In 2001, there were 88,000 acres of table grapes in California and the average production was 8.07 t/acre (1). The harvest season is from May through November, and table grapes can be sold as fresh fruit or for use in making juice, concentrate, or wine. Between 1991 and 2000, an average of 680,000 t of table grapes reached the fresh fruit market, each year. The average proportion of culled fruit in the fresh market is 25.5% (4). There­fore, we assume that 173,400 t of culled grapes would be available for use in ethanol production.

The average price for culled grapes diverted to other uses such as in the juice and concentrate markets during 1991 to 2000 was $161.70/t. We

use that price in our analysis because it represents the value of the next-best alternative to sale in the fresh fruit market. Table grapes produced in the San Joaquin Valley and sold in California must contain a minimum sugar content of 17% (5). That content implies an ethanol yield of 23.8 gal/t of grapes. This is determined by multiplying the sugar content by 100 and multiplying that result by a conversion coefficient of 1.4 gal of ethanol/t of grapes per unit of sugar (R. Murray, personal communication, 4/4/02). The estimated feedstock cost of culled table grapes becomes $6.79/gal of ethanol.

Raisins

The average annual production of raisins in California during 1991 through 2000 was 368,000 t. The Raisin Advisory Committee allocates a portion of the total production to "free tonnage" and the remainder to a "reserve pool." The reserve pool represents the potential feedstock source for ethanol production. Between 1979 and 2001, the average allocation to the reserve pool was 28% of total production. Using that proportion and the average production from 1991 through 2000 generates an expected annual reserve pool of 103,000 t of raisins. Although raisins are harvested from August through October, they can be stored for use as a feedstock in any month.

At present, there is an oversupply of raisins in California. The reserve pool for the 2000-2001 season was 203,330 t, or about 66% of total produc­tion (6). Changing dynamics in international trade and market develop­ments in the wine industry will continue to have an impact on the size of the reserve pool.

Between 1993 and 2001, growers received an average of $329/t for raisins in the reserve pool. That price fell to $250/t in 2001 (6). We use the average annual price of $329/t in our analysis, while noting that raisins will be available at a lower price in the future, if the condition of excess supply continues. Hence, we consider also an alternative raisin price of $250/t. About 98 gallons of ethanol can be produced/t of raisins. Using the average reserve pool price of $32/t, the feedstock cost would be $3.36/gal of etha­nol. The feedstock cost is $2.55/gal when the 2001 reserve pool price of $250/t of raisins is considered.