Fossil fuels are a significant source of greenhouse gases, and biofuels can be a vital part of the solution. Ethanol Production is a natural and renewable fuel that has the potential to reduce reliance on fossil fuels and contribute to climate change mitigation.
Ethanol is produced from a variety of sources, including sugarcane and corn. New technologies will soon be economically viable for converting other biomass resources, such as agricultural, forestry, and municipal solid wastes, to ethanol.
Feedstock
Almost any plant-based material can be used as an ethanol feedstock. The sugars in these materials are easy to extract and ferment, making ethanol production affordable.
Today’s ethanol is made from starch- and sugar-based feedstocks such as corn, wheat, barley, and rice. These materials are plentiful and easy to grow, meeting the renewable fuel standard (RFS) for biofuels.
However, these materials are limited to 15 billion gallons annually and can only be grown in some places. They also are expensive to cultivate and transport.
To increase ethanol production, researchers are trying to find ways to reduce these costs by using less-expensive feedstocks. They are also looking for ways to produce more ethanol with less energy and waste.
One approach is to mix different types of feedstock in a biorefinery process. Combining the hydrolysates of different feedstocks can reduce the need for adding fossil-derived detoxifying chemicals and mineral nutrient supplements during fermentation. This enables a self-detoxification effect and lowers the cost of processing by reducing the amount of distillation needed to produce ethanol.
Fermentation
Fermentation is a metabolic process in which certain bacteria and yeasts break down sugars into ethanol and carbon dioxide. It is essential in making bread, wine, cheese, soy sauce, and many other foods and beverages.
In alcoholic fermentation, yeasts grow in the presence of glucose (C6H12O6) to produce alcohol and CO2. A batch process can take a long time to produce enough ethanol.
The efficiency of the process depends on the concentration and type of sugars used as a substrate by the microorganisms. The most common organism is Saccharomyces cerevisiae, which converts a wide range of hexose sugars to ethanol via glycolysis.
In addition to producing ethanol, fermentation produces other byproducts, such as acetaldehyde and lactic acid. These byproducts are usually removed after the fermentative process is complete. In addition, ethanol is frequently mixed with the gasoline to make it more usable in vehicles. It is an environmentally friendly fuel that reduces our dependence on oil and fossil fuels.
Distillation
Distillation is when one liquid mixture is vaporized and condensed into another. This is a simple and powerful separation technique that requires little energy.
In distillation, the partial pressure of each component of a liquid mixture equals the product of its vapour pressure and mole fraction. This results from Dalton’s law of partial pressures and Raoult’s law of vapour-liquid equilibrium.
However, it is only possible to partially purify a mixture of components by distillation because the components have different boiling points at the given pressure. This is called the DeRosier problem.
Distillation can be done under reduced pressure, often using a vacuum pump. This can be useful when dealing with substances that generally boil at inconveniently high temperatures or that may decompose when boiling under normal atmospheric pressure.
Blending
Ethanol is a type of alcohol derived from corn, sugarcane or grain. It is a common fuel additive blended with gasoline to oxygenate it at the gas pump.
The ethanol industry seeks to increase the amount of ethanol mixed with the gasoline to meet the Renewable Fuel Standard (RFS). Blending increases the percentage of ethanol in the fuel supply, allowing more ethanol to be sold at the pump.
However, blending can also result in lower vehicle fuel economy. This is because ethanol contains 67% of the energy content of gasoline per gallon. Increasing ethanol production can be done through several methods, including grinding up grains, refining the ground-up material to obtain sugar, and fermentation. The ethanol can then be distilled and purified.