by Jim Kerr
Finally, diesel-powered vehicles are gaining in popularity in North America. Europe, of course, has long embraced this efficient powerplant because of its much higher fuel prices. As gasoline prices climb here, Canadians and Americans are warming up to diesel propulsion too. Recognising this trend, automobile manufacturers are planning more diesel vehicles, such as the Jeep Liberty diesel and Mercedes’ new E320 CDI diesel.
However, while the diesel engine is more efficient than gasoline engines, it still uses a non-renewable resource for fuel. This dependence on fossil fuels could decrease with the addition of bio-diesel into the marketplace.
Bio-diesel fuels are methyl or ethyl esters. Esters are oxygenated organic compounds derived from a broad variety of renewable sources such as vegetable oil, animal fat and cooking oil that can be used in compression ignition engines. Some of their key properties are comparable to those of diesel fuel. “Soy Methyl Ester” diesel (“SME” or “SOME”), from soybean oil, is the most common bio-diesel in the United States while “Rape Methyl Ester” diesel (“RME”), from rapeseed (Canola) oil, is the most common bio-diesel fuel available in Europe. Bio-diesel is produced by a process called transesterification: where various oils are converted into methyl esters through a chemical reaction with methanol in the presence of a catalyst such as sodium or potassium hydroxide.
There are several reasons to consider using bio-diesel. It reduces our dependency on petroleum-based fuels. Bio-diesel has the potential to provide emission reductions with direct emission advantages for current engines and potential to retrofit older technology engines. Bio-diesel provides lubricity improvements for the fuel system and engine components over conventional diesel fuels and finally, production of bio-diesel could boost domestic industries such as farming and fuel production facilities.
While it is possible to run a diesel engine on 100% bio-diesel, there are several concerns about using fuel at this level. Initially, 20% bio-diesel/80% regular diesel was seen at a practical target but even this has been reduced to only 5% bio-diesel because of vehicle manufacturer concerns. Even at 5%, bio-diesel could extend our non-renewable fuel resources greatly. Currently, much of Europe is using 5% bio-diesel but there are some slight differences in their vehicles to ensure good driveability.
One of the concerns with using bio-diesel has to be its cloud point. One hundred percent (B100) Bio-diesel starts to “cloud” or solidify at zero degrees C. This compares to regular #2 diesel with a cloud point of 15 C. Blending regular diesel with 5% bio-diesel keeps the cloud point near -15 C so there is negligible effect on vehicle operation. However, fuel line heaters and fuel tank heaters are used on some European vehicles to keep the fuel liquid at cold temperatures.
Another disadvantage of Bio-diesel is that B100 has an energy content about 11% lower than that of petroleum-based diesel fuel resulting in a loss of approximately 5-7% in maximum power output. This disadvantage is much less when 5% bio-diesel is used. Even though it has less energy, bio-diesel fuel has higher viscosity than petroleum-based diesel fuel, which tends to reduce injection pump barrel/plunger leakage and slightly improve injector efficiency.
The cost of Bio-diesel fuels varies depending on the basestock, geographic area, variability in crop production from season to season, production facilities and many other factors. This cost may be reduced if relatively inexpensive feedstock, such as waste oils or rendered animal fat, is used instead of soybean, corn or other plant oil – but still, the average cost of bio-diesel fuel still exceeds that of petroleum-based diesel fuel. However, the cost of converting to bio-diesel blends is much lower than the cost of converting to any other alternative fuel because no major engine, vehicle, or dispensing system changes are required.
Another advantage of bio-diesel is lower emissions. There is no significant sulphur content, and if we were able to use 20% bio-diesel, we would have only a +2% increase in NOx emissions but have 12% lower in particulate emissions, 20% lower in Hydrocarbon emissions and 12% lower in carbon monoxide emissions.
Bio-diesel is not coal slurry, raw unprocessed vegetable oil, used cooking oil from McDonalds or raw vegetable oil mixed with diesel. It is a processed fuel from renewable resources. While there is still much to learn about long term use of bio-diesel and how best to store the fuel, research is ongoing around the world. As petroleum-based fuels continue to increase in price, the attractiveness of using of bio-diesel will grow. Maybe those exhaust fumes will smell better too!