Fossil fuels have come to dominant society, and is a major driving force in our economy. Hardly a day goes by when the prices of fuel, or the risk on overseas oil supplies, makes the news.
And yet, despite this coverage, many consumers are still confused about the origins of fossil fuels, and one of the most confusing forms of fossil fuel, diesel.
There are many misconceptions surrounding diesel fuel: that it's dirty, that it's unreliable, or that it's inefficient. Yet, with some careful research into the subject, it becomes clear that diesel manufacturers are aware of these myths, and have undergone great strides to try and alleviate these concerns.
The Origins of Diesel Fuel
Rudolf Diesel originally designed the diesel engine using coal dust as his fuel. He also experimented with various oils, including vegetable oil, such as peanut oil.
Distillation is the first major process of refining crude oil. The oil is heated, causing different hydrocarbon compounds to separate by their boiling temperatures. The lightest components such as ethane and propane come off the top. The next heaviest components, called naphtha, are used for making gasoline.
The next heavier portion of crude oil coming from the distillation tower is used to make diesel fuel.
Sulphur Levels in Diesel
Diesel fuel is typically high in many different hydrochemicals, including sulphur, after the refining process. This was especially true in the earliest forms of diesel. Yet, as refining techniques have improved over the past few decades, diesel engines have become much cleaner.
In fact, there are two classifications for diesel: Ultra Low Suplhur Diesel, which must contain less than 15 parts per million of sulphur. As of September 1, 2006 all on-road diesel vehicles in Canada are required to be classified as Ultra Low Sulphur.
The second classification, Regular Sulphur Diesel, is used in all off-road vehicles, including farm machinery, marine vessels, or in forestry. As of October 1, 2007 all off-road vehicles in Canada must have sulphur levels below 500 parts per million.
Advantages of Diesel Fuel
Typically, diesel-powered vehicles actually have greater fuel efficiency than gasoline engines (20% - 40% better), and as a result, fewer greenhouse gas emissions are produced than in a gasoline-powered vehicles (10% - 30% fewer emissions).
Diesel fuel is also less flammable than traditional gasoline, making it the ideal fuel for use in armoured fighting vehicles like tanks. Moreover, diesel engines provide more torque, and are less likely to stall.
Disadvantages of Diesel Fuel
Diesel engines have no use for glow plugs for ignition, unlike gasoline engines, because the fuel is pumped directly into the cylinder, causing it to react (burn) when it encouters oxygen, thus producing power.
Yet a major drawback of this occurs in the winter. Diesel fuel viscosity increases when the temperature decreases, usually between -15 degrees celsius (5 degree F) and -19 degrees celsius (-2.2 degrees F). This was a major problem on older diesel engines, and made engines very difficult to start in the colder months of the year, but this is usually counteracted by plugging in an engine heater, or a block heater.
Another problem is the rare runaway failure. Since diesel engines do not require a spark to achieve ignition, they can sustain power as long as diesel fuel is supplied to the cylinder. Fuel is typically supplied via a fuel pump, and if the pump gets stuck in the "open" position, the supply of fuel cannot be regulated, and the engine will "runaway", incapable of being shut down.
Modifications to engine design, and improvements to fuel pump construction has also limited the likelihood of an engine runaway.
Biodiesel: Potential for Future Fuel Source?
Biodiesel can be obtained from vegetable oil, or animal fats; very similar to the initial diesel engine design by Rudolf Diesel.
Biodiesel is a non-fossil fuel, which means it is a cleaner burning alternative to petrodiesel.
Biodiesel has a lower viscosity point than petrodiesel as well, causing it to freeze more readily in the temperatures slightly warmer than the temperature range discussed earlier. This can be overcome by using a biodiesel/petrodiesel blend, or by installing a fuel heater, but this is only necessary during the colder months.
In the event of fuel spills, biodiesel is easily washed away with ordinary water and is nontoxic compared to other fuels.
Initially biodiesel received enormous funding by the George W. Bush presidential administration, who hailed it as the future of fuels in the USA. Yet, more recent research has shown that biodiesel is, in fact, not the cure for the worlds energy concerns, and investment has been scaled back tremendously by the Obama administration.
Alfred Philip Chalkley, Rudolf Diesel (1913). Diesel Engines for Land and Marine Work. Constable & Co. Ltd.
Ayhan Demirbas (2008). Biodiesel: A Realistic Fuel Alternative for Diesel Engines. Berlin: Springer.
Wellington, B.F.; Alan F. Asmus (1995). Diesel Engines and Fuel Systems. Longman Australia.
USDA, Production Estimates and Crop Assessment Division, Foreign Agricultural Service.
Energy Information Administration, Gasoline and Diesel Fuel Update.
