Biofuels- A How-To Guide

Biofuels include all biomass-derived fuels. Currently sourced from farms, they are mixed with either gasoline or diesel, depending on their characteristics and properties.

Biofuels (conventional channel)
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What Is a Biofuel?

There are two main types of biofuels:

Bioethanol

Used in gasoline engines, bioethanol is derived from sugar beet and sugar cane or cereal, such as corn and wheat. To obtain this biofuel, the sugars in the plants are extracted from the sugar crops. They are then fermented and converted into alcohol or bioethanol.


If cereals are used as a raw material, the starch is extracted. It is converted into sugar using a chemical reaction known as hydrolysis and the sugar is then fermented to make bioethanol.

Bioethanol is the most widely used biofuel in the world.

Bioethanol can be added to gasoline as is or in the form of a derivative called ETBE (Ethyl Tertio Butyl Ether). ETBE is obtained from a chemical reaction between ethanol and isobutylene (a compound recovered from the refining process) and is an excellent additive for gasoline.
Bioethanol is the most widely used biofuel in the world. Between them, Brazil and the United States produce almost 90% of the world’s bioethanol.

Biodiesel

This is used in diesel engines. It is derived from rapeseed, soy or palm oil.

To obtain biodiesel:

   • First the seeds of the plants are retrieved after harvesting.

   • Next, the seeds are sent to a crushing plant to be cleaned, crushed, and rinsed in a solvent to extract 96% of their oil. After crushing, the residue is used to make a protein-rich animal feed.

   • The oil is then mixed with methanol, an industrial alcohol produced in petrochemical plants. This causes a chemical reaction called transesterification takes place. The plant oil-methanol mixture is converted into vegetable oil methyl ester VOME and glycerine.

   • Finally, VOME is separated from the glycerine, which is reused as a raw material to make soap, shower gel or toothpaste.

In France, biodiesel production increased five-fold between 2002 and 2008. Diesel at the pumps contains up to 7% of biodiesel and in some professional fleets the figure is as high as 30%.


Compared to traditional fuels, biofuels help reduce greenhouse gas emissions. Moreover, they are a renewable resource, in contrast to fossil fuels.

Fuel Mixes are Carefully Tested to Ensure Optimal Quality

To power a vehicle, biofuel needs to be mixed with a petroleum-derived fuel in proportions set by European regulations and fuel quality standards. Conventional vehicles cannot run on gasoline or diesel containing large quantities of biofuels without causing engine trouble.

Currently, in 2011, no more than 10% of bioethanol can be mixed with gasoline (or 22% ETBE) and no more than 7% of biodiesel can be mixed with diesel sold in service stations.

Some vehicles with specially designed engines are powered solely by biofuel.

True and False. Previously in Brazil, vehicles were designed to run on pure ethanol. However, they had a small separate gasoline tank for starting the engine. The problem was that the vehicles could only run on ethanol and not on gasoline. In recent years, European car makers have introduced flex-fuel-vehicles, or FFVs. These are specially designed to run on gasoline or a biofuel mix containing up to 85% bioethanol, giving drivers greater flexibility.

To ascertain the proportion of biofuel that can be added to gasoline or diesel, car makers and oil companies have been conducting tests on both engines and vehicles. These tests involve analyzing the properties of biofuel mixes and any effects on the engine. These tests check for the following:

   • For gasoline engines:

     o Biofuel mix volatility (i.e. its propensity to evaporate). Ethanol increases gasoline's volatility, so it requires a specially adapted fuel base.

     o Stability when water is present- in this situation, ethanol separates from gasoline. Appropriate logistic measures need to be taken to ensure there is no water present.

     o It should be noted that incorporating ETBE does not pose the problems of increasing gasoline's volatility or demixing (i.e. separation) when water is present.

   • For diesel engines:

     o Mix stability- i.e. its conservation capacity and the way it reacts to temperature changes when exposed to oxygen

     o The nature of exhaust emissions.

Tests conducted by car makers have shown that:

   • All gasoline vehicles can run on a fuel containing 5% ethanol. Almost all vehicles placed on the market since 2000 can use a fuel containing up to 10% bioethanol.

   • All diesel engines run normally on a fuel containing up to 7% biodiesel. Some professional fleets can run on diesel containing 30% biodiesel. However, these vehicles require careful monitoring and specific maintenance procedures.