Browsing by Subject "Bioproducts and Bioenergy"

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Combustion Emissions Modeling and Testing of Neat Biodiesel Fuels
(American Society of Mechanical Engineers, 2010-05) Liu, H-P.; Strank, S.M.; Werst, M.D.; Hebner, R.E.; Osara, J.
This paper presents emissions modeling and testing of a four-stroke single cylinder diesel engine using pure soybean, cottonseed, and algae biodiesel fuels. A system level engine simulation tool developed by Gamma Technologies, GT-Power, has been used to perform predictive engine combustion simulations using direct-injection jet modeling technique. Various physical and thermodynamic properties of the biodiesel fuels in both liquid and vapor states are required by the GT-Power combustion simulations. However, many of these fuel properties either do not exist or are not available in published literatures. The properties of the individual fatty esters, that comprise a biofuel, determine the overall fuel properties of the biofuel. In this study, fatty acid profiles of the soybean, cottonseed, and algae methylester biodiesel fuels have been identified and used for fuel property calculations. The predicted thermo-physical properties of biodiesels were then provided as fuel property inputs in the biodiesel combustion simulations. Using the calculated biodiesel fuel properties and an assumed fuel injector sac pressure profile, engine emissions of the conventional diesel and biodiesel fuels have been predicted from combustion simulations to investigate emission impacts of the biodiesel fuels. Soybean biodiesel engine emissions, which include NOx, HC, CO and CO2 , measured at various engine speeds and loads in actual combustion emissions tests performed in this study were also compared to those predicted by the combustion simulations.
Comprehensive Evaluation of Algal Biofuel Production: Experimental and Target Results
(MDPI, 2012-06) Beal, C.M.; Hebner, R.E.; Webber, M.E.; Ruoff, R.S.; Seibert, A.F.; King, C.W.
Worldwide, algal biofuel research and development efforts have focused on increasing the competitiveness of algal biofuels by increasing the energy and financial return on investments, reducing water intensity and resource requirements, and increasing algal productivity. In this study, analyses are presented in each of these areas—costs, resource needs, and productivity—for two cases: (1) an Experimental Case, using mostly measured data for a lab-scale system, and (2) a theorized Highly Productive Case that represents an optimized commercial-scale production system, albeit one that relies on full-price water, nutrients, and carbon dioxide. For both cases, the analysis described herein concludes that the energy and financial return on investments are less than 1, the water intensity is greater than that for conventional fuels, and the amounts of required resources at a meaningful scale of production amount to significant fractions of current consumption (e.g., nitrogen). The analysis and presentation of results highlight critical areas for advancement and innovation that must occur for sustainable and profitable algal biofuel production can occur at a scale that yields significant petroleum displacement. To this end, targets for energy consumption, production cost, water consumption, and nutrient consumption are presented that would promote sustainable algal biofuel production. Furthermore, this work demonstrates a procedure and method by which subsequent advances in technology and biotechnology can be framed to track progress.
Designing transcranial magnetic stimulation systems
(IEEE, 2005-03) Davey, K.R.; Riehl, M.
We explain the process of designing optimized transcranial magnetic stimulation systems and outline a method for identifying optimal system parameters such as the number of turns, the capacitor size, the working voltage, and the size of the stimulation coil. The method combines field analysis, linear and nonlinear circuit analysis, and neural strength-duration response parameters. The method uses boundary-element analysis to predict the electric field as a function of depth, frequency, current, and excitation coil size. It then uses the field analysis to determine the inductance as a function of size and, in general, current when a saturable core is used. Circuit analysis allows these electric field computations to be indexed against system parameters, and optimized for total system energy and stimulation coil size. System optimizations depend on desired stimulation depth. A distinguishing feature of the method is that it inherently treats excitation frequency as an unknown to be determined from optimization.
Electrically Dewatering Microalgae
(IEEE, 2011-10) Pearsall, R.V.; Connelly, R.L.; Fountain, M.E.; Hearn, C.S.; Werst, M.D.; Hebner, R.E.; Kelley, E.F.
Microalgae are being developed as a source of fuels and/or chemicals. A processing challenge is dewatering the algae. Electrical approaches to dewatering include exploiting electrophoresis or electroflocculation. The reported experiments show that electrophoresis does occur but is complicated by the effects of the fluid motion. It appears that the coupling of the algal cell and the fluid can be sufficiently strong such that fluid motion effects can influence or dominate behavior. Electroflocculation appears to be a robust process. It does, however, inherently leave electrically induced trace metal flocculants in the dewatered algae.
Extraction of Algal LIpids and their Analysis by HPLC and Mass Spectrometry
(Springer Verlag, 2012-08) Jones, J.; Manning, S.; Montoya, M.; Keller, K.; Poenie, M.
Algae are a promising source of biofuel but claims about their lipid content can be ambiguous because extraction methods vary and lipid quantitation often does not distinguish between particular lipid classes. Here we compared methods for the extraction of algal lipids and showed that 2-ethoxyethanol (2-EE) provides superior lipid recovery (>150–200 %) compared to other common extraction solvents such as chloroform:methanol or hexane. Extractions of wet and dry algal biomass showed that 2-EE was more effective at extracting lipids from wet rather than dried algal pellets. To analyze lipid content we used normal-phase HPLC with parallel quantitation by an evaporative light scattering detector and a mass spectrometer. Analysis of crude lipid extracts showed that all major lipid classes could be identified and quantified and revealed a surprisingly large amount of saturated hydrocarbons (HC). This HC fraction was isolated from extracts of bioreactor-grown algae and further analyzed by HPLC/MS, NMR, and GC/MS. The results showed that the sample consisted of a mixture of saturated, straight- and branched-chain HC of different chain lengths. These algal HC could represent an alternative biofuel to triacylglycerols (TAG) that could feed directly into the current petroleum infrastructure.
A Framework to Report the Production of Renewable Diesel from Algae
(Springer Verlag, 2011-03) Beal, C.M.; Smith, C.H.; Webber, M.E.; Ruoff, R.S.; Hebner, R.E.
Recently, algae have received significant interest as a potential feedstock for renewable diesel (such as biodiesel), and many researchers have attempted to quantify this potential. Some of these attempts are less useful because they have not incorporated specific values of algal lipid content, have not included processing inefficiencies, or omitted processing steps required for renewable diesel production. Furthermore, the associated energy, materials, and costs requirements are sometimes omitted. The accuracy and applicability of these estimates can be improved by using data that are more specific, including all relevant information for renewable diesel production, and by presenting information with more relevant metrics. To determine whether algae are a viable source for renewable diesel, three questions that must be answered are (1) how much renewable diesel can be produced from algae, (2) what is the financial cost of production, and (3) what is the energy ratio of production? To help accurately answer these questions, we propose an analytical framework and associated nomenclature system for characterizing renewable diesel production from algae. The three production pathways discussed in this study are the transesterification of extracted algal lipids, thermochemical conversion of algal biomass, and conversion of secreted algal oils. The nomenclature system is initially presented from a top-level perspective that is applicable to all production pathways for renewable diesel from algae. Then, the nomenclature is expanded to characterize the production of renewable diesel (specifically, biodiesel) from extracted algal lipids in detail (cf. Appendix 2). The analytical framework uses the presented nomenclature system and includes three main principles: using appropriate reporting metrics, using symbolic notation to represent unknown values, and presenting results that are specific to algal species, growth conditions, and product composition.
Magnetic Field Stimulation - the Brain as a Conductor
(0000-00-00) Davey, K.R.;
The brain is an inhomogeneous conductor consisting of white matter, grey matter, and cerebral spinal fluid with conductivities, 0.48 S/m, 0.7 S/m, and 1.79 S/m respectively. The skull is essentially a zero current density region since its conductivity about 100 times smaller, 32-80 mS/m. Analysis shows that for the purposes of magnetic stimulation, the brain can be treated as a homogeneous conductor; differences in the computations of the induced electric field for the homogeneous and inhomogeneous models are insignificant. The currents induced in the brain are induced by a changing magnetic field, but they are too small to influence that field. The induction is a one way coupling, and thus the problem is not a true eddy current problem. Faraday and Ampere’s laws are easily applied to predict the induced current subject to the condition that the normal component of current density go to zero at the scalp interface. Iron core stimulators constructed as tape cores are more efficient than air core stimulators. With both air and iron core stimulators, the field will always be higher on the scalp than within the white and grey matter. The higher induced surface fields are the cause of pain in some patients. This effect can be mitigated by shields and stimulator topologies that spread out the field, but it can never be eliminated. No inversion can ever be realized wherein the induced field is larger at depth than at all places on the scalp. A properly designed brain stimulation system starts with the target stimulation depth, and it should incorporate the neural strength – duration response characteristics. Higher frequency pulses require stronger electric fields. At the heart of the process is the transfer of charge across the nerve membrane commensurate to raise its intracellular potential about 30-40 mV. Think of this membrane as a capacitance that behaves more like a short circuit at high frequency. A nerve’s chronaxie and rheobase values can be used to dictate the electric field required for stimulation as a function of frequency. The system’s parameters can then be chosen to minimize stimulator energy and size. Changes to TMS stimulators are not likely to come from the superconducting community, or the ultracapacitor and supercapacitor community. Because of the large air gaps involved, 3% grain oriented steels and vanadium cores are about as suitable for standard C cores as one might expect. The malleability offered by powdered cores might, however, offer interesting penetration and flexibility options for the TMS market.
Modeling the effects of electrical conductivity of the head on the induced electric field in the brain during magnetic simulation
(Elsevier, 2003-11) Davey, K.R.; Epstein, C.M.; George, M.S.; Bohning, D.E.
Objective: The objective of this document is to quantify the effect of changing conductivity within the brain in transcranial magnetic stimulation. Methods: Extreme examples of white and grey matter distributions as well as cerebral spinal fluid are analyzed with numerical boundary element methods to show that the induced E fields for these various distributions vary little from the homogeneous case. Results: Models representative of the brain that demarcate regions of white matter and grey matter add an unnecessary level of complexity to the design and analysis of magnetic stimulators. The induced E field varies little between a precise model with exact placement of white and grey matter from that of its homogeneous counterpart. The E field will increase in white matter, and decrease in grey, but the variation is small. The contour integral of the E field around a closed path is dictated by the flux change through that contour. Discussion: The maximum value of the variation of the electric field between a fully homogeneous medium, and one filled with different conductivity media is 1/2 the conductivity ratio of the media involved. Neuronal stimulation is more likely at the interface between dissimilar mediums, the greatest being between white matter and cerebral spinal fluid. The interface location where no normal electric field exists will witness a localized electric field 51% greater than the homogeneous E field on the white matter side of that interface. White–grey matter interfaces will have a maximum localized increase in the E field 22.9% greater than the homogeneous case. Conclusions: Variations in neural intracellular potential during a magnetic stimulation pulse will be small among patients. The most efficient modeling will follow by assuming the medium homogeneous, and noting that perturbations from this result will exist.
Progression of lipid profile and cell structure in a research-scale production pathway for algal biocrude
(Elsevier, 2013-02) Beal, C.M.; Hebner, R.E.; Romanovicz, D.K.; Mayer, C.C.; Connelly, R.L.
Although there has been a large research effort associated with individual parts of various algal biofuel production pathways, few studies have tracked changes in product composition throughout an integrated biofuel production process. This study uses microscopy and chromatography to analyze the progression of lipid profile and cell structure of algal cells throughout a research-scale production pathway for biocrude. For the specific processing methods used in this pathway, it is shown that TAG content decreased, while DAG and FFA content increased during processing. The changes in the lipid content corresponded to cell degradation that was observed by SEM and TEM throughout processing. These results demonstrate the dynamic nature of lipid composition in an algal culture used for biofuel production and emphasize the need to monitor changes in lipid profile, as those changes can directly impact biofuel productivity.
Pulmonary vascular permeability changes in an ovine model of methicillin-resistant Staphylococcus aureus sepsis
(BioMed Central, 2009-02) Jonkam, C. C.; Bansal, K.; Traber, D. L.; Hamahata, A.; Maybauer, M. O.; Maybauer, D. M.; Cox, R. A.; Lange, M.; Connelly, R. L.; Traber, L. D.; Djukom, C. D.; Salsbury, J. R.; Herndon, D. N.
Endothelial dysfunction is a hallmark of sepsis, associated with lung transvascular fluid flux and pulmonary dysfunction in septic patients. We tested the hypothesis that methicillin-resistant Staphylococcus aureus (MRSA) sepsis following smoke inhalation increases pulmonary transvascular fluid flux via excessive nitric oxide (NO) production.
Suppressing the surface field during transcranial magnetic stimulation
(IEEE, 2006-02) Davey, K.R.; Riehl, M.
Transcranial magnetic stimulation (TMS) is used commonly as both a diagnostic tool and as an alternative to electric shock therapy for the treatment of clinical depression. Among the clinical issues encountered in its use is the mitigation of accompanying pain. The objective becomes one of minimizing the induced surface field while still achieving the target field objective. Three techniques discussed for realizing this end are 1) placing a conducting shield over a portion of the central target region, 2) using supplementary coils of opposite polarity in tandem with the primary field, and 3) opening the core angle to distribute the field. Option (3) shows the greatest promise for reducing the ratio of the maximum surface field to the induced target field.
Thermodynamic analysis of algal biocrude production
(Elsevier, 2012-08) Beal, C.M.; Hebner, R.E.; Webber, M.E.
Although algal biofuels possess great potential, profitable production is quite challenging. Much of this challenge is rooted in the thermodynamic constraints associated with producing fuels with high energy, low entropy, and high exergy from dispersed materials. In this study, a preliminary thermodynamic analysis is presented that calculates the energy, entropy, and exergy of the intermediate products for algal biocrude production. These values are also used in an initial attempt to characterize the thermodynamic efficiency of that system. The production pathway is simplified by assuming ideal solutions throughout. Results for the energy and exergy efficiencies, and the first-order energy and exergy return on investment, of the system are given. The summary finding is that the first-order energy return on investment in the best case considered could be as high as 520, as compared to 1.7 × 10?3 in the experimental unit under development. While this analysis shows that significant improvement may be possible, the ultimate thermodynamic efficiency of algal biofuels likely lies closer to the moderate case examined here, which yielded a first-order energy return on investment of 10. For perspective, the first-order energy return on investment for oil and gas production has been estimated in the literature to be ?35.
Time course of nitric oxide synthases, nitrosative stress, and poly(ADP Ribosylation) in an ovine sepsis model
(BioMed Central, 2010) Lange, M.; Connelly, R. L.; Traber, D. L.; Hamahata, A.; Nakano, Y.; Esechie, A.; Jonkam, C.; Borzyskowski S. von, Traber, L. D.; Schmalstieg, F. C.; Herndon, D. N.; Enkhbaatar, P.
Introduction: Different isoforms of nitric oxide synthases (NOS) and determinants of oxidative/nitrosative stress play important roles in the pathophysiology of pulmonary dysfunction induced by acute lung injury (ALI) and sepsis. However, the time changes of these pathogenic factors are largely undetermined. Methods: Twenty-four chronically instrumented sheep were subjected to inhalation of 48 breaths of cotton smoke and instillation of live Pseudomonas aeruginosa into both lungs and were euthanized at 4, 8, 12, 18, and 24 hours postinjury. Additional sheep received sham injury and were euthanized after 24 hrs (control). All animals were mechanically ventilated and fluid resuscitated. Lung tissue was obtained at the respective time points for the measurement of neuronal, endothelial, and inducible NOS (nNOS, eNOS, iNOS) mRNA and their protein expression, calcium-dependent and -independent NOS activity, 3-nitrotyrosine (3-NT), and poly(ADP-ribose) (PAR) protein expression. Results: The injury induced severe pulmonary dysfunction as indicated by a progressive decline in oxygenation index and concomitant increase in pulmonary shunt fraction. These changes were associated with an early and transient increase in eNOS and an early and profound increase in iNOS expression, while expression of nNOS remained unchanged. Both 3-NT, a marker of protein nitration, and PAR, an indicator of DNA damage, increased early but only transiently. Conclusions: Identification of the time course of the described pathogenetic factors provides important additional information on the pulmonary response to ALI and sepsis in the ovine model. This information may be crucial for future studies, especially when considering the timing of novel treatment strategies including selective inhibition of NOS isoforms, modulation of peroxynitrite, and PARP.
Use of Anion Exchange Resins for One-Step Processing of Algae from Harvest to Biofuel
(MDPI, 2012-07) Jones, J.; Lee, C-H.; Wang, J.; Poenie, M.
Some microalgae are particularly attractive as a renewable feedstock for biodiesel production due to their rapid growth, high content of triacylglycerols, and ability to be grown on non-arable land. Unfortunately, obtaining oil from algae is currently cost prohibitive in part due to the need to pump and process large volumes of dilute algal suspensions. In an effort to circumvent this problem, we have explored the use of anion exchange resins for simplifying the processing of algae to biofuel. Anion exchange resins can bind and accumulate the algal cells out of suspension to form a dewatered concentrate. Treatment of the resin-bound algae with sulfuric acid/methanol elutes the algae and regenerates the resin while converting algal lipids to biodiesel. Hydrophobic polymers can remove biodiesel from the sulfuric acid/methanol, allowing the transesterification reagent to be reused. We show that in situ transesterification of algal lipids can efficiently convert algal lipids to fatty acid methyl esters while allowing the resin and transesterification reagent to be recycled numerous times without loss of effectiveness.
Working field theory problems with random walks
(Emerald Group Publishing Limited, 2005) Davey, K.R.;
Abstract Purpose – The purpose of this paper is to demonstrate how Monte Carlo methods can be applied to the solution of field theory problems. Design – This objective is achieved by building insight from Laplacian field problems. The point solution of a Laplacian field problem can be viewed as the solid angle average of the Dirichlet potentials from that point. Alternatively it can be viewed as the average of the termination potential of a number of random walks. Poisson and Helmholtz equations add the complexity of collecting a number of packets along this walk, and noting the termination of a random walk at a Dirichlet boundary. Findings – When approached as a Monte Carlo problem, Poisson type problems can be interpreted as collecting and summing source packets representative of current or charge. Helmholtz problems involve the multiplication of packets of information modified by a multiplier reflecting the conductivity of the medium. Practical implications – This method naturally lends itself to parallel processing computers. Originality/value – This is the first paper to explore random walk solutions for all classes of eddy current problems, including those involving velocity. In problems involving velocity, the random walk direction enters depending on the walk direction with respect to the local velocity. Keywords Finite difference methods, Monte Carlo methods, Random functions Paper type Technical paper