What is biodiesel?

A natural automotive fuel

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The use of biofuels has increased steadily in recent years, due to their importance in reducing the transportation and energy transition carbon footprint. They are another alternative, just like electrification, for the decarbonization of transportation.

What is biodiesel?

Biodiesel is a natural fuel. Its use makes it possible to reduce greenhouse gas emissions, as it is produced from organic matter (mainly vegetable oils or animal fats).

Biodiesel can be blended with mineral diesel by up to 7%. It can also be used for domestic heating, in specific biodiesel boilers. It is obtained through a chemical process where the oil reacts with an alcohol when a catalyst is present.

Depending on the amount of biodiesel in a fuel's composition, a nomenclature is used using the letter B and a number, indicating the proportion of biodiesel in the blend with diesel obtained from oil. So, at Service Stations, diesel of fossil origin is called B7, being able to contain up to 7% biodiesel.

Differences between Biodiesel and 100% renewable Diesel (HVO)

Biodiesel and 100% renewable diesel (HVO) are two totally different fuels:

Biodiesel, given its behavior in the cold, may not be suitable for all diesel vehicles, or require technical modifications in the vehicle, for its use. Biodiesel is obtained through transesterification, which is a chemical process where a triglyceride reacts with an alcohol, when a catalyst is present, such as sodium hydroxide or potassium. It complies with the quality regulations and specifications of EN 14214.
100% renewable diesel (HVO) is a paraffinic diesel compatible with all internal combustion diesel engines. 100% renewable diesel (HVO) can be produced by different technologies, but the process mainly consists of hydrogenation or hydrotreatment, where the oils and fats react with hydrogen when a catalyst is present. It complies with the quality regulations and specifications of EN 15940.

Types of biodiesel

Biodiesel can be classified in various ways, depending on the raw material it is made from. For example, depending on the raw material, the following types can be distinguished:

Biodiesel produced from vegetable oils

It is made from oil extracted from oleaginous plants such as rapeseed, sunflower, palm, soybean, and marine plants, such as algae. It is one of the most widespread methods of production, and raw materials are already being cultivated to produce biodiesel.

Biodiesel produced from animal fats

It is also possible to produce biodiesel from animal fats, by extracting and processing the lipids. In Spain, pork, bovine, or poultry fats are usually used.

Biodiesel extracted from used cooking oils

This is the most affordable option and the one that most promotes the circular economy and recycling, as it consists of using used oil in homes, the catering businesses, or the agri-food industry.

Biodiesel uses

The energy contained in biodiesel is so great that it can be put to many different uses, and most importantly, all in a satisfactory way. Some of the most noteworthy are the following:

Fuel for diesel engines and diesel vehicles
For heating systems
Electric generator
As an industrial solvent
As a lubricant, thanks to its sulfur reduction
Fuel for domestic kitchens

Advantages of biodiesel

The worldwide biodiesel boom can be explained by the fact that it's an affordable fuel. Numerous studies have shown that its CO₂, SO₂, or CO emissions, among others, are lower than other fuels of fossil origin. In fact, institutions such as the U.S. EPA (Environmental Protection Agency) estimate that the CO₂ reduction ranges between 57% and 86%. This makes it a very interesting alternative, but that’s not its only advantage:

It can be used in most diesel engines.
It does not contain sulfur, so does not emit this gas.
It can be produced locally, without the need to depend on imports.

Characteristics of biodiesel

Raw materials:
It is produced from vegetable oils (rapeseed, sunflower, palm, soybean,...), animal fats, or used cooking oils.
Production:
Biodiesel is obtained through transesterification, where the triglycerides present in oils and fats react with an alcohol (normally methanol) when a catalyst is present, to form fatty acid methyl esters (biodiesel) and glycerol as a by-product.
Chemical Composition:
Formed mainly by fatty acid methyl esters, which makes it chemically different from diesel of fossil origin and 100% renewable diesel.
Properties and Use:
It has similar properties to fossil fuel in terms of density, flash point, and energy content.
It may have stability problems at low temperatures, and may require additives or modifications in the engine.
It can be blended with fossil diesel in various proportions (e.g. B7, up to 7% biodiesel, B20, up to 20% biodiesel, B100, 100% biodiesel).
Environmental Impact:
It can reduce CO₂ emissions and other pollutants compared to diesel of fossil origin.