Corn has emerged as a significant source for generating fuel, offering a sustainable alternative to conventional fossil fuels. This transformation highlights how common crops can contribute to energy needs.
Ethanol Fuel
Ethanol, also known as ethyl alcohol, is the primary fuel derived from corn. Chemically, it is an organic compound with the formula C2H5OH. This clear, colorless, and flammable liquid boasts a higher octane number than gasoline. As a fuel, it can improve engine performance and reduce emissions, contributing to cleaner air.
Ethanol is categorized as a biofuel because it originates from plant materials, or biomass, making it a renewable energy source. Unlike finite fossil fuels, corn can be cultivated annually, ensuring a continuous supply for ethanol production. This renewability helps lessen reliance on non-renewable resources and offers a more sustainable path for transportation fuels.
Making Ethanol from Corn
The process of converting corn into ethanol typically involves several key steps in what is known as dry milling. First, corn kernels are ground into a fine powder, often called cornmeal. This milling increases the surface area of the cornstarch, preparing it for subsequent chemical reactions.
Next, the cornmeal is mixed with water and an enzyme, alpha-amylase, to form a slurry or mash in a step known as liquefaction. This mixture is then heated, breaking down the complex starch molecules into shorter chains called dextrins. This process reduces the mash’s viscosity, making it more manageable for the following stages.
Following liquefaction, another enzyme, glucoamylase, is added during saccharification. This enzyme further breaks down the dextrins into simple sugars, primarily glucose. These simple sugars are essential, as they serve as the food source for the yeast in the next phase.
The sugar-rich mash then moves into large fermentation tanks, where yeast (Saccharomyces cerevisiae) is introduced. Over a period of 40 to 60 hours, the yeast consumes the glucose in an anaerobic (oxygen-free) environment. This biological process converts the sugars into ethanol and carbon dioxide.
After fermentation, the mixture, now referred to as “beer,” contains about 10-15% ethanol. Distillation then separates the ethanol from this mixture. Since ethanol has a lower boiling point than water, heating causes it to vaporize first, which is then collected and condensed back into a liquid. This process typically yields ethanol with about 95% purity. To achieve fuel-grade ethanol (over 99% purity), the remaining water is removed through a dehydration step, often using molecular sieves.
Applications of Corn Ethanol
Corn ethanol primarily serves as a biofuel, contributing to the transportation sector. It is most commonly blended with gasoline to create various fuel mixtures. The most widespread blend in the United States is E10, which consists of 10% ethanol and 90% gasoline, and is compatible with nearly all vehicles on the road today.
Higher ethanol blends, such as E15 (15% ethanol) and E85 (up to 85% ethanol), are also available. E15 is approved for vehicles manufactured in 2001 or newer. E85 is specifically designed for “flexible-fuel vehicles,” engineered to run on a wide range of ethanol-gasoline mixtures. These blends increase gasoline’s octane rating and reduce harmful emissions.
Beyond its role as a fuel, ethanol has other industrial applications. It is used as a chemical solvent in various products, including perfumes, paints, and tinctures. Ethanol can also serve as a chemical feedstock for synthesizing other organic compounds, such as ethylene, a building block for plastics and other industrial chemicals.
Beyond Ethanol: Other Corn Gases
While ethanol is the predominant gas produced directly from corn kernels, other gaseous byproducts and fuels can be derived from corn or its residues. During ethanol fermentation, carbon dioxide is released as a byproduct. This carbon dioxide can be captured and utilized for various commercial purposes, such as carbonating beverages or producing dry ice.
The non-grain parts of the corn plant, such as corn stover (stalks, leaves, and cobs), can also be used to produce gases. Through anaerobic digestion, these agricultural residues are broken down by microorganisms in the absence of oxygen to generate biogas. Biogas is primarily composed of methane, a combustible gas that can be used for electricity generation or heating. This process utilizes corn biomass more fully, converting agricultural waste into additional energy resources.