Browsing by Subject "Biofuel"
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Item A Process Integration Approach to the Strategic Design and Scheduling of Biorefineries(2011-02-22) Elms, Rene ?DavinaThis work focused upon design and operation of biodiesel production facilities in support of the broader goal of developing a strategic approach to the development of biorefineries. Biodiesel production provided an appropriate starting point for these efforts. The work was segregated into two stages. Various feedstocks may be utilized to produce biodiesel, to include virgin vegetable oils and waste cooking oil. With changing prices, supply, and demand of feedstocks, a need exists to consider various feedstock options. The objective of the first stage was to develop a systematic procedure for scheduling and operation of flexible biodiesel plants accommodating a variety of feedstocks. This work employed a holistic approach and combination of process simulation, synthesis, and integration techniques to provide: process simulation of a biodiesel plant for various feedstocks, integration of energy and mass resources, optimization of process design and scheduling, and techno-economic assessment and sensitivity analysis of proposed schemes. An optimization formulation was developed to determine scheduling and operation for various feedstocks and a case study solved to illustrate the merits of the devised procedure. With increasing attention to the environmental impact of discharging greenhouse gases (GHGs), there has been growing public pressure to reduce the carbon footprint associated with fossil fuel use. In this context, one key strategy is substitution of fossil fuels with biofuels such as biodiesel. Design of biodiesel plants has traditionally been conducted based on technical and economic criteria. GHG policies have the potential to significantly alter design of these facilities, selection of feedstocks, and scheduling of multiple feedstocks. The objective of the second stage was to develop a systematic approach to design and scheduling of biodiesel production processes while accounting for the effect of GHG policies. An optimization formulation was developed to maximize profit of the process subject to flowsheet synthesis and performance modeling equations. The carbon footprint is accounted for through a life cycle analysis (LCA). The objective function includes a term reflecting the impact of the LCA of a feedstock and its processing to biodiesel. A multiperiod approach was used and a case study solved with several scenarios of feedstocks and GHG policies.Item Artificial Leaf for Biofuel Production and Harvesting: Transport Phenomena and Energy Conversion(2013-08) Murphy, Thomas Eugene; Berberoglu, HalilMicroalgae cultivation has received much research attention in recent decades due to its high photosynthetic productivity and ability to produce biofuel feedstocks as well as high value compounds for the health food, cosmetics, and agriculture markets. Microalgae are conventionally grown in open pond raceways or closed photobioreactors. Due to the high water contents of these cultivation systems, they require large energy inputs for pumping and mixing the dilute culture, as well as concentrating and dewatering the resultant biomass. The energy required to operate these systems is generally greater than the energy contained in the resultant biomass, which precludes their use in sustainable biofuel production. To address this challenge, we designed a novel photobioreactor inspired by higher plants. In this synthetic leaf system, a modified transpiration mechanism is used which delivers water and nutrients to photosynthetic cells that grow as a biofilm on a porous, wicking substrate. Nutrient medium flow through the reactor is driven by evaporation, thereby eliminating the need for a pump. This dissertation outlines the design, construction, operation, and modeling of such a synthetic leaf system for energy positive biofuel production. First, a scaled down synthetic leaf reactor was operated alongside a conventional stirred tank photobioreactor. It was demonstrated that the synthetic leaf system required only 4% the working water volume as the conventional reactor, and showed growth rates as high as four times that of the conventional reactor. However, inefficiencies in the synthetic leaf system were identified and attributed to light and nutrient limitation of growth in the biofilm. To address these issues, a modeling study was performed with the aim of balancing the fluxes of photons and nutrients in the synthetic leaf environment. The vascular nutrient medium transport system was also modeled, enabling calculation of nutrient delivery rates as a function of environmental parameters and material properties of the porous membrane. These models were validated using an experimental setup in which the nutrient delivery rate, growth rate, and photosynthetic yield were measured for single synthetic leaves. The synthetic leaf system was shown to be competitive with existing technologies in terms of biomass productivity, while requiring zero energy for nutrient and gas delivery to the microorganisms. Future studies should focus on utilizing the synthetic leaf system for passive harvesting of secreted products in addition to passive nutrient delivery.Item Comparison of Biological and Thermal (Pyrolysis) Pathways for Conversion of Lignocellulose to Biofuels(2012-11-30) Imam, Tahmina 1983-Because of the limited supply of imported crude oil and environmental degradation, renewable energy is becoming commercially feasible and environmentally desirable. In this research, biological and thermal (pyrolysis) conversion pathways for biofuel production from lignocellulosic feedstocks were compared. For biological conversions of sorghum, ethanol yield was improved using M81-E variety (0.072 g/g juice) over Umbrella (0.065 g/g juice) for first-generation biomass (sorghum juice), and 0.042 g/g sorghum was obtained from the cellulosic portion of second-generation biomass. When ultrasonication was combined with hot water pretreatment, yields increased by 15% and 7% for cellulose to glucose, and hemicellulose to pentose, respectively. Ethanol yield was 10% higher when this pretreatment was combined with Accellerase 1500+XC for saccharification. Biological conversion yielded 1,600?2,300 L ethanol/ha for first-generation biomass, and 4,300?4,500 L ethanol/ha from lignocellulosic biomass. For thermal (pyrolysis) conversion of lignocellulosic switchgrass at 600 degrees C, product yield was 37% bio-oil, 26% syngas, and 25% bio-char. At 400 degrees C, product yield was 22% bio-oil, 8% syngas, and 56% bio-char. Bio-oil from pyrolysis was highly oxygenated (37 wt%). It required chemical transformation to increase its volatility and thermal stability, and to reduce its viscosity by removing objectionable oxygen, so the product could be used as transportation fuel (gasoline). As a consequence of upgrading bio-oil by catalytic hydrogenation, bio-oil oxygen decreased from 37?2 wt%, carbon increased from 50?83 wt%, hydrogen increased from 9?15 wt% and heating value increased from 36?46 MJ/kg, resulting in a fuel that was comparable to gasoline. The upgraded product passed the thermal stability test when kept under an oxygen-rich environment. The upgraded product consisted of 14.8% parrafins, 21.7% iso-parrafins, 3% napthene, 42.6% aromatics, 4.7% olefin, 4.7% DMF, 8% alcohol, and 0.6% ketone on a mass basis. Comparing the two pathways, biological conversion had 11 wt% ethanol yield from sorghum, and thermal conversion had 13 wt% gasoline yield from switchgrass. For process efficiency, thermal conversion had 35% energy loss versus 45% energy loss for biological conversions. For the biological pathway, ethanol cost was $2.5/gallon ($4/gallon, gasoline equivalent), whereas for the thermal pathway, switchgrass gasoline cost was $3.7/gallon, both with 15% before tax profit.Item Constraints on algal biofuel production(2011-05) Beal, Colin McCartney; Ruoff, Rodney S.; Webber, Michael E., 1971-; Hebner, R. E. (Robert E.); Berberoglu, Halil; Seibert, A F.; King, Carey W.The aspiration for producing algal biofuel is motivated by the desire to replace conventional petroleum fuels, produce fuels domestically, and reduce greenhouse gas emissions. Although, in theory, algae have the potential to produce a large amount of petroleum fuel substitutes and capture carbon emissions, in practice, profitable algal biofuel production has proven quite challenging. This dissertation characterizes the production pathways for producing petroleum fuel substitutes from algae and evaluates constraints on algal biofuel production. Chapter 8 provides a summary of the entire dissertation. The first chapter provides a framework for reporting the production of renewable diesel from algae in a consistent way by using data that are specific and by presenting information with relevant metrics. The second chapter presents a review of analytical tools (i.e., microscopy, spectroscopy, and chromatography) that can be used to analyze the structure and composition of intermediate products in an algal biofuel production pathway. In chapters 3 through 6, the energy return on investment, water intensity, and financial return on investment are presented for three cases: 1) an Experimental Case in which data were measured during five batches of algal biocrude production with a combined processed volume of about 7600 L, 2) a hypothetical Reduced Case that assumes the same energy output as the Experimental Case, with reduced energy and material inputs, and 3) a Highly Productive Case that assumes higher energy outputs than the Experimental Case, with reduced energy and material inputs, similar to the Reduced Case. For all three cases, the second-order energy return on investment was determined to be significantly less than 1, which means that all three cases are energy negative. The water intensity (consumption and withdrawal) for all cases was determined to be much greater than that of conventional petroleum fuels and biofuels produced from non-irrigated crops. The financial return on investment was also found to be significantly less than 1 for all cases, indicating production would be unprofitable. Additionally, it was determined that large-scale algal biofuel production would be constrained by the availability of critical energy and material inputs (e.g., nitrogen and carbon dioxide). The final part of this dissertation presents a first-principles thermodynamic analysis that represents an initial attempt at characterizing the thermodynamic limits for algal biofuel production. In that analysis, the energy, entropy, and exergy is calculated for each intermediate product in the algal biofuel production pathway considered here. Based on the results presented in this body of work, game-changing technology and biotechnology developments are needed for sustainable and profitable algal biofuel production.Item Development of a novel algae biofilm photobioreactor for biofuel production(2012-08) Ozkan, Altan; Berberoglu, Halil; Kinney, Kerry; Katz, Lynn; Kirisits, Mary J.; Lawler, Desmond; Brand, Jerry; Cetiner, SelimAlgae are photosynthetic microorganisms that convert carbon dioxide and sunlight into biomass that can be used for biofuel production. Although they are usually cultivated in suspension, these microorganisms are capable of forming productive biofilms over substrata given the right conditions. This dissertation focuses on algal biofilms and their application in biofuel feedstock production. In particular it reports the construction and performance of an algae biofilm photobioreactor, the physico-chemical surface properties of different algal species and adhesion substrata, and cell-surface interactions based on experimental results and theoretical models. A novel algae biofilm photobioreactor was constructed and operated (i) to demonstrate the proof of concept, (ii) to analyze the performance of the system, and (iii) to determine the key advantages and short comings for further research. The results indicated that significant reductions in water and energy requirements were possible with the biofilm photobioreactor. Although the system achieved net energy ratio of about 6, the overall productivity was low as Botryococcus branunii is notoriously slow growing algae. Thus, further studies were focused on identification of algal species capable of biofilm growth with larger biomass and lipid productivities. Adhesion of cells to substrata precedes the formation of all biofilms. A comprehensive study has been conducted to determine the interactions of a planktonic and a benthic algal species with hydrophilic and hydrophobic substrata. The physico-chemical surface properties of the algal cells and substrata were determined and using these data, cell-substrata interactions were modeled with the thermodynamic, Derjaguin, Landau Verwey, Overbeek (DLVO) and Extended Derjaguin, Landau, Verwey, Overbeek (XDLVO) approaches and critical parameters for algal adhesion were identified. Finally, the adhesion rate and strength of algal species were quantified with parallel plate flow chamber experiments. The results indicated that both cell and substrata surface hydrophobicity played a critical role for the adhesion rate and strength of the cells and XDLVO approach was the most accurate model. Finally, based on these findings the physico-chemical surface properties of ten algal species and six substrata were quantified and a screening was done to determine algae species substratum couples favoring adhesion and biofilm formation.Item Growth Rate of Marine Microalgal Species using Sodium Bicarbonate for Biofuels(2013-08-05) Gore, MatthewWith additional research on species characteristics and continued work towards cost effective production methods, algae are viewed as a possible alternative biofuel crop to current feedstocks such as corn. Current open pond production methods involve bubbling carbon dioxide (CO_(2)) gas into the media to provide a carbon source for photosynthesis, but this can be very inefficient releasing most CO_(2) back into the atmosphere. This research began by investigating the effect of sodium bicarbonate (NaHCO_(3)) in the growth media as an alternative carbon source to bubbling CO_(2) into the cultures. The second part examined if NaHCO_(3) could act as a lipid trigger in higher (10.0 g/L) concentrations. The microalgae species Dunaliella tertiolecta (Chlorophyta), Mayamaea spp. (Baciallariophyta) and Synechoccocus sp. (Cyanophyta) were grown with 0.0 g/L, 0.5g/L, 1.0 g/L, 2.0 g/L and 5.0 g/L dissolved NaHCO_(3) in modified seawater (f/2) media. To investigate effects of NaHCO_(3) on lipid accumulation, growth media cultures were divided into two ?lipid phase? medias containing either 0.0g/L (non-boosted) or 10.0 g/L (boosted) NaHCO_(3) treatments. Culture densities were determined using spectrophotometry, which showed both all three species are able to successfully grow in media ameliorated with these high NaHCO_(3) concentrations. Highest growth phase culture densities occurred in NaHCO_(3) concentrations of 2.0 g/L for D. tertiolecta and Mayamaea spp., and the 5.0 g/L treatment for Synechoccocus sp. Highest growth rates occurred in the 5.0 g/L NaHCO_(3) concentration treatments for D. tertiolecta, Mayamaea spp., and Synechoccocus sp. (0.205 d-1 ?0.010, 0.119 d-1 ?0.004, and 0.372 d-1 ?0.003 respectively). As a lipid accumulation trigger two of the three species (D. tertiolecta and Mayamaea spp) had their highest end day oil indices in a 10.0 g/L treatment. Highest oil indices occurred in boosted 5.0 g/L Dunaliella tertiolecta and 2.0 g/L Mayamaea spp. (13136 ? 895 and 62844 ? 8080 respectively (relative units)). The results obtained indicate NaHCO3 could be used as a photosynthetic carbon source for growth in all three species and a lipid trigger for D. tertiolecta and Mayamaea spp.Item High-throughput Microfluidic Screening Platforms for Microalgae Study(2014-12-15) Kim, Hyun SooMicroalgae have been envisioned as a future source of renewable energy. Both fossil fuel depletion and environmental concern have drawn more interest in microalgal biofuels, but the production cost of these biofuels are not yet economically competitive. Significant improvements such as development of better performing microalgal strains, optimization of culture conditions, and better understanding of microalgal biology are required for commercial viability. To resolve these limitations, massively parallel studies are needed, however, current microalgae culture systems are lack of high-throughput screening capabilities, and thus not suitable for the parallel studies. Here, three different high-throughput microfluidic microalgae screening platforms have been developed, each of which addresses major bottlenecks towards economically feasible microalgal biofuel. The first platform, a high-throughput microfluidic photobioreactor array has been developed to investigate the effect of different culture conditions on microalgal growth and oil production. This platform can provide up to 64 different culture conditions on-chip, such as combinations of different light intensities, light cycles, and culture media/chemical compositions. Single cell/colony trapping sites in culture compartments allowed for long-term analysis of microalgal growth and oil production with single cell/colony resolution. The light conditions that induced 1.8-fold higher oil accumulation over the typically used culture conditions were successfully identified. The second platform, as a microalgae library screening tool, a high-throughput microfluidic single-cell screening and selection platform has been developed to examine growth and oil production of various microalgal strains, followed by selective extraction of particular microalgae showing desired traits to off-chip reservoirs for further analysis. Single microalga was isolated and cultured, and its growth and oil accumulation were analyzed through 1024 single-cell trapping/culturing sites in the platform, where opening and closing of each trap can be individually controlled with integrated microfluidic control layers. By opening only a specific site out of the 1024 trapping sites, microalgae in particular trapping sites were selectively released and successfully collected off-chip. The third platform, a high-throughput droplet microfluidics-based microalgae screening platform has been developed to investigate the growth and the oil production of microalgal libraries with much higher throughput. Growth was characterized by encapsulating a single microalga into a droplet (functions as an independent bioreactor) and tracking its behavior over time. Oil production was also quantified through on-chip staining process, the key feature of the platform, where oil content in microalgae can be stained and measured through on-chip fluorescent tagging. Growth and oil accumulation under different culture conditions were successfully analyzed and compared, demonstrating the capability of the platform as a high-throughput screening tool. We have developed series of high-throughput microfluidic screening platforms for microalgae study, which provides the capabilities of analyzing microalgal growth and oil production under different culture conditions or among large numbers of microalgal library. The developed platforms will serve as powerful tools to accelerate research in addressing the limitations of microalgal biofuels as well as to significantly advance the current state of microalgal biofuel production.Item Hydrothermal liquefaction of municipal sludge and biosolids(2015-05) Anthony, Joseph Roslyn; Berberoglu, Halil; Wang, YaguoThe conversion of municipal sludge and biosolids into bio-oil via hydrothermal liquefaction (HTL) can simultaneously provide a replacement to non-renewable crude oil while dealing with waste disposal issues. Hydrothermal liquefaction takes advantage of liquid water’s interesting properties at high temperatures near the critical point, which facilitate the break down and reformation of biomass into a more energy dense bio-oil. Several laboratory-scale batch HTL experiments have been conducted with algae, woody biomass and livestock manure, but few have considered municipal sludge or biosolids. Suzuki et al. (1988) and Vardon et al. (2011) conducted studies on the HTL of sludge and biosolids, however neither study explored the effect of processing conditions (1,2). This thesis presents a study that explored how bio-oil composition and yield were affected by residence time, heating rate, initial biomass solids percentage and initial biomass composition. The highest quality bio-oil had a higher heating value (HHV) of 31.46±0.37 MJ/kg with a conversion yield of 39.42±1.4%. The HHV of the bio-oil was increased when the initial biomass had a higher solids concentration or higher HHV. The conversion yield was larger at lower solids percentages and at a heating rate of 270˚C/min. Furthermore, very few continuous HTL systems have been developed even though they may be the most viable option for scaling up. This thesis also presents the design and construction of a continuous HTL system for the processing of municipal sludge and biosolids.Item Polymer applications for improved biofuel production from algae(2011-12) Jones, Jessica Naomi; Poenie, Martin F.; Brand, Jerry; Brodbelt, Jennifer; Georgiou, George; Roy, Krishnendu; Seibert, FrankBiofuel is a renewable and sustainable energy source with near-neutral carbon footprint. Algae are an ideal feedstock for biofuel production because they reproduce quickly and have high oil. Algae can be cultivated in non-arable land, and would not impact the food supply. Unfortunately, processing algae into biofuel is more expensive than land crops due to the large volumes of dilute algal suspension that must be harvested and concentrated. In order to improve algae-based biofuel economics, resins were developed that reduce costs associated with water pumping and transport. Hydrophobic resins were developed for binding oil out of an algal suspension so that the residual biomass could be recovered without solvent contamination. Binding behavior displayed lipid species specificity, and binding capacity was improved by ethanol treatment of the biomass. Algae was harvested by binding to anion exchange resin and directly converted into biodiesel. One-step, room temperature in situ transesterification of algae yielded nearly as much biodiesel as two-step, heated transesterification of dried biomass. Elution with transesterification reagent also regenerated the resin for subsequent algal binding. Functionalized resins were developed with high algal binding capacity at neutral pH. Binding was easily reversed, as treatment with buffer with pH higher than pKa of the resin functional group removed the algae and regenerated the resin for subsequent use. The resin bound 10% of its weight in algae and released it as a 100-fold concentrated suspension. The polymers developed can be scaled up for commercial processes and reduce algal harvesting and concentration costs.Item Rheology of algae slurries(2010-12) Bolhouse, Angel Michele; Berberoglu, Halil; Ferron, RaissaThis thesis reports the rheological properties of algae slurries as a function of cell concentration for three microalgae species: Nannochloris sp.,Chlorella vulgaris, and Phaeodactylum tricornutum. Rheological properties ofalgae slurries have a direct impact on the agitation and pumping power requirements as well as process design for producing algal biofuels. This study measures the rheological properties of eight diff erent concentrations of each species ranging from 0.5 to 80 kg dry biomass/m³. Strain-controlled steady rate sweep tests were performed for each sample with an ARES-TA rheometer using a double wall couette cup and bob attachment. Shear rates ranged from 5 - 270 s⁻¹, corresponding to typical expected conditions. The results showed that Nannochloris sp. slurry behaved as a Newtonian fluid for concentrations up to 20 kg/m³. Samples with concentrations above 40 kg/m³ behaved as a shear thinning non-Newtonian fluid. The effective viscosity increased with increased biomass concentration for a maximum value of 3.3x10⁻³ Pa-s. Similarly, C. vulgaris slurry behaved as a Newtonian fluid with concentrations of up to 40 kg/m³, above which it displayed a shear thinning non-Newtonianf behavior and a maximum eff ective viscosity of 3.5x10⁻² Pa-s. On the other hand, P. tricornutum slurry demonstrated solely Newtonian fluid behavior, with the dynamic viscosity increasing with increasing biomass concentration for a maximum value of 3.2x10⁻³ Pa-s. The maximum observed e ffective viscosity occurred at a concentration of 80 kg/m³ for all three species. Moreover, an energy analysis was performed where a non-dimensional bioenergy transport e ffectiveness was de termined as the ratio of the energy content of the transported algae biomass to the sum of the required pumping power and the harvesting power. The results show that the increase in major losses due to increase in viscosity was overcompensated by the increase in the transported biomass energy. Also, cultivating a more concentrated slurry requires less dewatering power and is the preferred option. The largest bioenergy transport eff ectiveness was observed for the slurries with the largest initial dry biomass concentrations. Finally, the relative viscosity of algae slurries was modeled using a Kelvin-Voit based model for dilute and concentrated viscoelastic par- ticle suspensions. The model, which depends primarily on the packing factor of the algae species, agrees with the measured viscosity with an average error of 18%, while the concentrated particle suspension model was slightly more accurate than the dilute suspension model.