In most newer ethanol plants, also known as "dry milling" plants, corn kernels are finely ground into small particles. Water is then added to the ground corn along with enzymes to transform the starch for fermentation. The mixture, also known as mash, is cooked to further break down the starch. The mash is removed from the cooker and allowed to cool, then a second enzyme (glucosinolytic enzyme) is added to the mash. This enzyme helps convert liquid starch into sugar. Yeast is added to the mash and ferments to produce ethanol and carbon dioxide. After about two days, the fermentation process is complete and the mash is heated again. During heating, ethanol evaporates into steam and is collected, while the remaining corn and yeast solids remain. The ethanol vapor is cooled and condensed into a liquid. The liquid is dehydrated to remove excess water from the ethanol, making "anhydrous" ethanol suitable for blending with gasoline.

There have been several recent major innovations in dry grinding:

Improve energy efficiency

Reduce water use

Reduce the size and complexity of ethanol plants

In addition to ethanol, carbon dioxide and distiller's grains, more value-added products are recovered from grain.

These innovative and ongoing process research are creating better economic opportunities for grain-based ethanol production and are changing the way ethanol plants are viewed as community investments.

Ethanol can also be produced through a wet milling process, which separates corn into several different components and provides a variety of options for the final product, including ethanol. Wet mills are much more complex and have a higher capital cost than dry mills.

Although ethanol plants have been established using starchy grains as feedstock, there are other interesting ways to make fuel alcohols through fermentation. Cellulose is the most abundant bio-based material on earth and consists of sugar molecules that can be broken down and fermented by certain organisms and/or enzymes. Currently, researchers are working on ways to make ethanol from cellulose derived from biomass such as corn cobs, corn stalks (stems and leaves), wheat or rice stalks, perennial herbs such as miscanthus and switchgrass, and wood waste. Forestry and paper industry.

Net energy gain in production

According to some authoritative life-cycle analyses, ethanol production provides a net energy gain -- generating about 67 percent more energy than it takes to grow corn and process it into ethanol. "The energy balance often cited can be misleading as the ethanol industry is rapidly changing to improve efficiency and produce more value added products from grain feedstocks. One way to increase this efficiency is to co-produce cellulosic ethanol. The product, DDGS, has been used in ethanol plants and uses corn cobs and corn stalks (leaves and stems) instead of natural gas as fuel.