Biofuels

11/25/2010

Biofuels are derived from biomass- the energy stored in organic matter in the form of sugar, oil or starch. Made from plants, they are mixed with standard fuels and then distributed in service stations. Both the greenhouse gas emissions from these fuels and the energy spent producing them are closely monitored. This is to ensure that the amount of energy spent producing them does not exceed the energy they provide, which would render their production useless.

What Are the Different Types of ‘Green' Fuels?

Current biofuels are produced from agricultural crops selected for their high-energy value (rapeseed, sunflower, sugar beet, sugar cane, etc.). When these plants are burnt as fuel, they release higher amounts of energy than other plants.








Organic waste of various origins can also be used to manufacture biofuels. In the future, technology will also allow us to use the energy contained in plant parts, such as cellulose (the substance that makes up plant cell walls) or lignin (the main component of wood). These are referred to as second generation biofuels.

There are two main types of biofuels:

  • Biodiesels can partly replace diesel in diesel engines. These are derived from oil-bearing plants like rapeseed, sunflower or palm oil. The pure vegetable oil obtained from these plants cannot be used directly in diesel engines, because it is too viscous and could damage them. This oil also does not self-ignite easily. It is therefore not compatible with diesel vehicles, which use fuels that ignite spontaneously when temperature and pressure rise. This is why this vegetable oil is mixed with methanol (alcohol), resulting in a chemical reaction that produces VOME (vegetable oil methyl ester), which is also called diester. Diester, which self-ignites easily, is then mixed with diesel in variable proportions representing up to 30% of the final fuel. It is then suitable for use in several types of diesel engine.

  • Bioethanol can be used as a gasoline substitute. It is derived from plants that are rich in either sugar (sugar beet and cane sugar) or starch (wheat, corn, and potato). These plants are fermented to obtain ethyl alcohol but this cannot be used as is in standard engines. It is currently mixed with isobutylene (a petroleum product manufactured in refineries) to obtain ETBE (ethyl tert-butyl ether). Standard engines tolerate ETBE when it is added to gasoline in proportions of up to 15%.

Producing Biofuels- Energy Performance, Carbon Footprint and Raw Material Sustainability

In 2008, biofuels accounted for 1.8% of all fuel consumed in the transport sector worldwide. Most biofuels manufactured in the world today are bioethanols produced in Brazil (from cane sugar) and the United States (from corn).

Energy is spent at each stage of the biofuel manufcturing process.

   • Cultivation, harvesting, and transporting plants requires the energy of agricultural machinery and trucks as well as the use of fertilizer.

   • Processing and conversion facilities to produce biofuels also use large amounts of energy.

In order for biofuel production to be useful, it is necessary to ensure that the end product will provide more energy than it uses - otherwise it would be easier to use the energy needed to manufacture it directly!

This is known as energy performance, whereby an input to output ratio is calculated for each biofuel (this is the ratio between the energy provided by the biofuel and non-renewable energy expended producing it). This ratio varies significantly depending on the plants used as raw materials:

   • It is 1.15-1.8 for wheat or sugar beet ethanol.

   • It is significantly higher for rapeseed diester, at 2.1-3.

Similarly, to ensure that biofuels have the best possible carbon footprint, greenhouse gas (GHG) emissions are minimized from production to consumption - "from field to wheel". To do this, the greenhouse gas emissions saved by using these fuels are compared to the emissions that generated to produce them.

Over the long term, biofuel production also depends on the availability of raw plant materials, without the risk of competition with arable land use for food and water resources.

Industrial and scientific stakeholders are carrying out research that takes account of these issues, to use biomass in the form of fuel sustainably and effectively. Along with the bioplastics sector, the biofuel sector represents one of the most promising opportunities for future biomass development.