Ecological and Economic Aspects of Biodiesel Use


Due to an increased willingness especially of the industialized countries to preserve a healthy living environment, and due to the foreseeable depletion of exploitable fossile fuel resources, the use of alternative energie sources is becoming increasingly interesting to the general public. Next to solar energy, wind power and the controversially discussed nuclear energy, the use of renewable raw materials is gaining in importance. Especially renewable energy sources have a reputation of being environmentally friendly and virtually inexhaustible.

Rapeseed methyl ester, which is produced from vegetable oil through the simple chemical process of transesterification, is one of these renewable raw materials. It is often also called biodiesel, or RME for short.

Using current technical literature as basis for argumentation, the study demonstrates the advantages and disadvantages of the use of rapeseed methyl ester (RME, biodiesel) in comparison to conventional diesel fuel. Special attention was paid to economic and ecological effects as well as special technological features.

Investigation Method

The assessment and evaluation of the effects of certain products on the environment is realized by calculating an ecological balance. In this balance, all potential environmental effects of the entire product life cycle are investigated and evaluated.

All of the product's input and output streams have to be compiled in a lifecycle inventory that covers its production, use and disposal. For a complete ecological evaluation, usable products that are created secondary to the main product are credited as co-products to the respective product system.

The result of an ecological balance calculation depends fundamentally on the depth and precision with which all products involved are detected and recorded. Therfore, it is necessary to set appropriate system limits in order to analyze all relevant interrelations with manageable effort.

To allow for the subsequent interpretation, the data compiled during the lifecycle inventory process is then matched with their relevant respective impact categories such as consumption of resources, greenhouse effect, acidification. The evaluation is executed with the help of impact indicators determined using weighting factors.

Ecological Comparison

The comparatison of the ecological balances of biodiesel und mineral diesel shows that both types of fuel have advantages and disadvantages in terms of environmental impact. Large amounts of fossile fuels are consumed during the production of conventional diesel. The cultivation of rapeseed crops for the production of biodiesel also requires the use of mineral resources. While the CO2 balance of RME is far more favorable than that of diesel, RME produces higher nitrogen emissions. The naturally low levels of sulfur, on the other hand, would support the use of biodiesel. A disadvantage of the cultivation of rapeseed is that it often requires a massive use of fertilizers and pesticides, which may pollute have the soil and ground water. However, the good biological degradability of RME itself is of advantage for the oceans and for inland bodies of water. In addition, RME is less hazardous for the environment in case of a transport accident.

Cost Comparison

We were able to determine that the use of RME has no overall disadvantages. Due to the price difference between RME and conventional diesel, even cost savings are likely. How long this price level can be maintained depends on on economic and political developments. It is to be expected, however, that with a growing demand of RME its price will approach its actual costs, because the subsidies for RME cultivation and oil tax exemption can not be increased indefinitely. 

Technical Requirements

Despite relatively large regional differences, it can be assumed that biodiesel will be comprehensively available as an alternative fuel. It is furthermore of advantage that it is often possible to mix mneral diesel and biodiesel during operation.

Usually, diesel engines can be operated with RME after slight modifications. Today, many vehicles are even approved for RME use from the start. Older vehicles first need to be tested for whether they are generally suited for modification. Plastic hoses and sealings have to be replaced in addition to the fuel filter. Furthermore, older vehicles should be retrofitted with an oxidation catalytic converter and the oil exchange intervals should be observed strictly. When in doubt, vheicle owners should contact the car manufacturer and/or their garage.

Generally, it should be noted that biodiesel is not to come into contact with car paint because of its dissolving properties.

Special Features

If handled properly, biodiesel can be stored safely for a longer period of time without any negative effects on its quality. Direct exposure to sun light is to be avoided. The storage tanks should be made of metal and their interior painting should be RME resistant. Due to their insuffiecient RME resistance, tanks made from PVC are not suitable for storage.

Similar to mineral diesel, RME is offered as winter fuel and as summer fuel, depending on the season. Summer diesel can be used up to a minimum temperature of 0 °C, winter diesel contains additives that make it usable up to -20 °C. The additives keep the crystals in the fuel small enough so that they can pass the fuel filter without any difficulties. In addition, they ensure that the crystals stay finely dispersed throughout the liquid and do not settle at the bottom of the tank.

Economic Efficiency

For reasons of general economic efficiency, the Umweltbundesamt (German Federal Environment Agency) does not approve the use of RME. It binds direct and indirect subsidies that could have a greater impact in terms of environmental protection if spent in different areas.

From the point of view of companies and industry, however, the use of biodiesel can be of advantage. The costs for a modification of their vehicles are relatively low, and very small additional expenses are to be expected in the short term compared to the use of conventional diesel fuel.