Corn, ethanol derived from

A variety of alternative fuels, including LPG, CNG, ethanol, methanol, as well as electricity, have been implemented on a small scale in the USA, but with limited success - the total number of alternative fuelled vehicles remains less than 1 % of the total fleet (Davis and Diegel, 2007). The largest alternative fuel used in the USA is ethanol derived from corn, which is currently blended with gasoline up to 10% by volume in some regions, and accounts for 3% of US transportation energy use. 

Ethanol derived from corn currently dominates the alternatives, with 40% of all gasoline now containing some ethanoL A blend of 10% ethanol and 90% gasohne, called ElO, is the most common blend because it can be used in virtually all vehicles. Blends of 85% ethanol and 15% gasoline, called E85, are also available but can be used only with specially modified engines ( FIGURE 1.20). 

These preliminary calculations indicate that ethanol by fermentation of sugarcane juice is close to equivalence with ethanol derived from petrole mi or natural gas liquids at 1.15/gal. As described above, the competitiveness of sugarcane with the nonrenewable resources depends heavily on the cost of the fermentable sugars. If one had to purchase molasses on the open market, the venture could be in deep trouble during times of high molasses prices, occasioned, perhaps, by a corn crop failure. 

Use of biomass for chemicals and materials is relatively small, apart from building materials (wood products). In the United States, more than 90% of total organic chemical production is based on fossil feedstocks. Biomass accounts for less than 1% of all liquid fuels, essentially all of it ethanol derived from corn. Approximately 7% of the total U.S. corn crop is processed into fuel ethanol, industrial starches, industrial ethanol and other chemicals. Not withstanding the relatively small size of the biomass-derived chemicals and fuels industry, this industry produces a very wide range of products including oils, inks, pigments, dyes, adhesives, lubricants, surfactants, organic acids and many other compounds. 

It is well known that fuel ethanol derived from corn must be subsidized to compete with gasoline. Raw material costs (primarily the eorn) alone are in the neighborhood of 1.00 per gallon of ethanol produced, without any allowance for processing costs. Therefore, it seems unlikely that corn ethanol will ever be able to compete economically with petroleum-derived fuels. Nonetheless, a large... 

Bioethanol is one of the first and the largest markets to profit from cheap biomass feedstock. Ethanol is usually produced from dextrose, which in the USA tends to derive from corn. The first ethanol biorefmery based on waste biomass is already online. It is a Canadian venture operated by Iogen and receiving investment from Shell, Petro Canada, and the Canadian government. With an annual capacity of 700,000 liters it is semi-commercial in scale and not cost-competitive with conventional ethanol refineries. However, the technology is expected to improve quickly. 

The average ethanol concentration derived from whole corn fermentations was 106.8 g/L. The average ethanol concentration from G/F minus corn was 118.7 g/L, an 11% increase. While the whole-corn fermentations finished (residual glucose of <1 g/L), the G/F minus corn fermentations did not finish (residual glucose average of 6 g/L). The best G/F minus corn fermentation reached a peak ethanol production of 123.2 g/L with a residual glucose of 4.9 g/L. It is expected that yeast strains more tolerant to high-density fermentations could achieve ethanol concentrations of approx 125 g/L. 

Currently, most biorefineries are based mainly on a single product line with potentially one or two byproducts. Thus, an ethanol plant produces ethanol from corn starch, with distiller s grain as a byproduct. Greater product flexibility and, consequently, greater opportunities for profitability would derive from a plant producing a variety of alcohols, especially higher alcohols whose market prices range from 0.77 to 1.87/kg. 

There are continuing efforts to develop cost-effective processes for fuel alcohol production, although the economics are often dependent on the availability of subsidized feedstocks to compete with traditional fuels derived from oil. The pretreatment and fermentation of such feedstocks, derived from corn, sugar cane, and even municipal waste, yields a dilute aqueous solution of ethanol which must be separated from a complex mixture of waste materials and then concentrated by distillation to remove water. Both batch and continuous production processes have been developed, with the requirement for effective bioseparations during both the pretreatment and ethanol recovery parts of the process. 

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