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Straight Vegetable as a Diesel ?

Concerns about U.S. reliance on imported and fluctuating fuel prices have led to growing interest in using , an made from vegetable . Some people have expressed interest in using straight (SVO), or waste oils from and other processes, as fuel. These oils seem to be appealing because they are obtainable from U.S. agricultural or industrial sources without intermediate processing. However, SVO iStock—8561648 and other waste oils are generally not considered acceptable vehicle Straight vegetable oil is not the same for large-scale or long-term use. as biodiesel and is generally not recommended for long-term vehicle use. Performance of SVO required boiling range for . While straight vegetable oil or mixtures The buildup doesn’t necessarily happen quickly but instead over a the problems to some degree, but do of SVO and diesel fuel have been used not eliminate them entirely. Studies by some over the years, research has longer period. These conclusions are consistent across a significant body show that carbon buildup continues shown that SVO has technical issues over time, resulting in higher that pose barriers to widespread of technical information in multiple articles and reports. maintenance costs and/or shorter acceptance. engine life. Figure 1 shows how the The published literature An SAE technical paper1 reviews tendency to form carbon deposits strongly indicates that the use of SVO published data on the use of SVO in increases when blending vegetable oil will to reduced engine life. This . Quoting from this paper: into a diesel fuel.2 reduced engine life is caused by the “Compared to No. 2 diesel fuel, all Another issue that is particularly buildup of carbon deposits inside the of the vegetable oils are much more critical for use of SVO is fuel . engine, as well as negative impacts viscous, are much more reactive As Figure 2 (see back) indicates, the of SVO on the engine . to , and have higher cloud viscosity of pure SVO is much higher Both carbon deposits and excessive point and pour point temperatures. than that of diesel fuel at normal buildup of SVO in the lubricant are operating temperatures.3 This can caused by the very high boiling point Diesel engines with vegetable cause premature of fuel and viscosity of SVO relative to the oils offer acceptable engine and and can also dramatically performance and emissions for alter the structure of the fuel spray 1.8 short-term operation. Long-term coming out of the injectors to increase 1.7 operation results in operational droplet size, decrease spray angle, 1.6 and durability problems.”

1.5 Some investigators have explored 1 Babu, A.K.; Devaradjane, G. “Vegetable Oils 1.4 modifying the vehicle to preheat and Their Derivatives as Fuels For CI Engines: An Overview.” SAE Technical Paper No. 2003-01-0767. 1.3 the SVO prior to injection into the 1.2 engine. Others have examined blends 2 Jones, Samuel T.; Peterson, Charles L.; Thompson, Joseph C. Biological and Agricultural Engineering 1.1 of vegetable oil with conventional Department, of Idaho, Moscow, Idaho. 1.0 diesel. These techniques may mitigate “Used Blend Comparisons Using Coking in a DI .” Presented

Coking Index Relative to Diesel 0.9 at 2001 ASAE Annual International Meeting, 0.8 Sacramento, Calif., July 30–August 1, 2001. SAE 0% 3% 5% 10% 15% 20% Paper No. 01-6051.

Percent Oil in Fuel 3 Bruwer, J.J., et al. “Use of Sunflower Oil in Diesel Engined .” Proceedings of the Figure 1. Buildup of Carbon Deposits in IV International Symposium on Alcohol Fuels Engine as a Function of Oil in Fuel2 ; October 5, 1980, Guaruja, SP, .

www.cleancities.energy.gov • May 2010 VEHICLE TECHNOLOGIES PROGRAM • May 2010 • Page 2

100 90 Where can I get more 80 information?

70 ■ The U.S. Department of Energy’s 100% Sunower Oil (DOE) Alternative Fuels Data 60 /second) Center at www.afdc.energy.gov 2 is a vast collection of information 50 on alternative fuels and 40 alternative fuel . 30 ■ The DOE’s Office of Energy Viscosity (mm Efficiency and 20 Web site at www.eere.energy. Diesel gov/ contains 10 information on biodiesel and production and policy. 0 18 28 38 48 58 68 78 88 ■ The is Temperature in ºC the national trade association representing the biodiesel Figure 2. Impact of Temperature on the Viscosity of and Diesel Fuel . Its Web site, www. biodiesel.org, serves as a clearinghouse of biodiesel- and increase spray penetration. All of process called that related information. these changes to the fuel spray will tend involves a reaction with using to increase wetting of engine internal caustic soda () as a ■ The National Renewable Energy surfaces with the fuel, leading to an catalyst. Biodiesel has substantially Laboratory’s Nonpetroleum increased tendency to form carbon different properties than SVO and Based Fuels Web site, located at www.nrel.gov/vehiclesandfuels/ deposits and dilute the lubricant. results in better engine performance. npbf, provides links to a variety In particular, biodiesel has a lower of documents. The long-term effect of using SVO boiling point and viscosity than SVO. in modern diesel engines that are Because of its improved qualities, ■ The EPA Biodiesel Emissions equipped with catalytic converters or vehicle and engine manufacturers Analysis Program at www.epa. filter traps is also a matter of concern. generally approve the use of biodiesel gov/otaq/models/biodsl.htm contains a biodiesel emissions Buildup of fuel in the lubricant is more blends in their products, though not all database. significant in these engines—even for approve blend levels as high as 20%. petroleum diesel—and would likely be severe with SVO. In general, these To ensure good performance in systems were not originally designed engines, biodiesel must meet quality Agency (EPA). For a complete list of with SVO in mind and can be seriously specifications developed by ASTM ASTM biodiesel requirements, see the damaged or poisoned by out-of-spec or International. The ASTM D6751 Biodiesel Handling and Use Guidelines contaminated fuel. specification is for pure biodiesel (B100), at www.nrel.gov/vehiclesandfuels/ which can be used in blends up to 20%. npbf/pdfs/43672.pdf. In addition, the Any biodiesel used for blending should biodiesel industry has instituted a Biodiesel: Fuel made meet this specification. Biodiesel that quality assurance program for biodiesel from SVO meets ASTM D6751 is also legally producers and marketers. To learn more Biodiesel is an alternative fuel that registered as a fuel and fuel additive about the BQ-9000 program, visit www. can be made from SVO in a chemical with the U.S. Environmental Protection bq-9000.org.

EERE Information Center Prepared by the National Renewable Energy Laboratory 1-877-EERE-INF (1-877-337-3463) (NREL), a national laboratory of the U.S. Department of www.eere.energy.gov/informationcenter Energy, Office of Energy Efficiency and Renewable Energy; NREL is operated by the Alliance for Sustainable Energy, LLC. Printed with a renewable-source on paper containing at least 50% wastepaper, DOE/GO-102010-2989 • May 2010 including 10% post consumer waste. CLEAN CITIES CLEAN