Biofuels
The Product
Biofuel is produced by the fermentation of carbohydrates found in grains and other biomass. Biofuel can be produced from a number of different types of grains as well as from other agricultural by products such as corn stovers, rice hulls, cheese whey, potato waste, brewery and beverage wastes and forestry by products. At present, the majority of biofuel in the United States is produced from corn because corn contains large quantities of carbohydrates and can be handled efficiently. Such carbohydrates convert into glucose more easily than most other kinds of biomass. The corn used for biofuel production is known as No. 2 yellow field corn which is indigestible to humans and goes primarily to the livestock feed industry. Outside the United States, sugarcane is the primary feedstock used in biofuel production. Bio-refineries also produce valuable co-products for the feed and biodiesel industries, including high protein distiller’s grains, corn oil, and syrup. CO2 is also captured in bio-refineries and is used primarily in the beverages industry.
The Industry
Ethanol is a $86 billion industry in the US that currently manufactures over 15 billion gallons of ethanol annually in around 200 plants across the country making it the largest fuel transportation supplier in the US with 20% of the market. The industry now ranks ahead of countries such as Saudi Arabia, Iraq, Venezuela and Algeria in supplying transportation fuel across America and is delivering on the targets set out by the Bush administration in 2007 on ensuring America reduces its over reliance on foreign oil.
The Process
Corn is received at the plants by truck or rail, which is then weighed and unloaded in a receiving building. Storage bins are utilized to store grain, which is passed through a scalper to remove rocks and debris prior to processing. Thereafter, the corn is transported to a hammer mill where it is ground into coarse flour and conveyed into a slurry tank for enzymatic processing. Water, heat and enzymes are added to convert the complex starch molecule into simpler carbohydrates. The slurry is heated to reduce the potential of microbial contamination and pumped to a liquefaction tank where additional enzymes are added. Next, the grain slurry is pumped into fermenters, where yeast, enzymes, and nutrients are added, to begin a batch fermentation process. A beer column, within the distillation system, separates the alcohol from the spent grain mash. Alcohol is then transported through a rectifier column, a side stripper and a molecular sieve system where it is dehydrated to 200 proof alcohol. The 200 proof alcohol is then pumped to a holding tank and blended with approximately two percent denaturant (usually natural gasoline) as it is pumped into finished product storage tanks. The mash is taken through a centrifuge following the distillation process where it is converted into syrup, corn oil, and a high protein feed distiller’s grains.
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