Vegetable oils

Vegetable oils are biogenic energy stores that are obtained by extracting them from plants. Rapeseed oil is mainly used in Germany, as well as international alternatives such as soy. They can be used directly as fuel without transesterification processes, which distinguishes them from biodiesel.

Definition
Vegetable oils are vegetable oils obtained from seeds by mechanical pressing or chemical extraction. They are used as environmentally friendly fuels and alternative energy sources and have different physical properties that influence their use in engines.

Background / Origin
Vegetable oils are produced by photosynthesis in plants and are thus known as dense biogenic energy stores. In Germany, rapeseed oil is the primary source, as rapeseed grows well here in terms of climate and can be produced cost-effectively. Other domestic options include sunflower oil and camelina, while soy is also used internationally.

Vegetable oil can be obtained by cold pressing or industrial extraction. In cold pressing, cleaned oilseeds are mechanically pressed out, whereby temperatures of up to 40°C are reached. Subsequent filtration or sedimentation processes remove suspended solids. Solvent extraction is often used on an industrial scale, where solvents, often hexane, are used after pressing to completely extract the oil. However, this leads to a higher contamination of the oil with undesirable accompanying substances, so that subsequent refining processes are required.

The requirements for the quality of rapeseed oil were defined in DIN 51605 in 2012. In order to comply with these limit values, post-treatment is often required to reduce the content of undesirable substances. Furthermore, other oil plants must also meet the guidelines in accordance with DIN 51623 to confirm their suitability as a fuel.

Properties
Vegetable oils differ in their chemical composition and physical properties. The calorific value of a liter of rapeseed oil fuel is about 0.97 liters of diesel fuel and exceeds the calorific value of gasoline per liter by about 10%.

The physical characteristics are decisive for its applicability in diesel engines. Pure vegetable oil has a higher viscosity and a lower cetane number, which often requires adjustments for modern engines to enable optimal use. Chemical characteristics include:

- High unsaturated fatty acid content
- Varying levels of calcium, magnesium and phosphorus, which are relevant to the quality of the oil

Application and importance on the market
Vegetable oils have a wide range of applications. They are used both in industrial production and in direct fuel use. They are used in stationary systems such as combined heat and power plants or heating systems. They can also be used as fuel in various vehicles, including cars, trucks, agricultural machinery and construction machinery.

The use of vegetable oil as a fuel often requires measures to convert modern engines. The insertion of new filters, adjustments to fuel lines and the installation of heat exchangers are often necessary in order to take into account the specific properties of vegetable oils. Particularly in winter, it is necessary to mix vegetable oil with diesel to ensure fluidity.

Differentiation from similar terms
In contrast to biodiesel, which is obtained from vegetable oils by transesterification, vegetable oils are extracted and purified directly. Biodiesel often deals with quality issues relating to its chemical properties and production processes, which are not relevant to vegetable oils.

Summary
Vegetable oils are biogenic energy stores derived from photosynthesis that are used as alternative fuels. Rapeseed oil in particular plays a central role in Germany, while international options such as soy are also important. It is produced by cold pressing or industrial extraction, with quality standards set out in DIN norms. Despite the suitability of vegetable oils in diesel engines, modern vehicles usually require special conversions to ensure optimal use.