Matching Items (18)
Filtering by
- All Subjects: Biofuels
- All Subjects: wastewater
- Creators: Chemical Engineering Program
- Status: Published
Description
Microbial fuel cells (MFCs) promote the sustainable conversion of organic matter in black water to electrical current, enabling the production of hydrogen peroxide (H2O2) while making waste water treatment energy neutral or positive. H2O2 is useful in remote locations such as U.S. military forward operating bases (FOBs) for on-site tertiary water treatment or as a medical disinfectant, among many other uses. Various carbon-based catalysts and binders for use at the cathode of a an MFC for H2O2 production are explored using linear sweep voltammetry (LSV) and rotating ring-disk electrode (RRDE) techniques. The oxygen reduction reaction (ORR) at the cathode has slow kinetics at conditions present in the MFC, making it important to find a catalyst type and loading which promote a 2e- (rather than 4e-) reaction to maximize H2O2 formation. Using LSV methods, I compared the cathodic overpotentials associated with graphite and Vulcan carbon catalysts as well as Nafion and AS-4 binders. Vulcan carbon catalyst with Nafion binder produced the lowest overpotentials of any binder/catalyst combinations. Additionally, I determined that pH control may be required at the cathode due to large potential losses caused by hydroxide (OH-) concentration gradients. Furthermore, RRDE tests indicate that Vulcan carbon catalyst with a Nafion binder has a higher H2O2 production efficiency at lower catalyst loadings, but the trade-off is a greater potential loss due to higher activation energy. Therefore, an intermediate catalyst loading of 0.5 mg/cm2 Vulcan carbon with Nafion binder is recommended for the final MFC design. The chosen catalyst, binder, and loading will maximize H2O2 production, optimize MFC performance, and minimize the need for additional energy input into the system.
ContributorsStadie, Mikaela Johanna (Author) / Torres, Cesar (Thesis director) / Popat, Sudeep (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
Description
Due to the environmental problems caused by global warming, it has become necessary to reduce greenhouse gas emissions across the planet. Biofuels, such as ethanol, have proven to release cleaner emissions when combusted. However, large scale production of these alcohols is uneconomical and inefficient due to limitations in standard separation processes, the most common being distillation. Pervaporation is a novel separation technique that utilizes a specialized membrane to separate multicomponent solutions. In this research project, pervaporation utilizing ZIF-71/PDMS mixed matrix membranes are investigated to see their ability to recover ethanol from an ethanol/aqueous separation. Membranes with varying nanoparticle concentrations were created and their performances were analyzed. While the final results indicate that no correlation exists between nanoparticle weight percentage and selectivity, this technology is still a promising avenue for biofuel production. Future work will be conducted to improve this existing process and enhance membrane selectivity.
ContributorsHoward, Chelsea Elizabeth (Author) / Lind, Mary Laura (Thesis director) / Nielsen, David (Committee member) / Greenlee, Lauren (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor) / Materials Science and Engineering Program (Contributor)
Created2015-05
Description
The R-specific alcohol dehydrogenase (RADH or LVIS_0347) from Lactobacillus brevis LB19 was found to possess activity on several short chain aldehydes and ketones. This broad substrate specificity was previously uncharacterized. To demonstrate its relevance to the biofuels industry as well as its broader utility for chiral reductions, a detailed characterization was performed to further investigate the activity and function of RADH.
ContributorsHalloum, Ibrahim (Co-author) / Pugh, Shawn (Co-author) / Nielsen, David R. (Thesis director) / Rege, Kaushal (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
Description
This study was conducted to better understand the making and measuring of renewable energy goals by the federal government. Three different energy types are studied: wind, solar, and biofuel, for two different federal departments: the Department of Defense and the Department of Energy. A statistical analysis and a meta-analysis of current literature will be the main pieces of information. These departments and energy types were chosen as they represent the highest potential for renewable energy production. It is important to understand any trends in goal setting by the federal government, as well as to understand what these trends represent in terms of predicting renewable energy production. The conclusion for this paper is that the federal government appears to set high goals for renewable energy initiatives. While the goals appear to be high, they are designed based on required characteristics described by the federal government. These characteristics are most often technological advancements, tax incentives, or increased production, with tax incentives having the highest priority. However, more often than not these characteristics are optimistic or simply not met. This leads to the resetting of goals before any goal can be evaluated, making it difficult to determine the goal-setting ability of the federal government.
ContributorsStapleton, Andrew (Co-author) / Charnell, Matthew (Co-author) / Printezis, Antonios (Thesis director) / Kull, Thomas (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor) / Department of Supply Chain Management (Contributor)
Created2015-05
Description
Ethanol is a widely used biofuel in the United States that is typically produced through the fermentation of biomass feedstocks. Demand for ethanol has grown significantly from 2000 to 2015 chiefly due to a desire to increase energy independence and reduce the emissions of greenhouse gases associated with transportation. As demand grows, new ethanol plants must be developed in order for supply to meet demand. This report covers some of the major considerations in developing these new plants such as the type of biomass used, feed treatment process, and product separation and investigates their effect on the economic viability and environmental benefits of the ethanol produced. The dry grind process for producing ethanol from corn, the most common method of production, is examined in greater detail. Analysis indicates that this process currently has the highest capacity for production and profitability but limited effect on greenhouse gas emissions compared to less common alternatives.
ContributorsSchrilla, John Paul (Author) / Kashiwagi, Dean (Thesis director) / Kashiwagi, Jacob (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
Description
This document outlines the research work done by Shona Becwar in the process design and refinement for the production of sustainable butanol from Clostridium, along with the required background knowledge on the subject. The process that the microbiological organisms go through to produce butanol must be an oxygen free environment for up to 21 days with multiple perforations made into the environment in this period. There was not previously a cost effective method to do this, even in small scale. It was determined that using a butyl rubber septa would allow for the environment to be sustained during the growth process. The pervaporation process was losing butanol product at a rate of approximately 60%, changing the tubing from silicon to stainless steel allowed for a mere 7% loss during the separation process, greatly increasing the prospective of upscaling this process. These improvements to the sustainable butanol production process will allow for a more efficient, therefore more economically competitive product which can be used as a drop in equivalent to the current butanol market.
ContributorsBecwar, Shona Marie (Author) / Nielsen, David R. (Thesis director) / Staggs, Kyle (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The recovery of biofuels permits renewable alternatives to present day fossil fuels that cause devastating effects on the planet. Pervaporation is a separation process that shows promise for the separation of ethanol from biologically fermentation broths. The performance of thin film composite membranes of polydimethylsiloxane (PDMS) and zeolite imidazolate frameworks (ZIF-71) dip coated onto a porous substrate are analyzed. Pervaporation performance factors of flux, separation factor and selectivity are measured for varying ZIF-71 loadings of pure PDMS, 5 wt%, 12.5 wt% and 25 wt% at 60 oC with a 2 wt% ethanol/water feed. The increase in ZIF-71 loadings increased the performance of PDMS to produce higher flux, higher separation factor and high selectivity than pure polymeric films.
ContributorsLau, Ching Yan (Author) / Lind, Mary Laura (Thesis director) / Durgun, Pinar Cay (Committee member) / Lively, Ryan (Committee member) / Barrett, The Honors College (Contributor) / School of International Letters and Cultures (Contributor) / Chemical Engineering Program (Contributor)
Created2014-05
Description
Nitrate (NO3- ) and selenate (SeO42-) are common contaminants found in mining wastewater. Biological treatment has proved successful using bacteria capable of respiring NO3- into nitrogen gas and SeO42- into Se°. The Membrane Biofilm Reactor (MBfR) utilizes biofilm communities on the surface of hollow-fiber membranes to transform oxidized water contaminants into innocuous reduced products. For this project, I set up two MBfRs in a lead and lag configuration to reduce NO3- [input at ~40-45 mg NO3-N/L] and SeO42- [0.62 mg/L], while avoiding sulfate (SO42-) [~1600-1660 mg/L] reduction. Over the course of three experimental phases, I controlled two operating conditions: the applied hydrogen pressure and the total electron acceptor loading. NO3- in the lead MBfR showed average reductions of 50%, 94%, and 91% for phases I, II, and III, respectively. In the lag MBfR, NO3- was reduced by 40%, 96%, and 100% for phases I, II, and III. NO2- was formed in Stage I when NO3- was not reduced completely; nevertheless NO2- accumulation was absent for the remainder of operation. In the lead MBfR, SeO42- was reduced by 65%, 87%, and 50% for phases I, II, and III. In the lag MBfR, SeO42- was reduced 60%, 27%, and 23% for phases I, II, and III. SO42- was not reduced in either MBfR. Biofilm communities were composed of denitrifying bacteria Rhodocyclales and Burkholderiales, Dechloromonas along with the well-known SeO42--reducing Thauera were abundant genera in the biofilm communities. Although SO42- reduction was suppressed, sulfate-reducing bacteria were present in the biofilm. To optimize competition for electron donor and space in the biofilm, optimal operational conditions were hydrogen pressures of 26 and 7 psig and total electron acceptor loading of 3.8 and 3.4 g H2/m2 day for the lead and lag MBfR, respectively.
ContributorsMehta, Sanya Vipul (Author) / Rittmann, Bruce (Thesis director) / Ontiveros-Valencia, Aura (Committee member) / Chemical Engineering Program (Contributor) / School of International Letters and Cultures (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Microbial fuel cells (MFCs) facilitate the conversion of organic matter to electrical current to make the total energy in black water treatment neutral or positive and produce hydrogen peroxide to assist the reuse of gray water. This research focuses on wastewater treatment at the U.S. military forward operating bases (FOBs). FOBs experience significant challenges with their wastewater treatment due to their isolation and dangers in transporting waste water and fresh water to and from the bases. Even though it is theoretically favorable to produce power in a MFC while treating black water, producing H2O2 is more useful and practical because it is a powerful cleaning agent that can reduce odor, disinfect, and aid in the treatment of gray water. Various acid forms of buffers were tested in the anode and cathode chamber to determine if the pH would lower in the cathode chamber while maintaining H2O2 efficiency, as well as to determine ion diffusion from the anode to the cathode via the membrane. For the catholyte experiments, phosphate and bicarbonate were tested as buffers while sodium chloride was the control. These experiments determined that the two buffers did not lower the pH. It was seen that the phosphate buffer reduced the H2O2 efficiency significantly while still staying at a high pH, while the bicarbonate buffer had the same efficiency as the NaCl control. For the anolyte experiments, it was shown that there was no diffusion of the buffers or MFC media across the membrane that would cause a decrease in the H2O2 production efficiency.
ContributorsThompson, Julia (Author) / Torres, Cesar (Thesis director) / Popat, Sudeep (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Hydrothermal Liquefaction of Algae represents one of many pathways for the sustainable replacement of fossil fuels in transportation. When processing and researching algal biofuel, determination of the higher heating value (HHV) is paramount. Bomb calorimetry represents to current method for direct determination of HHV. When determining HHV’s indirectly, the industry standard is using one of many linear correlations relating elemental composition to HHV. Most of these correlations were developed from coal industry data, meaning that they do not necessarily fit algal product data well. In this study bomb calorimetry data and CHNS/O elemental composition data were collected for Chlorella, Micract, GS 5587.1, Kirchnella, and Gal 87.1 MM8 algae species. This data was added to CHNS/O and HHV values for other algal products in literature, and utilized to test the accuracy of the Dulong, Gumz, Vandralek and Boie correlations for algae products. Several preliminary algae specific correlations were proposed through a linear regression model of the data. Of the 5 samples tested, Kirchnella exhibited the highest HHV (23.2405 ± 0.0216 MJ/kg) and Chlorella exhibited the lowest (20.2055 ± 0.0484 MJ/kg). For both the experimental, and literature CHNS/O vs HHV data, the Vandralek and Boie correlations provided the best approximations in this study. For the totality of the data collected and researched in this study, 6 of 8 proposed correlations outperformed the Vandralek equation for HHV approximation. The most promising proposed correlations incorporated multiple linear regressions for elemental fractions of CHS, CHSO and CHNSO. Being that only 20 distinct algal product samples were regressed to create the proposed correlations, more data should be incorporated before publication of a final correlation. This study should serve as a starting point for the compilation of an exhaustive database for algal product assay and HHV data.
ContributorsCopp, Connor Joseph (Author) / Deng, Shuguang (Thesis director) / Muppaneni, Tapaswy (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05