Ethanol - the Basics

There are many complicated issues facing the public these days, ranging from waste disposal, recycling, air and water emissions, energy generation and consumption, transportation, and many others. These issues have at their core some elements of science, whether it is chemistry, physics, biology, engineering, statistics, or some combination of these. With your help, I would like to explore some of these issues and examine the science in more detail and together we can understand what is going on, what we are being told, whether it makes scientific sense, and perhaps make a slightly better judgement about the issue. I hope to use my contacts and experience in the scientific community to assist you, the readers, in understanding these issues. I welcome your input.Our area (Eastern Ontario) is about to benefit from the construction and operation of an ethanol plant, and I thought it might be appropriate to look at some of the chemistry of ethanol and try to understand what it is, what it does (as a fuel additive) and what are the pros and cons.Most of us are familiar with ethanol in the form of alcoholic beverages: wine, beer and distilled spirits. It is suggested that the manufacture of alcoholic beverages counts as the first chemical industry, dating back thousands of years. The ethanol we drink is diluted, with water, fruit extracts and flavourings, to about 5% in beer, about 12% in wine, and about 40% in distilled spirits.Ethanol, or ethyl alcohol as it is known in chemistry, is a clear colourless flammable liquid, completely miscible (mixes with) water in all proportions. It is the second in a chain of alcohols, because of the two carbon atoms, the first being methanol. The chemical formula is C2H5OH, with the OH group giving the characteristics of an alcohol.The first and still most important way of making ethanol is via fermentation of sugar or starch. Grapes were among the first fruits to be fermented because grapes are naturally sweet, the enzyme that produces ethanol is found on grape skins, and ethanol production is very simple, and takes place at room temperature, especially if your room is in the Mediterranean basin. Many fruits, vegetables and grains have been fermented in pretty much the same way to arrive at ethanol with many flavours, but the basic chemistry remains the same.When you are making beer and wine, you allow the fermentation to proceed to a specific point then you stop it chemically, filter or decant your product, and depending on your patience, let it mellow a little before drinking. Because the enzymes that do the work are killed off when the ethanol concentration is above about 15%, no wine or beer is naturally stronger than this.If you are making spirits (such as rum, rye, vodka etc.) or industrial ethanol, you must distil your mixture. Because ethanol boils at a lower temperature than water, if the fermentation mixture is heated above the boiling point of ethanol (78°C) but below 100°C the ethanol will boil and can be captured by cooling the vapour, giving pure ethanol. So, our plant in Johnstown will be taking corn, the same corn we feed to cattle and other animals, and fermenting it, then distilling it on a large scale.Here is what is happening, shown another way:C6H12O6 à 2 CO2 + 2 C2H5OHglucose carbon dioxide ethanolThis is how we show a reaction in chemistry, and it isn’t really complicated. Glucose is the simplest sugar. What is really interesting is that for every kilogram of ethanol produced, we get, free and for nothing, 0.95 kilograms of carbon dioxide. So far, no-one has said anything about the carbon dioxide by-product of fermentation.Another issue with ethanol is this: Right now all the fermentation technology relies on acting on the fruit or the seed grain portion of the plant material, because that is where the sugar or starch is concentrated. As anyone who has shucked corn knows, there is a pile of the corn plant that is wasted. If we can figure our how to convert that waste material, mostly cellulose, into ethanol, we will have some real progress. Thankfully, an Ottawa company called IOGEN has developed a process to do exactly that, and when it is commercialised (it is currently in the pilot-plant stage) then ethanol may become a significant player in the alternate fuel debate.As we currently stand, the energy balance, that is, the amount of energy you have to put into making ethanol vs. the amount of energy you get out is subject to considerable controversy. We will take a look at this later.Now, ethanol may have significant benefits with respect to automotive emissions, and reducing our reliance on fossil fuels, but as you can see it certainly doesn’t get us off the hook with respect to carbon dioxide, one of the main greenhouse gases.Next week (?) we will take a look at what ethanol does when it is mixed with gasoline and diesel fuel.
Posted by Rod at 6:37 PM 0 comments