Bioethanol Production
It seems that Biodiesel has been getting all the press recently leaving Bioethanol largely unexplained and feeling somewhat left out. The Biodiesel hype is making it look like the blooming gorgeous flowers of the go-green garden, but it would be wise to also take note of the other Earth-savers of this bunch, like Bioethanol for example. After a question that was posted on our forum, I have decided to dedicate a page to explaining the production and use of Bioethanol
What is Bioethanol
The principle fuel used as a petroleum substitute is bioethanol. Bioethanol is mainly produced by the sugar fermentation process, although it can also be produced by the chemical process of reacting ethylene with steam. The main source of sugar required to produce ethanol comes from fuel or energy crops. These fuel crops are normally grown specifically for energy use and include maize, corn and wheat crops, waste straw, willow, sawdust, reed canary grass, cord grasses, jerusalem artichoke, myscanthus and sorghum plants. There is also ongoing research and development into the use of municipal solid wastes to produce ethanol fuel.
Brazil and the United States account for over 70 percent of all ethanol production in the world today with the USA producing an estimated 6,500 Million gallons a year
How Bioethanol is made
The basic steps for large scale production of ethanol are: fermentation of sugars, distillation, dehydration and denaturing (optional). Prior to fermentation, some crops require saccharification or hydrolysis of carbohydrates such as cellulose and starch into sugars. Saccharification of cellulose is called cellulolysis (see cellulosic ethanol). Enzymes are used to convert starch into sugar.
Fermentation
Ethanol is produced by microbial fermentation of the sugar. Microbial fermentation will currently only work directly with sugars. Two major components of plants, starch and cellulose, are both made up of sugars, and can in principle be converted to sugars for fermentation. Currently, only the sugar (e.g. sugar cane) and starch (e.g. corn) portions can be economically converted. However, there is much activity in the area of cellulosic ethanol, where the cellulose part of a plant is broken down to sugars and subsequently converted to ethanol.
Distillation
For the ethanol to be usable as a fuel, water must be removed. Most of the water is removed by distillation. The purity is limited to 95-96% due to the formation of a low-boiling water-ethanol azeotrope. This may be used as fuel alone but unlike anhydrous ethanol it is immiscible in Petrol meaning it can not be mixed i.e. E85. The water fraction is typically removed in further treatment in order to burn with in combination with petrol in petrol engines.
Dehydration
Currently, the most widely used purification method is a physical absorption process using a molecular sieve, for example, ZEOCHEM Z3-03 (a special 3A molecular sieve for EtOH dehydration). Another method, azeotropic distillation, is achieved by adding the hydrocarbon benzene which also denatures the ethanol (to render it undrinkable for duty purposes). A third method involves use of calcium oxide as a desiccant.
Can I produce Bioethanol at home?
There are many people producing Bioethanol at home for their own use. Many people opt for a home made "still" for the production process however obtaining a consistant proof can be very hard for most inexperienced producers
The market Biothanol Processors is not like the highly competitive Biodiesel market, I believe that this is due to the fact that many of todays cars are still not capable of running a Bioethanol Mix i.e. E85 for day to day use.
