Enjeux - Biofuels

Biofuels

With the inevitable dry-up of oil reserves, volatile barrel prices and the impact of carbon emissions on global warming, everyone agrees that we need to find alternative sources of energy. Biofuels, developed on a significant scale in the USA and Brazil for 30 years and in Europe since the mid-1980s, are a renewable energy source that can be used immediately. After an initial wave of enthusiasm in France, they have been widely criticised over the last two or three years. Let’s take a closer look at the viability of biofuels and try to understand today’s criticism in an attempt to determine whether the charges are justified.

THE CONCEPT

Definition

Biofuels, also known as agrifuels, result, like oil, from the transformation of organic plant matter. But unlike petrol, produced from fossilised matter produced and accumulated over hundreds of millions of years, biofuels are produced from yearly crops, which makes them a renewable source of energy. Biofuels are made by transforming sugar cane, sugar beets, wheat, corn, sunflower and soya bean, all of which are annual crops. In the future, if technological progress allows, the raw material will come from coppices of short-rotation trees and plants like miscanthus, crops that grow over several years. They may also be produced from by-products or waste, including straw, sawdust and green waste. 

Two types of biofuel exist: bioethanol and biodiesel. The best known brand of biodiesel in France is diester.

Bioethanol

Bioethanol today is produced mainly from sugar cane in Brazil, corn in the USA, and sugar beets, wheat and corn in Europe.  But it can also be produced from any source with a high content of sugar or starch, effectively long carbonaceous chains. The sugar contained in the raw material is transformed into alcohol through fermentation.  Bioethanol can be mixed with petrol, in blends containing 5% (in E5 fuel), 10% (in E10), 85% (E85) and even up to 100% bioethanol content in E100. Normal vehicle engines can run on blends containing up to 10% ethanol with no modifications necessary. Beyond that percentage, vehicles need to be fitted with flexfuel engines running on conventional petrol or petrol/ethanol mixes. E100 can only be used with special engines.

Biodiesel

Biodiesel is made from oil seeds with high oil content, including rapeseed and sunflower in Europe, soya bean in the USA and palm oil in Asia. It is the result of a chemical reaction called esterification between the vegetable oil extracted from the plants and an alcohol (methanol or ethanol), to the tune of one tonne of oil to 100 kg of alcohol. Biodiesel can be blended directly with diesel and used by all diesel-powered cars without engine modifications. The average content in diesel available at service stations in France today is 6%. Local authorities and businesses in the country have been using a 30% biodiesel/70% diesel blend for over ten years.

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Imprimer

Les autres dossiers :

• Les OGM au coeur de la controverse
• Les Biocarburants : une voie d'avenir ?
• La PAC est-elle indispensable ?
• Les phytosanitaires : à bannir ?
• L'agriculture : une menace pour la biodiversité ?
• Agriculture et gestion de l’eau, sont-elles incompatibles ?
• Les attaques contre la viande sont-elles justifiées ?