Bioethanol refers to ethanol produced from biomass. It can be produced by the alcoholic fermentation of various plants and plant parts (usually the fermentation of natural products, followed by repeated distillation) – from sugar crops such as sugar beet and sugarcane, starchy crops such as grain, potatoes and corn, or cellulosic crops such as wood. In Germany, feed grain and sugar beets are mainly used as raw materials. In chemical terms, bioethanol and synthetically produced ethanol from fossil fuels are identical.
During the production process, sugar and other carbohydrates are converted to alcohol by microorganisms using alcoholic fermentation and other metabolic products. This process continues until the metabolizable biomass is consumed or the maximum alcohol concentration is reached and the microorganisms cease their work.
The alcohol is then concentrated in several distillation steps. In the first step, an ethanol-water mixture and leftovers from the alcohol production (stillage) are separated. Next, the water is removed. To ensure that ethanol remains permanently blended with gasoline, it must be 99.5% to 99.9% pure, which is achieved by repeated distillation. Because ethanol evaporates more easily than water, this is a good way to separate the mixture.
Aside from carbohydrates, cellulose is another potential raw material for the production of bioethanol. Cellulose is the main component of plant cell walls and thus a very frequently occurring organic compound on Earth. The lignocellulose in woody plants in particular is a possible source of energy due to the vast quantities available. However, to be able to produce bioethanol from it, it must be biochemically split into its constituent sugars.
The most common use of bioethanol in Germany and worldwide is as a biofuel to be blended with gasoline (E5 and E10 – with the number indicating the percentage of ethanol by volume). DIN EN 228 allows for adding up to 10 vol.% of ethanol (E10) to gasoline in Germany. The added bioethanol must meet the quality requirements of DIN EN 15376. In Germany, around 90% of existing vehicles with gasoline engines can run on E10, and all new cars can use it.
Until 2015, E85, too was available via an extensive network in Europe and other countries, e.g. Germany, France, Sweden and the U.S. Until December 31, 2015, the bioethanol content in gasoline was exempt from oil tax in Germany. Since January 01, 2016 however, the ethanol component is fully taxed, meaning the fuel has lost its economic advantage and will disappear from filling stations in Germany. However, only vehicles in which all the materials in the fuel circuit (tank, fuel pump, fuel lines, injectors) are ethanol-compatible can fuel with E85. Bioethanol is not available as a pure fuel (E100) in Germany, because it cannot ensure reliable cold starting at low temperatures.
Bioethanol is also used beyond the above-mentioned areas of application for the production of the gasoline additive ethyl tertiary butyl ether (ETBE). ETBE is synthesized from bioethanol and isobutylene. Because of its high octane number and its low vapor pressure, this additive enables a reduction of gasoline components, whose production is energy intensive. According to the EU Fuel Quality Directive, ETBE can be blended up to a limit of 22 vol.%
Status: December 2016
All information subject to change. Errors and omissions excepted.