Progress 10/13/10 to 10/12/15
Outputs
Target Audience:Researchers in algae-based bioenergy systems Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Supported five MS students in Biological and Agricultural Engineering. How have the results been disseminated to communities of interest?Professional conferences, invited presentations, journal articles, theses What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
1.Design, develop, and evaluate unit operations to improve sustainability in algae to biofuel and bioproduct systems. Systems were successfully designed to grow microalgae in open ponds and photobioreactors. These systems were tested in the lab and at the Pecos, TX Research Center under outdoor conditions. Electgrolytic harvesting of green algaewas successfully developed and tested in both laboratory and pilot plant settings. Energy consumption was reduced by 90% over baseline values. 2.Develop and evaluate operational and logistics strategies for algae to biofuel and bioproduct systems in order to optimize the process. The algae biofuel production process was modeled using ExtendSim from laboratory scale to a full-size production facility of 1000 acre-ft of ponds. The model included sequenced batch growth, seasonal effects, labor use, random growth failures, and several different harvesting methods. Various operatin parameters were explored and senitivities were determined. Opportunities to reduce operating and capital costs were identified. 3.Apply life-cycle assessment (LCA) to evaluate the sustainability of algae to biofuel and bioproduct systems. Data from the full-scale model was evaluated in the context of overall biofuel economics by Monte Carlo simulation. It was determined that the amount of reduction required in capical and operating costs could not make algae biofuels profitable without additional income streams (e.g. high value co-products) and continued high crude oil prices.
Publications
- Type:
Theses/Dissertations
Status:
Accepted
Year Published:
2011
Citation:
Stepp, J. W. 2011. Discrete Event Model Development Of Pilot Plant Scale Microalgae Facilities: An Analysis Of Productivity And Costs. Master of Science. Texas A&M University, Biological and Agricultural Engineering, College Station, Texas
- Type:
Theses/Dissertations
Status:
Accepted
Year Published:
2014
Citation:
Murdock, J. D. 2014. Low Cost, Low Energy, Method Of Dewatering Cultures Of The Green Microalgae Nannochloris Oculata: Electrocoagulation. Texas A&M University, Biological and Agricultural Engineering, College Station, TX
- Type:
Theses/Dissertations
Status:
Accepted
Year Published:
2012
Citation:
Lassig, J. W. 2012. Determining An Appropriate Method To Simulate Pump Shear On The Diatom Nitzschia Sp. And A Methodology To Quantify The Effects. Texas A&M University, Biological and Agricultural Engineering, College Station, Texas
- Type:
Theses/Dissertations
Status:
Accepted
Year Published:
2012
Citation:
Morrison, T. L. 2012. Electrolytic Methods As A Cost And Energy Effective Alternative Of Harvesting Algae For Biofuel. Texas A&M University, Biolotical and Agricultural Engineering, College Station, TX
- Type:
Theses/Dissertations
Status:
Accepted
Year Published:
2011
Citation:
Luedecke, P. R. 2011. Developing Optimal Growth Parameters For The Green Microalgae Nannochloris Oculata And The Diatom Nitzschia Sp. For Large Scale Raceway Producton Texas A&M University, Biological and Agricultural Engineering, College Station, TX
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Progress 10/01/13 to 09/30/14
Outputs
Target Audience:
Nothing Reported
Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest? Published in a journal article and included in the final NAABB project report. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Work on electrocoagulation (EC) harvesting of algae was completed. EC was shown to concentrate N. oculata from approximately 0.1% to 6% at a cost of $0.04 per kg of algal biomass. This generated a significant savings in both capital and operating costs over the baseline technology of centrifugication. Data were provided for LCA and economic analysis.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Richardson, J. W., M. D. Johnson, R. Lacey, J. Oyler, and S. Capareda. 2014. Harvesting and extraction technology contributions to algae biofuels economic viability. Algal Research 5: 70-78.
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Researchers in algal-based bioenergy systems Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Supported one Master of Science graduate student. How have the results been disseminated to communities of interest? Professional conferences, invited presentations, journal articles, theses What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Two electrolytic methods were examined in the laboratory for their efficiency of concentrating NAABB species of microalgae from dilute solutions: electrolytic coagulation and electrolytic flocculation. Electrolytic coagulation uses reactive metallic electrodes to produce positively charged ions that induce coagulation of the negatively charged microalgae cells. This results in the algae cells being removed from the solution. Electro-flocculation utilizes inert electrodes and moves negatively charged algal cells to the positively charged anode. No ions are released into the solution. Once the cells reach the anode, the negative charge is dropped from the microalgae and they are able to form flocs, which settle and can be recovered. Both of the electrolytic harvesting methods tested have the potential for scale up to commercial volumes. The goal of this project was to demonstrate performance of electrocoagulation and electro-flocculation at laboratory scale (100 mL to 2.2 L) and at pilot scale (100 – 1000 L hr-1). The objectives of this research were to 1. Demonstrate the efficacy of electrocoagulation as a harvesting method for algae at lab and pilot scale and 2. Demonstrate the efficacy of electro-flocculation as a harvesting method for algae at lab and pilot scale. Electro-coagulation was found to offer reduced capital and operating costs compared to harvesting with a centrifuge. Operating costs for electrocoagulation was approximately 5% of the operating costs of the centrifuge. The greatest recovery of algae was obtained with no pretreatment processes. Aluminum was the preferred electrode based on laboratory studies yielding the greatest recovery at the least amount of energy input. Additionally, mineral tolerances in cattle feed for aluminum was higher (2x to 10x) compared with other electrode materials and aluminum had cost advantages over nickel. Two field tests of electrocoagulation at pilot scale were performed during 2011 and 2012 at the Texas A&M AgriLife Research Experiment Station in Pecos, Texas. The goal of these tests was to evaluate a commercial, electrocoagulation system for application to harvesting algae for biofuels production. Demonstrations during 2011 determined that the equipment, originally intended for wastewater treatment and much lower concentrations of contaminants, could effectively remove algae from a dilute solution (approximately 0.1% TVS). Lipid bearing algae could be harvested with equal facility as non-lipid bearing algae, but algae concentration was not as great as noted in the laboratory, with the final concentration of the sediment at 3 – 4% AFDW versus 6 – 8% AFDW seen in the lab. Consequently, a second stage of dewatering may be required at commercial scale depending on the lipid extraction method employed. Stainless steel electrodes were determined to perform better during pilot scale electrocoagulation experiments versus the aluminum electrodes used during the first year and found to be the best in the laboratory studies. However, separation with either electrode during the second year of pilot studies was not as good as in the first year. This was attributed to differences in the water source for the algae media, as all other factors were identical. A significant amount of sediment was generated from the Pecos well water during electrocoagulation and this was thought to contribute to the high ash content noted in harvested algae biomass. Lastly, an electrocoagulation system was operated at a much higher flow rate (15 gpm) and a complete 4550 gallon batch of algae was harvested. The electro-flocculation experiments at lab scale proved the technology to be viable and on a par with electrocoagulation in terms of energy consumption and biomass recovery. The performance curves for the range of culture densities did not vary significantly. The lack of variation may offer opportunities for flexibility in design of the harvesting system as a whole when considering growth/retention time of an algal culture. A advantage of using electro-flocculation technology was that no electrode material was consumed and thus, no mineral was deposited to the biomass. Electro-flocculation was not successfully implemented in the field, because the voltage rectifier did not sufficient controls to deliver low levels of current necessary to operate in that mode. Electrocoagulation and electro-flocculation appear to offer significant advantages over centrifuge harvesting, particularly with regard to reduced energy costs and the opportunity to automate and reduce labor costs. Centrifuges, even automated ones, require a trained operator attending to them whereas the electrocoagulation equipment was designed to be fully automated in typical wastewater treatment facilities. There is a need for additional understanding of the interaction of water chemistry with the electrolytic processes in order to better explain the observations during the second year field studies. There is also an opportunity to implement a field scale electro-flocculation system if a more precisely controlled rectifier were available. Electro-flocculation eliminates ion residue in the harvested biomass and would be a preferred method since the amount of separation and energy consumption were on par with electrocoagulation.
Publications
- Type:
Theses/Dissertations
Status:
Accepted
Year Published:
2013
Citation:
Kovalcik D. Algal harvesting for biodiesel production: Comparing Centrifugation and Electrocoagulation [Master of Science]. College Station, Texas: Texas A&M University
- Type:
Other
Status:
Awaiting Publication
Year Published:
2013
Citation:
Lacey RE. NAABB Final Report: Project 3.1.4 Electrolytic Harvesting Methods. College Station: Texas A&M University, 2013.
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: A commercial scale algae cultivation and harvesting facility was defined to incorporate 1000 ac-ft of water. At an expected 9-inch depth this will constitute 1,333 surface acres of pond area. This hypothetical cultivation facility was designed as twenty 50 ac-ft modules operated in parallel. This facility was modeled using discrete event modeling (DEM) techniques. A number of assumptions were necessary in order to model commercial scale algae production and determine the operating parameters. Specifically, four key assumptions were necessary to better approximate real world conditions: 1. Algal growth followed seasonal patterns, 2. There was inherent variability at each stage, 3. There was the probability of a failure and loss in a batch at any stage of the process, and 4. There was no surge capacity between stages. Algae grown in open, outdoor raceway ponds are subject to changes in ambient temperature, solar intensity, photoperiod, and other environmental factors. These factors result in a seasonal growth rate which was accounted for in the modeling process. The model was run over a 5-year time period and five of the 5-year runs were averaged per test in order to determine average productivity including seasonal growth and start-up delays. The model tracks nutrient use including CO2, electrical energy demand, water balance, and biomass production. PARTICIPANTS: Dr. Ronald Lacey, P.E., Professor, Texas A&M University, was the principal investigator on the project and did the modeling and analysis of the algae cultivation and harvesting system. Dr. James Richardson, Regents Professor, Texas A&M University has contributed economic data and analysis. TARGET AUDIENCES: The target audience is researchers in algal based biofuels, as well as potential producers and investors. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The model was run to simulate algae cultivation and harvesting over a five-year period. The results for each run were recorded and the annual average and standard deviation for five simulation runs of 5-years each was calculated. Lipid content was assumed to be 21% of the biomass produced. Annual productivity was 25.9 t Ha-1 (23,050 lbs ac-1) of biomass with 5358 L Ha-1 (564 gal ac-1) of lipids produced. The ratio of CO2 to biomass was 5.9. Net water used was the total water added plus the water lost to evaporation less the water recycled and was 7,292,232 m3 (5912 ac-ft). Assuming that the energy content of the lipid is 41.7 MJ kg-1 and lipid specific gravity is 0.92 the water footprint was 66 m3 GJ-1. ON a cost basis per metric ton of biomass, the itemized costs were CO2:$111.71, Nutrients: $484.26, Harvest Electricity: $5.40, Mixing Electricity: $323.86, Electricity for Pumping: $13.79, and Water: $27.72. The costs per gallon of lipid produced are estimated at $18 and do not include labor or downstream processing. In order to develop an economical, algae based biofuel, significant changes are required in the overall system concept to reach a more affordable level.
Publications
- No publications reported this period
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: A discrete event simulation (DES) model of algae-based biofuel cultivation and harvesting systems was developed for analysis of commercial scale performance and costs. Results of an open-pond, racetrack cultivation system with conventional disc centrifuge harvesting suggest that nutrient costs comprise 92.8% ($69.82 per L of lipid) of the operating costs in the cultivation & harvesting operations. The second highest cost contributor was electricity for agitation of the ponds (3.1% or $2.33 per L of lipid) with labor and water costs tied for third at 1.6% ($1.20 per L lipid and $1.17 per L lipid, respectively). Water costs are driven by evaporative losses. Electricity for harvesting operations represented only 0.6% of the total costs ($0.43 per L of lipid). Development of electrolytic methods of harvesting algae were focused on electrocoagulation (EC), a technique used in the wastewater and water treatment industries. Bench and pilot scale tests demonstrated a significant decrease in energy requirements for harvesting algae with EC technology (0.04 kWh per cu m for EC versus 1 kWh per cu m for centrifuge). A pilot scale test at the facility in Pecos, TX demonstrated that the technology operates equally well at scale and can be applied as needed. There are limitations in that aluminum ions remain in the algae biomass and may interfere with downstream operations or uses of the biomass residue but do not remain in the lipid fraction. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The DES modeling indicates that development of free nutrient sources is paramount in making an algae to biofuel industry economically viable. Historically, algae have been grown on wastewater and on livestock wastes, so this is a reasonable alternative source of nutrients. Additionally, costs for mixing must be reduced by utilizing natural convection and algal strains that are more productive in stagnant waters. Costs for water must be reduced through development of costal locations, where pumping costs are reduced and evaporative losses are less than desert sites. Labor costs must be reduced through the use of automation. Electrocoagulation harvesting has been demonstrated at pilot scale in partnership with a commercial vendor. Refinements in the system are being implemented and will be available for future testing and application.
Publications
- Zhang3, H., Y. Lan, R. Lacey, W. C. Hoffmann, and J. K. Westbrook. 2011. Spatial analysis of NDVI readings with different sampling density. Transactions of the ASABE. 54(1): 349-354.
- Huang, Y., Y. Lan, W. C. Hoffmann, and R. E. Lacey. 2011. A pixel-level method for multiple imaging sensor data fusion through artificial neural networks. Advances in Natural Science 4(1): 1-13.
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