By Jim Kerr
Yumm. It was close to suppertime and the smell of french fries was in the air. But where was that smell coming from? There was no restaurant to be found – the city bus idling on the corner was the only thing around. Then I saw the decals: “Fuelled with Biodiesel”. I was smelling the exhaust from the bus.
Biodiesel is a renewable fuel derived from vegetable oils, animal fat and cooking oils. Some think that these products are simply mixed with diesel to produce the fuel, but try to operate unrefined fats and oils in your diesel engine and you will soon be needing rebuilt fuel injectors and possibly an injection pump. Instead, the oils and fat are made into methyl or ethyl esters.
Soybean oil is the most common source of methyl ester in the United States, while Europe and Canada are more commonly using Canola to produce biodiesel. In a process called transesterification, the various oils (triglycerides) are converted into methyl esters through a chemical reaction with methanol in the presence of a catalyst, such as sodium or potassium hydroxide. Water, glycerols, the methanol and other trace produces are then removed from the biodiesel before it becomes a quality fuel. Sounds complicated. Making quality biodiesel isn’t something that can easily be done at home!
Why go to all the trouble of using biodiesel? The answer seems obvious – it is a renewable resource and will reduce our dependency on fossil fuels, but that may be only part of the advantage. Using biodiesel does mean we use less regular diesel, but the percentages of biodiesel used are relatively small. For example, most diesel vehicle manufacturers recommend only 5% biodiesel (B5) mixed with 95% regular diesel. In colder climates the percentage may be even less.
After initial testing over the past couple years, the City of Saskatoon transit system will start using 1% biodiesel in all their city buses. They will also operate some on B5 biodiesel to test the suitability of this fuel during cold weather. While a large fleet would have a significant reduction in the amount of regular diesel they use, economical driving techniques can easily save this much fuel and more. Driver training and monitoring would have a dramatic reduction on fuel usage.
One of the big advantages to using biodiesel shows up in the engine. Analysis done on the Saskatoon city buses showed that the improved lubrication qualities of the biodiesel may increase some major engine parts longevity by as much as 100 percent. That may not be as important for passenger car drivers, where engine durability is already matching the durability of the rest of the vehicle, but commercial vehicles may be used for decades and travel millions of kilometres. Increased longevity reduces maintenance costs.
Biodiesel is also good for reducing emissions. The fuel contains less than 15 parts per million sulphur, which enables it to meet the 2007 diesel fuel regulations. Hydrocarbon and carbon monoxide tailpipe emissions are also reduced slightly at B5 levels and more at higher
There are some disadvantages to using biodiesel. First, biodiesel has slightly less energy that regular diesel, so if we were to use a large percentage of biodiesel in a vehicle, the engine would either have less power or use more fuel to deliver equal power. Fortunately, at low percentages such as B5, the difference in energy compared to diesel without biodiesel added is very small.
Biodiesel also oxidizes faster due to its chemical makeup. Long term storage of the fuel is more difficult so additives must be mixed with the fuel to improve storage capability.
The biggest disadvantage of biodiesel is that pure biodiesel begins to freeze or solidify at temperatures above 0 degrees C. B5 diesel is commonly used in Europe and the use of tank heaters and fuel line heaters has enabled the use of biodiesel in even the colder climates.
Using biodiesel during a cold Canadian winter could be a problem in older diesel vehicles not equipped with fuel heaters, although blending the fuel with different grades of regular diesel will help prevent it from freezing.
The increased use of biodiesel is a benefit to the agricultural community, creating a demand for oil seed crops such as Canola. We probably will not see more than a B20 mixture of biodiesel used in our climate, and most blends will likely be B5 or less. Even so, biodiesel has many advantages, both economically and environmentally, to make it one of the fuels of the future.