Although whey and almonds are not considered feedstocks in this study, they might be recognized as potential, alternative feedstock choices. In 2002, there were 525,000 acres of bearing almond trees in Cali­fornia. In 2001, these alternate-bearing trees produced 450 million tons of unprocessed almonds. Almond hulls have a high sugar and protein con­tent. Currently, they are used as a feedstock for cattle because of the protein content. For this use, almond hulls received an average market price of $73/t between 1990 and 2000.

It may be possible to use the sugar in almond hulls for ethanol produc­tion, while leaving the protein for use by animals. Research and invest­ments may be required to develop a suitable production process and some time and effort may be required for market development. We recommend further study of the potential use of almond hulls for ethanol production in California.

Whey is a coproduct of cheese manufacturing. In 2000, California produced an estimated 1.5 billion lb of cheese, yielding 747,000 t of dried whey. It is costly to dispose whey in municipal water systems. Hence, an alternative use for whey would enhance the economics of cheese produc­tion. Currently, whey protein is used as a food additive, a protein supple­ment, and an animal feed. In addition, there are a few ethanol plants in California and the Midwest that use whey as a feedstock. The current Cali­fornia whey production would yield approx 4.7 million gal of ethanol.

The market price of whey used as animal feed is $340/t (7). As with almond hulls, it may be possible to utilize the sugar in whey for ethanol production, while enabling the protein in the byproduct to be used for animal feed. Hence, the net feedstock cost of whey in ethanol production may be less than $340/t of whey. Further research on the potential of expanding the use of whey as an ethanol feedstock would be helpful in evaluating the viability of this alternative.