How is Ethanol Made?

How is ethanol made? It takes some mechanical aptitude, but you can make fuel by fermenting appropriate feed stocks into 96 proof alcohol.

What if there were a fuel that was affordable, renewable, and produced right in your own community? If you’d lived 100 years ago, you would have known all about such a fuel. It was called alcohol, and it was a clean-burning fluid generally sold as lamp fuel. Only recently have we taken a renewed look at alcohol fuel — now more commonly known as ethanol — and its potential as a domestically sourced fuel for transportation.

I’m not here to tell you about the agri-industrial agenda to produce ethanol on a massive scale. What I am going to tell you is how to make your own fuel to use in your vehicle or in other gas engines, such as a motorcycle, tiller, or lawn tractor. You can modify these gas engines to run on straight alcohol (more on engine modifications in "Run Your Car on Ethanol," below).

If it's produced on a small-scale, ethanol can be made from grain you grow yourself — or from a wide range of other local and sustainable feedstocks including food waste and crop culls. With a little specialized equipment and know-how, you can turn these materials into alcohol fuel, and it will cost less than you would pay at the pump for gasoline or commercially produced ethanol.

You can produce your own ethanol for an ongoing cost of less than $2 per gallon. If you grow your own corn, you can distill more than 300 gallons of ethanol from 1 acre of corn. If you drive less than 10,000 miles per year, you could produce all your own fuel from 2 acres of corn — and, granted, a lot of labor. In short, when I talk about ethanol, I’m talking about do-it-yourself fuel, and practicing local self-reliance on an individual and community scale.

One of the strongest arguments for ethanol fuel is that we can make it ourselves, with no dependence on foreign resources. In 1925, Henry Ford told a New York Times reporter that "There's enough alcohol in one year's yield of an acre of potatoes to drive the machinery necessary to cultivate the fields for a hundred years." This self-made businessman recognized the value of the American farm, and more specifically, the importance of domestically sourced materials. He envisioned farms across the country providing the crops needed to make both fuel and food.

Another reason ethanol is such an attractive fuel option is that it's basically liquid energy. Ethanol is a clear liquid that packs a lot of energy into a usable, storable, and transportable form — only petroleum can compete with ethanol on an energy-per-volume basis. But ethanol has an added benefit in that it's oxygenated, meaning it has oxygen in its molecular structure, which results in a cleaner burn. Compared to gasoline, ethanol emits about 20 percent fewer hydrocarbons and carbon monoxide.

Would-be fuel producers must apply for a permit to make their own fuel, but after the energy crisis of the 1970s, the federal government substantially streamlined the permit process. Recognizing the difference between beverage and fuel spirits, the Department of the Treasury came up with a simplified application for an Alcohol Fuel Producer permit (Form 5110.74), which designates a small producer as one who can make up to 10,000 proof-gallons of fuel per year. (A proof gallon is one liquid gallon of spirits that is 50 percent alcohol at 60 degrees Fahrenheit.) That's enough to manufacture 5,263 gallons of 190-proof ethanol fuel. Each state has its own permit requirements, generally modeled after the federal rules. You’ll need to research taxes and any applicable state and local regulations. In any case, the fuel alcohol must be "denatured," or rendered unfit to drink, by the addition of at least 2 percent by volume kerosene or unleaded gasoline.

Ethanol production is a natural process that comes about through the fermentation of carbohydrates — organic compounds containing carbon, hydrogen, and oxygen. Plants and crops produce carbohydrates in the form of starches, sugars, and cellulose. The bonds in the molecular structure of celluloses are difficult to break, but most plant starches and sugars are easily broken down into simple sugars with the addition of heat, water, and enzymes. Once the simple sugars are established, yeast is added to feast upon the sugar, reproduce and, in the process, expel carbon dioxide and alcohol.

The choice of raw material is an important factor. Crops with a high sugar or starch content are ideal, but nearly any crop cull or surplus can work (if used before spoilage sets in), so you can choose the most economical and sustainable materials available to you. Apples and other small fruits, potatoes, beans, wheat, rye, and sorghum grains are all potential candidates — as is cheese whey, the milk sugar left over from processing. Food-processing wastes from the beverage, baking, snack, and confectionary industries are notoriously high in sugar (or starch) content and can provide an alternative to direct-from-field sourced feedstocks.

After fermentation is complete, the ethanol must be distilled from the water. This is best accomplished with a reflux still, which is equipped with a distillation column. The column uses a series of perforated plates or packed compartments to remove the water in a process called fractionation. As the heated water and alcohol vapors rise through each stage, a progressively stronger alcohol vapor is created. During distillation, column temperature must be controlled to take advantage of the different boiling points of the two fluids. The alcohol vapors rise, while the water condenses and drops back to be reintroduced as a vapor mix again and again.

The most potent alcohol vapors exit at the top of the column to be cooled by a water condenser and collected as 192-proof (96 percent pure) ethanol. Though it's possible to wring that last 4 percent out of the mix, it requires additional equipment and is usually cost-prohibitive for a small-scale operator. Besides, the small amount of water present does not hinder engine performance.

Car engines have to be modified to run on straight ethanol. The simplest engine modifications include advancing the ignition timing by several degrees, rejetting the carburetor's main fuel circuit to increase jet diameter by 30 to 35 percent in area, and adjusting or enlarging the idle circuit to allow more fuel flow. Fuel-injected engines can have their injectors replaced for greater flow, or the fuel pressure increased.

There are also aftermarket kits designed to trick the engine's microprocessor control unit into holding the fuel pulse open longer or compensating for an artificially lean condition by enriching the air-fuel mixture. Engines can be further optimized for ethanol by preheating the fuel and air, varying the heat range of the spark plugs and boosting the compression ratio.

So what does it take to set up a small-scale distillery? That depends on how small an operation you want. A simple batch still can be made from an old water heater and a length of 3-inch conduit and heated by wood or natural gas. A still this size will make about 1-1/2 gallons of fuel-grade ethanol per hour. For an investment of less than $100, you could be running a lawn tractor or small motorcycle on completely renewable, homemade fuel.

On a more practical scale, building a 6-inch column still will put you in the 6-gallons-per-hour production ballpark — a substantial yield, but one that comes with additional cost. At that size, you’d be best served with a hammermill or grinder to prep the feedstock, separate cooking and fermentation tanks, a storage vessel for stillage or spent beer with residuals (along with a press to separate the marketable distiller's grains), and storage for the ethanol itself. Centrifugal pumps, plumbing, and valves are also a necessary part of the plan, along with a hydrometer, several thermometers, and pH and sugar testing tools. A 6-inch column coupled to a 500 to 1,200-gallon tank will run a batch in four to seven hours.

If you use mild steel, you’ll be able to weld the components and build your column without needing any special skills or equipment — though the metal will eventually oxidize over time. Stainless steel is a better choice, but will probably be limited to vats and storage tanks unless you’ve got a sizable budget to pay for professional fabrication. Used distillation columns are sometimes available through farm and industrial auction dealers.

The cost to produce ethanol will depend on how much effort you put into the process. Even using culled feedstocks will not guarantee an economical product if you waste energy during production. The source, duration, and degree of heat input are significant factors that can be economized with the use of efficient enzymes and heat-recovery designs. Using alcohol-tolerant yeasts with nutrients improves conversion efficiencies as well, and making the most of useful byproducts (such as high-protein distillers grains) adds to the bottom line.

If you’re in a rural setting and choose to dedicate an acre or more of cropland to ethanol production, you’ll have to determine which locally suitable crop will strike the best balance between hardiness, water tolerance, harvesting effort and alcohol (sugar and starch) yield. The fermentable percentage of common grains and root crops varies drastically between 16 and nearly 80 percent. Probably more important is the alcohol yield per acre, which can range from about 300 gallons for field corn to 400 gallons for sugar beets, to nearly 600 gallons for sugar cane, sorghum, and Jerusalem artichokes. Other crops may have lower yields, but offer advantages in conversion, storage, or processing. The table below is a breakdown of representative costs and recovery for a small operation, which will vary depending upon your particular situation.

And keep this in mind: Whether you can make ethanol on a small scale for less than the cost of gasoline today is not the only question. You also have the knowledge that you’re using a clean-burning, sustainably produced fuel, and that no matter how high gas prices rise in the future, you’ll be able to make your own at a reasonable price.

Originally published as "Make Your Own Gas! Alcohol Fuel Basics" in the April/May 2010 issue of MOTHER EARTH NEWS.

Richard Freudenberger managed the research facilities of MOTHER EARTH NEWS from 1980 to 1990 and coordinated our Alcohol Fuel program during that time. He lives in Hendersonville, N.C., and is the publisher and technical editor of BackHome Magazine. He's also the author of Alcohol Fuel: Making and Using Ethanol as a Renewable Fuel.