David A. Grewell

Enhancing Biodiesel Production from Soybean Oil using Ultrasonics

Our objective was to determine the effect of ultrasonics on biodiesel production from soybean oil. In this study, ultrasonic energy was applied in two different modes: pulse and continuous sonication. Soybean oil was mixed with methanol and a catalytic amount of sodium hydroxide, and the mixture was sonicated at threelevelsofamplitude(60, 120,and 180 μm pp ) in pulse mode (5 s on/25 s off). In the continuous mode, the same reaction mixture was sonicated at 120 μm pp for 15 s. The reaction was monitored for biodiesel yield by stopping the reaction at selected time intervals and analyzing the biodiesel content by thermogravimetric analysis (TGA). The results werecompared to a control group, in which the same reactant composition was allowed to react at 60 °C for intervals ranging from 5 min to I h without ultrasonic treatment. It was observed that ultrasonic treatment resulted in a 96% by weight isolated yield of biodiesel in less than 90 s using the pulse mode, compared to 30-45 min for the unsonicated control sample with comparable yields (83-86%). In the pulse mode, the highest yield (96%) was obtained by sonicating the mixture at 120 μm pp amplitude. In the continuous sonication mode, the highest biodiesel yield was 86% by weight, which was obtained in 15 s.

Fabrication of diffractive optics by use of slow tool servo diamond turning process

In recent years, it has become possible to fabricate complicated optical surfaces using multi-axis ultraprecision machines. Two diffractive optical designs were fabricated using an ultraprecision diamond turning machine equipped with four independent axes. Unlike the conventional clean-room-based micromachining process, this research demonstrates the development of two innovative diamond tool trajectories that allow the entire diffractive pattern to be machined in a single operation directly, without going through multiple steps, as commonly used in conventional lithography processes. The machined diffractive optical elements were measured for curve geometry and surface roughness. In addition, the optical performance was also evaluated. Finally, a simple welding test setup was utilized to test the 256-level diffractive optical elements (DOEs). Compared to conventional approaches where feature indexing is difficult and unreliable, the slow tool servo (STS) process can be utilized to produce DOEs with accurate geometry and optical surface finish; therefore, the process may be called non-clean-room or maskless micromachining. Unlike its predecessors, this micromachining process which is based on ultraprecision diamond machining can be used to produce true three-dimensional (3D) features in a single operation, thus making it a promising technology for micro-optical, electromechanical component fabrication. Moreover, the 3D micro features can be readily applied to a freeform substrate, making this process a unique approach for fabrication of complicated micro-optical devices.

Influence of Ultrasonics in Ammonia Steeped Switchgrass for Enzymatic Hydrolysis

The bioconversion of lignocellulosic materials into fuels is of great environmental and economic importance, because of the large amounts of feedstock (est. over 1 billion tons per year), the potentially low cost of this feedstock, and the potentially high net energy balance the overall process. Switchgrass (Panicum virgatum L.) is a candidate dedicated lignocellulosic feedstock in the US. However, lignocellulosic materials, including switchgrass, are hampered by the recalcitrance of lignocellulose to enzymatic degradation into fermentable sugars. Various types of pretreatment have been developed to overcome this recalcitrance. In this study, we examined sequential ammonia-steeping and ultrasound pretreatment of switchgrass. The experimental variables included ultrasound energy dissipation and source amplitude, biomass concentrations, and antibacterial agents. Specifically, the 35-mL samples received either 2000 J or 5000 J, while biomass concentration was at 10% and 30% (mass basis). Antibacterial agents were employed to determine the extent to which sugars were being metabolized by naturally occurring bacteria in the unsterilized pretreated samples. Analytical glucose analysis was conducted to verify the amount of fermentable sugars released and low-vacuum SEM was used to establish the physical effect of ultrasonics on the biomass. The sequential ammonia steeping-ultrasonic pretreatment released about 10% more fermentable sugars than did ammonia steeping alone. However, the net energy balance (additional chemical in free sugars minus energy consumption of ultrasound process) was not favorable - this contrasts with Grewells work using ultrasonics for enhancing sugar release from starches. We recommend further investigations on re-evaluating the design and conditions which could make ultrasonic work better as a lignocellulosic pretreatment.

Ultrasonic Pretreatment of Corn Slurry in Batch and Continuous Systems

The effects of ultrasonication of corn slurry, on particle size distribution and enzymatic hydrolysis was studied for the dry-grind mill ethanol industry. Two independent ultrasonic experiments were conducted at a frequency of 20 kHz; in batch and continuous systems. The ground corn slurry (33% m/v) was pumped at flow rates 10-28 L/min in continuous flow experiments, and sonicated at constant amplitude (20µmpeak-to-peak(p-p)). Ultrasonic batch experiments were conducted at varying amplitudes of 192-320µmp-p. After ultrasonication, StargenTM001 enzyme was added to the samples and a short 3h hydrolysis followed. The treated samples were found to yield 2-3 times more reducing sugar compared to the control (untreated) samples. In terms of energy density, the batch ultrasonic system was found to deliver 25-times more energy than the continuous flow systems. Although the experiments conducted in continuous system released less reducing sugar than the batch system, the continuous system was more energy efficient. The particle size of the sonicated corn slurry (both batch and continuous) was reduced relative to the controls (without treatment). The reduction of particle size was directly proportional to the energy input during sonication. The study suggests that both batch and continuous flow ultrasonic systems enhances enzymatic hydrolysis yield, reduces particle size of corn slurry and could be a potential effective pretreatment for corn slurry.

Ultrasonic Enhanced Liquefaction and Saccharification of Corn for Bio-Fuel Production

Dry grind corn milling does not reach full efficiency of starch conversion to sugars and subsequently to ethanol because of limitations in the milling process. This paper examines the use of high-power ultrasonics to enhance the release of fermentable sugars from milled dry corn. In this work, 20 kHz ultrasonic energy was used to pretreat corn mash prior to enzymatic conversion of corn starch to glucose in a batch-mode. The ultrasonic amplitude was varied from 0, 191 to 320 µmpp. The corn mash was sonicated for 0 (control), 20 and 40 seconds. Other experimental variables that were studied included the effect of temperature and pretreatment sequencing, e.g., ultrasonic pretreatment before and after enzyme addition. It was found that the reaction rate kinetics of the enzymatic reactions increased threefold for sonicated samples. Energy balance (efficiency) analysis indicated that ultrasound pretreatment released twice as much energy (as sugar) when introduced during pretreatment. Based on scanning electron microscopy examination and particle size analysis, the enhancement of the conversion was primarily attributed to particle size reduction, resulting in an increase in the surface area to volume ratio, which in turn increased the available enzymatic reaction sites. One of the most striking findings was that enzymes were not degraded by low level ultrasonication. In addition, the most significant increase in sugar yield was seen when the enzymes were added before ultrasonic pretreatment. Ultrasound has the potential to enhance the ethanol yield from cornstarch and reduce the production cost significantly in commercial dry corn milling ethanol plants.

Laser Microwelding of Polystyrene and and Polycarbonate

Thermoplastics offer significant advantages in the fields of biomedical engineering, communications, and in particular applications related to Micro Electro Mechanical Systems (MEMS). For example, the low manufacturing costs of polymers may allow industry to fabricate disposable MEMS. Rapid, consistent, and inexpensive assembly or packaging is critical to the commercialization of polymer based MEMS. One method of laser welding that offers great promise of success is Through Transmission Infrared (TTIr) welding. TTIr works by passing a laser through one of the components to be joined and focusing it on the second which has an absorbing material (such as carbon black) added to it. In the following studies, the radiation from a 1u2005W laser diode (850u2005nm) was fiber coupled to a lens that focused the beam to a spot size of either 25 or 50u2005µm. Polycarbonate and polystyrene samples were welded by scanning the beam across the samples at rates from 8 to 60u2005mm/s. It was possible to generate welds below 15u2005µm in width. Some of the other key findings included: 1. Tensile testing of micro-welds is difficult because of problems with peeling 2. When rectangular samples were sealed (welded) the welds were hermetic and able to sustain burst pressures as high as 0.50u2005MPa 3. A distributed heat source model can accurately predict temperature fields in plastic laser welds 4. Distributed heat model predicts weld widths more accurately than point heat source models 5. For micro-welding of plastics, when the dimensionless distribution parameter is less than two, a point heat source model predicts similar widths to those predicted by a distributed heat source model 6. At relatively high travel speeds (>100u2005mm/s), the distributed model predicts a location within the plastic that experiences two peak temperatures 7. At relatively low power levels, (∼50u2005mW) it is possible to heat PC so that visible, temporary deformation occurs. Additional findings included the confirmation that the following observations made in traditional laser welding were also seen in micro-welding of plastics:At relatively higher heat input ablation can occur which reduces weld strength independent of weld width.Thermoplastics offer significant advantages in the fields of biomedical engineering, communications, and in particular applications related to Micro Electro Mechanical Systems (MEMS). For example, the low manufacturing costs of polymers may allow industry to fabricate disposable MEMS. Rapid, consistent, and inexpensive assembly or packaging is critical to the commercialization of polymer based MEMS. One method of laser welding that offers great promise of success is Through Transmission Infrared (TTIr) welding. TTIr works by passing a laser through one of the components to be joined and focusing it on the second which has an absorbing material (such as carbon black) added to it. In the following studies, the radiation from a 1u2005W laser diode (850u2005nm) was fiber coupled to a lens that focused the beam to a spot size of either 25 or 50u2005µm. Polycarbonate and polystyrene samples were welded by scanning the beam across the samples at rates from 8 to 60u2005mm/s. It was possible to generate welds below 15u2005µm in width...

Simultaneous Saccharification and Fermentation of Ultrasonically Treated Corn Slurry

The potential application of ultrasonics as a pretreatment process to enhance saccharification of starch in corn-to-ethanol plants is evaluated in this paper. Due to energy intensive use of steam in hydro-cooking, ultrasonics poses a promising alternative as a pretreatment method. Two independent ultrasonic experiments were conducted at a frequency of 20 kHz; batch and continuous flow treatment. Corn slurry was obtained from a nearby ethanol plant and sonicated in batch mode at amplitude of 144µmpeak-to-peak (p-p) for 90 s using a catenoidal horn with a 10 mm diameter face. In the continuous flow treatment, corn slurry was pumped through a reactor equipped with a Branson Ultrasonics “donut horn”. Jet-cooked samples were obtained from the same ethanol plant and analyzed for comparison in fermentation yield. Ethanol yields in sonicated samples were comparable to jet-cooked samples. The glucose levels decreased with consumption during the initial stage of the fermentation and suddenly dropped after 6 h as the ethanol increased. An economic comparison was also conducted on jet cooking and ultrasonics pretreatment methods. The analysis showed that capital cost for the ultrasonics system was higher compared to the capital cost of hydrocooking. However, due to the relatively large energy demand of jet cookers, the operating costs of the hydrocooker suggest that it is cost effective to use ultrasonics.

Novel Characterization Method of Biodiesel Produced from Soybean Oil using Thermogravimetric Analysis

The aim of this study was to demonstrate thermogravimetric analysis (TGA) as a potential method for monitoring biodiesel production. Soybean oil and commercial biodiesel were mixed in different proportions by weight. Mixtures of different biodiesel/soybean oil ratios were also created by interrupting a base-catalyzed transesterification process for producing biodiesel at various times. The mixtures produced by both approaches were analyzed with TGA. The results were then compared with data obtained by proton nuclear magnetic resonance spectroscopy (1HNMR spectroscopy). The relative weight losses in both sets of mixtures we generated correlated well to the proportion of biodiesel present in the sample. The results from both analytical methods were in good agreement and within a deviation of 5%. Thus, TGA is a simple, convenient and economical method for monitoring biodiesel production.

Ultrasonication in Soy Processing for Enhanced Protein and Sugar Yields and Subsequent Bacterial Nisin Production

Soy protein recovery from hexane-defatted soybean flakes using conventional methods is generally low. Importantly, some tightly-bound sugar in the soy flakes ends up in soy protein, thereby deteriorating the usefulness and quality of soy protein as a food ingredient. This research investigated the use of high-power ultrasound prior to soy protein extraction to simultaneously enhance protein yield and facilitate more sugar release in soy whey. The nutrient-rich soy whey was then used as a cheap growth medium to produce high-value nisin using Lactococcus lactis subsp. lactis. A nisin sensitive organism Micrococcus luteus was used as an indicator organism for international unit determination of nisin production as compared to standard. Soy flakes and water was mixed at the ratio of 1:10 (w/w). The slurry was then sonicated for 15, 30, 60 and 120 sec at a frequency of 20 kHz. The ultrasonic amplitude was maintained at 84 µmpp (peak to peak amplitude in µm) for all sonication durations. The results showed that with ultrasound pretreatment, the protein yield improved as much as by 46% in soy extract and sugar release by 50% with respect to nonsonicated samples (control). To maximize nisin production from soy whey, different parameters, such as aeration/agitation and incubation period were optimized. Nisin production from standard medium, DeMan, Rogosa and Sharpe (MRS) and soy whey was tested and compared. Maximum nisin production was achieved in stationary conditions and showed a continuous increase in yield till 48h of incubation (incubation period beyond that was not tested). Maximum nisin yield of 1.78 g/L of soy whey was obtained at 30°C and pH of 4.5 as opposed to 2.96 g/L of nisin with MRS medium

Modeling Heat Flow for a Distributed Moving Heat Source in Micro‐Laser Welding of Plastics

Polymer use in micro‐devices, especially in the medical industry has been rapidly increasing. During assembly of micro‐devices it is desirable to produce weld joints that are about 100 μm in width. This paper reviews the modeling of heat flow during through transmission infrared micro‐welding of plastic using fiber coupled laser diodes. Two models were used to predict the temperature distributions within welded samples. Both models were based on a moving heat source and moving coordinate system. For the simpler model a moving point heat source was used and for the more complex model a Gaussian distributed heat source was used. It was found that the distributed model can accurately predict temperature fields in plastic laser welds for all ranges of the parameters evaluated. However, the point heat source model was only able to accurately predict temperature fields with a relatively small laser focal spot (25 μm). In addition it was found that for micro‐welding of plastics, when the dimensionless distributi...