Biodiesel Versus Ethanol?

Ethanol is normally added to gasoline (at the 5-10% level) in many parts of the world. Current ethanol production in Canada for example, is about 200 million liters per year whereas gasoline consumption for the same year is about 38 billion liters. In the US, Ethanol is produced and used as an additive to gasoline to reduce air pollution, decrease dependence on imported oil and encouraging rural development.

Biodiesel is made from vegetable oils or animal fats, and involves a process wherein these oils and fats are reacted with alcohols in the presence of a catalyst to produce alcohol esters.
The products of this process are methyl or ethyl esters of fatty acids are called biodiesel. Because it is less viscous than the original oil or fat, it makes a better fuel for diesel engines. Western Europe is the main production area of biodiesel, where over 1.4 billion liters is produced annually. Biodiesel is added to diesel fuel to reduce air pollution but because it is more expensive, requires government subsidies to be actually used.

There are of course, controversies about fuel ethanol. One is, ethanol is more expensive than gasoline and needs incentives to compete, but this is apparent only to formative stages of research and implementation. Mature economies using ethanol such as Brazil, do not have subsidies. Process-wise, ethanol production is costly because of the cost of fermentation and the cost of developing move valuable co-products (such as electricity) to help offset the cost of ethanol production. Therefore, finding ways to reduce these costs would move ethanol production and use forward.

Another issue is efficiency. Using crops to produce ethanol has been found to be efficient and the efficiency ratings have been improving in the last 20 - 25 years or so. For example, studies showed that the energy costs to produce corn grain dropped from 3.36 GJ/t (gigajoules per tonne) in 1975 to 1.69 GJ/t in 1991. The cost of producing ethanol is now decreased significantly because the cost of raw materials decreased. The potential to reduce the energy costs of ethanol production also exists. High gravity fermentation for ethanol production will reduce energy and economic costs.

Some people question whether the production of ethanol will compete with the supply of food. Think of Canada for instance. If we replace 10% of the total gasoline used with ethanol, we are looking at 3.8 billion liters of ethanol! This would have a significant effect on food supply if ethanol is produced from grain. Thankfully, there are other sources of raw materials for ethanol production which could supplement or substitute grains if indeed ethanol production goes in the way of food supply.

Biodiesel on the other hand, is based on prices of vegetable oils and animal fats. Biodiesel has about 91% the energy value of diesel fuel and about 20 to 30% more expensive than diesel. Intuitively, this puts biodiesel at a price disadvantage. Large tax reductions and subsidies would be needed to make biodiesel competitive.

Another issue about biodiesel is the availability of oils and fats that can be used to produce it. Unlike ethanol which can be produced from grains and other cellulosic materials which can be expanded immensely, biodiesel cannot. And this posses a larger problem in terms of wider public acceptance for biodiesel.