One for the road
12.01.2009 - Volkswagen is placing its bets on ethanol fuel from cellulose
There are various approaches to achieving independence from fossil fuels. Biomass fuels are promising and have already been tried-and-tested for some time. At present, ethanol is by far the most widespread biofuel world-wide. Around 63 million cubic metres of this energy-rich alcohol are manufactured around the world. More than half, i.e. 32.3 million m³, come from the USA, a good 24 million m³ from Brazil. The volume produced looks set to more than double within the next twelve years. However, this ethanol is still a first generation biofuel.
As part of its integrated power train and fuel strategy, Volkswagen is placing its bets on second generation biofuels. In addition to the familiar SunDiesel® or BtL, these also include ethanol, albeit not from sugar cane, maize or cereal grain, but manufactured from cellulose. This is why it is called SunEthanol® at Volkswagen. Ethanol manufactured from cellulose can be obtained from straw for example, and is not therefore in competition with food production. In addition, SunEthanol® is very gentle on the climate, because it reveals CO2 savings of up to 88% in comparison with fossil fuels according to a European well-to-wheel study conducted by CONCAWE/EUCAR/JRC.
Up to 340 litres of ethanol from one tonne of straw
However, certain technical efforts are required before this saving effect can be exploited in full. Biotechnology company IOGEN from Ottawa in Canada has developed a method in which a combination of thermal, chemical and biochemical processes converts the biomass to cellulose ethanol. It enables up to 340 litres of bioethanol to be obtained from one tonne of straw. The residual substance lignin, a plant component which is unsuitable for obtaining ethanol, is used as process energy. This saves expensive primary fuels such as coal and natural gas with their additional CO2 emissions.
IOGEN, which is specialised in the production of cellulose ethanol, additionally develops, produces and sells enzymes to optimise natural fibre processing and modification within the textile, feed and paper industries. To manufacture ethanol, the company has modified a vapour explosion process in order to enlarge the surface of plant fibres and therefore facilitate the necessary enzymes' cracking work. The positive result is increased ethanol yield thanks to more efficient pre-treatment and lower overall costs. In addition to a highly-effective and efficient cellulose enzyme system, which specialises specifically in the specially pre-treated raw material, the Canadian specialists also boast highly-productive reactor systems which offer a high level of conversion from cellulose to sugar (glucose). This is achieved via separate hydrolysis and fermentation in a multi-stage process.
Micro organisms are put to work to achieve environmentally-friendly fuel
IOGEN uses modified micro organisms to convert C5 and C6 sugar into ethanol. The raw ethanol is then distilled in the convention manner. This leads to fuel grade SunEthanol®. Thanks to the use of the remaining lignin, the internally developed process also offers energy-efficient thermal integration, enabling the fuel to be manufactured almost without CO2. In addition, the water is reprocessed and by-products are generated, making the entire process efficient. IOGEN successfully operates this process in its cellulose ethanol demonstration plant since 2004.
According to European Union (EU) plans, biofuels are to be increasingly added to fossil petrol and diesel over the next few years, in order to perceptibly lower CO2 emissions. All modern engines are already able to cope with the addition of 5 percent ethanol by volume to petrol (E5) according to the applicable DIN EN 228 fuel standard. In addition, all new Volkswagen vehicles with petrol engines already enable the use of E10. As a result, larger volumes of SunEthanol® can already be used as petrol additives without the necessity of adapting the infrastructure.