Biofuels are fuels made from biomass. This is material of vegetable or animal origin, such as wood, maize, manure, food waste or vegetable oil. An important advantage of these raw materials is that they are renewable and therefore do not become depleted like fossil fuels, and are able to supply a continuous source of clean energy. There are different types of biofuels. Biodiesel is the best-known liquid fuel for transport. Below we list the various types of biofuels, with some of their properties and application options.
SVO or straight vegetable oil is oil extracted from oil bearing seeds, beans and fruits that can be used as fuel without modifications. The oil can be used in a diesel engine, although long term use could result in motor damages. The oil is slightly viscous. To use it in winter conditions, it must be heated. In general, vegetable and animal oils and fats are processed into biodiesel (FAME: Fatty Acid Methyl Ester).
FAME or Fatty Acid Methyl Ester is the well-known biodiesel that is usually sold mixed with fossil diesel. It is made from vegetable and animal oils and fats or waste products such as used cooking oil. At the moment FAME is for sale at the pump in Europe, as B7. This means that up to 7 per cent of the fuel is biobased. Higher blending percentages are also possible, especially for heavy road transport. Certain vehicle manufacturers allow running on B100 (pure FAME). Depending on the type of raw material used, specific names and abbreviations are used: RME: rapeseed methyl ester; SME: Soy methyl ester; UCOME: Used Cooking Oil methyl ester; TME: tallow methyl ester.
HVO or Hydrotreated Vegetable Oil is a type of biofuel that is made from vegetable and animal oils and fats or waste products such as used cooking oil. The processing makes the fuel chemically identical to fossil diesel. It is suitable for diesel engines.
Bioethanol is made by the fermentation of sugars. This can be sugar from sugar beet, sugar cane, but also from corn or grain. After fermentation, the alcohol-water mixture is distilled. That process is similar to alcohol in distilled beverages. This form of biofuel can be used in gasoline engines.
SAF or Sustainable Aviation Fuel is a collective name for biofuel suitable for aircraft. That means a low pour point because of the low temperatures that prevail at the high altitudes at which aircraft fly. SAF from vegetable and animal fats and oils and used frying fat are made through the same process as HVO, followed by a final distillation process.
RFNBO or Renewable Fuel of Non Biological Origin refers to fuels that are produced using energy from other renewable energy sources. In practice this means the use of renewable power from geothermal, solar or wind power, where a local excess production can result [in the production of so-called e-fuels, like hydrogen or methanol] during shorter or longer periods, thereby giving access to such energy at low costs. There are also developments using e.g. concentrated solar power or geothermal energy as a source for direct heat for use in fuel production. More specific it means the production of hydrogen and so called e-fuels. Electrofuels (E-fuels), Power-to-Gas (PtG) and Power-to-Liquid (PtL) refers to technologies, which convert renewable electric energy to another energy carrier, like for example methane, methanol or Fischer-Tropsch fuels.
In short, as a first stage, electricity is converted to hydrogen through electrolysis as described above. To produce a hydrocarbon or alcohol fuel, a carbon source is also required. This carbon source is typically CO2, which is readily available from many sources. These sources include biogenic CO2 from bakeries, ethanol fermentation in breweries or ethanol fuel plants. CO2 can also be obtained from biomethane upgrading or gasification plants. Additionally, it can come from fossil sources such as coal power plant flue gases or industrial waste gas streams in refineries and chemical plants.
The website of the European Technology and Innovation Platform gives more information on the topic. Click on the link for background information about hydrogen (in Dutch).
Bio-LNG or Bio Liquefied natural gas is liquefied gas (NH4) produced from the fermentation of organic waste. Vehicles that have been made suitable for running on gas can run on these types of biofuels. These can be both petrol and diesel engines. Bio-LNG is derived from renewable resources and can be produced at any site where anaerobic digestion takes place, making it a biofuel. Biogas mainly consists of biomethane and bio-CO₂ and contains other gases such as ethane and hydrogen sulfide to a lesser extent. The biogas is cleaned in an installation so that only biomethane remains. This is liquefied at -162 degrees Celsius and then transported to filling stations.
Ammonia can be used as fuel. Ammonia, unlike hydrogen gas, can be stored as a liquid in large tanks. It has a high energy density and can burn cleanly; with a suitable catalyst and not too much oxygen. Only water vapor and nitrogen are released. Ammonia gas is poisonous and explosive.
Hydrogen can be used as a fuel. It can be stored as a liquid at low temperature and high pressure in large tanks. Hydrogen has a low energy density and can burn cleanly. Depending on the production process, hydrogen is sustainable or not. Green Hydrogen made by using electricity from solar and wind energy, can be seen as a type of biofuel and is therefore sustainable. Grey Hydrogen produced using fossil energy is not considered sustainable. Click on the link for background information about hydrogen.
Fischer-Tropsch diesel (Bio FT diesel) is made by cracking feedstock. FT fuel is often made from fossil raw materials such as coal or natural gas. When biomass is used Bio FT is produced. Carbon monoxide is created by burning a carbon-containing fuel, such as coal, with a low oxygen content (partial oxidation). If steam is added during this process and the gas is led past a catalyst and the end product is then purified, the gas mixture of carbon monoxide and hydrogen produces synthesis gas, also known as syngas. Synthetic hydrocarbons can be made from syngas that form the basis of coal diesel and other products. For example, GTL (Gas to Liquid) is produced.
DME or Dimethyl ether is a nontoxic gas at normal conditions. Liquefied at about 6 bars it has similar properties as LPG. It has many applications such as propellant, power generation, fuel for heating and cooking, or as transportation fuel. DME can be produced from natural gas, coal or biomass.
HPO or Hydrotreated pyrolysis oil can be made from biomass or other feedstock. The pyrolysis oil needs chemical upgrading before it can be used as a fuel. Click here for more information about advanced biofuels from fast pyrolysis bio-oil.
MtD or Methanol-to-diesel is a synthetic diesel fuel, which can be considered as a type of biofuel when biomethanol is used as a feedstock. And it is a liquid alcohol ether mixture with appropriate amount of additives, which can be blended with diesel fuel at various levels.
