Turning crops to ethanol fuel: on the road to energy independence


By John Orr
Originally posted on August 17, 2004

Here is a chance to gain a cursory knowledge of one of the most widely used renewable fuels, ethanol. The intention of this article is to whet the appetite of those ready to claim petroleum independence and not wait for the crew in D.C. or giant farming corporations to lead the way.

Those of you who are mechanically inclined can take a leading role in creating a local fuel economy for your community, based on clean and sustainable biofuels, and have a blast doing it. An inexpensive alcohol distillery can turn a bad crop into a supplement to your farm’s income, or save money by creating tractor fuel from the sawdust of a nearby sawmill.

A small scale, on-farm ethanol production facility could benefit the farm economy through direct sales and by saving fuel expenses, and it could offer indirect benefits from the process byproducts. Perhaps most importantly, a cohesive effort to stimulate a local fuel economy through the initiative of creating a small-scale fuel production facility would create meaningful jobs while fueling the ability to farm sustainably.

The idea of ethanol for fuel is nothing new. When the internal-combustion engine was designed by Nikolaus Otto in 1872, 180 to 190 proof ethanol was the specified fuel. Until now, gasoline has been so cheap and easy to produce that alcohol (although a good fuel source) was put on the back burner. In the current energy situation of dwindling supplies of petroleum and environmental concerns surrounding polluting emissions, the need for alternative, clean and renewable energy sources is as important as fuel conservation. All of the emerging technologies—including wind, solar, geothermal, biofuels, fuel cells and fusion—have a niche to fill in the composite of our energy needs. Individuals need to make informed decisions as to which fuel source best fits their environment.

Alcohol fuels, particularly ethanol, are an indispensable part of the solution to our energy problems. Whether as a supplement to petroleum, an ingredient of biodiesel, or used alone, it is proving to be a necessary and profitable commodity. Although not the only answer, ethanol is emerging as a leading solution because of the ease at which it can be incorporated to the current fuel infrastructure. Chances are many of you reading this are driving a gasoline vehicle already fitted to run on a blend of 85-percent ethanol, known as E85.

Ethanol 101

2.7L Chrysler Sebring Convertible. This car is designed to run on 85 percent ethanol. Photo courtesy of Chrysler.

Ethanol, like gasoline, is a hydrocarbon. It is made of mostly carbon and hydrogen. The two fuels have many similar qualities, even though gasoline consists of a string of 8 to 10 carbons, while ethanol has only two carbons in its molecular structure. In figuring the energy return on fuel, it is important to consider the embodied energy of the molecule. When combusting hydrocarbons in an engine, the energy emitted is from the breaking of the carbon and hydrogen bonds ignited in the presence of oxygen from the air. Ethanol has 33 percent less embodied energy than gasoline. According to the U.S. Department of Energy (DOE), a gallon of ethanol contains 76,000 Btus (British thermal units) of energy, and a gallon of gasoline contains around 110,000 Btus of energy. So ethanol delivers fewer miles per gallon. However, because of its higher octane rating, it burns more efficiently in an engine. So none of the engine performance is diminished, but you’ll have to refill the gas tank more often. In order to properly combust with the amount of air used by conventional engines, more ethanol must be injected by the carburetors than petroleum. However, if ethanol is blended with petroleum, it increases the octane level of the fuel and creates a more complete combustion while reducing emissions.

Ideally, during combustion, the only gas formed would be nontoxic carbon dioxide, which we produce when we exhale and plants use to make sugars. Unfortunately, poisonous carbon monoxide is also formed during combustion. When burning ethanol, the amount of carbon monoxide produced is normally greatly lower than the amount produced from gasoline combustion. The sulfur dioxide and other particulate emissions coupled with gasoline are not found in ethanol, making the alcohol fuel a much cleaner burning alternative. When burning gasoline we release carbon dioxide that has been stored in the earth for millions of years. Carbon dioxide retains heat and acts like insulation for the earth’s atmosphere. The addition of large amounts of ancient carbon dioxide is increasing the amount of thermal insulation in the atmosphere, the primary reason for global warming.

Ethanol can be derived from annually grown crops; therefore, during combustion, it releases amounts of carbon dioxide that can be recycled by the next year’s crop. The crops naturally ingest sunlight, water and carbon dioxide to form sugars—like glucose— during the phenomena known as photosynthesis. The plant uses the sugars to create cellulose for structure or stores the solar energy as starches.

Carbon Dioxide + Water +Sunlight -> Sugar + Oxygen
6CO2 + 6H2 O +Sunlight ? C6H12O6 + 6O2
The chemical equation for photosynthesis.

After harvesting the plant material containing the sugars, we begin to reverse the process. When we eat plant starch, we naturally balance photosynthesis by converting the sugars into energy, water and carbon dioxide, and CO2 (which we exhale). When we convert the sugars into alcohol by fermentation, we release carbon dioxide and produce a flammable fuel that can be burned in an engine. During combustion, the fuel alcohol releases the embodied solar energy of photosynthesis and emits water and carbon dioxide.

Glucose Ethanol + Carbon Dioxide
C6H12O6(aq) 2 C2H5OH(aq) + 2 CO2(g)

The ethanol combustion reaction producing energy to turn wheels:

Ethanol + Oxygen ? Energy +Water + Carbon Dioxide
C2H5OH + 3O2 ? Energy + 3 H2O + 2 CO2

The system is a closed loop that successfully turn sunlight trapped in biomass to energy that drives our technology.

Making the Switch

There are two ways to use ethanol in your fuel tank. One way is to blend it with gasoline; another is to use ethanol fuel exclusively.

For vehicles not manufactured to burn E85, depending on the engine, blends of 10-, 20- or 25-percent ethanol in gasoline can be run with no modification. Generally, four-cylinder engines accept higher ratio blends than six or eight-cylinder vehicles. With slight modification of the carburetor, and maybe other minor changes like advancing the timing, some engines may run on blends of up to 40 percent ethanol. The high octane of ethanol increases engine performance. By using the alcohol as an additive, you also reduce the risk of knocking in your engine. The most important thing to know about blending ethanol with gasoline is that the ethanol has to be “dry”. When distilling ethanol, the highest purity possible with an efficient still is 95 percent. This is not good enough to mix with gasoline, therefore ethanol has to be 100 percent (200 proof ) to successfully blend. To achieve this purity, the alcohol has to go through a process that adds to the energy input and overall expense of the process and most often calls for some environmentally contaminating drying agents.

The other method of using 80 to 95 percent pure ethanol in a modified engine has its advantages. By rendering the drying process unnecessary, the cost of the ethanol is cheaper, and none of the performance is compromised. Once the engine is modified, however, gasoline can not be used; only ethanol. The major conversion needed to run on ethanol would be enlarging the carburetor jets. This is a relatively inexpensive job that should take a good mechanic only a couple of hours.

The alcohol can also be used to turn vegetable oil into diesel fuel. Biodiesel, the topic of the third part of the biofuels series, is a clean-burning and renewable alternative to petroleum diesel. In order to convert vegetable oil into biodiesel and alcohol (usually methanol or ethanol), it is mixed at a ratio of up to 4 parts veggie oil to 1 part alcohol. Methanol and ethanol are most commonly derived from cracking petroleum into smaller hydrocarbons. Producing ethanol for biodiesel production would overcome the need for petroleum alcohol and reduce costs.

Ethanol is corrosive and evaporates easily, making it hard to transport and not ideal for use in hot, arid climates. If it is treated like gasoline and stored in a corrosive-proof, underground, or shaded tank, there shouldn’t be any problems. Producing and using the fuel locally would reduce transportation complications.

The first article of the series outlines many of the concerns surrounding the ethanol production industry in this country. The most poignant argument for small-scale production is that the energy needed to grow, harvest, and process crops into ethanol may return little or no increase in the amount of energy the ethanol delivers. Ethanol can offer worthwhile returns if the inputs are kept minimal. Petroleum-created pesticides, herbicides and fertilizers constitute an expensive amount of energy. Using sustainable methods of organic farming would be the smartest means of producing fuel, because you negate the need for petroleum products to grow alternative fuel. Designing a process to be energy efficient is probably the most important strategy to reduce energy costs. Over the past 30 years, the ethanol industry has creatively found ways to most efficiently brew and distill plant matter into alcohol. With a little research of the available products, one could easily find or make an energy smart processor.

Moonshine with a Twist

The REVENOOR 25 Gallon Electric Continuous System 32 Gal. per day capacity is an example of a home model ethanol production facility. Photo courtesy of The Revenoor Company.

Ethanol fuel is the same thing as moonshine or grain alcohol. It is made by fermenting the simple six and 12 carbon sugars of carbohydrates. There are three basic feed stocks that can be used to gather carbohydrates and process into ethanol:

• Saccharide (sugar containing) materials harvested from sugar cane, sugar beets, fruits, citrus molasses, cane sorghum, whey and skim milk. These can be directly fermented into ethanol

• Starchy materials which contain more complex carbohydrates, including starch and insulin, require several steps before fermentation. The sources include corn, potatoes, barley, wheat, Jerusalem artichokes, cacti, and manioc. These materials can be broken down to simple six- and 12-carbon sugars by malting, a process utilizing acids or enzymes

• Cellulose material including wood, wood waste, paper, straw, corn stalks, corn cobs, cotton, and other bulky materials are inexpensive and easily accessible feed stocks for ethanol. The cellulose can be hydrolyzed by acid or enzymes, converted to glucose and then fermented with yeast to produce alcohol

As pointed out by Robin L. Graham, Wei Liu and Burton C. English in their paper The Environmental Benefits of Cellulosic Energy Crops at a Landscape Scale: Cellulose and carbohydrates both can be converted to ethanol, but more cellulose can be produced per unit land area than carbohydrates. Therefore, cellulose-based ethanol production is a more efficient use of land.

Saccharide is the easiest to process into ethanol, from a small-scale perspective, but the most expensive feedstock. Starchy materials offer the highest yield of ethanol for the weight of feedstock used, while cellulose is the cheapest feed stock. To convert saccharide materials into ethanol, the basic process includes:

• Extracting or crushing the sugars, allowing the yeast to access the sugars for fermentation

• Dilution, which is only necessary with certain materials. Dilution with water is needed so that the yeast will not be killed by too high of an alcohol content before complete fermentation

• Fermentation, where a suitable yeast strain digests the six or twelve carbon sugars and produces the two carbon alcohol, and

• Distillation, where the alcohol, which has a lower boiling point than the water, is boiled off of the alcohol/water mixture and collected.

In order to process starchy materials, milling is required to separate the carbohydrates from the rest of the crop. The starches are then diluted and cooked until dissolve. The dissolved carbohydrates need to be converted into simple sugars by hydrolyzing with acid or enzymes before fermentation and distillation. Cellulose materials have to go through a similar process to become starchy materials†.

Each crop has a different composition of carbohydrates and therefore some materials require more or less processing. Each step of the process can be modified to suit the required material.

Ethanol Demystified

Bagasse collected and ready to be processed into tractor fuel. Photo courtesy of the National Renewable Energy Laboratory.

The first consideration for someone toying with the idea of homemade fuel is determining which plant material is the cheapest and easiest for you to manifest. Will it give you the highest yield of ethanol for as little effort or expense as possible? The sources should have a consistent long-term supply to base your plant designs around. The energy cost of gathering, processing and transporting the materials needs to be overestimated and equated to make sure the invested energy of the ethanol yield is worth the trouble. If not thought out properly, making ethanol could be an expensive hobby.

If you know the amount of carbohydrates within a particular crop, you can calculate theoretical ethanol yields by visiting: http://www.eere.energy.gov/biomass/ethanol_yield_calculator.html.

Once you have harvested or bought your biomass, the science of bathtub gin begins. The art of fermenting and distilling alcohol is an accessible goal for a motivated team. Because of the age old relationship of man and alcohol, many the supplies needed to produce ethanol (from the brewers yeast strain Saccharimyces cerevasiae to efficient distilling units) are standardized and highly commercialized to suit any nuisances to your designs.

Designing Your Processor

There are a number of design criteria for each component of the ethanol processing system. Researching several guides will allow you to create the still that best suits your needs. The major factor in designing is the feedstock that is most efficient for you to convert. The link to the DOE’s Make Your Own Ethanol reading list offers approaches for several different plant materials. The size of the processor should be decided based on the amount of money you can invest to build the initial processor, the demand within the area, and the availability of the resources.

The cost of an ethanol facility depends on the size of the plant. I have seen quotes from $3,000 to $80,000 for small-scale processors. A good portion of the cost can be reduced by using pre-owned equipment. Different design techniques will have specific material requirement to withstand pressure, heat, acidity, and corrosion.

Ethanol is extremely flammable, and safety precautions should be taken to avoid accidents. Depending on the design chosen, many of the acids or bases used may be toxic and harmful. When these are used, safety glasses, gloves and other protection should be worn, and the processing equipment needs to have the proper specifications.

When working with living organism to metabolically transform your harvest into fuel, you’re creating a perfect environment to induce bacterial invasions; conversely, you could easily throw off the chemical balance and make it impossible for any micro-employee to manage. Subtle changes in sugar content, temperature, pH, or bad timing could mean a bunk batch. And whether a facility decides to use malt and yeast for enzymatic conversion or acidic conversions, the processor needs to be kept clean. Proper operation planning and protocol are essential to maintaining a profitable system.

Public awareness for the dire need for alternative energy has created the potential for community support to propel a motivated few into a network with the momentum to support their community’s fuel needs. Agricultural organizations as well as local colleges and universities are loaded with students, staff and professors willing to lend technical support. Local politicians’ offices like your governor, mayor, and county representatives as well as economic development associations are a great place to find help investigating specific federal and local regulations, tax requirements and other interested parties. Small business associations and bankers can help you create a persuasive business plan to entice investors. State and federal grants from the U.S. Department of Agriculture (USDA), DOE funds, and other sources offer another funding option. And all of the groups listed above can also be potential costumers, running their local vehicles on your fuel.

Projects that can turn a profit and bring healthy agricultural practices to the cutting edge of commercialized technology are the basis of the emerging and exciting field of renewable energy. The idea of creating our own fuel may seem like a daunting and nearly impossible goal for the generations addicted to cheap foreign oil. But the knowledge and connection that comes from closing the loops between the means of supporting our lifestyles and the natural resources to which life on this planet is dependent is worth the challenge. Even Democratic presidential candidate John Kerry has decided to put renewable fuels on the campaign agenda for 2004 by promising $30 billion for new, clean energy technology development and declaring: “We have to control our energy future.”

The logic and inevitability of the renewable energy industry is a sign of the times. Taking an active role in the advancement of local responsible technology development will likely be as profitable as it is rewarding.

References:
The Manual for Home and Farm Production of Alcohol Fuel, by S.W. Mathewson (1980, Ten Speed Press).

Fuel from Farms—A guide to Small-Scale Ethanol Production, (1982, U.S. Department of Energy Solar Energy Research Institute).

John Orr is director of the Biodeisel Production Project of Long Trail Biofuels, LLC, and Green Technologies, LLC, in Burlington, Vermont.

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