What is biodiesel ?

Biodiesel manufactured and sold in England is nearly always manufactured from the most important indigenous oil-bearing plant – rape. The oil is converted into a modern diesel fuel with flow and combustion properties very closely approximating those of conventional mineral fuels by a simple rebuilding process of its molecular chains.

Biodiesel thereby fulfils the highest requirements of engine technology such as the modern high-pressure fuel injection systems (Common Rail).

Biodiesel, is therefore a genuine alternative to conventional diesel. However, a complete substitution is impossible. It is estimated that five to seven percent of the diesel fuel consumption could be replaced by biodiesel production with indigenous raw materials. 10 percent is conceivable within the European Union.

Biodiesel is therefore now at the peak of all alternative fuels and, together with other concepts such as hydrogen engines and fuel cell technology, biodiesel will assume a supporting role in the mobility of the future, when the mineral oil wells have run dry

Biodiesel has a natural lead for its development in comparison with diesel fuel. Its high cetane index, its almost complete lack of sulphur, is significantly higher lubricating capability and its built-in oxygen proportion of around 11 percent make it an intrinsically modern hi-tech fuel

Cetane Improvement
The higher the cetane index of a diesel fuel, the better the ignition and combustion and the more regular and smoother the engine runs. Commonly available diesel fuels have a cetane index of 50 to 52, and values of 53 to 54 are achieved by the addition of ignition accelerators. In this, biodiesel has a natural advantage. Its primary components are similar to cetane and this fuel therefore has a natural cetane index of 56 to 58 and can easily fulfill the requirements of engine manufacturers for high-quality fuels with high inflammability without additives.

Ultra low sulphur level
Whereas the sulphur content of lowsulphur diesel fuel is reduced in the refinery in a high-energy process with additional CO2 emission and a loss of the intrinsic lubricating capability, biodiesel is naturally almost free of sulphur (max. 0.001 percent and thereby at the limit of its detectability). This characteristic of biodiesel also allows the simple and optimum use of an oxidation catalytic converter

Significantly Lubrication Capability
Biodiesel has a very good intrinsic lubrication capability. Trials have shown that biodiesel lies far below the values specified in the standard for mineral oil diesel. The so-called HFRR value is a measure of the lubrication capability. In general, the lower the HFRR value, the better the fuel. Highly desulphurised mineral oil diesel fuel has an HFRR value of 500 or higher without additives, but the limit specified by the standard for diesel fuel is 450. Mineral oil diesel fuel therefore requires additives. In contrast, the HFRR value of biodiesel is approx. 200. Biodiesel is therefore suitable as a good lubricating additive to conventional diesel when added in proportions of only 1 percent. In the operation of an engine approved for biodiesel, the engine wear is significantly reduced.

The biodiesel molecule contains around 11 percent of oxygen. This oxygen contingent leads to an improved combustion and thereby to substantially less soot. The residues left inside the engine by the fuel are significantly reduced.

Although the density of biodiesel is slightly different from that of mineral diesel fuel, both fuels can be mixed in any ratio due to their similar chemical structure. The mixture is stable and cannot be separated by mechanical methods. It is therefore also impossible to extract biodiesel which has escaped to the engine oil with partial flow filters. The subject of mixing will have more importance in the future in view of the more stringent emission requirements

Biodiesel compliant with EN 14124 has a flashpoint of over 110 °C and other properties which indicate a lower potential hazard. For this reason, it is not a hazardous material and its handling is not subject to the operational safety rules. This is a great advantage over mineral oil diesel in storage and handling.

With the development of the European standard EN 14214, the minimum requirements on the quality of biodiesel were specified mutually at a European level by engine manufacturers and the biodiesel industry. The European standard for biodiesel has now become internationally acknowledged and is a guideline for the standardization activities conducted by other countries.

Apart from all the technical advantages and features of biodiesel, there is another more significant aspect in its favor: its environmental friendliness. Biodiesel and its use are the origin of local and global effects. Its rapid biodegradability and its almost closed CO2 cycle set out the enormous bandwidth of its ecological value.

Numerous independent institutes have now confirmed the advantages of the emissions from biodiesel in comparison with conventional diesel. For example, when biodiesel is used with a catalytic converter, only one third of the quantity of particles is emitted in comparison with low-sulphur diesel fuel. Unburnt hydrocarbons are also reduced. Only slightly higher NOx values have been noted when biodiesel is used. However, this increase, which is caused by the higher combustion temperature of biodiesel, is an effect not typical of the fuel, but of the engine.

In contrast, mineral oil diesel fuel is classified as water-endangering and EN14214 Biodiesel is rapidly biodegradable. It has been demonstrated that biodiesel is biologically degraded by over 98 % within 21 days whereas mineral oil diesel fuel is degraded by only 70 %.

Since biodiesel became a serious alternative, there have been intensive discussions of the pros and cons of its use. Important aspects such as the material balance, the energy and CO2 balance has been extensively analysed. The fundamental advantage of all regenerative energy sources is their almost completely closed CO2 cycle. CO2 is released in all combustion processes. However, the CO2 produced in the combustion of biodiesel has been absorbed beforehand from the atmosphere by the rape plant during the photosynthesis process. In contrast to the use of fossil fuels, the combustion of biodiesel does not make a new addition. In this way, every litre of biodiesel which replaces fossil diesel reduces the greenhouse effect.

However, it cannot be denied that future developments in Biodiesel fuels new potentials for the use of native vegetable oils and these oil wells will never run dry.