A Environment Report On EFFLUENT TREATMENT PLANT Dairy Submitted By MR. PUSHKRAJ JADHAV DEPARTMENT OF MECHANICAL ENGINEERING TATYASAHEB KORE INSTITUTE OF ENGINEERING & TECHNOLOGY, WARANANAGAR-416113 2006-2007 TATYASAHEB KORE INSTITUTE OF ENGINEERING & TECHNOLOGY, WARANANAGAR-416113 DEPARTMENT OF CHEMICAL ENGINEERING CERTIFICATE This is certify that project report entitled “BIO-DIESEL” It is bonafied work of Mr. SHASHIKANT H. NIKAM In the practical fulfillment of the requirements for the award of degree of bachelor of Engineering in Chemical Engineering of the Shivaji university, Kolhapur. He has carried out the work under my supervision and guidance, during academic year 2006-07 Prof. B. R. Bagane, Examiner (Supervisior) Prof. S. V. ANEKAR (H.O.D.) Department of Chem Dr. C. R. Rao (Principal) ACKNOWLEDGEMENT It gives me an immense pleasure to present a report on the successful completion of my Environmental Science Report On “BIO-DIESEL” We express my deep sense of gratitude to my guide Prof. B. R. Bagane for his valuable guidance rendered in all phase of project. We are thankful for his wholehearted assistance, advice and expert guidance towards making our project a success. Our special thanks to honorable Principal Dr. C. R. Rao & Head of Department Prof. S. V. ANEKAR for their keen interest, encourage and excellent support. We are also like to express my thanks to all of other staff members of college & friends who helped me directly & indirectly during the completion of this Report. MR. SHASHIKANT H. NIKAM DECLARATION The Principal, Tatyasaheb Kore Institute of Engineering and Technology, Warananagar-416113. Sir, We undersigned hereby declare that the project report entitled “BIODIESEL”. Written & Submitted by us under the guidance of Prof. B.R.Bagane in my original work. The empirical findings in this report are based on the data collected by ourself. The matter collected in this report is not a reproduction from any source. We understand that, any such copying is liable to be punished in a way the institute authorities claim fit. Place: -Warananagar Date:- MR. SHASHIKANT H. NIKAM INDEX Sr. No. Contents Page No. 1. Introduction 1 2. Bio-Diesel As An Option For Energy Security 3 3. Chemistry of Bio-Diesel 5 4. Bio-Diesel Processing 19 5. Storage of Bio-Diesel 37 6. Specification of Bio-Diesel 39 7. Emission Norms 40 8. Advantages of Bio-Diesel 44 INTRODUCTION The use of vegetable oils as diesel fuel is nearly as old as the diesel engine itself. The Fuel and energy crisis and the concern of society for depleting world’s non- renewable resources initiates various sectors to look for alternative fuels. One of the most promising fuel alternative is the vegetable oils and their derivatives. Hundreds of scientific articles and research activities from around the world were printed and recorded. Oils from coconut, soy bean, sunflower, safflower, peanut, linseed and palm were used depending on what country they grow abundantly. In the Philippines alone, research activities on the use of vegetable oils as fuel substitute have already been done as early as the 1970s using coconut oil. In the United States, the primary interest as biodiesel source is soy bean oil while many European countries are concerned with rape seed oil and countries with tropical climate prefer to utilize coconut oil or palm oil. Several problems encountered cause delay in the widespread use of biodiesel. First is economics and second is the properties of biodiesel. Use of neat vegetable oils cause injector coking, engine deposits, ring sticking and thickening of the engine lubricant. To overcome this problem, various modifications of vegetable oils were suggested such as by transesterification, micro-emulsion formation and the use of viscosity reducers. Among these, transesterification was considered as the most suitable modification because technical properties of esters are nearly similar to diesel. What is Biodiesel? The term Biodiesel, in general, refers to neat vegetable oils used as diesel fuel as well as neat methyl esters prepared from vegetable oils or animal fats and even blends of conventional diesel fuel with vegetable oils or methyl esters. Due to problems encountered in the use of neat vegetable oil, Biodiesel is now referred to as the mono alkyl esters of long chain fatty acids derived from vegetable oils for use in compression ignition (diesel) engines. Methyl ester is usually made from 80-90% vegetable oil, 1020% alcohol and 0.35-1.5% catalyst. Why Use Biodiesel? Biodiesel fuel is reliable, renewable, biodegradable and non-toxic. It is less harmful to the environment for it contains practically no sulfur and substantially reduce emissions of unburned hydrocarbon, carbon monoxide, sulfates, polycyclic aromatic and particulate matter. It has fuel properties comparable to mineral diesel and because of great similarity, it can be mixed with mineral oil and used in standard diesel engines with minor or no modifications at all. Biodiesel works well with new technologies such as catalysts , particulate traps and exhaust gas re-circulation. It can be produced from any kind of oil both vegetable and animal source . Used frying oil can also be used and , therefore, be a very promising alternative for waste treatment. Being an agricultural product, all countries have the ability to produce and control this energy source which is a situation very different to the crude oil business. It can strengthen economy by creating more jobs and create independence from the imported depleting commodity petroleum. supporting agriculture. It can also be used as a way of stimulating and BIO-DIESEL AS AN OPTION FOR ENERGY SECURITY With petroleum product prices rising steadily; diesel alone has become 25 per cent costlier over the last year. Apart from the search for alternatives, it is the need to achieve energy independence that is directing so much focus on biofuels and the crops that will help yield these oils. If sugar mills are being encouraged to produce ethanol from sugarcane for blending with petrol, efforts are on to cultivate such crops as jatropha and pongamia, which yield oil that can either be blended with diesel or used independently. BIOFUELS, ethanol, jatropha, pongamia... Words till recently rarely mentioned outside a select circle are coming into common usage now. The reasons are not difficult to fathom: Petroleum product prices have been rising steadily; diesel alone has become 25 per cent costlier over the last year. Apart from the search for alternatives, it is the need to achieve energy independence that is directing so much focus on biofuels and the crops that will help yield these oils. Sugar mills are being encouraged to produce ethanol from sugarcane for blending with petrol, while efforts are on to cultivate such crops as jatropha and pongamia, which yield oil that can either be blended with diesel or used by themselves instead. Much potential While jatropha has clearly emerged as the preferred option for cultivation, pongamia, a traditional species that has been around for ages, too has great potential. The advantage with jatropha, a bush, is that it is easy to maintain and starts yielding from the fourth year, while pongamia, a tree, requires more area and yields can be expected from the seventh or eighth year on. Scientists, however, say that the Botanical Survey of India has identified more than 400 species of plants and trees that can yield such oils. The enthusiasm for biofuels must also be viewed against the backdrop of the country's thirst for oil — about 114 million tonnes every year — 75 per cent of which is imported at a cost of Rs 1,20,000 crore. About 112 million tonnes of oil is consumed just by the transportation sector. Experts feel that the problem of the huge oil import bill and the price uncertainty can be mitigated by cultivating biofuel crops on the over 60 million hectares of wasteland available in the country. Each hectare would yield up to three tonnes of seed, from which can be extracted one tonne of oil. This would translate to 30 million tonnes of oil. The problem is that these estimates represent a theoretical potential, say the National Bank for Agriculture and Rural Development and commercial banks. Studies are still at the academic level and banks need large-scale field data before they will commit funds. Even the economics of cultivating jatropha and the unit cost analysis available with banks are based on preliminary estimates by research institutes. Banks are for now only willing to wait and watch and have not extended any loans for jatropha cultivation. CHEMISTRY OF BIODIESEL The topic of biodiesel can be introduced in a variety of classes – chemistry, biology .Engineers in today’s world need to also focus on issues such as making their processes and products economical, and looking into related political issues, biodiesel presents an excellent example for students learning how science topics relate to nonscientific fields. I. Biology Being produced from biological matter, there are several options for topics that could be introduced or elaborated on through a discussion of biodiesel. The following are a few possibilities. I. a. Carbon Cycle The carbon cycle is a topic that many students – even a majority of adults – have difficulty understanding. Our UNH Biodiesel Group has given many presentations to legislators, members of the general public, students, and scientists. We have found that a discussion of how the carbon cycle works for biodiesel is very successful in engendering a better understanding of the carbon cycle in general. With regard to alternative fuels, the main importance of the carbon cycle is whether it is a closed or open cycle. Any fuel produced entirely from biomass would have a closed carbon cycle – since all of the carbon within the fuel came from the plants from which it was produced, and the carbon in the plants came from the atmosphere. As Figure 1 shows, plants get their carbon from CO2 in the atmosphere – converting the CO2 to O2 during photosynthesis, with the carbon being stored in the plant (as carbohydrates, oils, starch, etc.). Photosynthesis is the process by which plants convert carbon dioxide and water into glucose and oxygen, in the presence of chlorophyll and sunlight (which supplies the energy). In energy terms, the plants are converting the electromagnetic energy (sunlight) into chemical energy (glucose). CO2 2 The glucose can then be converted into other forms by the plant – other sugars, or fats, starches, proteins (which also requires nitrogen and sometimes sulfur), and so on. Plants can get everything they need to make sugars, oil, and starches from the air (CO2), sunlight, and water (H2O). That’s because those molecules are made only of carbon, hydrogen, and water. As far as the carbon cycle, the important point is that all of the carbon within a plant comes from carbon dioxide in the air. If the plant decays, much of that carbon finds its way back into the atmosphere as CO2 or methane (CH4). If the oil is extracted from the plant, and turned into biodiesel (the alcohol used to make the biodiesel could come from alcohol also made from the plant), all of the carbon in the biodiesel had to come from CO2 in the air. So, when we burn biodiesel, even though it gives off CO2, there is no net addition to atmospheric carbon (CO2) levels, since that same carbon we are releasing was taken from the atmosphere by the plants when they were growing. Contrast this to the carbon released when we burn any fossil fuels. The carbon in gasoline, for example, is from the petroleum we extract out of the ground. That carbon itself was likely in the atmosphere at one point – but billions of years ago, when the earth was much younger, and had much higher levels of atmospheric carbon dioxide. The bacteria that grew on the young earth took carbon out of the atmosphere, and over billions of years of dying, not fully decaying, “sequestered” that carbon within the earth (which resulted in atmospheric carbon dioxide levels dropping to the stable level they have been at now for millions of years – a level that results in the right amount of infrared insulation for maintaining a temperature here on earth that is suitable for humans, etc.). By burning a fossil fuel, we are adding carbon to the atmosphere (as CO2, with the oxygen portion coming from O2 already present in the atmosphere) that had not been in our atmosphere for billions of years. Through so doing, we gradually increase the atmospheric carbon level beyond the fairly stable level it has been at for millions of years, resulting in more heat held in through the greenhouse effect (another issue to be discussed). Figure 5 shows the increase in atmospheric carbon levels over the past 200 years since the Industrial revolution, when we began burning fossil fuels. Figure 4 plots the anthropogenic (man-made) emissions of carbon to the atmosphere (largely from burning fossil fuels). Some of this CO2 emitted was taken up by plants and the oceans (the green region), while the rest remains in the atmosphere, increasing the atmospheric level of CO2, the prime greenhouse gas. The current level is now up to 379 ppm.5 There have been minor fluctuations in the atmospheric carbon levels over the past few million years, but nothing close to the increase we have caused in the past 200 years alone. From the environmental standpoint, this is the most important reason for moving from fossil fuels to renewable biofuels, which result in no net addition to atmospheric carbon levels. I.b. Greenhouse Effect Note – This topic comes under environmental science and current events) This is a topic that could be covered in a variety of courses, yet is a topic covered very little in most current curriculum. The issue could be covered either briefly, or in excruciating detail. Being such an important topic, particularly as far as an issue with science and political crossover, it would be very desirable for students to garner a better understanding of the greenhouse effect. There are many valuable resources on the web providing a thorough discussion of it from a variety of perspectives (biology, chemistry, physics, public policy, etc.). One valuable reason for lessons on the greenhouse effect, and global climate change, is for students to learn that there are ongoing discussions and debates about many topics in science. Students often get the impression that science is a “finished book”. Learning that there are many questions scientists are still trying to answer, with many lively debates among scientists helps develop student interest in the subject. I.d. Plant Suitability Perhaps the most critical area of biodiesel research currently is finding or developing alternative crops that can be grown for producing biodiesel (or another alternative fuel). The crop used for producing a fuel is referred to as the feedstock. Currently, soybeans are the primary feedstock in the US for biodiesel production. The only reason for this is the fact that the US produces a large amount of surplus soybean oil as a by-product of the soy industry. Soybeans are growing in the US primarily for their protein content – with the bulk of that being for animal consumption (animals in the US grown for human consumption consume ten times as much protein every year as all of the humans in the US). But, other crops would make far better options for biodiesel production – from the perspective of biology, chemistry, and physics. One example the UNH Biodiesel Group is working on is hybrids of yellow mustard, bred to have higher concentrations of glucosinolates. These glucosinolates are broken down in soil by bacteria, creating isothiocyanates. The isiothiocyanates have strong pesticidal qualities, but themselves break down within a few days. The result is that the mustard meal (what is left after extracting the oil) could make an excellent organic pesticide, to replace much more harmful pesticides. The isiothiocyanates are as effective as pesticides currently used, but due to the fact that they themselves biodegrade quickly, there would be no concern about pesticidal residue on crops intended for consumption. The high economic value of the mustard meal then would allow the oil to be sold much more cheaply, resulting in lower cost biodiesel. This illustrates the multi-disciplinary nature of biofuels – this mustard example can incorporate the chemistry involved in the glucosinolate breakdown, understanding the biology of breeding mustard for higher glucosinolate levels, the effects of those glucosinolates on plants and animals, and the economics resulting from the same crop producing a very high value co-product. Another feedstock the UNH group is focusing on is high oil algaes, which are particularly appealing due to their extremely high growth rates (due to high photosynthetic efficiency and low amount of energy expended on things other than growing), and the potential for high oil content. The energy of photosynthetically active radiation (PAR, the portion of sunlight used for photosynthesis) reaching the landmass portion of earth is 2,250 times our current energy use. Algaes can achieve photosynthetic efficiencies of up to 25% - meaning that 25% of the PAR can be converted into chemical energy in the algae. This illustrates that we could meet all of our energy needs with a relatively small portion of our landmass – provided we do it as efficiently as possible. Biofuels essentially revolve around using photosynthesis as a means of “producing” our energy – rather than deriving it from fossil fuels (which are essentially chemical energy from plants that grew billions of years ago – so still a form of solar energy, but over a very long-term, with the carbon in the fuel having been out of our atmosphere for billions of years). II. Chemistry There are several lessons that can be initiated with a discussion of biodiesel. Many of the lesson ideas that are also mentioned under biology and physics could be included in the chemistry classroom. This section will focus on a few ideas that would be specific to chemistry, while the ones that overlap into other areas are listed in the area of overlap. Some possibilities specific to chemistry include: II.b. Organic Chemistry Terminology Discussing vegetable oils and transesterification presents a nice opportunity for students to learn about, or further their knowledge of various chemistry terminology and classification – in particular, alcohols, alkenes, alkanes, alkyls, acids, esters, and so on. In addition to examining the reactions involved in making biodiesel, it can also be valuable to examine the properties of the various types of molecules involved (from different types of oils). In particular, looking at the properties of the methyl esters of 18 carbon chain fatty acids can demonstrate the effect of double bonds, and why it is so important to have the many different names in chemistry to distinguish between seemingly minor differences. Most students would not expect initially that what appears to be a minor difference – one molecule having a double bond, and two less hydrogen, as compared to an otherwise identical molecule – would have such a large impact on the properties of the molecule. II.c. Freezing and Gelling Most liquid fuels consist of a number of different molecules, with different properties. As a result, the entire fuel does not have one single freezing point. Looking at Table 3 of the document “Biodiesel Chemistry”, included in the packet, shows typical profiles of a few different vegetable oils as well as an animal fat (beef tallow). From this, it can be seen that most potential biodiesel feedstock oils consist of a variety of fatty acids, anywhere from a few, up to nine or more. As a result, the properties of the biodiesel will depend on the makeup of the fatty acid profile, as well as the particular alcohol used in processing (for example, ethyl esters have lower melting points than methyl esters of the same oil, meaning ethanol would be a preferred alcohol to use for cold weather operation of the biodiesel. Ethanol has only minor impacts on the cetane number, lubricity, and viscosity of the fuel. However, producing biodiesel with ethanol is somewhat more finicky than with methanol. With methanol, the concentration of the reactants can be off slightly, and the reaction will still proceed successfully. Transesterification with ethanol is less forgiving. The main reason methanol is the prime alcohol used in the biodiesel industry, however, is the cheaper cost of methanol). There are a few different important properties for cold weather performance of any fuel. These include the “Cloud Point” (CP), “Cold Filter Plugging Point” (CFPP), and “Pour Point” (PP), also referred to as “Gel Point” (GP). The CP is the temperature at which some of the molecules in the fuel first begin to freeze, resulting in the appearance of crystals in the fuel, which give it a “cloudy” appearance initially. Since the Cloud Point is the temperature at which the highest freezing point molecules in the fuel begin to freeze, a casual analysis would leave students to believe that the CP is simply the freezing point of that biodiesel molecule (methyl ester, ethyl ester, etc.) in the fuel that has the highest freezing point. But, that is not the case. The molecules in the fuel with lower freezing points have an anti-freezing effect on the molecules with higher freezing points. This can be observed by looking closely at Tables 2 and 3 in the Biodiesel Chemistry handout. In soybean oil, ignoring the behenic acid and erucic acid, which are present in only very small percentages, the fatty acid whose methyl ester has the highest freezing point is stearic acid, which constitutes 3.6% of soybean oil. The next highest is palmitic acid, constituting 9.9%. The freezing points of methyl stearate and methyl palmitate, respectively (from Table 2), are 39.1º C and 30.5º C (102.4º F and 86.9º F). So, at first glance, we may expect that the “Cloud Point” for soy biodiesel (aka methyl soyate) would be 39.1º C, the freezing point for methyl stearate. But, looking at Table 3, we see that the CP is actually 3º C, considerably lower. The reason for this is the freezing point depressing effect of the other molecules in the fuel, which have considerably lower freezing points. Biodiesel therefore presents an interesting opportunity for discussion of how freezing point depression works. With liquids consisting of molecules of various freezing points, gelling occurs as a result of solid molecules entangling and crosslinking, to form a semi-rigid structure, even though the majority of the molecules may still be liquid. A gel, also referred to as a sol, would of course present a serious problem to a vehicle’s fuel system. Regular petroleum diesel can gel at anywhere from –20º C (-4º F) to -10º C (14º F), depending on the quality of the fuel. Since atmospheric temperatures can fall below that, the diesel fuel industry has developed techniques for “winterizing” the fuel, to prevent this gelling from happening. The temperature at which this gelling occurs is referred to as either the “Gel Point” (GP), or more commonly, the “Pour Point” (PP). With diesel fuel, in some cases the gelling issue is dealt with by blending in other liquids with lower freezing points, such as kerosene. This also has a freezing point depressing effect on the molecules in the diesel fuel, so it also lowers the cloud point. Another method of winterizing involves the addition of an “antigel additive”. These additives are generally added in very small quantities (0.1-0.2% by volume), but can significantly lower the PP. They do so, primarily, by bonding to frozen molecules when the fuel falls below the cloud point, and preventing those molecules from bonding/crosslinking with other frozen molecules. The molecules of an antigel additive are generally considerably smaller than the fuel molecules themselves, so 0.1% of the additive by volume can effectively block a much larger percentage of fuel molecules from having the ability to gel the fuel. Some additives can lower the PP of diesel fuel by 30ºC (48º F) or more. These same methods of winterization can also be used with biodiesel. Many of the same antigel additives that are effective with petroleum diesel are also effective with biodiesel. An issue of critical importance, however, is that most biodiesel fuels have a greater percentage of the highest freezing point molecules than most petroleum diesel, so while 0.1% by volume of the additive may be enough to bond to all of those high-freeze point molecules in petroleum diesel, they may not be enough for biodiesel. As a result, using the same amount may have no effect on the gel point. But, using a greater percentage, based on the percentage of high freeze point molecules in the biodiesel, a significant antigelling effect can be achieved. Most methyl soyate biodiesel has a gel/pour point slightly below 0ºC (-3ºC is the PP of the sample analyzed in the reference used for compiling Table 3). But, in tests performed by a member of the UNH Biodiesel Group (Michael Briggs), use of antigel additives in the appropriately higher percentage required successfully lowered the PP of soy biodiesel to below -23ºC. The cold flow properties of biodiesel present an excellent opportunity for lessons on freezing point depression as well as sols (gels), and applications of those concepts currently in use in the automotive fuel sector, as well as how they can be used with an alternative fuel entering the market. III.a. Thermodynamics, Energy Conservation An important issue when looking at fuels, and energy “production”, is the energy efficiency of the processes involved. For an automotive fuel, the more efficiently it can be produced, the less energy we need to create for the production of the fuel. This is an issue of critical importance in any discussion of alternative energy or fuel, and is something which is unfortunately often completely overlooked. A key concept for students to understand here is the conservation of energy. Energy can not be created or destroyed, it can only be changed from one form to another. When we say we “produce energy from coal”, for example, we are not actually creating energy, we are instead converting the chemical energy that was in the coal into electrical energy which we can more readily use. There are many different methods of examining the energy efficiency for a process. One of the most useful is referred to as the EROI – or Energy Return On Investment (or EROEI, Energy Return on Energy Invested). Essentially, this means how much energy we get back (in the form of a fuel, or usable energy) for each unit of energy we put into the process. The higher the EROI, the better the process. If the EROI is below one, then we actually lose energy through the process. A similar method often used is referred to as an energy balance. Energy balances can be performed in a number of ways, and at heart are the same as an EROI. But, energy balances are often done to only include a certain type of energy input. For example, fossil energy balances are often done to look at how efficiently something uses fossil fuels. A fossil energy balance is done to see how much energy we get back for each unit of fossil energy expended in the process – including the energy of any fossil fuel converted to a more usable form. To clarify, for analyzing the use of petroleum to make gasoline, diesel, etc., the EROI measure tells us how much energy we get in the form of those fuels for each unit of energy we expend on extracting the petroleum, refining, and transporting it. But, the EROI does not include the energy in the petroleum itself as an energy input. For the various petroleum products (gasoline, diesel, etc.), the EROI is generally around 10 to 20, depending on the quality of the petroleum and amount of processing involved (i.e. Middle Eastern oil is generally lighter, and requires less processing to get gasoline, than petroleum from the US). An EROI of 10 means that for each unit of energy we put into the process (including extracting the petroleum, refining it to fuel, transporting it, etc.), we get back an amount of fuel containing 10 units of energy. An EROI of 10 is not a violation of the conservation of energy. No energy is “created” in the process. The reason the EROI can be greater than 1 is that the energy contained in the petroleum itself is not counted as an energy input for this calculation. This is done since we do not have to put energy in ourselves to “make” the petroleum. It’s just sitting there, so if we can extract it, we can consider the petroleum energy “free” – at least for the purpose of an EROI calculation. An EROI of 10 simply means that all of the additional energy, which we have to put into the process, adds up to only one unit of energy for each unit of fuel we are able to process from the “free” petroleum (free in energy terms for this calculation). All of the energy input used for the process is included, even if that energy came from petroleum itself. By contrast, a fossil energy balance includes the energy in the petroleum as an input. The reason for such a calculation is that it’s often useful to know how efficiently we can convert fossil fuels to more usable fuels, since fossil fuels are after all not unlimited, and not “free”. So, for a fossil energy balance, the energy within the extracted petroleum is counted as an energy input. If we extract an amount of petroleum containing 11 units of energy, spend 1 unit of that energy in processing (i.e. burn some of the petroleum to produce heat and electricity for operating a refinery, etc.), and end up with 10 units of energy in the form of various petroleum fuels, our fossil energy balance would be 10 units of output energy to 11 units of input energy, 10:11, or a fossil energy balance of 10/11:1, 0.91:1. Such a fossil energy balance would be abbreviated as just 0.91, meaning we get 0.91 units of energy in the form of fuels for each unit of fossil energy input – including the energy within the petroleum being processed. So, while petroleum fuels may have an EROI of 10, they would have a fossil energy balance of 0.91. These analyses are useful for comparing other forms of alternative fuels and energy. If an alternative fuel has an EROI of only 1.4, to make enough fuel-energy to replace all of the petroleum fuel we currently use, we would have to generate far more energy to be used as input to the process than we currently do for processing petroleum fuels. Likewise, if the EROI or fossil energy balance is below 1, we would end up using up a greater amount of energy than we end up with as fuel (so it is not a truly renewable fuel). In energy terms, biofuels use the sun as their prime energy input. We may put energy into planting, fertilizing, harvesting, and processing the crops, but a great deal of energy input also comes from the sun. Since plants use photosynthesis to convert solar energy into chemical forms of energy (carbohydrates, fats, etc.), we can think of plants as “cheap” solar cells. They convert solar energy into a form more usable as a fuel. So, whereas for the purpose of an EROI analysis we can consider the energy in a fossil fuel we dig up out of the ground as “free” (except for the additional energy we expend getting it), we can also consider the energy in the plants free – except for the energy that we put into planting, fertilizing, and harvesting them. After all, “we” are not responsible for producing the solar energy the plants use as their prime energy source for making the chemical energy within the plant’s biomass. The U.S. Department of Energy (US DOE) performed a thorough fossil energy balance calculation for soybean biodiesel. In this analysis, they assumed that all energy inputs other than the energy within the soybeans themselves came from fossil fuels. So, for example, the tractors used for planting and harvesting were assumed to run on petroleum diesel – even though they could be run on biodiesel, so it would not be a fossil input. This assumption is useful to make, as for a biofuel it results in the fossil energy balance essentially being an EROI calculation. The reason being that this method for calculating a fossil energy balance assumes that all energy input (except the energy in the plant) is from fossil fuels. Therefore, the energy input for the EROI of a biofuel is the same as the energy input side of the equation for a fossil energy balance, when that assumption is made (since neither analysis would include the energy in the plant as an input). The fossil energy balance would be better if some inputs came from biofuels as well, such as running tractors on biodiesel, but it is more useful to know how much total energy input is required. The US DOE’s analysis yielded a value of 3.2 for the fossil energy balance (and henceforth EROI) of soybean biodiesel. This is considerably better than the fossil energy balance for petroleum fuels, but lower than the EROI of petroleum fuels. Other options for producing biodiesel can yield a considerably higher EROI, which makes it suitable as a potential wide-scale replacement for petroleum. This analysis also assumed that the methanol used was derived from natural gas – a reasonable assumption for now, since that is where most of our methanol comes from. But, there are many options for producing methanol from biomass, which could be used in the future. So, if those methods were used, the EROI and fossil energy balance could be increased substantially. An example of why energy analyses are so important in analyzing alternative fuels can be seen by looking at the furor over the notion of a “hydrogen economy”. One good example of this is included in the “Misconceptions” section later in this document. In essence, the relevant issue is that most media articles, and even many attempts at scientific analysis of hydrogen as a fuel completely ignore this issue. Deciding upon public energy decisions without including an energy analysis is extremely short-sighted. Table 4, “Analysis of Prototype and Production Vehicles on Various Fuels”, includes an example of using a fossil energy balance to examine various fuel options. This analysis includes vehicles running on gasoline, diesel, biodiesel, and hydrogen. The biodiesel vehicle included is a Volkswagen Jetta TDI Wagon, a vehicle currently in fullscale production. The hydrogen vehicle included is Honda’s Fuel Cell Vehicle (FCV) prototype, a vehicle which Honda previously estimated would sell for roughly $100,000 if in full-scale production in 2012 (they have since backed away from that estimate, saying it will not be possible). For such a cost, we should hope for a very high fossil energy balance – at least higher than for the Volkswagen available today for around $20,000, and running on 100% biodiesel. The most useful means of comparing vehicles on their energy efficiency is the total fossil energy input per mile. As the table shows, this quantity is a combination of the fossil energy balance for the fuel itself (FEB), the energy density of the fuel in Btu/gallon (ED), and the fuel efficiency of the vehicle in miles per gallon (FE). The total fossil energy input per mile then becomes: Fossil Energy Input per Mile = _____Energy Density_______ Fuel Efficiency * Fossil Energy Balance The fossil energy balance is used since it gives a better comparison of how efficiently we use fossil fuels, and the net CO2 emissions (since those only come from fossil fuels). For biofuels, as mentioned, the energy inputs could all come from non-fossil sources, but for this analysis, it is more meaningful to assume they come from fossil sources. For the hydrogen analysis, the method of generating hydrogen was assumed to be steam reformation of natural gas – the most common and cost effective method of producing hydrogen, and likely the primary method that would be used in a “hydrogen economy”. Large quantities of hydrogen are already produced via this method for various industrial uses. The cost and efficiency of this process is therefore very well established. A US DOE analysis calculated the fossil energy balance (FEB) for this process of producing hydrogen to be 0.66, meaning for each unit of fossil energy input, we get back 0.66 units of energy in the form of hydrogen. Using the specifications for Honda’s Fuel Cell Vehicle from Table 4 (FE = 5.7 mpg, ED = 9 Btu/gal, FEB = 0.66) , this yielded a fossil energy input per mile of 2.4 Btu/mile. By comparison, with the Volkswagen already on the market (FE = 44.75 mpg average between city/highway), running on soybean biodiesel (and assuming all energy inputs (tractors, etc.) are from fossil fuels, for a FEB of 3.2, and ED of 127 Btu/gal) yields an input of 0.89 Btu/mile. If biodiesel were used in the Dodge Intrepid ESX3, a diesel-electric hybrid prototype developed by Chrysler in 2000 (and with an expected full-scale production cost of $28,500), the input would be 0.55 Btu/mile. Table 4 - Analysis of Prototype and Production Vehicles on Various Fuels Jetta TDI on Jetta TDI on Jetta 2.0L Toyota biodiesel petroleum gasoline Prius diesel engine gasoline Honda on Cell Fuel vehicle (hydrogen) Dodge ESX3 (dieselhybrid) biodiesel Vehicle cost $19,970 $19,970 $18,790 $21,520 $100,0003 $28,500 Fuel efficiency 41/48.5 42/50 24/31 52/45 5.74 72 Vehicle range 609/711 609/711 348/450 619/536 155 ??? Power (hp) 90 90 115 70 110 ??? Torque (ft-lbs) 155 155 122 82 (EM?) 188 ??? Cost/mile2 $0.047 $0.040 $0.062 $0.035 $0.195 $0.03 141 123 123 9 127 0.83 0.74 0.74 0.667 3.2 3.7 6.0 3.4 2.4 0.55 Energy density of 127 fuel (Thousands of BTUs/gal) Fossil Fuel Energy 3.2 Balance6 Total fossil energy 0.89 input/mile8 (Thousand BTU/mile) 2 .5 Ho nd a' s F uel C ell V ehicle 2 1.5 V W , so yb ean B io d iesel D o d g e Int r ep id , d iesel- elect r ic hyb r id 1 0 .5 0 F EI, B t u/ M ile The Total Fossil Energy Inputs per mile are shown in Figure 6. This important analysis shows that the most likely scenario for the hydrogen economy would yield on vehicles which would still require considerably more fossil energy input per mile than vehicles available today, running on biodiesel. Unfortunately, such energy analyses are rarely done by the media, or even the panels making recommendations on public energy policy. BIO-DIESEL PROCESSING Biodiesel is a clean, renewable and domestically produced diesel fuel, which has many characteristics of a promising alternative energy resource. The most common process for making biodiesel is known as transesterification. This process involves combining any natural oil (vegetable or animal) with virtually any alcohol, and a catalyst. There are other thermochemical processes available for making biodiesel, but transesterification is the most commonly used one due to the simplicity and high energy efficiency. The high energy efficiency of transesterification is an important aspect of Biodiesel, which makes it favorable in the competitive energy market. The following is a transesterification reference guide that can be used to process Biodiesel on an experimental scale for classroom demonstrations. It can be done with basic equipment and common chemicals. Be sure to use extreme caution when carrying out this procedure, the methanol and catalyst are toxic, and give off potentially harmful vapors. Proper personal protection is imperative, including thorough ventilation. Links will also be given for more information on building more sophisticated small-scale biodiesel processors. This demonstration can be done with a food processor or a large, empty (and clean) soda bottle (using shaking to mix the oil and methoxide). Materials Biodiesel consists of three principal feed stocks; 1. Oil: Glycerides are commonly known as oils or fats, chemically speaking these are long chain fatty acids joined by a glycerin backbone. They appear most often with three fatty acid chains connected to the glycerin, making them trigylcerides. In the US, the primary triglycerides used currently for biodiesel production are soybean oil and waste vegetable oil (which is often used soybean oil). During the process of being used in fryolators, some of the triglycerides are broken apart into mono or diglycerides, leaving free fatty acids (FFAs) in the oil. To counter this, additional catalyst must be added according to the acidity of the specific oil, since the FFAs will bond with and neutralize some of the alkali catalyst. 2. Alcohol: Although a variety of alcohols can be used to produce Biodiesel, such as, ethanol or butanol, this experiment will focus on methanol as it is most readily available, and most frequently used (the reaction is also more complicated with larger alcohols, which will be explained later). Therefore the Biodiesel produced is referred to as methyl esters. Methanol is one of the most common industrial alcohols; because of its abundant supply it’s most often the least expensive alcohol as well. 3. Catalyst: the third reactant needed is a catalyst that initiates the reaction and allows the esters to detach. The strong base solutions typically used are sodium hydroxide (NaOH) and potassium hydroxide (KOH). This classroom experiment will be using NaOH as catalyst. Safety: Extreme caution must be taken when working with methanol and especially with sodium methoxide. Safety Goggles, Chemical gloves and ventilation apparatus must be used at all times. Have plenty of water and vinegar (to neutralize the base) on hand. Processing guidelines: 1. To get a more complete reaction, the oil should first be heated to around 120-130º F to help the reaction proceed more quickly. Used Vegetable oil should also be filtered first (after heating) to remove particulates. Used oil may also have water in it which would need to be removed. With this small batch of oil, this can be accomplished by heating to above 100º C to boil off the water. Water removal can also be done (with less energy) by using a vacuum pump to decrease the boiling point of water, or by using molecular sieves. 2. Approximately 3.5g of NaOH per L of oil is needed when using virgin oil. However when using waste oils (which therefore have free fatty acid (FFA) content), the pH must first be determined (by titration) to calculate the additional amount of NaOH needed. The titration (for used oils, or older oils that could have degraded some, producing FFAs) is done as follows: Dissolve one gram of NaOH into 1 liter of distilled water. Dissolve 1ml of the filtered oil into 10ml of isopropyl alcohol and add two drops of phenolphthalein, an acid base indicator. Now slowly add, by calibrated dropper or pipet, the NaOH(aq) solution to the oil solution, mix intermittently. When the oil solution turns pink and stays pink for ten seconds the titration is complete. The volume of NaOH(aq) solution in milliliters necessary to neutralize the free fatty acids corresponds directly with the number of additional grams per liter of NaOH needed for transesterification. 3. Methanol makes up approximately 10% of the Biodiesel, but to force the reaction, an excess is generally added – usually totaling 20% of the volume of the oil (well designed processors can use methanol recovery systems to recover this surplus methanol after the reaction, after removal of the glycerin). So for a reaction with one liter of oil; 200 ml of methanol is first mixed with 3.5 grams of NaOH, plus any additional NaOH in regards to the free fatty acid titration (only necessary if using used/waste vegetable oil). Ensure the NaOH is completely dissolved; this reaction creates sodium methoxide. Again, Caution! Sodium methoxide is extremely toxic. Provide thorough ventilation and wear protective equipment. 4. Add the sodium methoxide to the oil. Mix thoroughly - for this small demonstration, a blender on a low setting for an hour or more is ideal; however, vigorous shaking for a couple minutes will suffice (although if this method is used, you’ll need to re-shake the solution after twenty minutes or so, and at least one more time). In actual biodiesel processors, the oil is heated to 120-130º F to aid the reaction, so it can be done in only an hour. If done at room temperature, longer reaction time is needed for a complete reaction – but repeated shakings separated by 10-20 minutes can suffice. If building a larger processor, an ideal solution is to use an old electric water heater as your processing tank, with a recirculating pump to send the oil/methoxide mix up to the top of the tank, allowing it to splash down into the tank for splash blending. See the “Biodiesel Homebrew Guide” reference for more details on this design. 5. Allow the solution to sit. After about ten minutes, the beginning of separation can be observed. However, after about eight hours the glycerin molecules will have mostly settled to the bottom of the container and the methyl esters (biodiesel) will be on top. Analyze results Possible errors: 1. Soap formation. You can get this if using waste vegetable oil that is heavily used, or using too much catalyst. Any Free Fatty Acids (FFAs) will combine with the alkaline catalyst (NaOH or KOH) to make soap (which is why you need to use extra NaOH when dealing with used oils with FFAs). These soaps need to be removed from the biodiesel by “washing” it (discussed later). A large amount of FFAs can result in enough soap forming to turn the entire reaction into a bunch of “glop” (non-scientific term). If using WVO with high levels of FFAs (determined via titration), a slightly different process can be used, known as an “acid-base” process (whereas this process discussed is strictly a base catalyzed process). In the acid-base process, you first add some acid (hydrochloric typically) and a small amount of methanol to esterify the FFAs into biodiesel, and then do the normal base catalysed process to conver the triglycerides into biodiesel. With high FFA oils, the normal base process doesn’t yield as much biodiesel, since the FFAs are being turned into soap (and removed through washing). The acid-base process allows you to turn those FFAs into biodiesel. 2. Not enough ly, resulting in unreacted oil. 3. Not enough alcohol (reaction does not proceed to completion), can also get more soap formation. 4. Water in oil (results in catalyst being broken apart, and more soap formation) 5. Not enough reaction time (a common problem with demonstration batches like this. Ideally you want to mix for an hour or so, at a slightly elevated temperature (120-130º F). The reaction does not proceed instantly from triglycerides (oils) to 3 biodiesel molecules (per triglyceride). Instead, the methoxide first cleaves off one fatty acid (making one biodiesel molecule from it, by combining with the methanol), leaving a diglyceride (DG). If there is further agitation, the DG is broken apart by the methoxide to make another biodiesel molecule and leaving a monoglyceride (MG). Further agitation breaks that MG apart, making the third biodiesel molecule and leaving free glycerin. If the agitation does not continue long enough (or is not repeated multiple times), you will likely not see full conversion of triglycerides to biodiesel, instead being left with some MGs and DGs, which will often show up as white “chunks” when the fuel cools down to room temperature. Washing “Washing” is done primarily to remove soap from the biodiesel (which forms from the combination of the alkali catalyst and free fatty acids). The glycerin primarily settles out (provided enough time is given), the methanol either evaporates or is recovered (and mostly goes with the glycerin), the catalyst goes out with the glycerin, but the soaps can remain in the biodiesel unless washed. More sophisticated processing techniques (such as using organometallic catalysts instead of alkali catalysts) can eliminate the need for washing by preventing soap formation. Washing is done through one of two methods – mist washing or bubble washing (or both). Mist washing consists of gently misting water down onto the biodiesel, so that as it falls down through it (since the water is more dense) the soaps dissolve into the water, being pulled out of the biodiesel. Bubble washing consists of using an aerator (such as used in a small household aquarium) to bubble water and air up through the biodiesel, with the soaps dissolving into the water as it travels up (with the air) and then falls back down. Bubble washing is more effective, but causes more agitation – which can result in an emulsification forming if there is too much soap. So, an ideal approach is to first do one gentle mist wash, drain the water, and then do a couple of bubble washes. Washing is generally done multiple times (with each wash taking as much as a couple of hours), only stopping when a wash does not pull out any more soap (evidenced by the wash water remaining clear). Washing is generally done in a specific “wash tank”, often the same tank used for settling. You need a tank that can be drained from the bottom – either a conical bottom tank with a drain at the base, or a cylindrical tank with two drains on the bottom, one of which has a stand pipe going up into the tank far enough that the biodiesel can be drained separate from the water or glycerin on the bottom. A conical bottom tank is ideal, although more expensive. Biodiesel Chemistry Biodiesel Chemically, biodiesel (from transesterification) refers to mono alkyl esters of long chain fatty acids derived from natural oils. We’ll look a little closer into what exactly that means. Ester An ester is the product of combining an acid (abbreviated as R1-COOH) with an alcohol (abbreviated as R2OH). Esters in general are often abbreviated as R1-COOR2, where R1COO represents the residue of an oxygen acid (The residue is what’s left when the hydrogen is lost), and R2 represents an alkyl – from an alcohol that lost its OH group. So, through the combination, an H is lost, and an OH (although in reality the O could come from either the alcohol or the acid), yielding a water molecule (H2O), and the ester, made up of everything else remaining of the acid and alcohol except the H2O. Esters vary depending on the type of acid (R1COOH, often abbreviated as R1 for simplicity) and the type of alcohol (R2OH, often abbreviated R2). Vegetable Oil Vegetable oils are triglycerides, which are esters of glycerin (an tri-hydroxy alcohol, aka glycerol) and three fatty acids (which can be different types). A glycerin molecule looks like: CH2OH | CHOH | CH2OH Figure 1 – Glycerin (glycerol) Each vegetable oil molecule is a triglyceride, meaning it is made of the combination of three fatty acids (which can be of different types) and a glycerin backbone. So, while some esters consist of just one acid (R1OH), vegetable oil molecules have three acids combined with an alcohol. When speaking about vegetable oils in particular, the three acids are often referred to as R1, R2, and R3, and the alcohol as R4. In reality, the acids are R1OOH, R2OOH, etc., where “R” represents a chain of carbon atoms with hydrogen atoms attached, but with the carbon on one end being a carboxyl group (carbon with OOH attached). Rather than an entire glycerin backbone, it is actually the alkyl group of glycerin, essentially glycerin with just oxygen atoms in place of the hydroxy (OH) groups (so remove the three Hs on the right of Figure 1). When fatty acids and glycerin are added to make triglycerides, the glycerin loses the three Hs on the end, and the acids lose the hydroxy group on the end, making water. A triglyceride (vegetable oil) can then be drawn as: O H2COR1 CH2OOR1 | | HCOR2O or simplified as CHOOR2 | | H2COR3 CH2OOR3 O Figure 2 – A triglyceride (vegetable oil molecule) The extra oxygens on the triglyceride are attached to the carbon on the end of the fatty acid’s alkyl group with a double bond (one oxygen atom has a double bond to the carbon atom at the end of the fatty acid alkyl group, the other oxygen has one bond to that carbon atom, and its second bond is to one of the carbons in the glycerol itself). The chemical diagram on the left of Figure 2 illustrates more appropriately the structure of the glycerol, while the diagram on the right is the convention more commonly used. The fatty acids involved are R1OOH, R2OOH, and R3OOH (the hydrogen atoms and one oxygen atom are lost when the acid is combined with the alcohol to make the triglyceride, with the alcohol losing a hydrogen atom, creating water), Alcohol An alcohol is a molecule in which any carbon atoms have the maximum number of hydrogen atoms attached possible, except for one carbon atom which has an OH group connected. The simplest alcohol, and the one used most often in biodiesel production, is methanol. Methanol consists of only one carbon atom, with three hydrogen atoms attached, and one oxygen attached. The oxygen atom also has a hydrogen atom attached. Thus, methanol is often written as CH3OH. The next simplest alcohol is ethanol, which has one more carbon atoms, with two hydrogen atoms attached, in between the CH3 group and the OH group. Ethanol is written as either CH3CH2OH, or C2H5OH. The former method is often used to give more of a description of the structure (since it consists of a carbon with three hydrogen atoms attached, connected to another carbon with two hydrogens attached, connected to an oxygen with one hydrogen attached). These alcohols are abbreviated as ROH, where the R is the alkyl group (hydrocarbon chain (consisting of CnH2n+1)), and determines what type of alcohol it is. Typical Fatty Acids in vegetable oils Below is a table of typical fatty acids found in alcohol, and some of their properties. The “Acronym” is a chemical abbreviation for the molecule. The first number refers to the number of carbon atoms in the chain, and the second number refers to the number of double bonds in the molecule. Thus, Linoleic acid, for example, is a fatty acid consisting of a chain of 18 carbon atoms, with two double bonds. Notice that the more double bonds in the acid, the lower the melting point. This is an important issue regarding the cold weather suitability of the oil or the biodiesel produced from the oil, and will be discussed further. The double bonds also lower the boiling point, which does not make a significant difference on the operability of the fuel since all biodiesel molecules have boiling points so high as to make vaporization not an issue. Table 1 – Properties of Fatty Acids commonly found in vegetable oils 1 Fatty Acid Acronym Molecular Melt Boil Cetane Number (kg-cal/mole) Weight ºC/ºF ºC/ºF Heat Combust Caprylic 8:0 144.2 16.5/61.7 239.3/462.7 Capric 10:0 172.27 31.5/88.7 270.0/518.0 47.6 Lauric 12:0 200.32 44.0/111.2 131.0/267.8 1763.25 Myristic 14:0 228.38 58.0/136.4 250.5/482.9 2073.91 Palmitic 16:0 256.43 63.0/145.4 350.0/662.0 2384.76 Stearic 18:0 284.43 71.0/159.8 360.0/680.0 2696.12 Oleic 18:1 282.47 16.0/60.8 286.0/546.8 2657.4 Linoleic 18:2 280.45 -5.0/23.0 230.0/446.0 Linolenic 18:3 278.44 -11.0/12.2 232.0/449.6 Erucic 22:1 338.58 33.0/91.4 265.0/509.0 1453.07 Saturated Fatty Acids A saturated fatty acid is one containing no double bonds. Since fatty acids are acids with a COOH group at the end, a saturated acid is one in which the rest of the carbon chain is an alkane – i.e., the carbon atoms in the chain have the maximum number of hydrogen atoms bonded possible (every bonding location is filled with a hydrogen atom, except for single bonds to neighboring carbon atoms). Stearic acid (18:0) is an example of a saturated fatty acid, as it has no double bonds. The chemical formula for stearic acid is CH3(CH2)16COOH. Unsaturated Fatty Acids An unsaturated fatty acid is one containing one or more alkene functional groups – those being hydrocarbons with double bonds between two carbon atoms. An alkene does not have the maximum number of hydrogen atoms possible on all of the carbon atoms, as two adjacent carbons have a double bond between them, and therefore one less hydrogen attached each. Oleic acid is an unsaturated acid of the same length as stearic acid, but with a double bond between two of the carbon atoms, and therefore two less hydrogen atoms. Molecules with double bonds are often written using an equals sign (“=”) to show where the double bond is. For example, oleic acid has its one double bond as the ninth carbon-carbon bond, counting from the chain most distant from the carboxyl group (COOH). Thus, oleic acid would be written as CH3(CH2)7CH=CH(CH2)7COOH. Thus, the molecule has a methyl group (CH3), then 7 carbons with single bonds between them, each having two hydrogens attached ((CH2)7), then the carbon that has one end of the double bond (leaving only room left for one hydrogen atom, so it’s a CH), the double bond connecting to another CH, followed by 7 more CH2 groups, and finally the carboxyly group (COOH). This molecule is exactly the same as the stearic acid molecule (CH3(CH2)16COOH, no double bonds), except for the double bond between the 9th and 10th carbon atoms (so the 9th carbon-carbon bond). Thus, in the middle of the molecule, a set of two CH2 groups is replaced by CH=CH (double bond between the carbons, only one hydrogen each). This seemingly minor difference results in a significant change in some of the properties of the molecule, most notably the melting point. The cold flow properties of the oils, and the resulting molecules can thus be a nice method for introducing this topic of how minor differences in a molecule can have large effects, and in particular, double bonds lower the melting point of molecules (generally). The oleic acid molecule could have another double bond added, which would turn it into linoleic acid (18:2). A third double bond would make linolenic acid. Many vegetable oils normally consist of a significant percentage of these particular 18 carbon acids with double bonds. When the oil is hydrogenated (usually through high temperatures, such as when oil is used in a fryolator), that is when some of these double bonds are lost, replacing a CH=CH group with CH2CH2. The acid (or the oil that the acid is a part of) acquires two more hydrogens, and loses a double bond. The result is an increasing of the melting temperature of the acid, or oil of which it is part. This is an important consideration as far as using waste vegetable oils as feedstocks for producing biodiesel. The more heavily used the oil is, the more hydrogenated it becomes, resulting in higher melting points for the molecules. Therefore, caution should be taken when using heavily used (hydrogenated) oils for making biodiesel, as the higher freezing/melting points of the molecules would result in a greater tendency of the fuel to clog fuel filters, or possibly gel entirely. Transesterification Chemically, transesterification is the process of exchanging the alkyl group (from an alcohol) of an ester with another alkyl, from a different alcohol. In the case of biodiesel, a vegetable oil ester is combined with a simple alcohol and a catalyst, resulting in the breakup of the triglyceride ester (three fatty acids connected to a single glycerol (alcohol)), and the joining of the fatty acids with the added simple alcohols. The glycerin alkyls are replaced with the alkyl of the added alcohol (i.e. methyl for methanol, ethyl for ethanol, etc.). The separated glycerol is the waste product. This reaction is shown below: CH2OOR1 catalyst CH2OH | CHOOR2 + 3CH3 3OORx + CHOH | | CH2OOR3 CH2OH Vegetable oil 3 Methanols Biodiesel Glycerin Figure 3 – Transesterification Rx is used since the biodiesel produced will consist of different types of mono-alkyl esters, because of the various fatty acids (R1, R2, R3) in the vegetable oil. The reaction can proceed both ways, so it is necessary to add an excess of methanol to force the reaction to the right. Since it is not desirable to have free methanol in the biodiesel fuel, it is then necessary to recover the methanol either by water washing, or a pressurecondensing method. But, the glycerin must be removed first (and actually, most of the excess alcohol stays with the glycerin). If you remove the surplus methanol while the glycerin is still present with the biodiesel, the process will start gradually reversing – biodiesel and glycerin combining to re-make vegetable oil and methanol. The glycerin is more dense than the biodiesel, so it will gradually settle to the bottom in the reactor, simplifying separation. Now, since we first react the catalyst with the methanol to form a methoxide (potassium or sodium methoxide), the reaction doesn’t actually proceed exactly as shown in Figure 3. If we use NaOH as our catalyst, it combines with methanol (CH3OH) to form sodium methoxide (NaO-CH3) and a water: NaOH + CH3OH 3 + H2O. Sodium Methoxide is a quite hazardous material, so it is extremely important to handle it with care – it is explosive and toxic. Well designed biodiesel processors (whether small home-scale or large commercial scale) keep the methoxide completely contained in reaction vessels, and free from any sparks (you don’t want to use a mechanical mixer that could cause sparks – this is why a pump/splash blending process is desirable). You need to make sure that your alcohol and catalyst are very dry (no water), otherwise its presence will prevent a full conversion to methoxide. When the methoxide is added to the triglyceride, the conversion shown in Figure 3 actually happens in a series of reactions – the triglyceride first uses one fatty acid group and becomes a diglyceride, then loses a second, becoming a monoglyceride, and the third fatty acid is finally stripped off, leaving free glycerin. Each of the fatty acids are converted into biodiesel (methyl ester) as they are stripped off. Each step of this reaction occurs by the methoxide “attacking” the end carbon atom of each fatty acid alkyl group where they attach to the glycerol backbone. The metal ion of the methoxide (Na or K) breaks off, so you are left essentially with the methanol without a hydrogen atom (CH3O) with a negative charge. The carbon on the end of each fatty acid alkyl group in the triglyceride has a slight positive charge, with the oxygens on that carbon having a slight negative charge, particularly in the double bond between one of the oxygens and the carbon. This is where the methoxide “attacks”, free of the metal ion. This carbon being attacked (since it has a slight positive charge and the CH 3O- is negative) loses its double bond to the oxygen, and the CH3O bonds to the carbon. This carbon separates from the oxygen of the glycerol that it had been attached to, with the carbon-oxygen double-bond reforming. The result is one biodiesel molecule has been made, and the triglyceride has been turned into a diglyceride. The first step essentially looks like this (the water comes from the creation of the methoxide): Vegetable oil + NaMethoxide + H2O Diglyceride + Biodiesel + NaOH – First step of transesterification – triglyceride turns to diglyceride, one methoxide joins freed fatty acid to make biodiesel This process is repeated during the transesterification, with the additional methoxides further breaking down the diglyceride into a monoglyceride (and making one more biodiesel molecule), and then the monoglyceride being broken down into a glycerol (and the final biodiesel molecule). The sodium separates from the sodium methoxide at each step, combining with an OH- from the water (the other H goes onto the diglyceride), reforming the catalyst NaOH. If the mixing time is too short, the reaction could stop before finished, leaving you with a mix of biodiesel, monoglycerides, diglycerides, and triglycerides. As can be seen, the NaOH is not used up in the reaction – although procedurally it effectively is (since it comes out in the glycerin, and is typically not easily recoverable). Water is formed during the creation of the methoxide, but is also used up in the recreation of the NaOH during each esterification reaction. Research on more novel catalysts, such as organometallics, has lead to the development of catalysts that can be fixed to a substrate, so that the alcohol and oil can be mixed together directly (no methoxide step), and the transesterification occurs as the mix flows across the catalytic substrate. This is an excellent option for new industrial scale biodiesel plants, as it eliminates the need to continually buy new catalyst (such as NaOH), and simplifies the glycerin purification (since there is no NaOH in it). Biodiesel – Mono Alkyl Esters As mentioned previously, biodiesel molecules are referred to as mono-alkyl esters, since they are esters with one alkyl (from the alcohol) per fatty acid, in contrast to the triglycerides in the vegetable oil, which had three fatty acids for each glycerol. If the alcohol used in making the biodiesel was methanol, then the biodiesel is referred to as a methyl ester. If the alcohol was ethanol, the biodiesel would consist of ethyl esters. Table 2 below shows a list of the methyl esters made from the fatty acids listed in Table 1, and their properties. Note that the methyl esters of fatty acids with more double bonds have lower melting points than those without double bonds, just as the fatty acids themselves do. Also notice that the melting points of the methyl esters are lower than the melting points of the fatty acids themselves. An interesting point of discussion is that the boiling points are not all affected similarly, from fatty acids being turned into mono alkyl esters. Note that methyl stearate has a much higher boiling point than stearic acid, while methyl linolenate has a much lower boiling point than linolenic acid. Fortunately, the boiling points don’t have any significant affect on the use of the chemicals as fuels. Table 2 – Properties of Methyl Esters from Vegetable Oils 1 Methyl Ester Acid Molecular Melt Acronym Weight ºC/ºF Boil Cetane Heat Combust ºC/ºF Number (kg-cal/mole) Methyl Caprylate 8:0 158.24 193.0/379.4 33.6 1313 Methyl Caprate 10:0 186.30 224.0/435.2 47.7 1625 Methyl Laurate 12:0 214.35 5.0/41.0 266.0/510.8 61.4 1940 Methyl Myristate 14:0 242.41 18.5/65.3 295.0/563.0 66.2 2254 Methyl Palmitate 16:0 270.46 30.5/86.9 418.0/784.4 74.5 2550 Methyl Stearate 18:0 298.51 39.1/102.4 443.0/829.4 86.9 2859 Methyl Oleate 18:1 296.49 -20.0/-4.0 218.5/425.3 47.2 2828 Methyl Linoleate 18:2 294.48 -35.0/-31.0 215.0/419.0 28.5 2794 Methyl Linoleneate 18:3 292.46 -57.0/-70.6 109.0/228.2 20.6 2750 Methyl Erucate 352.60 222.0/431.6 76.0 6454 22:1 Why not use the straight oil? Biodiesel is intended to replace petroleum diesel as a fuel in Diesel engines. A common question (which students may have, since much of the public does) is why not just use the straight vegetable oil (SVO), rather than going to the trouble to convert it into biodiesel. After all, Rudolf Diesel did initially invent his diesel engine to run on pure vegetable oil. There are a couple of reasons why SVO isn’t as appealing as biodiesel. First and foremost, is the fact that modern diesel engines use high tech injection pumps, which don’t tolerate very viscous fluids. The viscosity of vegetable oil is considerably higher than the biodiesel made from that oil. Most vegetable oils have viscosities around 30-50 “centistokes”, while most biodiesel has a viscosity around 5-6 centistokes.2 If a person were to just pour vegetable oil into their fuel tank, with most diesel vehicles, the fuel pump would fail fairly quickly due to the strain of pumping the very viscous oil. That problem can be skirted somewhat by using a system to heat the vegetable oil before it gets to the pump, reducing its viscosity to an acceptable level. In fact, this approach has been taken by many people as it provides a method for them to run their diesel vehicle on free waste vegetable oil from restaurants, without having to go to the trouble of turning it into biodiesel. The most common approach is to put in a second fuel tank for the oil, and use the coolant system of the vehicle to heat the second tank. The car would be started on either diesel or biodiesel, and once the engine (and therefore the coolant) has heated up to operating temperature - usually around 200F on most vehicles – the car can switch to pulling fuel from the auxiliary tank holding heated vegetable oil. This approach can work, but is not ideal for a few reasons. But, it can present an interesting project for mechanically inclined students, and at several high schools and colleges around the country, students have modified older diesel vehicles to run on straight vegetable oil in this manner. The main drawbacks of this approach are that most modern fuel injection pumps suffer from increased wear from the high temperature of the fuel. The pumps simply aren’t designed to tolerate having 200F liquid flowing through them. Additionally, the straight vegetable oil does not burn as cleanly as biodiesel (due in large part due to the presence of the glycerin in the SVO), resulting in worse emissions, and carbon buildup on fuel injectors and inside the engine. Together, the effects to the injectors, injection pump, and inside the engine make a vehicle running on SVO less reliable, and more polluting than a vehicle running on biodiesel. A final reason for converting the vegetable oil into biodiesel can be seen by comparing the melting points for the fatty acids shown in Table 1 to those of their methyl esters shown in Table 2. The methyl esters all have lower melting points than their corresponding fatty acids (and henceforth, the triglycerides made of those fatty acids). The result is that straight vegetable oil would be more difficult to use in cold or even moderate temperatures than biodiesel. An important point to notice is that for the most part, the methyl esters with the lower (and therefore preferable) melting points, unfortunately have lower (and therefore less preferable) cetane numbers. Modern diesel engines generally require a cetane number of at least 40, preferably 45 or higher. So, while from looking at Table 2, we might think that the ideal biodiesel would be composed entirely of methyl linoleneate, due to the extremely low melting/freezing point (-70º F), we should also notice that the cetane number is far too low (20.6) for a fuel composed entirely of methyl linoleneate to be acceptable. Another point of interest is that other alcohols produce biodiesel molecules with lower melting points. For example, isopropyl stearate has a melting point of 28º C, compared to 39.1º C for methyl palmitate. 3 But, the reaction can be more difficult with longer alcohols, due to steric hindrance – longer alcohols do not fit as readily in the space around the carbon with the double bond to oxygen during the esterification, slowing reaction rates. The shorter the alcohol (methanol being the shortest), the easier it fits, and the faster the reaction. Differences between various vegetable oils Looking at the properties of the various methyl esters demonstrates that the properties of biodiesel – in particular the cold weather properties, could vary considerably depending on what oil it is made from. Table 3 below lists a few different vegetable oils, and the levels of various fatty acids they contain (bare in mind, in the oil the fatty acids are bound to glycerin as triglycerides. The table lists the fatty acids themselves, but is not meant to imply that they exist as free fatty acids in the oil). The fatty acid profiles are generalities, as various plants (and animal fats, such as the tallow included) do have variability among them, depending on growing conditions and other factors. A field in biodiesel research focuses on breeding varities of various plants for ideal fatty acid profiles. The table also includes the gel point, cloud point (these qualities are explained in section II.c of the Lesson Ideas portion of this document), and cetane number for methyl ester made from each oil. Table 3 – Fatty Acid profile, and properties of methyl esters for various oils2 Rapeseed Canola Tallow Soybean Myristic (14:0 0 0.0 3.0 0.0 Palmitic (16:0 2.2 4.0 23.3 9.9 Stearic (18:0 0.9 2.4 17.9 3.6 Oleic (18:1) 12.6 65.0 38.0 19.1 Linoleic (18:2) 12.1 17.3 0.0 55.6 Linolenic (18:3) 8.0 7.8 0.0 10.2 Elcosenoic (20:1) 7.4 1.3 0.0 0.2 Behenic (22:0) 0.7 0.4 0.0 0.3 Erucic (22:1) 49.9 0.1 0.0 0.0 Properties of Methyl Esters of the oils Cetane number 61.8 57.9 72.7 54.8 Cloud Point ºC 0 1 16 3 Gel/Pour Point ºC -15 -9 16 -3 Data taken from http://www.biofuels.fsnet.co.uk/comparison.htm Soap Formation Soap can be made by combining sodium hydroxide (NaOH), water, and vegetable oil. The water separates the sodium hydroxide, resulting in free Na+ ions. The vegetable oil triglycerides are broken apart, separating the fatty acids and glycerin. The Na+ ions attach to the fatty acids in the same place that the alkyl groups attach during transesterification to produce biodiesel. The fatty acids with a sodium ion attached make a soap (i.e. sodium palmitate). Since a base is used both for making soap from vegetable oil and also as the catalyst for breaking apart the vegetable oil molecule during transesterification, care needs to be taken that one doesn’t inadvertantly make soap. The NaOH is combined with the alcohol to make sodium methoxide, which is then added to the vegetable oil. Using too much NaOH can result in soap formation, due to the excess sodium joining the fatty acids after the vegetable oil molecules are separated. With waste vegetable oils, free fatty acids are generally already present. These free fatty acids will essentially always combine with a sodium ion during the processing, resulting in saponification (soap formation). Unfortunately, that is an unavoidable result when using this base-catalysed transesterification process (and is a reason why methods have been developed for performing the reaction without a catalyst, with a non-alkali catalyst, or an acid-base processes that first esterifies the FFAs into biodiesel). Since these free fatty acids consume the catalyst, when waste vegetable oils are used, extra catalyst needs to be added to account for that. Otherwise, not enough catalyst would be left for breaking apart the triglycerides in the oil, as some would be consumed by the free fatty acids (FFAs). This is the reason for doing the titration when using a waste vegetable oil feedstock, so that extra catalyst can be added to account for the fact that some catalyst will be consumed by the FFAs. When oils with free fatty acids are used, the free fatty acids will be turned into soaps by the alkali catalyst. As a result, the yield of biodiesel is lower for these oils, and the soap needs to be removed. The process used for cleaning the biodiesel is known as “washing”, in particular used for removing soaps. This process involves either bubbling water up through the biodiesel (after glycerin separation), or misting water down on the top and letting it flow down through the biodiesel (or a combination of both). The water pulls the soaps out of the biodiesel as it passes through. The water eventually settles to the bottom, and can be separated readily from the biodiesel. STORAGE OF BIO-DIESEL The flash point of biodiesel is higher than 100 degrees celsius (in fact, it is around 120 degrees). Thus, biodiesel is not subject to the regulations for flammable liquids and has not been classified a dangerous substance. Due to its quick biological degradability biodiesel is graded water hazard class 1, i.e. it is only of minor harmfulness. When storing biodiesel you ought to take the following points into consideration: Storage location o As biodiesel is an 'organic' substance it reacts to influences encouraging oxidation, such as temperature, light and oxygen. Therefore, direct sunlight should be avoided when storing biodiesel. o It is of particular importance that the exchange of air as well as water intake are avoided as biodiesel is hydrophilic. Storage vessels: tanks o Metal tanks are the most suitable vessels for the storage of biodiesel. The varnish inside the tank must be resistant to biodiesel. o Tanks with an inner coating of PVC are not suitable for the storage of biodiesel. Cleaning the tank Biodiesel has the properties of a solvent. Thus, the deposits formed in the system by diesel fuels are dissolved by biodiesel. That is why long-serving storage vessels ought to be cleaned before filling them with biodiesel. With the set-up of public petrol stations building regulations and safety measures concerning water protectorates have to be taken that depend on the size of the tanks and the respective local conditions. The common safety precautions for the storage of flammable liquids in closed areas do not apply as biodiesel is not subject to the regulations for flammable liquids for its high flash point. Expensive building measures such as keeping attached rooms resistant to fire and providing fire-fighting equipment are not necessary. The maxime of environmental concern, however, does apply to biodiesel: plants for the production, the treatment and utilization of substances that put water protectorates at risk must be constructed, set up and run in a way that prevents the contamination of waters or other long-term changes of their properties (§ 19g.Abs.1.WHG). Due to the quick biodegradability of biodiesel and the very low degree of water toxicity the following safety precautions ought to be taken depending on the size and shape of the storage vessel: 1. It is sufficient to provide a leakproof, impermeable mounting similar to the type of material used in roadworks (e.g. asphalt, concrete, cobbled floorspaces). The area to be secured has got to comprise the area of action of the petrol pump (length of the hose plus one metre). 2. Retention basins are to hold back potential small and large leakages from faulty seals as well as the volume of the biggest receptacle (canisters, vats, containers) and pallets for reloading. 3. Provide retention receptacles for the leakage volume that may occur until automatic safety measures come into action (level indicator). If you use automatic safety devices, you have got to consider the whole system of filling and evacuation when you approximate the potential leakage volume. 4. If there are no automatic safety devices, you have to provide detention receptacles for the leakage volume that may escape until suitable measures come into action. 5. Provide a connection to the local sewage system or a similar system (direct passing-in, e.g. a waterproof shaft with overflow). Also, there should be a device that monitors the level of condensed water which accumulates during filling and handling. 6. In case the storage area is roofed, the measures described under point three are unnecessary. 7. Single containers as well as systems of combined containers for cost reasons have to be equipped with devices indicating the boundary limit. If containers are set up outdoors, they must have crash protection. EMMISION NORMS Biodiesel properties are competitive with conventional diesel fuel in some emission categories but problems were also identified for other kinds of emissions. It was shown that poly-aromatic hydrocarbon (PAH) emissions were lower for neat vegetable oils especially the alkylated PAHs which are common in the emission of conventional diesel fuel (DF). Besides higher NOx levels, aldehydes are reported to present problems with neat vegetable oils. Total aldehyde increased dramatically with vegetable oils and formaldehyde formation was consistently higher than with DF. It was also reported that component triglycerides (TGs) in vegetable oil can lead to formation of aromatics via acrolein (CH2=CH-CHO) from the glycerin moiety. Most studies conducted report that for short-term trials, neat oils gave satisfactory engine performance and power output are often equal to or even slightly better than conventional DF. However, vegetable oils cause engine problems. Studies on sunflower oil, coconut and other oils as fuel noted coking of injector nozzles, sticking piston rings, crankcase oil dilution, lubricating oil contamination and other problems. The causes of these problems were attributed to the polymerization of TGs via their double bonds which leads to formation of engine deposits as well as the low volatility and high viscosity with resulting poor atomization patterns. Alkyl esters. Biodiesel emissions are substantially lower than petroleum diesel emissions. Compared to gasoline, biodiesel produces no sulfur dioxide, no net carbon dioxide, up to 20 times less carbon monoxide, and more free oxygen. Biodiesel has the following emission characteristics when compared to petroleum diesel fuel: Reduction of net carbon dioxide (CO2) and sulfur dioxide (SO2)emissions by 100%. Reduction of soot emissions by 40-60%. Reduction of carbon monoxide (CO) and hydrocarbon emissions by 10 - 50%. Reduction of all polycyclic aromatic hydrocarbons (PAHs) and specifically the reduction of the following Carcinogenic PAHs: Reduction of phenanthren by 97%. Reduction of benzofloroanthen by 56%. Reduction of benzapyren by 71%. Reduction of aldehydes and aromatic compounds by 13%. Reduction or increase of nitrous oxide (Nox) emissions by 5-10% depending on Opacity or "K" Reading (m-1) the age of the vehicle and the tuning of the engine. 2.5 2.32 2 1.5 1.24 1.03 1 0.81 0.43 0.5 0.35 0.24 0 0 200 1,400 3,900 5,033 15,663 16,928 Road Run Kilom eter (Km ) Figure 1. Reduction of Smoke Emission after Blending Petroleum Diesel with 1% CME Illustration No. 1. Effect of CME on the Engine POWER TORQUE CURVE TORQUE (kg-m) LSD 10.80 1% CM E-13 10.60 10.40 10.20 1% CM E-15 10.00 5% CM E-15 2% CM E-13 2% CM E-15 5% CM E-13 9.80 9.60 9.40 9.20 9.00 8.80 1500 2000 2500 3000 RPM 3500 4000 4500 3 Opacity or "K" Reading (m-1) 2.65 2.5 with 1% CME w/o CME 1.9 1.89 2 1.6 1.53 1.5 1.05 1 0.79 0.54 0.5 0.39 0.28 0.19 0.26 0 0 900 1800 2700 3600 4500 Distance Travelled (Km) Fig. 3. Dynamometer Test Result On C-190 Isuzu Diesel Engine. Illustration No. 2. California Buses Opacity Test Result Biodiesel Standard Pursuant to the intent of the Clean Air Act to develop and utilize cleaner alternative fuels, the Technical Committee on Petroleum products and Additives of the Department of Energy (DOE/TCPPA) prepared a Philippine Coconut Oil Biodiesel Product Standard and is adopted as the Philippine National Standard (PNS) for Biodiesel by the Bureau of Product Standard (BPS) which the manufacturers should comply to ensure its effectiveness when used either in its pure state or as a blend. The ASTM standard being used in the United States was used as basis for this specification. Table 1 shows the prepared PNS specifications. Critical key points on CME fuel quality include; Flash point whose limit is set at 100oC to ensure the removal of excess methanol used during the manufacturing process. Presence of residual methanol even at small amount reduces flash point. It can also affect fuel pumps, seals and can result to poor combustion, Sulfated Ash ensures the removal of catalyst. High level of catalyst in the fuel can result in injector deposits or filter plugging, Acid number limits to 0.5 maximum. Higher than the set limit may cause fuel system deposits and reduce the life of fuel pumps and filters, and Free and Total Glycerin Number which measure the degree of conversion of oil into ester. If the value is too high, fuel gumming and engine fouling will occur. DOE/TCPPA also come up with conclusive inter-laboratory fuel test results (wherein the petroleum laboratories participated) that 1%, 2% and 5% CME-PDF Blend (by volume basis) still conform to the PNS for Diesel Fuel. Table 1. PNS Specification for Biodiesel and the Test Method Used Property CME Limit Test Method Flash point Pensky Martens oC, min. 100.0 PNS 613 / ASTM D 93 Water & Sediments % vol. Max. 0.050 PNS 707 / ASTM D 2709 Kinematic viscosity @ 40oC, mm2/s 2.0 – 4.5 PNS 407 / ASTM D 445 Sulfated ash % mass max. 0.020 PNS 2025 / ASTM D 874 Sulfur @ mass max. 0.050 PNS 504 / ASTM D 2622 Copper strip corrosion 3 hrs @ 50oC max. No. 3 PNS 379 / ASTM D 130 Cetane number, min. 42a PNS 653 / ASTM D 613 Cloud point, oC max. Report PNS 706 / ASTM D 2500 Carbon residue,100% sample,% mass, max. 0.050 PNS 708 / ASTM D 4530 Acid number, mg KOH/g,max. 0.50 PNS 2024 / ASTM D 664 PNS 2026 / ASTM D 974 Free glycerin, % mass, max. 0.02a PNS 2022 / AOCS Ea6-51 (1989)a Total glycerin, % mass, max. 0.24a PNS 2023 / AOCS Ca 14 -- 56 (1997)a Phosphorus,% mass,max. 0.001 PNS 2028 / ASTM D 4951 Distillation AET 90% recovered oC, max. 360 PNS 2027 / ASTM D 1160 a Transition standard ADVANTAGES OF BIO-DIESEL Biodiesel fuel has numerous advantages over conventional diesel that make it desirable to consumers. First, the molecular construction of Biodiesel relative to conventional diesel will, when burned, increase engine lubricity (a measure of an engine’s efficiency at performing the essential task of lubrication). Given the importance of lubrication in both the efficiency and lifespan of an engine, this is a significant benefit of the fuel. Second, Biodiesel has a high ignition temperature compared to regular petroleum diesel fuel (150°C vs. 52°C), which means that it can be transported quite safely with normal vehicles. Third, as a result of its organic origins, Biodiesel is both biodegradable and non-toxic; in fact, 100% Biodiesel is as biodegradable as sugar and less toxic than table salt. Therefore, in the event of a fuel spill, there would be far less damage to the affected environment than would occur with conventional diesel. Finally, although not an advantage of the fuel itself, it should also be noted that Biodiesel can be used in any diesel engine without major engine or fuel tank modifications. This is significant because it means that consumers will have negligible switching costs in adopting Biodiesel for their vehicles. As mentioned above, switching costs to Biodiesel are low. However, they do exist: while the use of Biodiesel does not require major infrastructure changes to the engine, deterioration of rubber fuel hoses may occur with the use of Biodiesel due to the methanol content in the fuel. As a result, rubber fuel hoses and seals may need to be replaced with synthetic fluroelastomer equivalents such as Viton®. These products can, however, be found in most auto supply stores or replaced easily by any auto mechanic for a nominal charge. SPECIFICATION OF BIO-DIESEL The comparison of properties of Jatropha curcas oil and standard specifications of diesel oil Specification Standard specification of Jatropha curcas oil Specific gravity 0.9186 Flash point 240/110°C Carbon residue 0.64 Cetane value 51 Distillation point 295°C Kinematics Viscosity 50.73 cs Sulpher % 0.13% Calorific value 9,470 kcal/kg Pour point 8°C Colour 4 Physical and chemical properties of diesel fuel and Jatropha curcas oil. Property Jatropha curcas Oil Viscosity (cp) (30°C) Speciflc gravity (15°C/4°C) 0.917/ 0.923(0.881) Solidfying Point (°C) Cetane Value Flash Point (°C) 110 / 340 Carbon Residue (%) Distillation (°C) 284 to 295 Sulfur (%) 0.13 to 0.16 Acid Value 1.0 to 38.2 Saponification Value 188 to 198 Iodine Value 90.8 to 112.5 Refractive Index (30°C) Standard specification of Diesel 0.82/0.84 50°C 0.15 or less > 50.0 350°C > 2.7 cs 1.2 % or less 10,170 kcal/kg 10°C 4 or less Diesel Oil 5.51 3.6 0.841 / 0.85 2 51 47.8 to 59 0.14 80 0.64 < 0.05 to < 0.15 < 350 to < 370 < 1.0 to 1.2 1.47