Biodiesel Technology
Biodiesel is defined as the mono alkyl esters of long chain fatty acids derived from
renewable liquid feedstocks, such as vegetable oils and animal fats for use in diesel
engines. The most common biodiesel fuel is made by the transesterfication of soy or
rapeseed triacyglycerides with methanol in the presence of a strong base catalyst such as
sodium hydroxide, potassium hydroxide, or sodium methoxide.
Biodiesel has some favorable properties when used, as a fuel component. The US EPA has
analyzed B-20 blends (20% biodiesel blended with 80% conventional diesel) and has
concluded that these blends can reduce VOC emissions by 20%, CO and PM emissions by
10%, NOx emissions were increased by 2% in the EPA study.
The World-Wide Fuel Charter, a compilation of fuel quality requirements endorsed by the
Alliance of Automobile Manufacturers, the European Automobile Manufacturers Association
(ACEA), the Engine Manufacturers Association, the Japanese Automobile Manufacturers
Association and a number of other automobile manufacturer trade associations around the
world, does not endorse fuels that contain more than 5% biodiesel for fuels sold in WWFC
defined category 1-3 areas (most of the world). International Truck and Engine Company
has stated that the use of biodiesel in their engines - some of which are in Ford products - at
greater than 5% concentration, is solely at the discretion and risk of the customer.
In the US, the ASTM (American Society for Testing and Materials) recently adopted D6751,
which specifies properties for neat biodiesel intended for blending with diesel fuel containing
up to 500-ppm sulfur. ASTM also plans to develop a standard for biodiesel that can be
blended with ultra- low sulfur diesel fuel (15 ppm max). This standard has no requirement
for feedstock quality.
European standards organization, CEN (Comité Européen de Normalisation) has released
specifications for biodiesel, EN 14214, which specifies properties and the test methods
needed to determine compliance. This standard allows any feedstock to be used, but its
specifications are most easily met by rapeseed methyl esters.
Ford Motor Company Position
Fuels containing no more than 5% biodiesel may be used in Ford diesel powered vehicles.
Consistent with WWFC (World-Wide Fuel Charter) category 1-3, “Fatty Acid Methyl Esters
(FAME) used in commercial fuel must meet both the EN 14214 and ASTM D 6751
specifications”.
There are still some unresolved technical concerns with the use of biodiesel at
concentration greater than 5%. Some of the concerns are:
Requires special care at low temperatures to avoid excessive rise in viscosity and loss of
fluidity
Storage is a problem due to higher then normal risk of microbial contamination due to
water absorption as well as a higher rate of oxidation stability which creates insoluble
gums and sediment deposits
Being hygroscopic, the fuel tends to have increased water content, which increases the
risk of corrosion
Biodiesel tends to cause higher engine deposit formations
The methyl esters in biodiesel fuel may attack the seals and composite materials used in
vehicle fuel systems
It may attack certain metals such as zinc, copper based alloys, cast iron, tin, lead, cobalt,
and manganese
It is an effective solvent, and can act as a paint stripper, whilst it will tend to loosen
deposits in the bottom of fuel tanks of vehicles previously run on mineral diesel
Ford believes that it is unlikely that the emission benefits of biodiesel will be sufficient to
achieve Tier 2 emission standards with out catalysts and particulate filters. Ford is working
aggressively on technologies, including engine improvements, new catalysts and particulate
filters that will remove HC, CO, NOx and soot from diesel exhaust. Renewable fuels or
blends containing renewable components can help reduce the total lifecycle CO2 impact
and may be used when available, but they are not the key step to achieving Tier 2 emission
standards.
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