Advances in Biofuels

Processing corn byproducts to create hydrogen and butanol fuels benefits the environment, reduces petrochemical dependence, and provides a potential new market for farmers.

What Is Butanol?

Butanol is a four carbon alcohol. It has double the amount of carbon of ethanol, which equates to a 25 percent increase in harvestable energy (Btu's).

Butanol is produced by fermentation, from corn, grass, leaves, agricultural waste and other biomass.

Butanol is safer to handle with a Reid Value of 0.33 psi, which is a measure of a fluid's rate of evaporation when compared to gasoline at 4.5 and ethanol at 2.0 psi.

Butanol is an alcohol that can be but does not have to be blended with fossil fuels.

Butanol when consumed in an internal combustion engine yields no SOX, NOX or carbon monoxide all environmentally harmful byproducts of combustion. CO2 is the combustion byproduct of butanol, and is considered environmentally 'green'.

Butanol is far less corrosive than ethanol and can be shipped and distributed through existing pipelines and filling stations.

Butanol solves the safety problems associated with the infrastructure of the hydrogen supply. Reformed butanol has four more hydrogen atoms than ethanol, resulting in a higher energy output and is used as a fuel cell fuel.

Butanol is an industrial commodity, with a 370 million gallons per year market with a selling price of $3.75 per gallon.

Hydrogen generated during the butanol fermentation process is easily recovered, increasing the energy yield of a bushel of corn by an additional 18 percent over the energy yield of ethanol produced from the same quantity of corn.

Advances in Biofuels
Alternative Energy & New Markets for Farmers
David Ramey

There is abundant biomass present in low value agricultural commodities or processing wastes requiring proper disposal to avoid our pollution problem, for example, the corn refinery industry generates more than 10 million metric tones of corn byproducts that are currently of limited use and pose significant environmental problems. Similarly, there are 60 billion pounds of cheese whey generated annually in the dairy industry much of this byproduct has no economical use at the present time and requires costly disposal because of its high biological oxygen demand. These various forms of biomass are inexpensive feedstocks for hydrogen, chemicals and power grade alcohol fuel (butanol) production.

Production of industrial butanol and acetone via fermentation, using Clostridia acetobutylicum, started in 1916, during World War I. Chime Wizemann, a student of Louis Pasture, isolated the microbe that made acetone. England approached the young microbiologist and asked for the rights to make acetone for cordite. Up until the 1920s acetone was the product sought, but for every pound of acetone fermented, two pounds of butanol were formed. A growing automotive paint industry turned the market around, and by 1927 butanol was primary and acetone became the byproduct.

The production of butanol by fermentation declined from the 1940s through the 1950s, mainly because the price of petrochemicals dropped below that of starch and sugar substrates such as corn and molasses. The labor intensive batch fermentation system's overhead combined with the low yields contributed to the situation. Fermentation-derived acetone and butanol production ceased in the late 1950s.

In the 1970s the primary focus for alternative fuels was on ethanol -- people were familiar with its production and did not realize that dehydration (a very energy-consuming step) was necessary in order to blend it with fossil fuels. Nor did we realize the difficulty of distribution, since ethanol cannot be transferred through the existing pipeline infrastructure. The selection of ethanol, a lower-grade, corrosive, hard-to-purify, dangerously explosive, and very evaporative alcohol is the result. Ethanol is still subsidized by the government, since it is not profitable enough to compete with gasoline. Over the past 30 years, however, the very energy-intensive ethanol process has not solved our fuel, power or clean-air requirements.


Acetone butanol ethanol (ABE) fermentation by Clostridium acetobutylicum is one of the oldest known industrial fermentations. It was ranked second only to ethanol fermentation by yeast in its scale of production, and is one of the largest biotechnological processes ever known. The actual fermentation, however, has been quite complicated and difficult to control. ABE fermentation has declined continuously since the 1950s, and almost all butanol is now produced via petrochemical routes . Butanol is an important industrial solvent and potentially a better fuel extender than ethanol. Current butanol prices as a chemical are at $3.75 per gallon, with a worldwide market of 370 million gallons per year. The market demand is expected to increase dramatically if green butanol can be produced economically from low cost biomass.

In a typical ABE fermentation, butyric, propionic, lactic and acetic acids are first produced by C. acetobutylicum, the culture pH drops and undergoes a metabolic “butterfly” shift, and butanol, acetone, isopropanol and ethanol are formed.

In conventional ABE fermentations, the butanol yield from glucose is low, typically around 15 percent and rarely exceeding 25 percent. The production of butanol was limited by severe product inhibition. Butanol at a concentration of 1 percent can significantly inhibit cell growth and the fermentation process. Consequently, butanol concentration in conventional ABE fermentations is usually lower than 1.3 percent.

In the past 20+ years, there have been numerous engineering attempts to improve butanol production in ABE fermentation, including cell recycling and cell immobilization to increase cell density and reactor productivity and using extractive fermentation to minimize product inhibition. Despite many efforts, the best results ever obtained for ABE fermentations to date are still less than 2 percent in butanol concentration, 4.46 g/L/h productivity, and a yield of less than 25 percent from glucose. Optimizing the ABE fermentation process has long been a goal of the industry.

With that in mind, a new process has been developed using continuous immobilized cultures of Clostridium tyrobutyricum and Clostridium acetobutylicum to produce an optimal butanol productivity of 4.64 g/L/h and yield of 42 percent. In simple terms, one microbe maximizes the production of hydrogen and butyric acid, while the other converts butyric acid to butanol.

Compared to conventional ABE fermentation, this new process eliminates acetic, lactic and propionic acids, acetone, isopropanol and ethanol production. The fermentation only produces hydrogen, butyric acid, butanol and carbon dioxide, and doubles the yield of butanol from a bushel of corn from 1.3 to 2.5 gallons per bushel. That matches ethanol's track record -- and ethanol fermentations do not yield hydrogen. Commercialization of this new technology has the potential to reduce our nation's dependence on foreign oil, protect our fuel generation grid from sudden disruption while developing our agricultural base and reduce global warming.


Butanol is a pure alcohol with an energy content similar to that of gasoline. It does not have to be stored in high pressure vessels like natural gas, and can be but does not have to be blended (10 to 100 percent) with any fossil fuel. Butanol can also be transported through existing pipelines for distribution. Butanol can help solve the hydrogen distribution infrastructure problems faced with fuel cell development. The employment of fuel-cell technology is held up by the safety issues associated with hydrogen distribution, but butanol can be very easily reformed for its hydrogen content and can be distributed through existing gas stations in the purity required for either fuel cells or vehicles.
Growing consumer acceptance and name recognition for butanol, incentives to agriculture and industry, falling production costs, increasing prices and taxes for fossil fuels, and the desire for cleaner-burning sources of energy should drive an increase in butanol production.

Building new, smaller, turnkey biorefineries of 5 to 30 million gallons per year for small municipalities and surrounding farming communities could introduce state of the art technologies at a faster rate than has been adopted in the past. These local biorefineries would address many overwhelming problems associated with the environment, such as regional landfill burdens, and by disseminating fuel generation throughout the Corn and Bio-Belt, any prospective disruption by terrorism is made more difficult, thus improving “Homeland Security.” Cooperatively owned facilities would allow the agricultural sector to employ more people and retain profits within the local economy, bringing the resulting sevenfold multiplication.

The production of butanol (15,500 BTU/lb. or 104,800 BTU/gallon) and hydrogen (61,000 BTU/lb.) from biomass is not constrained by technological difficulties as is the manufacturing of ethanol (12,800 BTU/lb or 84,250 BTU/gal). New higher-value uses for co products of fermentation are an even more likely source of new revenues and could reduce the cost of butanol and hydrogen.

Recent advances in the fields of biotechnology and bioprocessing have resulted in a renewed interest in the fermentation production of chemicals and fuels, including n butanol. With continuous fermentation technology, butanol can be produced at higher yields, concentrations and production rates.

David Ramey can be contacted at
P.O. Box 15, Blacklick, Ohio 43004,
phone (614) 864 5650, fax (614) 864 0120,
Thanks to Acres USA November 2004


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