Biodiesel: five questions and answers



1. What is biodiesel?

The fuel generally known as 'biodiesel' is actually rape methyl ester (RME), which is produced by the chemical treatment of rapeseed oil in a process called transesterification. This improves its fluidity and ignitability, thus making rape methyl ester very similar to conventional diesel fuel in its essential properties.

2. Can I run my car on biodiesel?

Only cars explicitly labelled by the manufacturer as suitable for biodiesel should be run on it. Otherwise, according to the German automobile club ADAC, there is a possibility of damage being caused, e.g. to the fuel-injection pump. It will also mean that you cannot claim under warranty or guarantee and that the manufacturer is unlikely to offer any compensatory gesture of goodwill. So before you fill up, do check your user manual to ensure your car is biodiesel compatible. If you have any doubts, it is safer to ask the manufacturer. In the current 'new car programme' (Euro 4 standard on exhaust gases), only the VW Golf V and Skoda Octavia II are approved for biodiesel – but only if they have been ordered with the special biodiesel option at an additional charge. Audi, BMW, Mercedes, Peugeot, Seat, Skoda, Volvo and VW have given biodiesel approval to some older models.


3. Where can I fill up with biodiesel?

Around 1,900 petrol stations in Germany offer biodiesel. A good 1,400 of these have joined AGQM, the German association for quality management in biodiesel, to help guarantee standards across the board. According to UFOP, the German union that promotes the use of oil and high-protein plants, only biodiesel made from rapeseed oil will be available at these filling stations. The pumps carry the AGQM symbol, next to the sign which confirms that the oil meets the German standard 'DIN EN 14214'. Random quality control checks are made of the fuel in the oil mills, during storage and transportation, as well as at the fuel pumps. The AGQM advises biodiesel purchasers to keep all fuel receipts, so that if it damages their car in any way they will be able to prove that they filled up only at quality-controlled stations.

4. Is biodiesel cheaper than ordinary diesel?

There are wide regional variations in the price of biodiesel at filling stations but, on average, it costs around 20 euro cents per litre less than conventional diesel. The cheaper price comes from the fact that it is taxed less than mineral oil (conventional diesel fuel is subject to a tax of 47 euro cents per litre). Since the new law on energy tax came into force on 1st August 2006, biodiesel has become subject to annually-increasing taxes, starting at nine euro cents per litre. By 2012, the highest tax rate of 45 euro cents should be reached. Cars that run on biodiesel can use up to 10% more fuel than those using 'normal' diesel, due to the low energy content of RME.

5. Is biodiesel better for the environment?

CO2 neutrality is often cited as a substantial benefit of biodiesel. This assumes that the burning of rapeseed oil releases only as much climate-damaging carbon dioxide (CO2) as the rapeseed plants have absorbed from the atmosphere during cultivation. However, in the process of growing them, extracting the oil and converting it into RME, conventional fuels are normally used, so this is not actually a closed carbon cycle. In the growing of rapeseed, we cannot ignore the fact that small quantities of the greenhouse gas N20 are released into the soil. The plants also emit ozone-producing hydrocarbons. If the rapeseed plants are cultivated and fertilised as a single crop (monoculture), they cause harm to the soil and water table. According to ADAC, any conclusions about whether biodiesel leads to greater CO2 reductions than diesel derived from mineral sources will also depend on how its by-products, such as rapeseed meal and glycerine, are used. Different ways of looking at the situation mean that the CO2 balance sheet is open to many different interpretations. According to the federal environmental agency in Berlin (UBA), there is a CO2 reduction of up to 65% per unit of biodiesel compared to mineral diesel – depending on how its by-products are evaluated. There is a significant decrease in particle emissions (diesel soot) of around 50% in engines not fitted with a particle filter. The use of biodiesel usually leads to a reduction in carbon dioxide and methane emissions, but with a corresponding increase in nitrogen oxides. However, the values in individual cases will primarily depend on a vehicle's operating conditions and the engine and fuel injection technology used. As biodiesel contains virtually no sulphur, it produces almost no harmful SO2 or sulphate emissions. (Source: ADAC)

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