MICROALGAE BIODIESEL AS A SUBSTITUTE FOR JET FUEL

MICROALGAE BIODIESEL AS A SUBSTITUTE FOR JET FUEL Chandan Sohi B.S., University of California, Davis, 2005 THESIS Submitted in partial satisfaction of the requirements for the degree of MASTER OF SCIENCE in MECHANICAL ENGINEERING at CALIFORNIA STATE UNIVERSITY, SACRAMENTO SPRING 2010 © 2010 Chandan Sohi ALL RIGHTS RESERVED ii MICROALGAE BIODIESEL AS A SUBSTITUTE FOR JET FUEL A Thesis by Chandan Sohi Approved by: , Committee Chair Timothy Marbach, Ph.D , Second Reader Ilhan Tuzcu, Ph.D Date iii Student: Chandan Sohi I certify that this student has met the requirements for format contained in the University format manual, and that this thesis is suitable for shelving in the Library and credit is to be awarded for the thesis , Department Chair _ Susan Holl, Ph.D Date Department of Mechanical Engineering iv Abstract of MICROALGAE BIODIESEL AS A SUBSTITUTE FOR JET FUEL by Chandan Sohi With dwindling petroleum resources, the need for alternate fuel resources has become immense Any new fuel source needs to be home grown, economically feasible, and environmentally friendly Although many such fuels are available for ground transportation, such as ethanol, there are not many options for alternate aviation fuels One possible replacement fuel for jet fuel is biodiesel Biodiesel has many similar properties to jet fuel, such as energy density and specific energy However, production issues, low temperature properties, oxidative degradation provide significant challenges for implementation of biodiesel as an aviation fuel This author studied these challenges by examining biodiesel produced from microalgae feedstock The high production rates of microalgae make it an ideal feedstock Furthermore, the growth of microalgae does not require arable land for growth Hence, it does not figure into the land concerns of the “fuel vs food” debate The author examined methods of improving low temperature properties such as winterization and additives For fighting oxidative degradation, this author examined research evaluating the procedure of adding antioxidants to lengthen oxidative stability The study concluded that although pure microalgae biodiesel fuel would meet the criteria of being home grown, economically feasible, and environmentally friendly, the implementation of the fuel is still several years away However, blends of petroleum diesel and microalgae biodiesel containing up to 30-vol% biodiesel can be implemented due to the better fuel properties of petroleum diesel _, Committee Chair Timothy Marbach, Ph.D _ Date v TABLE OF CONTENTS Page List of Tables vii List of Figures viii Chapter INTRODUCTION …………… ……………………………………………………… 1.1 Need for Alternative Fuels 1.2 Choosing a Fuel BIOFUELS… 2.1 Brief History 2.2 Biomass……………………………………………………………………….… 2.3 Biofuel Sources………………………………………………………… … … 2.4 Production of Biofuels…………………………………………………… … 11 2.5 Benefits and Impacts……………………………………………… ………… 17 WHY MICROALGAE BIODIESEL? 20 3.1 Production 20 3.2 Fuel Properties 23 PRODUCTION 31 4.1 Strain Selection 31 4.2 Production Technologies 33 4.3 Harvesting 38 4.4 Conversion Technologies 38 4.5 Microalgae Biodiesel Pathways 43 AVIATION CHALLENGES 48 5.1 Low Temperature Properties 48 5.2 Oxidative Degradation 58 PRODUCTION 60 Bibliography…… …….………….… 63 vi LIST OF TABLES Page 3.1 Oil Yields of Feedstock Crops……………………….……………………… 22 3.2 Characteristics of Different Fuel Types ………….……….……………… 24 3.3 Comparison of Biodiesel vs Conventional Jet Fuel……………………….… 26 4.1 Lipid Content of Many Microalgae Species………………………………… 32 4.2 Expected Yield for Pyrolysis Conversion Process…………………………… 42 5.1 Effects of Winterization on Fatty Acid Composition of Long Chain Methyl Ester…………………………………………………………………………… 52 5.2 Effects of Additives on Cloud Point and Pour Point Properties of Biodiesel Based Fuels…………….……………………………………………………… 55 5.3 Effects of Additives on Kinematic Viscosity of Biodiesel Based Fuels… 57 vii LIST OF FIGURES Page 1.1 Annual Energy Consumption Values for Selected Countries.………………… 2.1 Current Biofuel Pathways.………………….…………………………… …… 2.2 Two-Stage Gasification…………………….…………………….……….…… 12 2.3 Alcohol Fermentation……………………….…………………………….…… 15 2.4 Anaerobic Digestion……………………………………………………….…… 16 2.5 Percent Reduction in Pollutants for Biodiesel as Compared to Petroleum Based Diesel………………………………………………………… ………….…… 18 3.1 Mass of Fuel vs Volume of Fuel per Unit Energy……………………… 25 4.1 Tubular Bioreactors…………………………………………………….……… 35 4.2 Algal Biomass Conversion Pathways………………………………… ….… 39 4.3 Transesterification Process……………………………………………….…… 45 4.4 Current and Emerging Pathways for Biofuels………………………………… 46 4.5 Microalgal Biofuel Production Cycle………………………………………… 47 5.1 Airplane Fuel System………….……………………………………………… 49 viii Chapter INTRODUCTION Purpose of the Study One of the most pressing political/economic needs faced today is the need to reduce our dependence on foreign oil There are several new options available as alternatives to gasoline for ground transportation Over time, as new technology and processes are developed, our dependence on gasoline will become negligible Some of this will come through better fuel cell technology for hybrid or electric vehicles while other improvements will come through continuous development of biofuels Today we have biofuels such as ethanol and biodiesel available in the marketplace Currently ethanol displaces 2% of all gasoline Further advances in technology will allow us to produce the ethanol out of cellulosic material, which will further decrease our dependence on gasoline [1] However, we still not have a suitable replacement for jet fuel The prevalent alternative fuel options for ground transportation are not suitable for the aviation industry For airplanes, the specific energy, energy density, and the low temperature fuel properties for any alternative option are quite important Ethanol does not have the specific energy or energy density that is suitable for aircrafts Biodiesel has suitable energy density (about 80% that of jet fuel) however it has a propensity to freeze at the low temperatures that airplanes are likely to encounter at high altitude cruising Another limitation that biofuels face is the production capacity of these fuels The amount of biofuel presently produced is very limited In order to increase production of biofuels, more land and resources will need redirection These resources would need shifting from use for crops whose primary function is to provide food to crops whose primary function is of feedstock to produce biofuels Redirection of only a limited amount of these resources is possible, before the redirection starts hampering food production and causing shortages in food supply Hence, biofuel feedstock crops that not require arable land need further investigation Technology for production of these alternative fuels need to be developed and improved 1.1 Need for Alternative Fuels Political, economic, and environmental issues that have risen over the past several decades have brought fourth the need for alternative jet fuels that are home grown, economically viable, and environmentally clean The need for alternative fuel sources first came to the forefront during the energy crisis of the 1970’s During this period, most of the industrialized economies were heavily dependent on crude oil The oil supply along with the oil prices were at the time controlled heavily by the Organization Petroleum Exporting Countries (OPEC) In 1973, the US government decided to re-supply the Israeli military during the Yom Kippur War A move that did not go down well with the Arab nations, so as a response the Organization of Arab Petroleum Exporting Countries (OAPEC) a large portion of OPEC decided to place an oil embargo on the United States thus limiting oil supplies and sending oil prices skywards The oil embargo highlighted the United States’ dependence to solidify, biodiesel can plug pipelines thus causing damage to pumps by overstressing A decrease in feed rate of the fuel for lubrication purposes is also possible [16] 5.1.3 Viscosity Viscosity describes the fluids resistance to flow Flights at high altitude, approximately 30,000 ft, experience much higher viscosity than airplanes flying at lower altitude Thus, it is much tougher for the fuel to flow through the pipes for highflying airplanes 5.1.4 Current Research Although not enough research is available on improving the low temperature properties of microalgae, there has been extensive research done on improving the low temperature properties of biodiesel produced from other feedstock Researchers have used several different approaches to fight the challenges provided by the low temperature properties of biodiesel Primary among these approaches are winterization and addition of cold-flow additives Implementation of similar approaches on microalgae based biodiesel to improve the low temperature properties of the fuel needs investigation 5.1.4.1 Winterization Winterization is not a new process or technique It refers to a process of separating the part of oil that has a solidification temperature that is below a specific cutoff value The food industry employs this process for easier handling and pouring of vegetable oils and their byproducts Winterization of biodiesel refers to balancing an inactive mixture of methyl esters at a temperature that is between its cloud point and pour point During this process, 51 saturated methyl esters tend to “precipitate and form a suspension of small, wax- like crystals in a liquid phase.” Filtering out these formed solid particles results in a liquid biodiesel with improved methyl esters This liquid should have better cold flow properties A similar study performed on soybean-based biodiesel has provided encouraging results The study winterized biodiesel until it withstood a minimum of three hours at a bath temperature of -10 °C with no clouding visible During the many trial of this process, the cloud point and pour point temperatures never measured above -16 °C The results achieved were not quite at the level required however the significant improvements made in lowering the cloud point temperature and pour point temperature from roughly °C to -16 °C is significant none the less The process however is not without its flaws The multiple iterations of the process that were required to lower the cloud point temperature and the pour point temperature ended up decreasing the total amount of methyl esters The results from the experimentation showed an average product yield, from one trial to the other, of about 25% or 0.32 Kg A mass balance from the trailing trial revealed a total loss of starting material to be 20% Information detailing the losses in methyl esters is available in Table 5.1 During the study, methyl hexadecanoate experienced the largest decrease of over three times its initial value On the other hand, methyl octadecatrienoate had the largest increase in the methyl ester content, almost increasing by 50% 52 Fatty Acid Untreated (wt %) Winterized (wt %) Hexadecanoate (C16:0) 12.9 4.3 Octadecanoate (C18:0) 5.2 1.3 Octadecenoate (C18:1) 23.8 30.3 Octadecadieonate (C18:2) 46.6 49.6 Octadecatrieonate (C18:3) 7.8 11.9 Other 3.7 2.6 Table 5.1: Effects of Winterization on Fatty Acid Composition of Long Chain Methyl Esters [18] 53 The study found that a small amount of saturated long chained methyl esters within the winterized methyl esters had drastic effect on the cold temperature properties on the transesterified and winterized soybean methyl esters A blend containing 68.3% linoleate, 26% methyl oleate, and 5.7% methyl linolenate produced a cloud point of -23 °C and pour point of -48 °C; about 7-32 °C below those for winterized soy bean methyl esters containing only 5.6 wt% of saturated methyl esters Removal of such a large fraction of material is not ideal for large-scale production of biodiesel [18] An alternate approach would be to alter the biodiesel feedstock to change genetically the fatty acid portion of oilseeds The feedstock would need modification to produce oil with elevated oleic acid and reduced polyunsaturated and saturated fatty acids This altered oil would produce biodiesel that has increased oxidative stability with improved cold temperature properties [18] A similar approach can be utilized for largescale production of microalgae based biodiesel with improved low temperature properties However, much research and development is required before the implementation of such techniques 5.1.4.2 Additives Currently low temperature property targets, cloud point temperature of -10 °C, are reachable by adding petroleum diesel to biodiesel However, achieving this requires using low proportions of biodiesel, to about 30% Using similar approach low temperature property targets for biodiesel based aviation fuel is also possible This would require further reduction in the proportion of biodiesel to as little as % [18] 54 Generally, additives can be categorized within three types; they are pour point depressants, wax crystalline modifiers, and cloud point depressants Pour point depressants inhibit growth of crystalline and wax crystalline modifiers disrupt the crystalline process by growing a large quantity of small and compact wax crystals The filters capture most of these crystals; however, “the cake layers formed on the filter surface is considerably more permeable to fuel flow.” As the fuel re-cycles back to the fuel tank, warming of the fuel will melt the formed cake layer and the engine will operate as intended Research conducted on cloud point depressants has produced encouraging results The process involves increasing the solubility of long chained paraffins and reducing the temperature of the nucleation (a physical reaction that occurs when components in the solution start to precipitate out) [18] Similar to winterization, much research is not available in adding additives to microalgae based biodiesel However, researchers have investigated the affects of additives to biodiesel from other feedstock A study performed by Dunn et al investigated the effects of additives on low temperature properties The first part of the study examined the effects of additives on the pour point temperature The study required mixing additives to different fuel types; 100% soybean biodiesel, a 30% soybean biodiesel blended with petroleum diesel, and 20% soybean biodiesel blended with petroleum diesel The results of the experimentation are available in Table 5.2 For the 20% and 30% blends, the pour point temperatures were quite low For the 20% blend, the pour point temperatures ranged from -18 °C to -29 °C for the varying additives For the 30% blend, the pour point temperature ranged from 55 Table 5.2: Effects of Additives on Cloud Point and Pour Point Properties of Biodiesel Based Fuels [18] 56 -25 °C to -49°C Compared to these values the addition of soybean biodiesel and additives provided pour point temperatures ranging between -2 °C and -8 °C The cloud point temperature values were also quite low but not as much as those for the pour point were For the 20% blend, the cloud point temperature ranged from -12 °C to -15 °C for the varying additives For the 30% blend, the cloud point temperatures ranged from -13 °C to -21 °C Similarly, to how the pour point temperatures were higher for the pure biodiesel, the cloud point temperatures were also higher for the pure biodiesel than the two blends For the pure biodiesel, the cloud point temperatures ranged from °C to -2 °C Dunn et al also examined the effects of additives on kinematic viscosity The experiment required adding varying additives at different doses to the 20% blend fuel at two separate temperatures The experiment measured kinematic viscosity at 40 °C and -3 °C for 0, 500, 1000, 1500, and 2000 ppm of additives As expected, the results showed viscosities to be much higher for -3 °C to be much higher than those at 40 °C The amount of additives added reduced the viscosity (Table 5.3) [18] The results from the study were a bit inconclusive They showed that addition of additives helped lower the pour point temperature but had little effect on the cloud point temperature Increasing the amount of additives to the fuel had no effect on the cloud point temperature The data gathered also showed that the addition of additives helped lower the kinematic viscosity However, the effects of additives used in the study were minimal To make the method a viable option for improving the low-temperature 57 Table 5.3: Effects of Additives on Kinematic Viscosity of Biodiesel Based Fuels [18] 58 properties of biodiesel produced from microalgae feedstock it requires further research and development New additives need exploration and processes to lower the low temperature properties need refinement 5.2 Oxidative Degradation One of the main issues with using biodiesel as a replacement fuel for jet fuel is oxidation Oxidation occurs due to any of several factors, chief among them are exposure to oxygen through air, presence of light, high temperatures, and peroxides Since the biooils, used to produce biodiesel through trasesterification, carry a large fraction of fatty acids with double bonds, oxidative stability becomes an issue when storing the fuel for extended period aerobically Once that happens, the fuel starts to degrade, breaking down Hence, storing biodiesel for extended period is an issue that needs investigation Presently there is very little research on improving the oxidative stability of microalgae based biodiesel However, researches conducted on other forms of biodiesel provide the framework for tackling the issue with microalgae base biodiesel A possible solution is through the addition of oxidation inhibitors or antioxidants, which delay the start of oxidation Treatment of fuel with antioxidants is beneficial since doing so allows keeping current storage tanks and systems for fuel handling No new technological advancements in technology are required The design of the aircraft can stay constant [19] 59 There are two types of antioxidants Those that occur naturally within the bio-oils, such as vitamin E, and the ones synthetically added There are several synthetic antioxidants; some examples include butylated hydroxytoluene, butylated hydroxyanisol, and propyl gallate Several factors determine the success of an antioxidant These factors include fatty acid profile of the oil, amount of naturally occurring antioxidants, and storage conditions It requires much research and development to identify those antioxidants that are most suitable for microalgae based biodiesel Other methods to improve the oxidative stability of microalgae based biodiesel need investigation before implementing it as a replacement for jet fuel 60 Chapter CONCLUSION Biodiesel produced from microalgae feedstock is an excellent short-term replacement for jet fuel Production of the microalgae biodiesel is possible within the United States, it is environmental friendly, and overtime can become an economically feasible As shown previously, completion of the entire production cycle of microalgae biodiesel within the United State is possible Many of the challenges associated with large-scale production of other biofuels not affect microalgae biodiesel Growth of microalgae requires a lot less land than biofuels produced from other feedstock such as corn and soybean would Furthermore, the land required can be non-arable The production also has very little issues with water supply as all the water requirements can be met with brackish water Still much research and development is required within the production cycle to make the development of microalgae biodiesel feasible technologically and economically Current production capacity for growing microalgae does not match the amount of feedstock that would be required to meet the demand of replacing jet fuel completely In addition, the cost of producing such large capacity of microalgae with current technology is quite high Thus technological advancement in production systems for growing microalgae need to made Mixotrophic production systems, a combination of both photoautotrophic and heterotrophic, need further investigation 61 Ways to increase the bio-oil output needs pursuing These desired results are reachable through one of two ways, biological or thermochemically Algae strains can be bio-engineered to carry more oil or processes that convert biomass into bio-oil need improvement Special attention toward processes that produce bio-oils is necessary Flash Pyrolisis produces up 75% of its resulting fuel as bio-oil; ways to increase this percentage need research and development Some aviation factors that also cause hindrance in replacing jet fuel with microalgae based biodiesel need further research and development Ways to improve the low temperature properties (cloud point temperature, pour point temperature, and kinematic viscosity) need further study Improvements to current approaches such as winterization and addition of additives should be made as well as new approaches investigated Studies of the effects of winterization and addition of additives on microalgae biodiesel need accomplishing Without improvement in these low temperature properties replacement of jet fuel with microalgae biodiesel is impossible Another aspect microalgae biodiesel that needs advancement is the fuels storage life Due to oxidative degradation, microalgae biodiesel have very limited shelf life Ways of improving this shelf life is necessary Current research is using antioxidants to bring oxidative stability and hence extending the shelf life of the fuel seems to be working for blends of petroleum diesel and biodiesel However, the results are very limited for 100% biodiesel fuels It requires much research to prolong the shelf life for microalgae biodiesel 62 Due to the above listed issues, replacement of jet fuel by 100% microalgae biodiesel is not possible with the current technology Improvements in all aspects of production and implementation are necessary However, blends of biodiesel have shown to be suitable for replacement of jet fuel These blends are suitable drop-in fuels for aviation until the necessary advancements with 100% microalgae biodiesel are completed The use of these blend of biodiesel, to a certain extent, help ease our reliance on foreign oil The biodiesel blends are also likely to provide the environment a break by reducing the amount of petroleum burned All in all microalgae based biodiesel is an excellent candidate to replace jet fuel There are still issues that are being resolved, that need technological advancement However, we should continue to investigate other fuel sources as well 63 BIBLIOGRAPHY [1] Ashworth, John “Jet Fuel From Microalgal Lipids.” United States Department of Energy July 2006 National Renewable Energy Laboratory PDF Document Mar 2010 [2] Horton, Sarah 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Oil-Derived Methyl Esters.” Journal of the American Oil Chemists’ Society, Volume 73, December 1996: 1719-1728 Web 15 Mar 2010 [19] Knothe, Gerhard “Some Aspeccts of Biodiesel Oxidative Stability.” Fuel Processing Technology, Volume 88, July 2007: 669-677 Web 15 Mar 2010 ... the advantages and disadvantages of using biodiesel as a replacement fuel for conventional jet fuel This author will evaluate the fuel properties of biodiesel against those of jet fuel Areas of... Waste and water treatment plants use anaerobic digestion; however, it also occurs naturally at landfills and bottom of lakes The resulting biogas useful as an alternative for natural gas, transportation... conventional jet fuel Discussion performed on the advantages and disadvantages of microalgae as a feedstock and biodiesel as a fuel Examination of the factors preventing the fuel from becoming a “drop-in”