Biodiesel - Fuel quality, Standards and Properties
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Fuel quality, Standards and Properties
Biodiesel is a clear amber-yellow liquid with a viscosity similar to petrodiesel (the industry term for diesel produced from petroleum). Much of the world uses a system known as the "BD factor" to state the amount of biodiesel in any fuel mix, in contrast to the "BA" system used for bioalcohol mixes. For example, 20% biodiesel is labeled BD20. Pure biodiesel, 100%, is referred to as BD100. In the United States, a similar system is used, but the "D" is dropped (B100, B20, B5, etc.).
The international standard for biodiesel is ISO 14214. Another is the ASTM International standard ASTM D 6751, which is the most common standard referenced in the United States. In Germany, the requirements for biodiesels are fixed in a DIN standard. There are standards for three different varieties of biodiesel, which is made of different oils:
RME (rapeseed methyl ester, from rape products, according to DIN E 51606)
PME (vegetable methyl ester, purely vegetable products, according to DIN E
51606)
FME (fat methyl ester, vegetable and animal products, according to DIN V 51606)
The standards make sure that the following important factors in the fuel production
process are satisfied:
Complete reaction.
Removal of glycerin.
Removal of catalyst.
Removal of alcohol.
Absence of free fatty acids.
The basic industrial tests to see if the product conforms to the standard typically includes gas chromatography that verifies only the more important of the variables above. More complete testings cost more. Fuel meeting the quality standards is very non-toxic, with a toxicity rating (LD50) of greater than 50 ml/kg. This translates to greater than 3 liters having to be consumed for an average 60 kg person to cause death 50% of the time. The common comparison is that this makes biodiesel ten times less toxic than table salt.
Biodiesel can be mixed with petroleum diesel at any concentration in most modern engines, although it has the disadvantage of degrading rubber gaskets and hoses in older vehicles (prior to 1992). Biodiesel is a better solvent than petrodiesel and has been known to break down deposits of residue in the fuel lines of vehicles which usually run on petroleum. Fuel filters may become clogged with particulates if a quick transition to pure biodiesel is made, but the biodiesel cleans the engine in the process.
In a study at a U.S. military base, a biodiesel blend was used as a replacement for heating oil at housing on the base. Due to the solvent power of biodiesel, residues that had been present in fuel tanks for decades were dissolved. The particulate component of the residues caused repeated clogging of fuel strainers, requiring repeated replacement, cleaning, and in some cases installation of higher capacity filters. Due to the relatively smaller surface area and service life of fuel tanks in motor vehicles and mobile equipment, filter clogging is less prevalent but still a factor to be considered.
From Wikipedia.