Progress 12/15/12 to 12/14/13
Outputs
Target Audience: Presentations have been made to, and discussions have proceeded, with industrial practitioners developing processes for conversion of lignocellulosic biomass into ethanol and other valuable biorenewable products. Publications have been made in leading biotechnology and bioprocessing journals highlighting major results and discoveries from this project. In addition, project directors have communicated with scientific researchers at other academic institutions who have requested information about the processes. Collaborative work has also been completed with Argonne National Laboratory and discussed with the National Renewable Energy Laboratory. Classroom instruction has included lecture and laboratory sessions with emphasis placed on the most current results of this study, which will improve biorenewable processing. In addition, tours of laboratories and industrial facilities have been included. The primary participant has been college undergraduate students, along with a small number of K-12 students and college graduate students. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Graduate students working on the project have had many opportunities to learn valuable skills associated research and development of biorenewalbe products. All students have not only learned general methodologies associated with conducting reserach, but have also had ample hands-on opportunities to operate technical instruments such as SEM, AFM, FT-IR, UV-Vis, HPLC/UPLC, GC, and fermentation equipment. Many have also designed and manufactured custom instrumentation needed for the different goals of the project. Throughout the duration of the project, all students have completed work within a specifically designed program of study to take courses closely alligned with the biorenewable processing industry, as all participants have been associated with the Ph.D. program in Chemical and Biological Engineering at the South Dakota School of Mines and Technology. In addition to technical competencies acquired, students have had opportunities to more fully develop soft skills such as management (working with undergraduate students) and communication (publications, presentations, discussions with peers at national/international meeings, etc.). How have the results been disseminated to communities of interest? The results have been disseminated through multiple publications, presentations, classroom lectures and outreach presentations. Publications and presentations have been detailed within the "Products" section of this report. Outreach activities have included hands-on demostrations, active participation exercises and tours for K-12 students, including Engineers Week, Girls Day, Science and Technology Camps and the Native American GEAR UP Program. Over 500 K-12 students from a variety of grade levels and demographics have participated in the activities. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Major accomplishments associated with Thrusts One of the project goals have been completed and described in previous reports. Work during this reproting period focused primarily on Thrusts Two and Three. Within Thrust Two, the overall goalduring this report periodwas to develop and optimize a chemostat with cell recycle system (CWCR) to ferment a concentrated pine hydrolysate. Higher ethanol productivities have been demonstrated previously in CWCR fermentors for high gravity (concentrated sugars) feedstocks; in addition, it was hypothesized that HMF-furfural reduction in a CWCR would minimize their inhibition effects. Before a CWCR system could be designed, a working kinetic model with appropriate inhibition terms was needed. Because fermentation inhibition is highly dependent on hydrolysate composition and the yeast strain used, batch experiments were used to obtain kinetic data specific to our fermentation system. Rather than using a trial-and-error approach to determine the necessary kinetic inhibition terms, we developed a novel DoE-based method for determining which inhibitors had a significant effect on our hydrolysate fermentation kinetics. This method correctly identified ethanol as the major inhibitor for our system; but because it was designed to only look for two factor interactions, it did not identify a significant three-factor, sum of inhibitors (acetic acid + HMF + furfural) term. A working kinetic model with the necessary inhibition terms was then regressed from our batch fermentation data; r2 values for individual runs varied from 0.77 to 0.97. Bench-scale CWCR fermentations were then used to validate our batch-derived kinetic model and its predictions for enhanced ethanol productivity. To optimize the CWCR system, membranes with pore sizes varying from 300 KDa to 0.65 micron were tested; smaller pore sizes led to less flux decline, indicating that ultrafiltration membranes are more resistant to fouling in our system. CWCR performance with ethanol as the only inhibitor matched kinetic model predictions; ethanol productivities up to 36 g/l/h (a 10 fold improvement over low cell density batch runs) and cell densities up to 85 gDW/l were observed. When our CWCR was fed a real high gravity pine hydrolysate, an 8 fold improvement in ethanol productivity (16 g/l/h) over low cell density batch fermentation was observed. This improvement was partly due to an 80% reduction in the combined HMF-furfural concentration compared to the feed concentration. Within Thrust Three, a techno-economic analysis compared proposed process improvements (concentration of the raw hydrolysate by evaporation or nanofiltration and use of a CWCR fermentor) to a base process with no concentration and batch fermentation. Rigorous designs were used to estimate capital and operating costs for the proposed alternatives. This analysis indicated that hydrolysate sugars concentration has the potential to reduce distillation energy requirements by 75% (when concentrated to 200 g/l); however, overall savings are dependent on the concentration process with nanofiltration being the preferred option. A CWCR system has the potential to reduce equivalent annual operating cost (EAOC) by up to 9% over batch operation by significantly reducing fermentor size, but its benefit is highly dependent on recycle loop filtration performance and cost.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Gautam, A.K., Menkhaus, T.J. Performance and Fouling Analysis of Lignocellulosic Biomass Hydrolysate using Reverse Osmosis and Nanofiltration. Journal of Membrane Science, 2014, 451, 252-265.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Gurram, R.N., Menkhaus, T.J. Analysis and characterization of heat transfer fouling during evaporation of a lignocellulosic biomass process stream. Industrial and Engineering Chemistry Research, 2013, 52(32), 11111-11121.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Gurram, R.N., Menkhaus, T.J. Effects of pH, Slurry Composition and Operating Conditions on Heat Transfer Fouling during Evaporation of a Lignocellulosic Biomass Process Stream. Industrial and Engineering Chemistry Research, 2013, 52(32), 11122-11131.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Leberknight, J., Gautam, A.K., Menkhaus, T.J. Membrane separations for solid-liquid clarification within lignocellulosic biorefining processes. Biotechnology Progress, 2013, 29(5), 1246 1254.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Menkhaus, T.J. Guaram, R.N., Gautam, A.K. High efficiency production of biofuels using a continuous process with high sugar concentrations. Presented at the 35th Symposium on Biotechnology for Fuels and Chemicals, Portland, OR, May, 2013.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Schneiderman, S., Menkhaus, T.J., Gilcrease, P.C. Continuous Fermentation and Microfiltration Cell Recycle Applied to a Solids-free, Very High Gravity Lignocellulose Hydrolysate. Submitted to present at the 35th Symposium on Biotechnology for Fuels and Chemicals, Portland, OR, May, 2013.
- Type:
Conference Papers and Presentations
Status:
Under Review
Year Published:
2014
Citation:
Schneiderman, S., Rensch, G., Menkhaus, T.J., Gilcrease, P.C. .Continuous ethanol fermentation with tangential flow filtration cell recycle applied to a concentrated, solids-free softwood hydrolysate. Submitted for Presentation at the 36th Symposium on Biotechnology for Fuels and Chemicals, Clearwater Beach, FL, April, 2014.
- Type:
Conference Papers and Presentations
Status:
Under Review
Year Published:
2014
Citation:
Schneiderman, S., Gurram, R., Menkhaus, T.J., Gilcrease, P.C. .Techno-economic analysis of a softwood ethanol process featuring sugars concentration and continuous fermentation with cell recycle. Submitted for Presentation at the 36th Symposium on Biotechnology for Fuels and Chemicals, Clearwater Beach, FL, April, 2014.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2013
Citation:
Gautam, A.K. High Efficiency Membrane Materials for Biorenewable Processing. Ph.D. Dissertation, South Dakota School of Mines and Technology, Rapid City, SD, Dec, 2013.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2013
Citation:
Gurram, R.N. Evaluation, Optimization, and Implementation of Advanced Separation Processes for Next Generation Biorenewable Processing. Ph.D. Dissertation, South Dakota School of Mines and Technology, Rapid City, SD, September, 2013.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2013
Citation:
Leberknight, J. Integration of Membrane Separation Technologies within Biorefining:Performance Evaluation, Fouling Analysis, Modeling, and New Membrane Development.Ph.D. Dissertation, South Dakota School of Mines and Technology, Rapid City, SD, July,2013.
|
Progress 12/15/09 to 12/14/13
Outputs
Target Audience: Presentations have been made to, and discussions have proceeded, with industrial practitioners developing processes for conversion of lignocellulosic biomass into ethanol and other valuable biorenewable products. Publications have been made in leading biotechnology and bioprocessing journals highlighting major results and discoveries from this project. In addition, project directors have communicated with scientific researchers at other academic institutions who have requested information about the processes. Collaborative work has also been completed with Argonne National Laboratory and discussed with the National Renewable Energy Laboratory. Classroom instruction has included lecture and laboratory sessions with emphasis placed on the most current results of this study, which will improve biorenewable processing. In addition, tours of laboratories and industrial facilities have been included. The primary participant has been college undergraduate students, along with a small number of K-12 students and college graduate students. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Graduate students (5 total) working on the project have had many opportunities to learn valuable skills associated research and development of biorenewalbe products. All students have not only learned general methodologies associated with conducting research, but have also had ample hands-on opportunities to operate technical instruments such as SEM, AFM, FT-IR, UV-Vis, HPLC/UPLC, GC, and fermentation equipment. Many have also designed and manufactured custom instrumentation needed for the different goals of the project. Throughout the duration of the project, all students have completed work within a specifically designed program of study to take courses closely aligned with the biorenewable processing industry, as all participants have been associated with the Ph.D. program in Chemical and Biological Engineering at the South Dakota School of Mines and Technology. In addition to technical competencies acquired, students have had opportunities to more fully develop soft skills such as management (working with undergraduate students – 2 total) and communication (publications, presentations, discussions with peers at national/international meetings, etc.). How have the results been disseminated to communities of interest? The results have been disseminated through multiple publications, presentations, classroom lectures and outreach presentations. Publications and presentations have been detailed within the "Products" section of this report. Outreach activities have included hands-on demonstrations, active participation exercises and tours for K-12 students, including: Engineers Week, Girls Day, Science and Technology Camps and the Native American GEAR UP Program. Over 500 K-12 students from a variety of grade levels and demographics have participated in the activities. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
For evaporation, it was determined that crystallization of inorganic salts was a major contributor to surface fouling. This could be controlled by using lower temperatures for the operation and eliminating large amounts of acid/base additions during pretreatment processes. In addition, while removing insoluble solids did reduce some temporary fouling (lignin was easily removed from the evaporator surface after operation), the inclusion of insoluble solids actually reduced the more problematic “permanent” fouling (very difficult to remove without extensive cleaning – physically and chemically) caused by polymerization of sugar and other soluble compounds at the surface. Similarly, operating conditions were determined that minimized the severe fouling observed. By increasing hydrodynamic shear at the evaporator surface the fouling induction period (time before fouling was initiated) and rate of fouling were both dramatically reduced. In addition, by avoiding conditions where full surface film boiling was prominent, fouling was also reduced. During the evaporation process, glucose was concentrated in direct proportion to the amount of vapor removed with no generation of sugar degradation products. Furfural was completely collected in the condensate, while hydroxymethyl furfural and acetic became more concentrated with the sugars in the final product, even though a portion of these inhibitory compounds were evaporated. For reverse osmosis (RO) it was found that even though fouling of the membrane surface was an important consideration that reduced permeate flux, the most influential resistance came from soluble compounds, including the concentrated sugars themselves. The osmotic pressure generated on the feed side of the membrane during concentration of the sugars was responsible for the majority of the flux decline. Thus, there were severe flux declines at approximately 80 g/L of total sugars limited the applicability of RO for concentrating hydrolysate. However, removal of other soluble compounds (especially acetic acid, which has a disproportionately high osmotic pressure) helped alleviate this concern to some extent. Using different RO and nanofiltration (NF) membranes it was determined that NF was capable of separating inhibitory compounds from sugars. NF membranes concentrated sugars while removing/separating inhibitory compounds such as acetic acid, furfural and hydroxymethyl furfural. It was also found that complete removal of all insoluble solids was essential for successful operation. Thus, extensive microfiltration prior to RO would likely be needed for industrial application. Modified membrane surfaces were used to correlate membrane properties to fouling. It was found that by incorporating weak acid or weak base modifiers on the membrane surface, fouling was substantially reduced. We determined that lignin components (both soluble and insoluble) were the primary fouling constituents and by using charged (either positive or negative) hydrophilic mono-layers at the surface the fouling interaction was mitigated. A defined hydrolysate was prepared based on the assumption of a 4 fold sugars concentration via evaporation after inhibitor removal. This was compared to a defined “raw” hydrolysate representing a non-concentrated, inhibitor rich medium. The results of fermentation of these two media showed a 2.8 times higher ethanol production rate with 4.2 times higher final ethanol concentration in the concentrated, treated hydrolysate as compared to the “raw” hydrolysate, demonstrating the benefits of concentrating the hydrolysate prior to fermentation. The kinetic model developed previously was used to predict operating conditions for a continuous fermentation with microfiltration cell recycle. Filtration fouling severely reduced productivity by limiting the dilution rate at the desired recycle rate. After demonstrating the feasibility of operating the continuous system, focus was shifted back to studying the effects of inhibitory compounds on S. cerevisiae. Because the furan inhibitors are metabolizable, they may be held at very low concentrations in a continuous system by being reduced by the organism as they are added. As expected, higher cell densities led to faster overall rates and metabolism of inhibitors, but yields were affected, with lower cell mass produced at higher starting cell density. The experiment also showed there may be a change in specific growth and production rates at very high cell masses. The overall goal was to develop and optimize a chemostat with cell recycle system (CWCR) to ferment a concentrated pine hydrolysate. Higher ethanol productivities have been demonstrated previously in CWCR fermentors for high gravity (concentrated sugars) feedstocks; in addition, it was hypothesized that HMF-furfural reduction in a CWCR would minimize their inhibition effects. Before a CWCR system could be designed, a working kinetic model with appropriate inhibition terms was needed. Because fermentation inhibition is highly dependent on hydrolysate composition and the yeast strain used, batch experiments were used to obtain kinetic data specific to our fermentation system. Rather than using a trial-and-error approach to determine the necessary kinetic inhibition terms, we developed a novel DoE-based method for determining which inhibitors had a significant effect on our hydrolysate fermentation kinetics. This method correctly identified ethanol as the major inhibitor for our system; but because it was designed to only look for two factor interactions, it did not identify a significant three-factor, sum ofinhibitors (acetic acid + HMF + furfural) term. A working kinetic model with the necessary inhibition terms was then regressed from our batch fermentation data; r2 values for individual runs varied from 0.77 to 0.97. Bench-scale CWCR fermentations were then used to validate our batch-derived kinetic model and its predictions for enhanced ethanol productivity. To optimize the CWCR system, membranes with pore sizes varying from 300 KDa to 0.65 micron were tested; smaller pore sizes led to less flux decline, indicating that ultrafiltration membranes are more resistant to fouling in our system. CWCR performance with ethanol as the only inhibitor matched kinetic model predictions; ethanol productivities up to 36 g/l/h (a 10 fold improvement over low cell density batch runs) and cell densities up to 85 gDW/l were observed. When our CWCR was fed a real high gravity pine hydrolysate, an 8 fold improvement in ethanol productivity (16 g/l/h) over low cell density batch fermentation was observed. This improvement was partly due to an 80%reduction in the combined HMF-furfural concentration compared to the feed concentration. A specially developed techno-economic analysis model was developed using AspenPlus simulation software. The model compared the proposed process improvements (concentration of the raw hydrolysate by evaporation or nanofiltration and use of a CWCR fermentor) to a base process with no concentration and batch fermentation. Rigorous designs were used to estimate capital and operating costs for the proposed alternatives. This analysis indicated that hydrolysate sugars concentration has the potential to reduce distillation energy requirements by 75% (when concentrated to 200 g/l); however, overall savings are dependent on the concentration process with nanofiltration being the preferred option. A CWCR system has the potential to reduce equivalent annual operating cost (EAOC) by up to 9% over batch operation by significantly reducing fermentor size, but its benefit is highly dependent on recycle loop filtration performance and cost.
Publications
|
Progress 12/15/11 to 12/14/12
Outputs
OUTPUTS: Activities in the third year of the project were again divided into two parallel tasks: (1) evaluation of separations operations (evaporation, reverse osmosis [RO], and solids/cells removal) required for concentrating sugars and recycling fermentation organisms, and (2) evaluation of fermentation alternatives (including continuous fermentations) with varying sugars and inhibitory compound concentrations. The two tasks were also merged by evaluating fermentation efficiencies using concentrated biomass hydrolysate in batch and continuous modes. In all cases, dilute acid pretreatment and standard enzymatic hydrolysis of a ponderosa pine substrate with commercial enzymes was used as the test slurry. Having established operating windows for each separation operation in year one and completing a pragmatic evaluation of not only the ability to concentrate sugars, but also on the fate of potential inhibitory compounds in year two, we focused on options to increase process efficiencies in year three. We continued fundamental investigations exploring fouling of the heat exchanger or membrane surfaces using a combination of spectroscopic, microscopic, and mathematical modeling techniques. For evaporation a specially designed annular fouling probe made from stainless steel was employed, while for RO thin-film polyamide chemistry was used extensively. In both cases tailored surface chemistries were explored to minimize fouling and improve process robustness, ease of cleaning, and reduce operating costs, including use of a new UV-chamber for surface modifications. Using these techniques we were able to improve evaporation processing time before threshold fouling by over 8-fold and reduced RO membrane fouling by a factor of 20. Within the fermentation studies, a new collaboration was formed with the math department at the South Dakota School of Mines and Technology to establish rigorous statistical methods and analysis of the complex interactions taking place during fermentation. Experimental systems were established and tested that allow our team to evaluate complex continuous fermentations with cell recycle. Fermentation research in in year three focused on two main areas: Experiments to validate and extend the kinetic inhibition model developed in 2011, and preliminary continuous fermentations with cell recycle. During the third year of the project, four graduate students pursuing a Ph.D in chemical engineering, and one undergraduate chemical engineering student were financially supported and trained through the activities mentioned above. Project investigators presented at several major conferences, including the 34th Symposium on Biotechnology for Fuels and Chemicals (two presentations), the Materials Research Society Annual Meeting (one presentation), the American Filtration and Separation Society Annual Meeting (two presentations) and the North American Membrane Society Annual Meeting (one presentation). In addition, one invited seminar was presented at the National Renewable Energy Laboratory. PARTICIPANTS: Dr. Todd J. Menkhaus, Assistant Professor of Chemical Engineering at South Dakota School of Mines and Technology, acted as PI of the project with primary direction of biomass processing and separations operations. Dr. Patrick C. Gilcrease, Associate Professor of Chemical Engineering at South Dakota School of Mines and Technology, acted as Co-PI of the project with primary direction of fermentation evaluations. Mr. Amit Kumar Gautam, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the reverse osmosis aspects of the project. Mr. Raghu Nandan Gurram, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the evaporation aspects of the project. Mrs. Jennifer Leberknight, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the clarification of hydrolysate and fermentation broth (cell recycle) aspects of the project. Mr. Steven Schneiderman, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the fermentation analysis aspects of the project. Ms. Rosemary Squillace, B.S. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the membrane separation aspects of the project. TARGET AUDIENCES: Presentations have been made to, and discussions have proceeded, with industrial practitioners developing processes for conversion of lignocellulosic biomass into ethanol and other valuable biorenewable products. In addition project directors have communicated with scientific researchers at other academic institutions who have requested information about the processes. Collaborative work has also been completed with Argonne National Laboratory and discussed with the National Renewable Energy Laboratory. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
For evaporation, operating conditions were determined that minimized the severe fouling observed. By increasing hydrodynamic shear at the evaporator surface the fouling induction period (time before fouling was initiated) and rate of fouling were both dramatically reduced. In addition, by avoiding conditions where full surface film boiling was prominent, fouling was also reduced. For reverse osmosis (RO) and microfiltration, it was found that by incorporating weak acid or weak base modifiers on the membrane surface, fouling was substantially reduced. We determined that lignin components (both soluble and insoluble) were the primary fouling constituents and by using charged (either positive or negative) hydrophilic monolayears at the surface the fouling interaction was mitigated. The kinetic model developed previously was used to predict operating conditions for a continuous fermentation with microfiltration cell recycle. A Biostat B 2 liter fermentor (B. Braun) was connected to a 0.65 micron pore size tangential flow filtration unit (Millipore) fed with a peristaltic pump (Masterflex). The fermentor was continuously fed fresh media via another pump (Watson-Marlow) connected to a 50 liter media reservoir. The system was inoculated with S. cerevisiae D5A and operated for over 120 hours with the single filtration cartridge. Filtration fouling severely reduced productivity by limiting the dilution rate at the desired recycle rate. However, the results were encouraging, demonstrating the potential to operate the system for long periods of time and reach high steady state cell densities. After demonstrating the feasibility of operating the continuous system, focus was shifted back to studying the effects of inhibitory compounds on S. cerevisiae. Because the furan inhibitors are metabolizable, they may be held at very low concentrations in a continuous system by being reduced by the organism as they are added. An acetic acid screening showed that between 10 and 15 g/l acetic acid, a severe decrease in growth and ethanol productivity occurs, establishing an upper limit for the amount of acetic acid the system can tolerate. As expected, higher cell densities led to faster overall rates and metabolism of inhibitors, but yields were affected, with lower cell mass produced at higher starting cell density. The experiment also showed there may be a change in specific growth and production rates at very high cell masses. The preliminary model experiments are currently being integrated with data from the screening experiments to check for model accuracy and create a more detailed model of the process. A new program, ACSLX (Aegis Technologies) was recently acquired by the research group to numerically integrate differential equations while simultaneously fitting them to experimental data. Preliminary work with the program demonstrates a better fit to the experimental data than previously obtained. Future work during the one year no cost extension will focus on validating the improved model with more continuous fermentation runs and improving filtration flux and reducing fouling to improve overall productivity.
Publications
- Gautam, A.K., and Menkhaus, T.J. Surface Modified Reverse Osmosis and Nano-Filtration Membranes for the Production of Biorenewable Fuels and Chemicals. Proceedings, 2012 Materials Research Society Annual Meeting, Boston, MA, December, 2012.
- Schneiderman, S., Menkhaus, T.J., Gilcrease, P.C. Continuous Fermentation and Microfiltration Cell Recycle Applied to a Solids-free, Very High Gravity Lignocellulose Hydrolysate. Book of Abstracts, 34th Symposium on Biotechnology for Fuels and Chemicals, New Orleans, LA, May, 2012.
- Menkhaus, T.J. Guaram, R.N., Gautam, A.K. Performance Evaluation and Fouling Analysis of Reverse Osmosis Membranes and Evaporator Heating Surfaces during Concentration of Enzymatic Hydrolysate Sugars. Book of Abstracts, 34th Symposium on Biotechnology for Fuels and Chemicals, New Orleans, LA, May, 2012.
- Gautam, A.K and Menkhaus, T.J. Analysis of membrane fouling during protein recovery from whole corn kernel extracts. Book of Abstracts, 21st Annual North American Membrane Society Meeting, New Orleans, LA, July, 2012.
- Leberknight, J. and Menkhaus, T.J. Membrane Technology Integration within Lignocellulosic Biorefining: Fouling Analysis, Modeling, and New Membrane Development. Book of Abstracts, 2012 American Filtration Society Annual Meeting, Philadelphia, PA, October, 2012.
- Leberknight, J. and Menkhaus, T.J. Functionalized Nanofiber Membranes as a Separation Medium. Book of Abstracts, 2012 American Filtration Society Annual Meeting, Philadelphia, PA, October, 2012.
- Menkhaus, T.J. Advanced Separations for the Biopharmaceutical and Biorenewable Energy Industries. A Workshop presented at the 2012 AICHE Regional Conference, Rapid City, SD, March, 2012.
- Guaram, R. and Menkhaus, T.J. Opportunities and Challenges for Separations in Advanced Biorenewable Processing. Abstracts, National Renewable Energy Laboratory, Golden, CO, January, 2013.
|
Progress 12/15/10 to 12/14/11
Outputs
OUTPUTS: Activities in the second year of the project were again divided into two parallel tasks: (1) evaluation of separations operations (evaporation, reverse osmosis [RO], and solids/cells removal) required for concentrating sugars and recycling fermentation organisms, and (2) evaluation of fermentation alternatives with varying sugars and inhibitory compound concentrations. The two tasks were also merged by evaluating fermentation efficiencies using concentrated biomass hydrolysate. In all cases, dilute acid pretreatment and standard enzymatic hydrolysis of a ponderosa pine substrate with commercial enzymes was used as the test slurry. Having established operating windows for each separation operation, focus was placed on pragmatic evaluation of not only the ability to concentrate sugars, but also on the fate of potential inhibitory compounds. In addition, fundamental investigations exploring fouling of the heat exchanger or membrane surfaces were completed using a combination of spectroscopic, microscopic, and mathematical modeling techniques. For evaporation a specially designed annular fouling probe made from stainless steel was employed, while for RO thin-film polyamide chemistry was used extensively. Within the fermentation studies, a primary objective was to establish a mock fermentation medium that would mimic the results of actual hydrolysate. This was done in order to simplify analytical measurements of the fermentation experiments and to provide a reproducible and easily controlled medium for reliable and timely analysis of this operation. Statistical design of experiments was employed throughout the fermentation studies to help understand important two-factor relationships between various competing variables (e.g., input levels of sugar concentrations, inhibitor concentrations, and output parameters such as production efficiency). By careful control of the different operating variables and measurement of output characteristics, a detailed kinetic model was created to quantify and predict fermentation performance based on chosen inputs. During the second year of the project, four graduate students pursuing a Ph.D in chemical engineering, and one undergraduate chemical engineering student were financially supported and trained through the activities mentioned above. Project investigators attended the 2011 National American Institute of Chemical Engineers Conference in Minneapolis, MN, to present results and discuss related projects with other scientists and engineers. PARTICIPANTS: Dr. Todd J. Menkhaus, Assistant Professor of Chemical Engineering at South Dakota School of Mines and Technology, acted as PI of the project with primary direction of biomass processing and separations operations. Dr. Patrick C. Gilcrease, Associate Professor of Chemical Engineering at South Dakota School of Mines and Technology, acted as Co-PI of the project with primary direction of fermentation evaluations. Mr. Amit Kumar Gautam, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the reverse osmosis aspects of the project. Mr. Raghu Nandan Gurram, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the evaporation aspects of the project. Mrs. Jennifer Leberknight, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the clarification of hydrolysate and fermentation broth (cell recycle) aspects of the project. Mr. Steven Schneiderman, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the fermentation analysis aspects of the project. Ms. Rosemary Squillace, B.S. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the membrane separation aspects of the project. TARGET AUDIENCES: Presentations have been made to, and discussions have proceeded, with industrial practitioners developing processes for conversion of lignocellulosic biomass into ethanol and other valuable biorenewable products. In addition project directors have communicated with scientific researchers at other academic institutions who have requested information about the processes. Collaborative work has also been completed with Argonne National Laboratory. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
For evaporation, it was determined that crystallization of inorganic salts was a major contributor to surface fouling. This could be controlled by using lower temperatures for the operation and eliminating large amounts of acid/base additions during pretreatment processes. In addition, while removing insoluble solids did reduce some temporary fouling (lignin was easily removed from the evaporator surface after operation), the inclusion of insoluble solids actually reduced the more problematic "permanent" fouling (very difficult to remove without extensive cleaning - physically and chemically) caused by polymerization of sugar and other soluble compounds at the surface. For reverse osmosis (RO) it was found that even though fouling of the membrane surface was an important consideration that reduced permeate flux, the most influential resistance came from the concentrated sugars themselves. The osmotic pressure generated on the feed side of the membrane during concentration of the sugars was responsible for the majority of the flux decline. Thus, there were severe flux declines at approximately 80 g/L of total sugars limited the applicability of RO for concentrating hydrolysate. However, removal of other soluble compounds (especially acetic acid, which has a disproportionately high osmotic pressure) helped alleviate this concern to some extent. It was also found that complete removal of all insoluble solids was essential for successful operation. Thus, nanofiltration prior to RO would likely be needed for industrial application. Experimentally determined specific growth rates and yield coefficients were used to regress the kinetic fermentation parameters needed to predict the time profiles of cell mass, glucose concentration, and ethanol concentration. The resulting model indicated that furfural was the most inhibitory on a per unit mass basis, followed by acetic acid and HMF. Because acetic acid was the inhibitor present in largest quantity in acid pre-treated pine wood hydrolysate, a screening experiment was designed to isolate its effect when the other inhibitor concentrations are held constant. It was demonstrated that a large decrease in performance occurred at acetic acid concentrations greater than 10 g/l, with a 40% decrease in volumetric ethanol productivity when adjusting acetic acid from 10 to 15 g/l. This suggested an upper limit for acetate concentration that would have to be met, and suggested that some acetate removal process is needed (raw hydrolysate has acetic acid concentrations ranging from 7 to 12 g/l). A defined hydrolysate was prepared based on the assumption of a 4 fold sugars concentration via evaporation after inhibitor removal. This was compared to a defined "raw" hydrolysate representing a non-concentrated, inhibitor rich medium. The results of fermentation of these two media showed a 2.8 times higher ethanol production rate with 4.2 times higher final ethanol concentration in the concentrated, treated hydrolysate as compared to the "raw" hydrolysate, demonstrating the benefits of concentrating the hydrolysate prior to fermentation.
Publications
- Gurram, R.N., Datta, S., Lin, Y.J., Snyder, S.W., Menkhaus, T.J. Removal of enzymatic and fermentation inhibitory compounds from biomass slurries for enhanced biorefinery process efficiencies. Bioresource Technology, 102 (17), 7850-7859, 2011.
- Menkhaus, T.J. Guaram, R.N., Lin, Y, Data, S., Snyder, S. Removal of Inhibitory Compounds from Biomass Slurries for Enhanced Enzymatic Hydrolysis and Fermentation Efficiencies. Book of abstracts, Society of Industrial Microbiology, 33rd Symposium on Biotechnology for Fuels and Chemicals, Seattle, WA, May, 2011.
- Leberknight, J.; Gautam, A.; Menkhaus, T. Evaluation of Membrane Separations Opportunities within Lignocellulosic Biorefining Processes: Tailoring Membrane Properties. Book of Abstracts, 2011 AIChE National Conference, Minneapolis, MN, October, 2011.
- Gurram, R.; Gilcrease, P.; Menkhaus, T. Analysis of Heat Transfer Fouling Characteristics during Evaporation of Lignocellulosic Biomass Process Streams. Book of Abstracts, 2011 AIChE National Conference, Minneapolis, MN, October, 2011.
- Gautam, A.; Gilcrease, P.; Menkhaus, T. Characterization, Evaluation, and Fouling Analysis of Reverse Osmosis Membranes for Concentrating Sugars In a Lignocellulosic Biomass Hydrolysate. Book of Abstracts, 2011 AIChE National Conference, Minneapolis, MN, October, 2011.
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Progress 12/15/09 to 12/14/10
Outputs
OUTPUTS: Activities in the first year of the project were divided into two parallel tasks: (1) evaluation of separations operations (evaporation, reverse osmosis [RO], and solids/cells removal) required for concentrating sugars and recycling fermentation organisms, and (2) evaluation of fermentation alternatives with varying sugars and inhibitory compound concentrations. Experimental equipment and arrangements have been designed and produced for all phases of the project, including design and fabrication of an annular evaporation fouling probe capable of measuring fouling characteristics during evaporation of biomass-derived slurries, a reverse osmosis unit capable of evaluating membrane fouling during water removal from lignocellulosic enzyme hydrolysate, and a solid-liquid membrane separation unit for studying requisite suspended solids removal prior to RO or evaporation and for recycling of fermentation organisms. In all cases, dilute acid pretreatment and standard enzymatic hydrolysis of a ponderosa pine substrate with commercial enzymes was used as the test slurry. Experiments were conducted within each separation operation to determine feasibility limits and initial operating expectations. Batch fermentation experiments were completed with both defined mixtures and real hydrolysate to evaluate the impact of different concentrations of sugars and inhibitory compounds on the ability of Saccharomyces Cerevisiae D5A strain to produce ethanol. In one case a small pilot scale batch (4 L) of pine hydrolysate was treated by evaporation to concentrate sugars and used to establish an initial gauge for fermentation robustness with high sugar concentration pine wood slurry. During the first year of the project, four graduate students pursuing a Ph.D in chemical engineering were financially supported and trained through the activities mentioned above. Project investigators attended the 2010 National American Institute of Chemical Engineers Conference in Salt Lake City, Utah, to present results and discuss related projects with other scientists and engineers. PARTICIPANTS: Dr. Todd J. Menkhaus, Assistant Professor of Chemical Engineering at South Dakota School of Mines and Technology, acted as PI of the project with primary direction of biomass processing and separations operations. Dr. Patrick C. Gilcrease, Associate Professor of Chemical Engineering at South Dakota School of Mines and Technology, acted as Co-PI of the project with primary direction of fermentation evaluations. Mr. Amit Kumar Gautam, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the reverse osmosis aspects of the project. Mr. Raghu Nandan Gurram, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the evaporation aspects of the project. Mrs. Jennifer Leberknight, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the clarification of hydrolysate and fermentation broth (cell recycle) aspects of the project. Mr. Steven Schneiderman, Ph.D. chemical engineering student at South Dakota School of Mines and Technology, was trained in experimental procedures and conducted laboratory work associated primarily with the fermentation analysis aspects of the project. TARGET AUDIENCES: Presentations have been made to, and discussions have proceeded, with industrial practitioners developing processes for conversion of lignocellulosic biomass into ethanol and other valuable biorenewable products. In addition project directors have communicated with scientific researchers at other academic institutions who have requested information about the processes. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Task one involved the initial evaluation of separations operations required for concentrating sugars and recycling/re-using fermentation organisms. Three operations were investigated: (1) evaporation, (2) reverse osmosis (RO), and (3) solid-liquid clarifications. For evaporation, it was determined that the rate of fouling was greatly influenced by the concentration of insoluble solids (primarily lignin) in the feed stream as well as the Reynolds number associated with flow within the evaporator. Lower concentrations of suspended solids in the slurry resulted in reduced fouling rates, lower heat transfer resistance and a higher overall heat transfer coefficient. Similarly, increasing the Reynolds number within the laminar flow regime allowed for improved heat transfer, although established heat transfer coefficient correlations were not predictive of results for the biomass slurry. During the evaporation process, being operated at a bulk temperature of 100 C and 1 atm, glucose was concentrated in direct proportion to the amount of vapor removed with no generation of sugar degradation products. Furfural was completely collected in the condensate, while hydroxymethyl furfural and acetic became more concentrated with the sugars in the final product. Future studies will evaluate different solution conditions and evaporator operating conditions to decrease the rate of fouling and maximize the concentration of sugars in the final product with low levels of inhibitory compounds. For RO, a thin-film composite polyamide membrane was found to provide the best flux with both a pure sugars solution as well as a pine wood hydrolysate. Sugar yield was above 95% with the majority of flux decline due to elevated osmotic pressure of the concentrated solution, and some permanent fouling. However, modification of membrane properties and/or RO process (e.g., careful selection of the upstream clarification operations) may improve the process, and this will be the focus of future work. Similarly, solid-liquid clarifications by membrane filtration, either as a pre-treatment step for RO or as the cell recycle/re-use operation associated with fermentation, were greatly influenced by the composition of the feed stream and properties of the membrane. The presence of lignin (insoluble and soluble) was speculated to have caused the greatest degree of irreversible fouling, especially with synthetic polymer membranes. New membrane materials and operating conditions are being explored to minimize this detrimental fouling. For task two, evaluation of fermentation alternatives with concentrated sugar streams, evaluations have shown that the presence of inhibitory compounds (acetic acid, furfural, hydroxymethyl furfural, and phenolics) greatly influence the rates and yields associated with fermentation, regardless of the concentration of sugars. No cell growth, sugar consumption, or ethanol production were observed when using an enzymatic hydrolysate that had been concentrated by evaporation. Detailed studies are on-going to fully understand the effects of sugars and inhibitory concentrations on the fermentation process.
Publications
- Gautam, A.K., Gilcrease, P.C., Christopher, L., and Menkhaus, T.J. Concentration of Fermentable Sugars within Lignocellulosic Biomass Hydrolysate by Reverse Osmosis: Effect of Membrane and Hydrolysate Properties and Operating Conditions. Book of Abstracts, 2010 AIChE National Conference, Salt Lake City, UT, November, 2010.
- Gurram, R.N., Gilcrease, P.C., Christopher, L., and Menkhaus, T.J. Analysis of Heat Transfer Fouling Characteristics during Evaporation of Clarified Pine Wood Hydrolysate to Concentrate Sugars. Book of Abstracts, 2010 AIChE National Conference, Salt Lake City, UT, November, 2010.
- Leberknight, J., Gautam, A.K., Gilcrease, P.C., Christopher, L., and Menkhaus, T.J. Evaluation of Microfiltration Membrane Fouling Mechanisms for Separations Applications with a Lignocellulosic Biorefinery. Book of Abstracts, 2010 AIChE National Conference, Salt Lake City, UT, November, 2010.
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