Biodiesel, an alternative diesel fuel consisting of the alkyl monoesters of fatty acids from vegetable oils and animal fats, can be used in existing diesel engines without modifications. However, property changes associated with the differences in chemical structure between biodiesel and petroleum-based diesel fuel may change the engine's injection timing. These injection timing changes can cause different exhaust emissions and performance than the optimized settings chosen by the engine manufacturer. The properties that will have the greatest effect on the fuel injection timing are the speed of sound, the isentropic bulk modulus, and the viscosity. The objective of this study was to measure the isentropic bulk modulus and speed of sound of biodiesel and the pure esters that are the constituents of biodiesel at temperatures from 20°C to 100°C and at pressures from atmospheric to 34.5 MPa. Future work to identify the effect of viscosity is anticipated. The measured values of density, speed of sound, and isentropic bulk modulus are shown and correlations showing the dependence of pressure at each temperature are provided. A simple analysis using measured values of biodiesel and diesel fuel properties indicates that property changes could cause approximately 1° of injection timing advance. Since NO x emissions increase with advanced timing, this effect may be partially responsible for the increase in NO x sometimes observed in the exhaust of biodiesel fueled engines.

Biodiesel is a non-toxic, biodegradable and renewable alternative fuel that can be used with little or no engine modifications. Biodiesel is currently expensive but would be more cost effective if it could be produced from low-cost oils (restaurant waste, frying oils, animal fats). These low-cost feedstocks are more challenging to process because they contain high levels of free fatty acids. A process for converting these feedstocks to fuel-grade biodiesel has been developed and described previously. The objective of this study was to investigate the effect of the biodiesel produced from high free fatty acid feedstocks on engine performance and emissions. Two different biodiesels were prepared from animal fat-based yellow grease with 9% free fatty acids and from soybean oil. The neat fuels and their 20% blends with No. 2 diesel fuel were studied at steady-state engine operating conditions in a four-cylinder turbocharged diesel engine. Although both biodiesel fuels provided significant reductions in particulates, carbon monoxide, and unburned hydrocarbons, the oxides of nitrogen increased by 11% and 13% for the yellow grease methyl ester and soybean oil methyl ester, respectively. The conversion of the biodiesel fuel's energy to work was equal to that from diesel fuel.

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The specific gravities of biodiesel and 75, 50, and 20% blends with No. 1 and No. 2 diesel fuels were measured as a function of temperature from the onset of crystallization to 100°C. The results indicate that biodiesel and its blends demonstrate temperature-dependent behavior that is qualitatively similar to the diesel fuels. The temperature dependence of the specific gravity for biodiesel and its blends was compared with the ASTM D 1250-80 procedure for the temperature correction of hydrocarbon fuels, and the procedure was found to provide accurate corrections. A blending equation was developed that allows the specific gravity of blends to be calculated from the specific gravities of the biodiesel and diesel fuels.A large amount of research has been conducted in recent years to investigate alternative fuels for transportation. Renewable biomass resources such as plant seed oils and animal fats could play a role in meeting our society's future energy needs in an environmentally sound way. While the high viscosity of vegetable oils and animal fats tends to cause problems when used directly in diesel engines (1-4), if the oils and fats are transesterified using short-chain alcohols, the resulting monoesters have viscosities that are closer to petroleum-based diesel fuel (5-7). These monoesters have come to be known as biodiesel.The specific gravity of biodiesel will depend on the fatty acid composition of the mixed esters and their purity. In a similar manner, the specific gravity of petroleum-based diesel fuel varies depending on the refinery feedstock and day-today variability of the blending streams in the diesel fuel boiling range. The specific gravity of diesel fuel is constantly monitored and many performance indicators, such as cetane number and heating value, are correlated against it. However, the specific gravities of hydrocarbons are strongly affected by temperature. Since specific gravity measurements made outside the laboratory are usually at nonstandard temperatures, ASTM standard D 1250 (8) was developed to correct measured specific gravities back to a reference temperature. The standard consists of a series of tables relating specific gravity and temperature.As biodiesel moves closer to commercialization, a similar procedure for correcting measured specific gravity data will be needed. The specific objective of the research described in this paper was to measure the specific gravity of biodiesel and its blends with diesel fuel as a function of temperature, to compare the temperature-dependent behavior with that predicted by ASTM D 1250, and, if necessary, to develop a new correction table.Equipment and procedure. In this study, commercially available soybean oil-based biodiesel (NOPEC Corporation, Lakeland, FL) was used and its properties are shown in Table 1. Commercial grades of No. 1 and No. 2 diesel fuel were obtained from local fuel suppliers and their properties are given in Table 2. Blends of 20, 50, and 75% biodiesel with No. 1 and No. 2 diesel fuels were prepared by weight. Owing to the d...

Biodiesel, an alternative diesel fuel consisting of the alkyl monoesters of fatty acids from vegetable oils and animal fats, can be used in existing diesel engines without modification. However, property changes associated with the differences in chemical structure between biodiesel and petroleumbased diesel fuel may change the engine's injection timing. These injection timing changes can change the exhaust emissions and performance from the optimized settings chosen by the engine manufacturer. This study presents the results of measurements of the speed of sound and the isentropic bulk modulus for methyl and ethyl esters of fatty acids from soybean oil and compares them with No. 1 and No. 2 diesel fuel. Data are presented at 21 ± 1°C and for pressures from atmospheric to 34.74 MPa. The results indicate that the speed of sound and bulk modulus of the monoesters of soybean oil are higher than those for diesel fuel and these can cause changes in the fuel injection timing of diesel engines. Linear equations were used to fit the data as a function of pressure, and the correlation constants are given.Biodiesel has come to be defined as the alkyl monoesters of fatty acids from vegetable oils or animal fats. It can be used as an alternative fuel for diesel engines. Many researchers have reported that oxides of nitrogen (NOx) increase, and particulate matter, carbon monoxide, and unburned hydrocarbons decrease when biodiesel is used in heavy-duty diesel engines (1,2). The reason for the higher NOx emissions is not currently understood but could be due to changes in the chemical composition and the physical properties of the fuel. A major difference between petroleum-based diesel fuel and biodiesel is the 10-11% oxygen content of the biodiesel. The oxygen could change the stoichiometry of the combustion process in a way that produces more NOx. Biodiesel also generally has a higher cetane number than petroleum-based diesel fuel. The cetane number is a diesel fuel property that quantifies the fuel's readiness to autoignite. Higher cetane number corresponds to a shorter ignition delay after the fuel is injected into the cylinder. This results in earlier combustion timing, which tends to increase NOx, and less of the fuel participating in the rapid combustion of the fuel that has premixed during the ignition delay period, which will reduce NOx. These two effects partially offset each other, but higher cetane number in petroleum-based diesel fuels is generally observed to reduce NOx (3). The contribution of biodiesel's higher cetane number to NOx production is still not understood. Changes in physical properties such as viscosity, speed of sound, and bulk modulus also may contribute to higher NOx levels. Injection system anomalies, such as longer injection duration, higher injection pressure, and early injection have been reported by other researchers (4-6).Diesel engines operate by compressing fuel to a high pressure and injecting it into the cylinder where the fuel spontaneously ignites. The fuel is compressed with a piston ...

Biodiesel is an alternative diesel fuel consisting of the alkyl monoesters of fatty acids from vegetable oils or animal fats. Currently, m ost biodiesel is made from soybean oil, methanol, and an alkaline catalyst. However, there are large amounts of fats and oils that are unsuitable for human consumption that could be converted to biodiesel at lower cost. The problem with processing these waste oils is that they often contain large amounts of free fatty acids that cannot be converted to biodiesel using an alkaline catalyst. These free fatty acids react with the alkaline catalyst to produce soaps that inhibit the separation of the biodiesel, glycerin, and wash water. Previous research has developed a process for pretreating these high free fatty acid feedstocks using acid catalysts which do not form soaps. The objective of this study was to construct a pilot plant to produce biodiesel from a wide variety of feedstocks including those with high free fatty acids. A 50-gallon batch pilot plant has been built which can process high free fatty acid feedstocks using an acid-catalyzed pretreatment followed by an alkaline-catalyzed transesterification. Case studies of pilot plant-scale production of biodiesel from soybean oil, yellow grease with 9% free fatty acids, and brown grease with 40% free fatty acids are presented. The effect of varying the reaction parameters is discussed and the separation and washing processes are described. Estimates of the fuel cost using different feedstocks are also provided.

SummaryPhenotypic characterization of soybean event 335-13, which possesses oil with an increased oleic acid content (> 85%) and reduced palmitic acid content (< 5%), was conducted across multiple environments during 2004 and 2005. Under these conditions, the stability of the novel fatty acid profile of the oil was not influenced by environment. Importantly, the novel soybean event 335-13 was not compromised in yield in both irrigated and non-irrigated production schemes. Moreover, seed characteristics, including total oil and protein, as well as amino acid profile, were not altered as a result of the large shift in the fatty acid profile.The novel oil trait was inherited in a simple Mendelian fashion. The event 335-13 was also evaluated as a feedstock for biodiesel. Extruded oil from event 335-13 produced a biodiesel with improved cold flow and enhanced oxidative stability, two critical fuel parameters that can limit the utility of this renewable transportation fuel.

As the use of biodiesel becomes more widespread, engine manufacturers have expressed concern about biodiesel's higher viscosity. In particular, they are concerned that biodiesel may exhibit different viscosity-temperature characteristics that could result in higher fuel injection pressures at low engine operating temperatures. This study presents data for the kinematic viscosity of biodiesel and its blends with No. 1 and No. 2 diesel fuels at 75, 50, and 20% biodiesel, from close to their melting point to 100°C. The results indicate that while their viscosity is higher, biodiesel and its blends demonstrate temperature-dependent behavior similar to that of No. 1 and No. 2 diesel fuels. Equations of the same general form are shown to correlate viscosity data for both biodiesel and diesel fuel, and for their blends. A blending equation is presented that allows the kinematic viscosity to be calculated as a function of the biodiesel fraction.Paper no. J9166 in JAOCS 76, 1511-1513 (December 1999).