Bioethanol: time to stop comparing apples to oranges
5/17/13

What about using biofuels to replace fossil fuels? Let’s not be too hasty! From a strictly environmental point of view, this is not always a win-win process. Indeed, if we are to succeed in comparing like with like, many other factors need to be taken into account such as the reduction of greenhouse gases which is required by European regulation. If we want to objectively consider all the environmental impacts of biofuel, one method in particular seems appropriate: Life Cycle Assessment. Implemented by a chemical engineer at the University of Liege, this method has yielded informative results with regard to the use of bioethanol.

bioethanol fuelPerhaps you are familiar with “E 5”? This is the technical name for a mixture of petrol and bioethanol as used in several European countries including Belgium. A gasoline-powered car uses fuel which is composed of 95 % traditional petrol and 5 % bioethanol. Whatever the mixture may be (sometimes, the proportion of bioethanol can be as high as 85 %), bioethanol is most often produced from sugar beet. However, corn, wheat or sugar cane are also sometimes used, the latter being used in South America, in particular, where it grows in abundance. In fact Brazil has been one of the main producers of bioethanol in the world for more than forty years. Over there, motorists are able to get around thanks to a fuel mixture which is rich in “green” fuel. Biofuels (also called agrofuels) are also very popular in North America. In the US, plant fuel is mainly produced from corn and wheat. The same applies in Europe although over here we can add sugar beet to the list of raw materials most commonly used to produce biofuels.

The use of these non-fossil fuels is good for economies that are dependent on fossil fuel energy. It also represents an interesting alternative from an environmental point of view because it results in a reduction of greenhouse gas emissions. However, we will need to be very cautious if we are to succeed in this noble objective.  If we transform carbon-rich soils into areas for growing the raw materials for biofuel, the carbon can be released into the atmosphere and we do not reach the target levels. Even worse, we are doomed to failure, for example, if the fabrication process for factory-produced biofuel uses a lot of fossil fuel because this also contributes to high levels of greenhouse gas emissions (GHG). This is why the following important European regulation was passed: in order to be accepted for use in our tanks, biofuels must lead to a reduction of at least 35 % of GHG in relation to fossil fuels. A note of caution here: it is the entire life cycle of biofuels which is targeted here, including the fabrication procedure and direct land use change (LUC) resulting from the decision to grow the raw materials for these fuels.

This environmental condition, which is part of an EU directive, could also be extended to include other factors. This is because the impact of biofuel fabrication on the environment is far from being merely limited to greenhouse gases. Growing crops such as corn, wheat, sugar beet and sugar cane inevitably has consequences for water-use, the conservation of biodiversity or the emission of other pollutants not to mention the fact that industrial transformation requires the use of various chemical products. All these environmental impacts must be taken into account when the ethanol produced by plant fermentation is used for the fabrication of a fuel, but also when it is used for the fabrication of ethylene (1), the monomer necessary for the plastics industry which we refer to as the “bioplastics” sector.

(1) By extracting a molecule of water from bioethanol- known as catalytic dehydration, we obtain bioethylene which can be used for the manufacture of plastic.

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