Archive for November, 2007

Nov 19 2007

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Ethanol and Biodiesel: A Biofuel Comparison

The two most widely used types of biofuels are ethanol and biodiesel. Just a brief review, ethanol is an alcohol fuel derived from sugarcane, wheat, corn and biomass, thus including wasted cooking oil. It can be blended with conventional petroleum diesel to improve its octane level resulting in reduced greenhouse gas emissions. On the other hand, biodiesel is made from natural oils such as animal fats or vegetable oils.

Presently, experts states that the main biofuels, ethanol and biodiesel, have a positive effect to the environment. Each of them has its pros and cons. The utilization of both ethanol and biodiesel will result to a decrease reliance on foreign conventional fossil fuels and a reduction on harmful, toxic emissions.

There are various methods to compare ethanol and biodiesel. Below are some of them.


The two processes that can generate fuel-grade ethanol are wet milling and dry milling. But the most widely used is the dry-mill method. In it simplest explanation, yeast, sugars and starch are fermented. From starch, it is fermented into sugar, afterwards it is fermented again into alcohol.

Biodiesel is produced through a chemical process termed as transesterification. In this method, the two byproducts, methyl esters and glycerin which are not good for engines, are left behind.

Environmental Benefit

Both biofuels can reduce harmful emissions. Both biodiesel and ethanol could provide significant environmental benefit. The two have a great probability of decreasing the greenhouse gas emissions because of the fact that these biofuels are primarily derived from crops which absorb carbon dioxide. Thus, the balance of carbon dioxide is sustained and maintained in the atmosphere.


Biodiesel can run in any diesel generated engines. However, it is not yet clear if it is the same when using 100% ethanol since it is recommended to be blended with fossil fuel like gasoline. Therefore, it is only compatible with selected gasoline powered automobiles. In the United States, almost all ethanol produced can be blended with gasoline.


Currently, commercial biodiesel is more expensive than ethanol.

Gallons per acre

In the perspective of land use and agricultural efficiency, ethanol seems to be a good choice. The reason is that about 420 gallons of ethanol can be generated per acre in contrast to 60 gallons of biodiesel per acre soybeans. Consequently, the cost of soybean oil would significantly increase if biodiesel production is increased as well.


Many reports stated that biodiesel provides 93% more net energy per gallon than is necessary for its manufacture. On the other hand ethanol produces only 25% more net energy.

Greenhouse-gas Emissions (GHG)

The production and combustion of ethanol ends in 12% less greenhouse gas emission than the production and combustion of regular diesel. On the other hand, the generation and combustion of biodiesel from soybeans results in 41% diminution compared to conventional gasoline.

Stated above are some of the many facts about ethanol and biodiesel with the end view of comparing the two biofuels on which one is better. The pursuit to lessen our reliance on non-renewable fossil fuels will not be realized with a single alternative fuel. It necessitates a blend of ethanol, biodiesel and perhaps some yet-to-be discovered alternative fuel.

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