When corn is harvested in the field, only the grain is collected for transport and sale. However, the rest of the corn plant — stalks, cobs, etc. referred to as stover — also contains carbohydrates (58% wt/wt) that could potentially serve as a fermentation substrate [31]. For each pound of harvested corn grain, 1.0-1.5 pounds of stover are produced, and some estimate that about half of this could be harvested without negatively affecting soil quality. However, a number of constraints limit utilization of this type of feedstock, and currently there are no commercial plants that convert corn fiber or stover to ethanol. Instead, growth in production of ethanol outside the U. S. corn belt may be driven in the near term by use of alternate starch feedstocks. The Renewable Fuels Association reports that 12% of the U. S. domestic sorghum crop was fermented to ethanol in 2004. Starch from wheat, barley, rye, and cassava, and sucrose from sugar cane and sugar beets, are also fermented to ethanol around the world. Other crops such as hulless barley, field peas, and even cattails have been explored as fermentation feedstocks. In addition, ethanol fermentation can be used as an alternative to waste disposal for residues such as whey and potato processing solids in some localities.