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
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. Visit
the following links for information on flex fuel vehicles
built to use gasoline/ethanol blends and filling stations
near you: National Ethanol Vehicle Coalition http://www.e85fuel.com/;
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
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.
+ Water +Sunlight -> Sugar + Oxygen
6CO2 + 6H2 O +Sunlight ? C6H12O6 + 6O2
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.
+ Carbon Dioxide
C6H12O6(aq) 2 C2H5OH(aq) + 2 CO2(g)
The ethanol combustion reaction producing energy to turn
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
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
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
The first article of the series [link] 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
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
- 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
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, where a suitable yeast strain digests the
six or twelve carbon sugars and produces the two carbon
- 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
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.
To give an idea of the variety of applicable crops and their
theoretic yields, the following web sites will be useful:
If you know the amount of carbohydrates within a particular
crop, you can calculate theoretical ethanol yields by visiting:
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
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.
†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
John Orr is director of the Biodeisel Production Project
of Long Trail Biofuels, LLC, and Green Technologies, LLC,
in Burlington, Vermont.