Is biodiesel a viable alternative to diesel from fossil fuels for trucks and buses?


Definition of biodiesel

- Vegetable oil or animal fat which is chemically reacted with an alcohol to produce mono-alkyl esters of fatty acids. (BECON Biodiesel Education n.d.) Social relevance

- Biodiesel is environmentally friendly.

- Biodegradable, a renewable source of energy and has less emission as compared to standard petroleum diesel. Thus, reducing pollution. (M. Scott Hess 2003)

2)Chemical Background

Structure of biodiesel



Triglyceride + methanol mixture of fatty esters (biodiesel) + glycerol (BECON Biodiesel Education n.d.)

-triglyceride molecule is reacted with excess alcohol to form glycerin & fatty esters Physical properties of biodiesel

-slightly lower heat of combustion on account of its oxygen content (Von Wedel, Randall(Ph.D) 1999)

-non-volatile & high flash point (Von Wedel, Randall(PhD) 1999)

-high lubricity (Von Wedel, Randall(PhD) 1999)

-high cetane number (BECON Biodiesel Education n.d.)

3)Points of view

Advantages of biodiesel

i) Biodegradability and Nontoxicity

-ideal choice of fuel to be used in environmentally sensitive areas such as parklands or marine habitats due to its biodegradability (Kemp, William H. 2006)

-biodiesel biodegrades twice as fast as petroleum diesel because it is a simple, straight carbon chain with two oxygen atoms at both ends (Von Wedel, Randall(PhD) 1999)

-petroleum diesel is harder to biodegrade because the hydrocarbons lack oxygen and are made up of multiple double bonds, branched, cyclic and cross linked chains (Von Wedel, Randall(PhD) 1999)

-more readily metabolized by bacteria that breaks down fats and oils in the environment (Von Wedel, Randall(PhD) 1999)

-less toxic than table salt, almost nontoxic (Kemp, William H. 2006)

ii) High lubricity

-defined as: “The property of a lubricant that causes a difference in friction under conditions of boundary lubrication when all the known factors except the lubricant itself are the same. The lower the friction the higher the lubricity” (BECON Biodiesel Education n.d.)

-has much better lubricating properties compared to petroleum diesel (Kemp, William H. 2006)

-biodiesel acts as a solvent which helps loosen deposits from the insides of an engine that could potentially cause clogs (M. Scott Hess 2003)

-pure biodiesel which leaves no deposits of its own reduces engine wear which results in the increase in engine life (M. Scott Hess 2003)

Table 2: SLBOCLE for #2 Diesel 2004 Tier 2 Fuel, Biodiesel, and Biodiesel Blends (BECON Biodiesel Education n.d.)

iii) Low Emissions

Table 1: Percent change in emissions against percentage of biodiesel (Kemp, William H. 2006)

-emissions of carbon dioxide, particulate matter is greatly reduced

-improved combustion which reduces emission of unburnt hydrocarbons (Kemp,William H. 2006)

iv) High Flash Point

-biodiesel has flash point of above 160 degrees Celsius, therefore its risk of explosion is decreased

-transportation, storage and utilization of biodiesel will be easier due to the decreased fire hazard (BECON Biodiesel Education, n.d.)

v) No Noxious or Carcinogenic Fumes

-biodiesel has no volatile organic compounds, therefore it would not produce any poisonous or noxious fumes.

-biodiesel does not contain lead or sulfur to react and release harmful gases

-biodiesel has no aromatic hydrocarbons i.e. benzene, toluene, xylene. (Von Wedel, Randall(PhD) 1999)

Disadvantages of biodiesel

i) Increase in NOx emissions

-due to the decrease in amount of particulate matter, there is an increase in nitrogen oxides which contributes to smog formation (M. Scott Hess 2003)

ii) Cold Flow Issues

-when temperatures drop below the cloud point of biodiesel, there would be a loss of engine power or complete fuel starvation due to a thickening condition known as “waxing” or “gelling” (Kemp, William H. 2006)

-biodiesel gels at cold temperatures because microscopic crystals begin to form. From these microscopic crystals, they agglomerate with one another to form a gel and eventually solidify. This causes fuel lines and filters to be blocked (Kemp, William H. 2006)

iii) Decreased fuel economy & power

-fuel consumption increased by 2% for a B20 blend with methyl esters and by 14% when methyl ester biodiesel was used at 100% (Von Wedel, Randall(PhD) 1999)

-There is a 15% net decline in mileage when using biodiesel as compared to petroleum diesel (Von Wedel, Randall(PhD) 1999)

-there is an average of 10% reduction in power with the use of biodiesel (M. Scott Hess 2003)

iv) Biodiesel's solvent effect on engine parts

-biodiesel is a solvent which takes effect on natural rubber and several soft plastics. The use of 100% neat biodiesel may cause older diesel vehicles parts such as the rubber fuel lines and gaskets to be degraded, which causes them to get sticky or soften, causing leaks. (Von Wedel, Randall(PhD) 1999)

-older diesel vehicles may experience clogging with the use of high concentrations of biodiesel because of its ability to loosen deposits inside the engine. This causes the fuel filter to be jammed with the deposits. (M. Scott Hess 2003)


-biodiesel is a viable alternative to diesel from fossil fuels

-with the decrease in global warming causing emissions as compared to diesel, it is evident that biodiesel helps to reduce global warming

-the advantages outweighs the disadvantages, making biodiesel a viable alternative in the future

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