Production

The oilseed rape plant is the most important renewable raw material for bio-diesel production. Oil mills process the seeds (with an oil content of approx. 40 to 45 per cent) into natural rape oil as the basis for the alternative fuel. In 2008 the oilseed rape plant was cultivated on 1.4 million hectares across Germany. This corresponds to some twelve per cent of the area of arable land available. Approx. 1,600 litres of plant oil can be produced from each hectare.

Before the raw material is introduced into diesel vehicles as a fuel, its structure must first be refined by means of a simple chemical reaction (transesterification). Methanol is added to the starting product – plant oil, recycled oils or fats. This mixture is then heated in the presence of a catalyst. In this process glycerine and methanol exchange places and three individual fatty-acid-methyl-ester chains are formed, as is one free glycerine molecule. Next the excess methanol, amongst other chemicals, is removed once again by distillation in a number of cleaning stages. It is only through this process that the bio-diesel develops its optimal flow characteristics and full quality.

Particularly to be highlighted is the fact that the principle of the closed material cycle is upheld during the whole of the production process . At an early stage in the oil mill processing of the oilseed rape the rape meal by-product is available as an important source of protein. Thus one kilogram of high-quality animal feed is acquired per litre of rape methyl ester (RME). In the bio-diesel plant production the valuable glycerine by-product is also generated from the transesterification process in addition to the main product of bio-diesel. This also finds further use, e.g. in the chemicals industry.