In the current quest for economically feasible alternative fuels, ethanol derived from corn has captured much of the world's attention. However, some biodiesel fuel developers are looking towards a different, and some claim far more economical, source of ethanol-producing plant material. Both sugar cane and switch grass can be used during the fermentation process as ethanol sugar, which converts to pure alcohol when combined with yeast and water. Inedible forms of sugar could be purchased inexpensively, converted into pure ethanol and then mixed with gasoline.
Ethanol sugar is not a new concept in many countries where the climate can support the production of sugar cane. In the same way the United States government subsidizes the production of corn for ethanol production, the Brazilian government subsidizes sugar cane production for use as ethanol sugar. Although sugar is generally less expensive to produce than corn, the United States does not have an ideal climate for sugar cane production. Only a few states such as Florida and Louisiana have a suitable climate for domestic sugar production.
The difficulty with producing a viable alternative fuel from ethanol sugar or any other organic material lies with the nature of fermentation. In order for ethanol to mix with gasoline to form a flex fuel blend, it must be considered 100%anhydrous, or water-free. The standard fermentation and distillation process can only create an ethanol product which is 95% water-free at best. This would be the equivalent of a 190 proof pure grain alcohol.
In order to remove the final 5% water content, the ethanol must be passed through a number of membranes and filters. This process can be time-consuming and expensive, which in turn raises the final cost of the ethanol fuel. Some researchers, however, have developed special ethanol production tanks which first create the 95% dry ethanol base, then run the solution through membranes which remove the rest of the water. The result is a storage tank containing pure ethanol, which can then be combined with standard gasoline or used to power farm equipment designed to run on pure ethanol.
At this writing, it is difficult to tell if ethanol sugar produced from inedible sugar from Mexico or Brazil will successfully compete with corn ethanol. Another alternative source may be a perennial cover crop known as switch grass. Much like sugar cane, switch grass grows rapidly and can be harvested for many years before replanting becomes necessary. The concept for converting sugar cane or switch grass into usable ethanol is roughly the same, and switch grass can be grown in many regions of the United States.
While other countries continue to develop their own ethanol sugar programs, the United States is more likely to remain committed to corn sugar as its primary source for domestic ethanol fuel.