Page 303 - Synthetic Fuels Handbook
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FUELS FROM CROPS                     289

             fuel containing 20 percent biodiesel is labeled B20. Pure biodiesel is referred to as B100.
             Blends of 20 percent biodiesel with 80 percent petroleum diesel (B20) can generally be
             used in unmodified diesel engines. Biodiesel can also be used in its pure form (B100), but
             may require certain engine modifications to avoid maintenance and performance prob-
             lems. Biodiesel has about 5 to 8 percent less energy density, but better lubricity and more
             complete combustion can make the energy output of a diesel engine only 2 percent less per
             volume when compared to petrodiesel—or about 35 MJ/L.


             9.5.7 Technical Standards
             The common international standard for biodiesel is EN 14214 while ASTM D6751 is
             the most common standard referenced in the United States and Canada. In Germany, the
             requirements for biodiesel are fixed in the DIN EN 14214 standard and in the UK the
             requirements for biodiesel is fixed in the BS EN 14214 standard, although these last two
             standards are essentially the same as EN 14214 and are just prefixed with the respective
             national standards institution codes.
               There are standards for three different varieties of biodiesel, which are made of different
             oils: (a) RME, rapeseed methyl ester, DIN E51606, (b) PME, vegetable methyl ester, purely
             vegetable products, DIN E51606), and (c) FME, fat methyl ester, vegetable and animal
             products, according to DIN V51606. The standards ensure that the following important
             factors in the fuel production process are satisfied: (a) complete reaction, (b) removal of
             glycerin, (c) removal of catalyst, (d) removal of alcohol, (e) absence of free fatty acids, and
             (f) low sulfur content.
               Basic industrial tests to determine whether the products conform to the standards typi-
             cally include gas chromatography, a test that verifies only the more important of the vari-
             ables above. Tests that are more complete are more expensive. Fuel meeting the quality
             standards is very nontoxic, with a toxicity rating (LD ) of greater than 50 mL/kg.
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             9.5.8 Uses
             Biodiesel can be used in pure form (B100) or may be blended with petroleum diesel at any
             concentration in most modern diesel engines. Biodiesel will degrade natural rubber gaskets
             and hoses in vehicles (mostly found in vehicles manufactured before 1992), although these
             tend to wear out naturally and most likely will have already been replaced to gaskets that
             are nonreactive to biodiesel. The higher lubricity index of biodiesel compared to petrodiesel
             is an advantage and can contribute to longer fuel injector life. However, biodiesel is a better
             solvent than petrodiesel, and has been known to break down deposits of residue in the fuel
             lines of vehicles that have previously been run on petrodiesel. As a result, fuel filters and
             injectors may become clogged with particulates if a quick transition to pure biodiesel is
             made, as biodiesel cleans the engine in the process.
               Pure, nonblended biodiesel can be poured straight into the tank of any diesel vehicle.
             As with normal diesel, low-temperature biodiesel is sold during winter months to prevent
             viscosity problems. Some older diesel engines still have natural rubber parts which will be
             affected by biodiesel.
               The temperature at which pure (B100) biodiesel starts to gel varies significantly and
             depends upon the mix of esters and therefore the feedstock oil used to produce the biodie-
             sel. For example, biodiesel produced from low erucic acid varieties of canola seed (RME)
             starts to gel at approximately −10°C. Biodiesel produced from tallow tends to gel at around
             +16°C. As of 2006, there are a very limited number of products that will significantly lower
             the gel point of straight biodiesel. Winter operation is possible with biodiesel blended with
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