author "Cundiff, John S."

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Analysis and Simulation of Switchgrass Harvest Systems for Large-scale Biofuel Production
McCullough, Devita (Virginia Tech, 2012-08-15)
In the United States, the Energy Independence and Security Act of 2007 mandates the annual production of 136 billion liters of renewable fuel in the US by 2022 (US Congress, 2007). As the nation moves towards energy independence, it is critical to address the current challenges associated with large-scale biofuel production. The biomass logistics network considered consists of three core operations: farmgate operations, highway-hauling operations, and receiving facility operations. To date, decision-making has been limited in post-production management (harvesting, in-field hauling, and storage) in farmgate operations. In this thesis, we study the impacts in the logistics network resulting from the selection of one of four harvest scenarios. A simulation model was developed, which simulated the harvest and filling of a Satellite Storage Location (SSL), using conventional hay harvest equipment, specifically, a round baler. The model evaluated the impacts of four harvest scenarios (ranging from short, October-December, to extended, July-March), on baler equipment requirements, baler utilization, and the storage capacity requirements of round bales, across a harvest production region. The production region selected for this study encompassed a 32-km radius surrounding a hypothetical bio-crude plant in Gretna, VA, and considered 141 optimally selected SSLs. The production region was divided into 6 sub-regions (i.e. tours). The total production region consisted of 15,438 ha and 682 fields. The fields ranged in size from 6 to 156 ha. Of the four scenarios examined in the analysis, each displayed similar trends across the six tours. Variations in the baler requirements that were observed among the tours resulted from variability in field size distribution, field to baler allocations, and total production area. The available work hours were found to have a significant impact on the resource requirements to fulfill harvest operations and resource requirements were greatly reduced when harvest operations were extended throughout the 9-month harvest season. Beginning harvest in July and extending harvest through March resulted in reductions in round balers ranging from 50-63%, as compared to the short harvest scenario, on a sub-regional basis. On a regional basis, beginning harvest in July and extending harvest through March resulted in baler reductions up to 58.2%, as compared to the short harvest scenario. For a 9-month harvest, harvesting approximately 50% of total switchgrass harvest in July-September, as compared to harvesting approximately 50% in October-December, resulted in reductions in round balers ranging from 33.3- 43.5%. An extended (9-month) harvest resulted in the lowest annual baler requirements, and on average lower baler utilization rates. The reduced harvest scenarios, when compared to the extended harvest scenarios, resulted in a significant increase in the number of annual balers required for harvest operations. However, among the reduced harvest scenarios (i.e. Scenario 3 and 4), the number of annual balers required for harvest operations showed significantly less variation than between the extended harvest scenarios (i.e. Scenarios 1 and 2). As a result, an increased utilization of the balers in the system, short harvest scenarios resulted in the highest average baler utilization rates. Storage capacity requirements were however found to be greater for short harvest scenarios. For the reduced harvest scenario, employing an October-December harvest window, approximately 50% of harvest was completed by the end of October, and 100% of total harvest was completed by the third month of harvest (i.e. December).
Application of Alternative Technologies to Eliminate Vibrios spp. in Raw Oysters
Hu, Xiaopei (Virginia Tech, 2004-12-15)
High pressure processing (HPP) and gamma irradiation were applied to inactivate Vibrio vulnificus (MO624) and Vibrio parahaemolyticus (O3:K6 TX2103) in pure culture and in inoculated live oysters. Vibrio pure culture and inoculated oysters were exposed to pressures of 207 MPa (30 kpsi) to 552 MPa (80 kpsi) for 0 min to maximum of 20 min. More than 5.4 log reductions of V. vulnificus occurred at 345 MPa for 0 min in oysters; 345 MPa for 2 min can achieve 4 log reductions on V. parahaemolyticus. Dosage of 1 kGy gamma-irradiation was proved to be effective in producing Vibrio free oysters with comparable organoleptic quality to raw oysters. Thermal conductivity of shucked oysters was measured to be 0.58 to 0.68 W/m°C, as temperature increased from 0 to 50 °C, using a line heat source probe. The specific heat was measured by differential scanning calorimeter methods. It increased from 3.80 to 4.05 kJ/kg °C, when temperature rose from 10 to 50 °C. The thermal diffusivity was calculated employing the data of thermal conductivity, specific heat and density of shucked oysters. The results showed that, under the tested temperature range, thermal properties did not change significantly with temperature. The dielectric constant and loss factor of oysters were determined by an open-ended coaxial line probe connected to a network analyzer at frequency of 30 MHz to 3000 MHz from 1 to 55 °C. The penetration depth of dielectric heating was calculated to be 1.1 cm with the dielectric constant of 55 and loss factor of 14. A two-dimensional mathematical model was established to simulate the heat transfer of microwave heating using a fish gel. Finite difference method was utilized to solve partial differential heat transfer equations. The model was able to predict the temperature distribution in heated fish gel with an accuracy of ± 8°C. Applying the developed mathematical model, the lethality of Vibrio spp., artificially inoculated in live oysters, was estimated collectively by integrating the individual localized lethality of designated heating units. The predicted lethality was compared with microwave enumeration data on Vibrios in oysters. The observed maximum log reductions by microbial enumeration were 4.4 and 3.4 for V. vulnificus and V. parahaemolyticus, respectively. The lethality calculated by integrating temperature profiles was acceptable. The discrepancy between the estimated lethality and microbial test was attributed to the simplified model construction. The quality of processed oysters, including color, aroma and texture properties, was evaluated instrumentally by a digital image system, an electronic nose and universal testing machine. The performance of two electronic nose systems on their abilities to detect oyster aroma and classify the aroma data into distinct groups was evaluated using a trained sensory panel and microbial tests. Cyranose 320 system has demonstrated potential as a quality assessment tool due to its sound correlation with microbial quality data and sensory evaluation scores. According to the quality measurement results, high pressure processing conditions were recommended to be at 345 MPa for less than 3 min and 379 MPa for less than 1.5 min. Deterioration of the quality was distinct for oyster meats exposed to 60 °C or above by thermal processing. The critical thermal processing condition was identified to be 55 °C for 2 min. With careful control, microwave processing could be considered as a candidate for seafood processing to reduce potential bacterial hazard but still retain the quality of the product.
A Case Study on the Economic Feasibility of Producing Maple liners in a Traditional Tobacco Greenhouse
Wilkerson, Joseph Edward (Virginia Tech, 2002-04-26)
The goal of this case study was to investigate the economic feasibility of a new enterprise for Southside Virginia farmers to help alleviate problems stemming from a loss of income and excess production capacity of a tobacco greenhouse. Maple liner production in a tobacco greenhouse was determined to not be economically feasible by this study. The control scenario, as well as the sensitivity analysis revealed that maple liner production would yield a loss when produced in a tobacco greenhouse. The breakeven number of plants to be sold was 43% of the cuttings planted, and could exceed 50% under some conditions of the sensitivity analysis. While the maple liner production schedule was determined to be culturally suitable as a supplemental greenhouse activity, the tobacco greenhouse engineering design was deemed inadequate for maple liner production. Modifications were needed to the ventilation and irrigation systems. This economic study was based on a field trial conducted in Halifax County, Virginia.
Central Control for Optimized Herbaceous Feedstock Delivery to a Biorefinery from Satellite Storage Locations
Resop, Jonathan P.; Cundiff, John S.; Grisso, Robert D. (MDPI, 2022-06-17)
The delivery of herbaceous feedstock from satellite storage locations (SSLs) to a biorefinery or preprocessing depot is a logistics problem that must be optimized before a new bioenergy industry can be realized. Both load-out productivity, defined as the loading of 5 × 4 round bales into a 20-bale rack at the SSL, and truck productivity, defined as the hauling of bales from the SSLs to the biorefinery, must be maximized. Productivity (Mg/d) is maximized and cost (USD/Mg) is minimized when approximately the same number the loads is received each day. To achieve this, a central control model is proposed, where a feedstock manager at the biorefinery can dispatch a truck to any SSL where a load will be available when the truck arrives. Simulations of this central control model for different numbers of simultaneous load-out operations were performed using a database of potential production fields within a 50 km radius of a theoretical biorefinery in Gretna, VA. The minimum delivered cost (i.e., load-out plus truck) was achieved with nine load-outs and a fleet of eight trucks. The estimated cost was 11.24 and 11.62 USD/Mg of annual biorefinery capacity (assuming 24/7 operation over 48 wk/y for a total of approximately 150,000 Mg/y) for the load-out and truck, respectively. The two costs were approximately equal, reinforcing the desirability of a central control to maximize the productivity of these two key operations simultaneously.
Characterization of protein microstructure by various chromatographic techniques
Pathange, Lakshmi Prasad (Virginia Tech, 2007-02-28)
Due to the rising health care costs and with the advent of biogenerics, there is a growing demand to develop new and reliable techniques to characterize proteins and biopharmaceuticals. In addition, characterization aids in understanding the intricate relationship between a protein's structure and its function. To address this challenge, two protein structural parameters, 1) amino acid surface area and 2) amino acid microstructure, were chosen to be investigated. Two chromatographic techniques, 1) ion exchange chromatography (IEC) and 2) immobilized metal affinity chromatography (IMAC), were used to characterize the above-mentioned protein structure parameters. The model protein chosen for our work is T4 lysozyme. The protein consists of 164 amino acids with molecular weight ~ 18 kD. SYBYL 7.1 software was used to generate in silico point mutants. Two categories of protein variants (point mutants) were generated using site-directed protein mutagenesis. The goal for generating point mutants was to obtain mutants that vary in the two structural parameters. The first category point mutants vary in the surface accessibility of a surface accessible histidine residue. The second category point mutants predominantly vary in protein net charge and the amino acid microstructure. In total, seventeen point mutants were generated: 1) category I consists of seven variants that vary predominantly in their histidine surface accessibility, and were obtained by replacing a charged amino acid residue at different locations on the surface of the protein molecule, and 2) category II consists of ten variants that vary in both net charge and charge distribution were obtained by replacing charged and neutral amino acid residues at different locations (different microenvironments) on the protein surface. PCR technique was used to generate the point mutants. Gene and protein sequencing were employed to confirm the veracity of point mutation. CD and Lysozyme activity assays were performed to determine whether or not the 3D structure of all the protein variants was intact. Zonal analysis was used to obtain the binding strength values of all seventeen variants in IMAC with copper as the immobilized metal ions, and gradient elution method was used to obtain the relative retention times (rRT) values of all the variants in IEC. The seven lysozyme variants generated in category I each contains one surface histidine residue. In IMAC, there is a correlation between the surface accessibility of the lone surface histidine and the protein's binding strength with R²⁺= 0.76. In IEC, the correlation between the protein's microstructure, which predominantly consists the surface accessibility of the histidine residue, and the protein's retention times was R²⁺= 0.95. However, there were few outlier variants (e.g. variant K83H) which did not follow the correlations. The variations presented by few outlier variants can be attributed to the presence of intramolecular bonds, which restrict the mobility of the amino acid side chains and subsequently hinder the specific interaction between the amino acid residue and chromatographic media. For category II variants, short and medium range charge perturbations around the sole histidine residue in T4 lysozyme were engineered within 15 Ã distance of histidine. There was a strong correlation (R²⁺ = 0.96) between the theoretical (DeltaDeltaGElec) values, calculated using simple Coulomb's law, and the experimental (DeltaDeltaGB) values, which were obtained by measuring the protein binding strength values using IMAC. Similar correlation (R²⁺= 0.93) was obtained between the change in net charge (-2 to +2 units) and the relative retention times in IEC. Similarly, there were few variants (e.g. S136K, R76D) that did not follow the trends. The deviations of the few outlier variants can be attributed to the presence of unique microstructure effects around the histidine residue. These microstructure effects were quantified in IMAC as (DeltaDeltaGMicro), and in IEC they were quantified by the change in rRT values. In summary, all seventeen variants had different binding strengths and rRT values indicating the variation in the protein structure around the histidine residue. Our work reveals that it is possible to capture the microstructural effects of a protein through the combination of protein molecular modeling and simple chromatographic experiments.
Cost Comparison for Emerging Technologies to Haul Round Bales for the Biorefinery Industry
Cundiff, John S.; Grisso, Robert D.; Webb, Erin G. (MDPI, 2024-05-30)
Between 20 and 30% of the feedstock delivered cost is the highway hauling. In order to achieve maximum truck productivity, and thus minimize hauling cost, the hauling technology needs to provide for rapid loading and unloading. Three prototype technologies have been proposed to address the hauling issue. The first was developed by Stinger to secure a load of large rectangular bales, and it is identified as the Advanced Load Securing System (ALSS). For this study, the ALSS technology is applied on two trailers hooked in tandem (ALSS-2) loaded with 20 bales each. The second technology (Cable), is a cable system for securing a load of bales (round or rectangular) on a standard flatbed trailer. With the third technology (Rack), bales are loaded into a 20-bale rack at an SSL, and this rack is unloaded as a unit at the biorefinery. Bales remain in the rack until processed, thus avoiding single-bale handling at the receiving facility. A cost comparison, which begins with bales in single-layer ambient storage in SSLs and ends with bales in single file on a conveyor into the biorefinery, was done for the three hauling technologies paired with three load-out technologies. Cost for the nine options ranged from 48.56 USD/Mg (11 load-outs, Cable hauling) to 34.90 USD/Mg (8 loads-outs, ALSS-2 hauling). The most significant cost issue was the reduction in truck cost; 25.54 USD/Mg (20 trucks, Cable) and 15.15 USD/Mg (10 trucks, Rack).
Curing Quality Peanuts in Virginia
Cundiff, John S.; Baker, Kevin D. (Virginia Cooperative Extension, 2009)
Discusses methods for curing peanuts.
Design of Tactical and Operational Decisions for Biomass Feedstock Logistics Chain
Ramachandran, Rahul (Virginia Tech, 2016-07-12)
The global energy requirement is increasing at a rapid pace and fossil fuels have been one of the major players in meeting this growing energy demand. However, the resources for fossil fuels are finite. Therefore, it is essential to develop renewable energy sources like biofuels to help address growing energy needs. A key aspect in the production of biofuel is the biomass logistics chain that constitutes a complex collection of activities, which must be judiciously executed for a cost-effective operation. In this thesis, we introduce a two-phase optimization-simulation approach to determine tactical biomass logistics-related decisions cost effectively in view of the uncertainties encountered in real-life. These decisions include number of trucks to haul biomass from storage locations to a bio-refinery, the number of unloading equipment sets required at storage locations, and the number of satellite storage locations required to serve as collection points for the biomass secured from the fields. Later, an operational-level decision support tool is introduced to aid the "feedstock manager" at the bio-refinery by recommending which satellite storage facilities to unload, how much biomass to ship, how to allocate existing resources (trucks and unloading equipment sets) during each time period, and how to route unloading equipment sets between storage facilities. Another problem studied is the "Bale Collection Problem" associated with the farmgate operation. It is essentially a capacitated vehicle routing problem with unit demand (CVRP-UD), and its solution defines a cost-effective sequence for collecting bales from the field after harvest.
Design, Simulation, Analysis and Optimization of Transportation System for a Biomass to Ethanol Conversion Plant
Ravula, Poorna Pradeep (Virginia Tech, 2007-04-25)
The US Department of Energy has set an ambitious goal of replacing 30% of current petroleum consumption with biomass and its products by the year 2030. To achieve this goal, various systems capable of handling biomass at this magnitude have to be designed and built. The transportation system for a cotton gin was studied and modeled with the current management policy (FIFO) used by the gin to gain understanding of a logistic system where the processing plant (gin) pays for the transportation of the feedstock. Alternate management policies for transporting cotton modules showed significant time savings of 24% in days-to-haul. To design a logistics system and management strategy that will minimize the cost of biomass delivery (round bales of switchgrass), a seven-county region in southern Piedmont region of Virginia was selected as the location for a 50 Mg/h bioprocessing plant which operates 24 h/day, 7 days/week. Some of the equipment are not be commercially available and need to be developed. The transport equipment (trucks, loaders and unloaders) was defined and the operational parameters estimated. One hundred and fifty-five secondary storage locations (SSLs) along with a 3.2-km procurement area for each SSL were determined for the region. The travel time from each SSL to the plant was calculated based on a network flow analysis. Seven different policies (strategies) for scheduling loaders were studied. The two key variables were maximum number of trucks required and the maximum at-plant inventory. Five policies were based on "Shortest Travel Time - Longest Travel Time" allocation and two policies were based on "Sector-based" allocation. Policies generating schedules with minimum truck requirement and at-plant storage were simulated. A discrete event simulation model for the logistic system was constructed and the productive operating times for system equipment and inventory was computed. Lowest delivered cost was $14.68/Mg with truck cost averaging $8.44/Mg and loader cost averaging $2.98/Mg. The at-plant inventory levels were held to a maximum of 390 loads. The loaders operated less than 9,500 hours and the unloaders operated for a total of 2,700 hours for both systems simulated.
Design, Synthesis and Characterization of Heme-proteins: Developing Potential Catalysts for Bio-remediation
Shah, Kinjalkumar K. (Virginia Tech, 2004-12-16)
The next generation of toxic chemicals and hazardous wastes from sophisticated chemical industries will demand the environmental agencies to employ biological methods over the conventional physical and chemical remediation methods. Over the past decade, natural metallo-enzymes have been identified to degrade some of the major chemical contaminants through electron transfer pathways. However, these natural enzymes are less stable in organic solvents and they are not effective for the degradation of toxic compounds such as polychlorinated biphenyls or dioxins. This thesis explores the use of protein design approaches to produce chemically and molecularly modified enzymes, which are highly stable, possess little substrate specificity, and have higher activity than the natural enzymes. The experiments presented in this thesis make use of solid phase synthesis and site-directed mutagenesis for the synthesis and production of these enzymes and popular chromatographic techniques for their purification. The partial characterization of these proteins revealed the essential structural features of these proteins, and their catalytic activity was demonstrated by the use of peroxidase assays.
Development of a whole-stalk sweet sorghum harvester
Rains, Glen Christopher (Virginia Tech, 1989-04-15)
Sweet sorghum produces more carbohydrates and more biomass per unit land area than com in the Eastern U. S. Piedmont. An equipment system for harvesting and processing whole-stalk sweet sorghum is being developed, with the expectation that sweet sorghum can be commercialized as an ethanol feedstock. A whole-stalk harvester was designed, constructed, and tested during the 1988 harvest season. The harvester captured a row of stalks between two counter rotating gathering belts, cut them at the base with a disk cutter (basecutter), and, at the rear of the machine, rotated the stalks 90° by capturing the stalk butts between to spring-loaded disks, called the stalk flipper. At a field speed of 6.7 km/h, the machine worked best when the flipper tangential velocity was 24 percent higher than the gathering belt Linear velocity, which was approximately (within six percent) equal to ground speed. The harvester was pulled behind a tractor and powered with a universal joint drive line. Two computer software packages, Computer-Graphic Augmented Design and Manufacturing (CADAM) and Integrated Mechanisms Program (IMP), were used to design the hitch and drive line. Calculated angular accelerations in the 3-joint drive line were excessive during a right or left turn; consequently a constant velocity joint was used at the tractor PTO. The hitch was designed with three position settings. With the hitch in the Field 1 position, the harvester was offset sufficiently to capture a row with the gathering belts. In the travel position, the harvester trailed behind the tractor within the 2.4 m legal road width.
Discrimination of Retained Solvent Levels in Printed Food-Packaging Using Electronic Nose Systems
Van Deventer, David (Virginia Tech, 2000-07-14)
The expanding role of electronic nose instrumentation, as a quality-monitoring tool for food-packaging materials, is examined and reviewed. The food industry is interested in determining the applicability of using an electronic nose for odor analysis of retained printing solvent levels in packaging. Three electronic nose systems were optimized for this application and their performance assessed. These include the FOX 3000, the Cyranose 320, and the QMB6. Response surface methodology was used to generate 2nd order models of sensor response as a function of system and experimental parameters for the three electronic nose systems. Forty-seven of 50 sensor models generated were found to be significant at an a-level of 0.05. Optimum settings, that allowed adequate signals to be obtained for the full range of examined retained solvents levels, were selected for the remaining work using these models. Performance analyses of these systems, which use three leading sensor technologies, showed that the conducting polymer sensor technology demonstrated the most discriminatory power. All three technologies proved able to discriminate among different levels of retained solvents. Each complete electronic nose system was also able to discriminate between assorted packaging having either conforming or non-conforming levels of retained solvents. Each system correctly identified 100% of unknown samples. Sensor technology had a greater effect on performance than the number of sensors used. Based on discriminatory power and practical features, the FOX 3000 and the Cyranose 320 were superior. The results indicate that electronic nose instrumentation can be used as a complimentary discriminatory tool in quality control.
Dry matter loss and compositional analysis of large switchgrass round bales during ambient storage in Virginia
Brumback, Clay T. (Virginia Tech, 1995-08-07)
Two varieties of switchgrass, Cave-N-Rock and Alamo, were baled into 1.8-m diameter by 1.2-m wide round bales and stored outside for 12 months. String-wrapped bales were stored on sad and net-wrapped bales on rock. Six bales (three-string-wrapped, three netwrapped) were destructively sampled at four, eight, and 12 months. Samples were collected for moisture content and compositional analysis. As expected, there was a large moisture content gradient from the weathered layer to the inner core, depending on drying conditions since the last precipitation. In one instance weathered layer moisture content was three times the core moisture content Netwrapped bales were drier than string-wrapped bales. Negligible dry matter loss (DML) was reported at four and eight months for Cave-N-Rock with DML no greater than 7% after 12 months of storage. Calculated DML was highly variable but no more than 16% of original dry matter after 12 months of storage for Alamo. For one set of six bales (Cave-N-Rock, sampled at eight months), the calculated dry matter loss was negative (meaning the bales gained dry matter during storage). This result is physically impossible and illustrates the difficulty in accurately measuring dry matter loss. DML was less for net-wrapped bales on rock than string-wrapped bales on sod.
The Effect of Novel Frying Methods on Quality of Breaded Fried Foods
Bengtson, Rhonda J. (Virginia Tech, 2006-07-17)
Fried foods are popular around the world. They are also high in fat and considered unhealthy by many people. Reducing the fat content of fried food may allow for even more growth in their popularity, while allowing for healthier eating. Furthermore, vacuum-frying and frying with nitrogen gas have both been shown to extend the life of frying oil. In this study, the use of novel frying methods as a way to reduce fat content of breaded fried foods was evaluated. A pressure fryer was modified so that fish sticks could be vacuum-fried and fried using external gas (nitrogen and compressed air) as the pressurizing media. These products were compared to those pressure fried and fried atmospherically in terms of crust color, moisture content, oil content, texture, and juiciness. Overall, products fried using nitrogen and air were not found to be significantly different (p < 0.05) from each other. These products were both more tender and lower in oil content than steam-fried fish sticks. The energy to peak load of fish sticks fried with air was 123.10 J/kg, fish sticks fried with nitrogen had an energy to peak load of 134.64 J/kg, and fish sticks fried with traditional pressure frying had a peak load of 158.97 J/kg. The crust oil contents of fish sticks fried with air, nitrogen, and steam were 17.35%, 15.88%, and 23.31% oil by weight, respectively. In other words, using nitrogen or air to fry fish sticks reduced the fat uptake in the crust by 31.8% and 25.6% compared to traditional pressure frying, respectively. The only area where vacuum-frying had a significant effect, when compared to pressure-fried and atmospherically-fried fish sticks, was in juiciness. Vacuum-frying created significantly juicier fish sticks than the other two frying methods. Vacuum-fried fish sticks had juiciness of 43.03% (120oC) and 41.31% (150oC), while pressure-fried fish sticks had juiciness of 30.01% (175oC) and 32.93% (190oC), and atmospherically-fried fish sticks had juiciness of 31.56% (175oC) and 29.38% (190oC). In addition, vacuum-fried fish sticks were more tender than atmospherically-fried fish sticks. The results of this study demonstrated that frying with external pressurizing media can be used to reduce oil content in fish sticks, while also creating products that are more tender than conventionally pressure-fried fish sticks. In addition, vacuum-frying, which has been shown to extend oil life compared to pressure frying because of the lower temperatures involved, can be used to create fish sticks that are comparable to pressure-fried fish sticks, but juicier.
Energetics of low-input corn production
Ess, Daniel R. (Virginia Tech, 1990-12-05)
This study compares the energy costs of synthesizing, distributing, and applying manufactured nitrogen fertilizer to the overall energy costs associated with nitrogen-fixing legume production and use. The energetics of com silage and com grain production under standard and alternative practices are examined. Economic analyses of crop production practices are used to aid the selection of recommended alternative practices. In corn silage production, cover-cropped treatments had a significant advantage over standard practice treatments in terms of overall energy expenditures for field operations. Cover-cropped no-till treatments required an average energy expenditure of 9026 MJ/ha compared to 19,763 MJ/ha required by the standard-practice no-till treatment. Cover-cropped treatments that used disking to kill the cover crops required an average energy expenditure of 9781 MJ/ha compared to 18,488 MJ /ha required by the standard-practice winter-fallow treatment. Alternative-practice treatments that utilized vetches to provide nitrogen for com production performed significantly better than standard-practice treatments in terms of energy use per unit of crop output. In addition, the alternative hairy vetch - no-till treatment produced a $33/ha greater average net revenue than the standard-practice no-till treatment. Weed control energy requirements for cover-cropped ridge-tillage com grain production were compared. Broadcast application of pre-emergence herbicides required an energy expenditure of 1160 MJ fha. Cultivation of ridges to control weeds consumed 380 MJ/ha. Economic costs of ridge cultivation were $14/ha. Broadcast application of pre-emergence herbicides cost $49/ha.
An expert system for preliminary selection of hydrostatic transmission components
Baifang, Li (Virginia Tech, 1989-04-07)
The selection and sizing of the components for the design of a hydrostatic transmission is a tedious process. Necessary procedures include: analyzing the load profile, choosing a suitable configuration, determining the required size of components, selecting components, evaluating the performance of selected units, and then adjusting or selecting alternate components for improved performance. A. rule-based expert system, called HSTX, was developed to aid the selection and sizing of the major components-- pump, motor, and final drive-- of a hydrostatic transmission. Four types of options were considered. For the first, output speed and torque are both constant. For the second, horsepower output is constant at different speeds. For the third type, the output torque is constant at different speeds. For the last, torque and horsepower outputs can vary over a wide range of speeds. The program selects one of the four combinations of fixed pump and fixed motor, fixed pump and variable motor, variable pump and fixed motor, or variable pump and variable motor to match the desired outputs. The HSTX program includes databases which contain the specifications of hydraulic pumps and motors from selected manufacturers. HSTX interactively prompts the user to enter basic problem constraints and performance requirements. The program then recommends system configuration and selects components from the databases to meet the performance requirements specified. To assist inexperienced designers, HSTX is designed in such a way that the program gives easily understood hints, explanations, and guidance. The program, HSTX, can analyze the load profile, size the components, select available components from a database, evaluate the performance, and output the final results. Trial runs with different operators indicate that HSTX can be effectively used by a designer with a background in hydraulic systems but with little background in HST design.
Feedstock Contract Considerations for a Piedmont Biorefinery
Cundiff, John S.; Grisso, Robert D.; Fike, John H. (MDPI, 2020-12-14)
A biorefinery purchasing feedstock (perennial grass) must offer contracts that provide the same opportunity to earn a profit for a feedstock contractor located 50 or 5 km from the biorefinery. The business plan presented here specifies that the biomass is purchased in satellite storage locations (SSLs), and the load-out and hauling costs are paid by the biorefinery. Contracts can be offered for harvest in September, October, and November, a three-month harvest window, or the harvest window can be extended to December, January, and February, a six-month harvest window. Required total storage capacity is 75% of annual consumption for the three-month window and 50% for the six-month window, a significant difference in total storage capacity (cost). The storage cost difference paid by the biorefinery is 5.27 and 3.52 USD/Mg for the three-month and six-month, respectively. Several issues must be addressed in the feedstock contracts: (1) earlier harvest, before plant senescence, means less nutrients are translocated back into the soil and more are removed at harvest; (2) harvest losses are higher for all harvests after the September harvest; and (3) storage losses increase with storage time in the SSL. Time of removal from the SSL is dictated by the biorefinery; thus, the feedstock contractor must be compensated. The contracts paid by the biorefinery, averaged across the entire annual consumption, were about the same for the three-month window, and six-month window. This result was obtained because fertilizer cost decreases and harvest losses increase as the harvest date increases; thus, the two factors tend to offset. Using a 77 USD/Mg base cost, representative feedstock payment at the SSL (no storage losses included) for contractors with various month contracts are September (84.30), October (85.54), November (86.72), December 88.63), January (89.98), and February (90.58). Subsequent compensation for storage losses depends on the amount of time the particular unit of biomass is in storage before shipment.
Improving Fried Product and Frying Oil Quality Using Nitrogen Gas in A Pressure Frying System
Innawong, Bhundit (Virginia Tech, 2001-07-20)
The commercial pressure frying has been limited to frying huge amount of products due to its dependence on the amount of moisture released from the food for generating the desired pressure. This study investigated the feasibility of using nitrogen gas as a substitute for steam in the pressure frying system. The effects of various process conditions (source of pressure, frying temperature and pressure) on fried product and frying oil qualities were evaluated. Frying experiments were performed on breaded/battered poultry products including chicken nuggets (homogenous) and chicken fillets (marinated, intact muscle). Efforts were also made to develop rapid methods to determine frying oil quality and discriminate among fresh, marginal and discarded oils using a chemosensory (also known as electronic nose) or Fourier transform infrared spectroscopy (FTIR-ATR). Frying temperature and pressure affected fried food quality. An increase in frying pressure resulted in tender, juicier products with less oil uptake due to high moisture retention. An increase in frying oil temperature resulted in an increased moisture loss, oil uptake resulting in less tender and juicier products. Compared with frying using steam released from food, using nitrogen provided similar or better quality fried products in terms of moisture retention, juiciness and texture. The reused oils from the fryer using nitrogen gas was better in quality than the system using steam as evidenced from the physical, chemical and chemosensory measurements.
In-Field Performance of Biomass Balers
Grisso, Robert D.; Webb, Erin G.; Cundiff, John S. (MDPI, 2020-12-04)
Herbaceous biomass will contribute significantly to meeting renewable energy goals. Harvesting equipment for hay is generally suitable for mowing, raking, and baling grasses such as switchgrass; however, there is a need for field data to better understand machine performance in energy crops. The purpose of this study was to collect field data to estimate baler field capacity, throughput, and speed. Data gathered with a Differential Global Positioning System (DGPS) unit during baling provided time-motion studies of baler productivity. Six fields were used to compare field capacity, speed, and throughput results from four round balers and one large-square baler. The results show that in-field performance of round balers is significantly affected by yield, but that the relationship can be represented with machinery management concepts, knowledge of maximum throughput, and wrap-eject time. Baler performance will be overestimated if the yield, maximum throughput, and wrap-eject time are not correctly accounted for.
Investigation of a simulation model for peanut drying incorporating air recirculation
Kulasiri, Don (Virginia Tech, 1988-02-25)
Virginia type peanuts were dried in three laboratory dryers to verify a simulation model based on Troeger and Butler's drying equations. The energy saving potential of air recirculation was also investigated. Four tests consisting of eleven drying experiments were conducted in Fall, 1986. Two air recirculation schedules were employed and three average air flow rates were used. An experimental procedure was developed to measure input and output parameters of the drying system. The weight loss of the top layer of the peanut bed was recorded with a data acquisition system. The electrical energy input to the heaters was also recorded. Based on the analysis of the data, the following conclusions were made: (1) The Troeger model predicted a lower moisture release rate than the actual rate for Virginia type peanuts. (2) If the break points in the Troeger model were changed to 0.20 and 0.70 from 0.12 and 0.40, respectively, the model predicted the final moisture content more accurately. (3) Energy savings as high as 50 percent were achieved using the recirculation schedules.

Browsing by Author "Cundiff, John S."

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