David H. Vaughan

OFF-STREAM WATER SOURCES FOR GRAZING CATTLE AS A STREAM BANK STABILIZATION AND WATER QUALITY BMP

A multi-disciplinary study was conducted to evaluate effectiveness of providing cattle with an off-stream water source (i.e., water trough) in reducing stream bank erosion and fostering water quality improvements. This study was conducted on two commercial cow-calf operations in southwest Virginia which used rotational stocking. When given the choice, cattle were observed to drink from a water trough 92% of the time, compared to the time which they spent drinking from the stream. Stream bank erosion was reduced by 77% due to installation of the alternative water source. Concentrations of total suspended solids, total nitrogen, and total phosphorus reduced by 90, 54, and 81%, respectively when an alternative water source was provided. Similar reductions were observed in concentrations of fecal coliform and fecal streptococcus. Concentrations of dissolved nutrients such as nitrate and orthophosphorus, however, were adversely affected by installation of the BMP. The study results clearly indicate that off-stream water sources for grazing cattle are effective BMPs for reducing the loss of sediment and sediment-bound pollutants to adjacent streams without resorting to stream bank fencing.

Continuous culture of the microalgae Schizochytrium limacinum on biodiesel-derived crude glycerol for producing docosahexaenoic acid

Crude glycerol is a major byproduct of the biodiesel industry; previous research has proved the feasibility of producing docosahexaenoic acid (DHA, 22:6 n-3) through fermentation of the algae Schizochytrium limacinum on crude glycerol. The objective of this work is to investigate the cell growth kinetics, substrate utilization efficiency, and DHA production of the algae through a continuous culture. Steady-state biomass yield, biomass productivity, growth yield on glycerol, specific glycerol consumption rate, and fatty acid composition were investigated within the range of dilution rate (D) from 0.2 to 0.6 day(-1), and the range of feed crude glycerol concentration (S(0)) from 15 to 120 g/L. The maximum specific growth rate was determined as 0.692 day(-1). The cells had a true growth yield of 0.283 g/g but with a relatively high maintenance coefficient (0.2216 day(-1)). The highest biomass productivity of 3.88 g/L-day was obtained at D=0.3 day(-1) and S(0)=60 g/L, while the highest DHA productivity (0.52 g/L-day) was obtained at D=0.3 day(-1) and S(0)=90 g/L due to the higher DHA content at S(0)=90 g/L. The biomass and DHA productivity of the continuous culture was comparable to those of batch culture, while lower than the fed-batch culture, mainly because of the lower DHA content obtained by the continuous culture. Overall, the results show that continuous culture is a powerful tool to investigate the cell growth kinetics and physiological behaviors of the algae growing on biodiesel-derived crude glycerol.

Energy analysis of ethanol production from sweet sorghum

Abstract The Piedmont System is a collection of equipment for efficiently removing the juice from sweet sorghum stalks for the production of ethanol. The concept is to separate the whole stalks into pith and rind-leaf fractions, pass only the pith fraction through a screw press, and thus achieve an improvement in juice-expression efficiency and press capacity. An energy analysis was done for two options of this proposed harvesting/processing system: (Option 1) The juice is evaporated to syrup and used throughout the year to produce ethanol, and the by-products are used as cattle feed. (Option 2) The juice is fermented as it is harvested, and the by-products (along with other cellulosic materials) are used as feedstock for the remainder of the year. Energy ratios (energy output/energy input) of 0·9, 1·1 and 0·8 were found for sweet sorghum Option 1, sweet sorghum Option 2, and corn, respectively, as feedstocks for ethanol. If only liquid fuels are considered, the ratios are increased to 3·5, 7·9 and 4·5.

Work in progress - spiral curriculum approach to reformulate engineering curriculum

A theme-based spiral curriculum approach is being adopted to initiate the department-level reform (DLR) of the freshman engineering and the bioprocess engineering curricula at Virginia Tech. A large number of engineering faculty members are collaborating with experts in educational psychology and academic assessment to accomplish the objectives of this 3-year NSF supported project that began in September 2004. Successful implementation of the spiral approach will be used as a model for incorporating similar reforms in other engineering departments and elsewhere

Energy and economic savings from the use of legume cover crops in Virginia corn production

Energy analysis provides a measure of the effectiveness of sustainable agricultural systems in reducing inputs purchased from off-farm sources. This study compares the total (direct plus indirect) energy costs of growing corn for silage using manufactured N fertilizer or N-fixing legume cover crops. The cover crop either was killed with herbicide in a no-till system or disked in the spring. Economically competitive alternative crop production practices are identified. In both the no-till and the disked versions, cover-cropped treatments used about half as much energy per hectare as the corresponding winter fallow N-fertilizer treatments. Using vetch to provide N significantly lowered energy use per unit of crop output compared with the N-fertilized treatments. For the treatments that used hairy vetch, either alone or in combination with big/lower vetch, net revenue was statistically equivalent to that of standard-practice treatments in each year of the study.

Development of a whole-stalk sweet sorghum harvester.

ABSTRACT Sweet sorghum can be readily grown in the Eastern U.S. Piedmont, but irregular-shaped fields on rolling terrain present a challenge to mechanical harvesting. An Atkinson sugarcane harvester was converted from a three-point hitch to a pull-type machine. Gathering chains captured the stalks as they were cut at the base, and elevated them at a 30° angle. The stalk was gripped between two rotating disks and flipped to the horizontal position. Disk tangential velocity was 24% greater than chain velocity. Total power required was 33 kW (44 hp) with 67% for the chains and 28% for drawbar pull.

Influence of sweet sorghum spacing on stalk pith yield

Abstract Sweet sorghum was planted at two locations in 1987 and three locations in 1988 to test the hypothesis that higher populations producing smaller stalks are less desirable than lower populations of larger stalks, because the higher pith-to-rind ratio of the larger stalks should favor sugar recovery through juice expression. Total biomass yield, total sugar yield, and calculated pith (stalk core) volume were compared among achieved populations ranging from 50 000 to 170 000 plants ha−1 in each year and between conventional and strip-till planting in three 1988 trials. Measured parameters were largely unaffected by planting method, strip-till versus conventional. Theexpected tendency for higher populations to yield smaller stalks was not found for all location/years. In general, however, each cm increase in mean spacing in the range 13–21 cm increased per-stalk pith volume by 1·5–3·5% and decreased biomass yield by 0·5–4%. The sorghum was able to take only partial advantage of the additional growing space to increase in size; consequently, the total pith volume per hectare decreased 2–5·5% cm−1 increase in mean stalk spacing, or slightly more than the decrease in biomass yield. Results suggest planting a target population of 80 000 plants ha−1, recognizing that the achieved population will range from 68 000 to 56 000 plants ha−1, or lower. This intermediate target population represents a compromise to optimize per-stalk yield of the sugar-rich pith with a modest reduction in total biomass yield.

optimization of Sweet Sorghum Processing Parameters

ABSTRACT PRODUCTION of fuel ethanol from renewable biomass sources has gained popularity in recent years. Sweet sorghum is one of the crops identified as an efficient producer of the sugars needed for ethanol production. The juice in the sweet sorghum pith contains the greatest proportion of nonstructural carbohydrates, the presumed fermentable material. Sugar cane milling procedures have previously been used to extract the juices from sweet sorghum. The research reported herein relates to a new method of juice extraction expected to provide higher juice extraction efficiencies than previous methods. The sweet sorghum stalks are chopped and the sugar-laden pith fraction is separated from the fibrous rind-leaf. The pith portion only is then fed through a screw press for juice extraction. Several chopping and separating parameters were evaluated, and a statistical linear regression analysis was employed to evaluate the effects of cutting interval, chopper knife speed, feed rate, and percent of whole stalk mass segregated into the pith fraction on juice yield. Pith fraction had the most significant positive effect on juice yield calculated as a percent of whole stalk mass. The highest pith fraction provided the highest juice yield. Feed rate had a negative effect on juice yield, meaning that slower feed rates were better, but this was the least significant parameter. The chopping interval had a positive effect, meaning that the largest value used in the analysis provided for the highest juice yield. The knife speed parameter had no effect on juice yield.

Sweet sorghum for ethanol industry for the Piedmont.

Abstract Approximately one-third of the idle cropland in the Piedmont counties of the five southern states, Virginia, North Carolina, South Carolina, Georgia and Alabama, would have to be planted in sweet sorghum with an average yield of 40 t/ha to produce a volume of ethanol equal tro the volume of petroleum fuel purchased by farmers in the Piedmont counties (518 million L/year), assuming that 65% of the fermentable sugar is extracted. If the by-products are ensiled for cattle feed, it is sufficient to feed 1.5 times the entire cattle population of the Piedmont of Virginia, and 3.0, 0.78, 1.25 and 1.16 times the Piedmont cattle population in North Carolina, South Carolina, Georgia and Alabama, respectively.

A general-purpose simulation program for agricultural operations

Abstract A detailed stochastic computer model was developed to simulate a forage harvesting operation. It was written to be general enough to simulate any agricultural operation using mobile machinery with minimal additional programming. The program used the simulation software package SLAM II, and most of the additional programming involved developing a SLAM network to simulate the system to be modeled. No significant differences were found between the simulated and observed quantities for the forage harvesting operation, but the model cannot be considered completely validated.