Bio-diesel is a clean burning bio-fuel that may be used in compression-ignition (diesel) engines with little or no modifications. Bio-diesel contains no petroleum, but it can be blended in any proportion with petroleum and diesel. It is a form of renewable energy which is bio-degradable, non-toxic, and essentially free of sulphur and aromatics.
It is made through a chemical process called trans-esterification, whereby glycerin is separated from the fat or vegetable oil, leaving behind two products — methyl esters (the chemical name for bio-diesel) and glycerin (a valuable byproduct usually sold to be used in soaps and other products).
Today, there is an increased impetus for refining and developing bio-fuels or clean fuel technologies. However, the idea of bio-fuels, and especially bio-diesel, is not new. In fact, when Rudolf Diesel designed his prototype diesel engine a century ago, his fuel of choice was peanut oil. However, when petroleum diesel fuel arrived in the market, it was cheap, reasonably efficient and readily available, and, therefore, quickly replaced bio-diesel.
In recent years, bio-diesel is back in vogue. It is the only alternative to fossil fuels that has fully completed the health effects testing requirements of the 1990 Clean Air Act Amendments. Bio-diesel that meets ASTM D6751 and is legally registered with the US Environmental Protection Agency (EPA) is a legal motor fuel for sale and distribution.
 Why Bio-Diesel?
The EPA, under the Clean Air Act Section 211(b), has made a thorough evaluation of bio-diesel's emission results and potential health effects. In fact, it is the first and only alternative fuel to have achieved this. Bio-diesel has many proven advantages over conventional fuels.
First, the ozone (smog) forming potential of bio-diesel hydrocarbons is 50 per cent less than that of diesel fuel.
Exhaust emissions of sulphur are essentially eliminated by using bio-diesel as against diesel.
Criteria pollutants are reduced with bio-diesel use. Studies have shown that the use of bio-diesel in diesel engines results in substantial reductions of unburned hydrocarbons, carbon monoxide and particulate matter. Emissions of nitrogen oxides stay the same or are slightly increased.
The exhaust emissions of carbon monoxide (a poisonous gas) from bio-diesel are on average 48 per cent lower than carbon monoxide emissions from diesel, so it's carbon footprint is much smaller.
The exhaust emissions of particulate matter from bio-diesel are about 47 per cent lower than overall particulate matter emissions from diesel.
The exhaust emissions of total hydrocarbons (a contributing factor in the localised formation of smog and ozone) are on average 67 per cent lower for bio-diesel than for diesel. Also, the exhaust from bio-diesel powered engines does not smell as foul as exhaust from petrol or diesel engines.
Bio-diesel emissions show decreased levels of polycyclic aromatic hydrocarbons (PAH) and nitrated polycyclic aromatic hydrocarbons (nPAH), which have been identified as potentially carcinogenic.
Bio-diesel has been shown to perform similarly to diesel in more than 80 million successful road kilometres, using virtually all types of diesel engines, a great deal of off-road distance and countless marine hours. There are now more than 300 major fleets using the fuel in the US alone.
 Myths and Facts
Myth: Bio-diesel does not perform as well as diesel.
Fact: Bio-diesel can be used in existing engines and fuel injection equipment without any negative impact on operating performance. In fact, it is the only alternative fuel that can actually extend engine life because of its superior lubricating properties. Visit  for a statistical comparison of the heating value of diesel and different types of bio-diesel.
Myth: Bio-diesel doesn't perform well in cold weather.
Fact: Although bio-diesel does gel in very cold temperatures, so does conventional grade-2 diesel. Both forms of diesel may be controlled with the same fuel management techniques, after which their performance is at par.
Myth: A low-blend of bio-diesel in diesel fuel will become too expensive.
Fact: Using a 2 per cent blend of bio-diesel is estimated to increase the cost of diesel by 2 or 3 cents per gallon, taking into account the fuel, transportation, storage and blending costs. This marginal price increase will be offset by the increase in diesel quality since low-blend levels of bio-diesel greatly enhance the lubricity of diesel fuel.
Myth: Bio-diesel requires special storage and has a shorter shelf life.
Fact: Both conventional diesel and bio-diesel may be stored and dispensed in the same way.
Myth: Bio-diesel’s safety is moot.
Fact: Bio-diesel has a very high flash point (300°F) making it one of the safest of all alternative fuels.