We examine seven feedstocks with respect to supply, seasonality, price, and ethanol yield. In particular, we describe the price/t, the gallons of ethanol produced/t, and the feedstock cost/gal of ethanol. We examine both Midwestern corn and California-grown corn, because either crop might be used for ethanol production. In addition, the analysis for Mid­western corn provides a benchmark for comparison with corn and other feedstocks produced in California. Those alternatives include grapes, rai­sins, oranges, other tree fruit, almond hulls, and whey.

We describe the potential ethanol yield from almond hulls and whey, but we do not consider these materials for use in the ethanol facility. The technology exists to process almond hulls and whey for ethanol, while retaining their value as animal feed, but that activity requires an additional capital investment that is beyond the scope of this study.

Oranges

We examine oranges, rather than all citrus crops, because oranges are the primary citrus crop produced in the San Joaquin Valley. We consider both Navel and Valencia oranges. The yield and total production of or­anges can vary substantially from year to year. Considering both Navel and Valencia production removes much of the seasonality from supply consid­eration; Navel oranges are harvested during November through May, and Valencia oranges are harvested during June through October.

Currently, about 195,000 acres are planted in Navel and Valencia or­anges in California, and most of that area is within the San Joaquin Valley. Oranges from Tulare and Fresno Counties accounted for 53.6 and 14.8%, respectively, of the value of California’s production in 2001 (1). California oranges are grown primarily for the fresh fruit industry. Between 1991 and 2000, the estimated average annual total pack was 110 million cartons, or

2.6 million t of oranges. On average, 515,000 t (about 25%) were culled from the total harvest during the packing process. Fruit culled from the fresh orange industry is diverted for juice. We consider this culled fruit segment a potential source of biomass for ethanol production.

The average price received by orange growers in the southern San Joaquin Valley for culled oranges diverted to processing for juice between 1991 and 2000 was $51/t. We use that price in our analysis. The estimated yield of ethanol is 13 gal/t of culled oranges (2), resulting in an average feedstock cost of $3.92/gal of ethanol.

The skeletal remains of a plant may look quite different than it did as a living entity. For trees, the skeletal remains look, for many years, almost exactly like the living plant. Truly the only telltale sign that the plant is dead is the lack of leaves. Conversely, the skeletal remains of a succulent herba­ceous plant are almost nonexistent. It "melts away," leaving virtually no trace of its previous existence.

The difference between these two examples is the tissue construction of the living plant. Although there are a variety of tissue structures in each plant, the basic cells in succulents are thin walled and filled with a dilute solution of carbohydrates and other organic molecules. The cellulose present in the cell walls outside those cells is bathed in aqueous solution. At the first frost, the water freezes and enlarges the cell past its burst point, which then thaws to allow the water to drain out and leave no remaining structure. The plant "melts" to the ground and disappears rapidly.

The cells of woody plants have thick walls and encase a stronger, thicker solution of carbohydrate and cellulose. The freezing point of this solution is much lower than that of water, and if the cells do freeze, the cell walls are able to withstand the hydrostatic force, and therefore remain intact (6).

To be more specific, the wall of a plant cell consists of three layers: primary wall, middle lamella, and secondary wall. The primary wall is thin and the middle lamella is more an adhesive gel than an actual structure. It is the secondary wall that is thick and gives the rigid structure to the cell. In a succulent, the secondary cell wall does not develop and the cell wall has little mass or strength. In cells of a woody plant, not only is the secondary wall thick but often it contains the organic compound lignin. Lignin is a material that is high in carbon, very hard, and very strong. Succulent plants contain virtually no lignin and therefore have a fragile structure and leave almost no skeletal remains. Nut shells are high in lignin and take on an almost rocklike hardness, and their skeletal remains look identical to those of their live counterpart. Lignin is the second most abundant organic com­pound on earth, second only to cellulose. Woody plant species typically contain 15-25% lignin. Lignin has a higher carbon concentration than cel­lulose and therefore has a high heating value.

In herbaceous plants that have persistent lignified stalks ("sclerified stalks") (stems), the variety of tissues in the stem may have characteristics of succulents and some may have characteristics of wood. The result is that the skeletal remains may have some components that remain intact after death and others that essentially disappear.

To describe what the stem of a skeletal herbaceous stalked plant looks like, we begin with the stem parts of a living plant. The parts of a vascular plant stem, be it herbaceous or woody, are basically the same. The stem consists of epidermis (for outer protection), phloem (for transport of food to the plant), xylem (for transport of water to the upper reaches of the plant), and pith (a center core for the incubation of new cells). Of these four parts, the bulk of the mass of the stem cross section consists of xylem and pith. The pith is usually a very light, spongy, almost styrofoam-like mate­rial. In wood, pith is almost nonexistent except in new bud stems. In stalked herbaceous plants, the pith is a significant part of the stem.

It is in the xylem that the mass of the stem resides. Both in woods and in stalked herbaceous plants, the burnable portion of the stem is primarily xylem. If the overall purpose of an energy crop is to fix carbon from the CO2 of the air into a solid form that can be burned for the release of heat, then an energy crop must be one that accomplishes this fixation the best. The fixing of carbon is done through the photosynthesis process while the stor­ing of that carbon is accomplished by the creation of cells and cell walls, which comprise tissue. The photosynthesis process is powered by sunlight; therefore, biofuel energy sources are really one type of solar energy. A good energy crop must not just "fix" carbon but store it as burnable mass. Con­sidering the other demands for the energy the plant may have, such as making leaves, and making fruit or seeds, an energy crop is a plant that efficiently makes harvestable biomass.

To best describe the ability of a plant to create xylem, there are some technical indicators that can be used. Figure 1 illustrates that an SSP skel­etal stem is basically tubular. The "tube" itself is primarily xylem because the epidermal phloem and pith cell walls are usually very thin. For energy crops, it is best to have this tube as large and substantial as possible. In monocot plants and some dicots, the xylem and phloem are not created in tubes but are "bundled" together as highly efficient string elements that are located in the pith. There is not much mass to these bundles and, therefore, not much mass to their skeletal remains. SSPs typically are the dicots that do not form xylem bundles but, rather, xylem rings.

Critical parameters concerning the skeletal stem include the stem diameter (D); the ratio of the stem diameter to the pith core diameter (D/P); the xylem thickness/pith diameter ratio (X/P); and the xylem-to — pith ratio, defined as XPR. The reason for both X/P and XPR is that X/P

ratios the single wall thickness against the total pith diameter, while XPR ratios twice the xylem wall thickness against the pith diameter (or the wall thickness against the pith radius). Another important physical prop­erty of the stem is the density of the dried xylem tissue (kg/m3).

Raisin growers receive a lower price for raisins sold from the reserve pool than from the free market, in part because storing raisins in reserve generates a storage cost. The monthly allocation of raisins from reserves is determined by the Raisin Advisory Committee. When it is possible to sell raisins for use in ethanol production, the committee might increase its net revenue by selling a portion of the reserve pool in that market. The net returns obtained from selling raisins in both the food and ethanol markets can be described as follows:

m

Net returns = X [Pf — cm’jQF + PEQE (1)

in which PF is the price of raisins in the food market ($/t), PE is the price of raisins in the ethanol market ($/t), c is the per-unit cost of storage ($/t, per month), m is the month in storage, m is the month in which net price in the food market equals the price in the ethanol market, QFm is the quantity of raisins sold in the food market (t/mo), and QE is the quantity of raisins sold in the ethanol market (t/mo).

By construction of the model,

In this model, the reserve quantity, R, is determined by the marketing order. We assume that the monthly allocation, QFm, is determined by the Raisin Advisory Committee. Hence, neither the reserve pool nor the monthly reserve allocation to food markets is a choice variable. The per — unit cost of storage, c, also is determined outside of the model.

The Raisin Advisory Committee can maximize net revenue by storing raisins for the food market only while net price in the food market (PF — cm) is greater than the price in the ethanol market (PE). The net price in the food market declines as the number of months in storage increases. We use m to represent the month in which the net price in the food market becomes equal to the price in the ethanol market (i. e., PF — cm = PE). The empirical value of m is determined by the relationship of the fixed parameters PF, PE, and c. In particular,

The number of months, m, will be larger in years when PF is relatively high, and smaller in years when PE is relatively high.

One of the principal objectives of the federal biomass program is to improve the lot of farmers and rural communities. History teaches us that simply expanding demand for plant matter will not automatically benefit the cultivators of that plant matter. As farmers are aware more than any­one, expanded markets in the past have not resulted in increased net income to the farmer. This is because, as John F. Kennedy once observed, "The farmer is the only man in our economy who buys everything retail, sells everything he sells wholesale and pays the freight both ways."4

In 1910, of every dollar generated by agriculture, the farmer received 41^. By 1990, the farmer’s share had dwindled by more than 75%, to just 9^. And today it is closer to 7tf. Yet this reduction in the farmer’s income has not resulted in a reduction in the retail prices of the products made from the farmer’s raw materials. The price of a pound of corn flakes has gone up some 50% in the last 15 yr while the price of a pound of corn has gone down.5 What this means is that for the farmer to significantly benefit from federal biomass policies, these policies must enable the farmer to gain an income from the value-added steps in converting the commodity crop into a whole­sale and retail product.

I serve on a congressionally created committee that advises the Secre­taries of Energy and Agriculture on biomass R&D efforts. In 2002, the Bio­mass R&D Technical Advisory Committee delivered its first annual report, which acknowledged, "Expanding the use of biomass for non-food and feed purposes will benefit farmers and rural areas only indirectly and modestly. A more significant development would occur if farmers them­selves were able to produce the biofuels or bioproducts, either on the farm or as owners in a local production plant."6

Consider the emergence of bioethanol as an instructive example. The federal excise exemption for ethanol plus Clean Air Act regulations has created a 2.5 billion gal/yr ethanol industry. Evidence from Minnesota and Missouri indicates that this has increased the price that farmers are getting for their corn from local ethanol plants by 5-10^/bushel. 7

However, if farmers own the ethanol plant, they receive the additional price that results from increased markets plus they receive a part of the profit generated at the manufacturing level. Information on returns on ethanol investments is closely guarded and the returns vary dramatically from year to year and from plant to plant. Nevertheless, it is not unusual for the dividend in an average year to be 25-50^/bushel. One unreleased study of the farmer-owned Minnesota Corn Processors ethanol plant found that farmer-investors earned about 18% annually over the 20-yr life of the plant as a cooperative.

To evaluate how the formulation components affect extrusion prod­uct performance, a fractional factorial design was created for statistical analysis. The fractional design is shown for the Neat and treated straw composite testing in Table 2. As already noted, Degrade1 and Degrade2 represent wheat straw that was inoculated with P. ostreatus and incubated for 6 and 12 wk, respectively. The values in Table 2 are percentages required to make a 2-kg batch for extrusion.

Composite formulations were prepared as follows: The straw samples as received from INEEL were ground to 0.69 mm in a hammer mill and oven dried to 1.1% moisture. The dried straw samples were then blended with various amounts of high-density polyethylene (HDPE), lubricants, and maleated polyethylene blends (MAPE) (see Table 2). The mixed formula­tions were then extruded with a 35-mm Cincinnati Milacron® Model CMT 35 counterrotating conical twin screw extruder (Cincinnati Milacron, Batavia, OH), which produced a 9.525 x 38.1 mm2 solid cross-section. Flex­ural strength, density, and water sorption were measured for the extruded samples according to ASTM Standard Methods (13,14).

Eliana M. Alhadeff, Andrea M. Salgado,

Nei Pereira Jr., and Belkis Valdman[6]

Depabtamento de Engenhabia Qumica, Ehcola de Qumica,
CT/UFRJ, Ilha do Fundao, Cidade Univebhitabia,

CEP 21.949.900, Rio de Janeibo, RJ, Bbahil,

E-mail: belkih@eq. ufrj. bb

Abstract

An automated flow injection analysis (FIA) system for quantifying etha­nol was developed using alcohol oxidase, horseradish peroxidase, 4-amino- phenazone, and phenol. A colorimetric detection method was developed using two different methods of analysis, with free and immobilized enzymes. The system with free enzymes permitted analysis of standard ethanol solution in a range of 0.05-1.0 g of ethanol/L without external dilution, a sampling frequency of 15 analyses/h, and relative SD of 3.5%.

A new system was designed consisting of a microreactor with a 0.91-mL internal volume filled with alcohol oxidase immobilized on glass beads and an addition of free peroxidase, adapted in an FIA line, for continued reuse. This integrated biosensor-FIA system is being used for quality con­trol of biofuels, gasohol, and hydrated ethanol. The FIA system integrated with the microreactor showed a calibration curve in the range of 0.05-1.5 g of ethanol/L, and good results were obtained compared with the ethanol content measured by high-performance liquid chromatography and gas chromatography standard methods.

Index Entries: Biosensors; gasohol; immobilized enzymes; alcohol oxi­dase; horseradish peroxidase.

Introduction

Since 1975, Brazil has supported a governmental program to design a new car engine technology using (95%) hydrated ethanol as biofuel.

Table 1 Enzymatic Ethanol Biosensors Enzyme Support Transductor Detection range Alcohol dehydrogenase (6) Flat glass Amperometric 0.4-3.9 M ethanol in air AOD and HRP (8) poli(carbamoil)sulfonate — poliethilenimine hydrogel Amperometric 0.02-3.75 mM AODand HRP (4) Not immobilized Spectrophotometric 1.1-21.7 mM AOD and HRP (9) Chitosan Spectrofluorometric 0.01-0.04 mM Alcohol dehydrogenases and NAD+/ NADH (5) Not immobilized Spectrophotometric 0.01-2.5 mM AOD and catalase (10) Controlled pore glass Thermometric 1.9-3.9 M Alcohol dehydrogenase and diaphorase (11) Semiconductor chip X-ray photoelectron spectroscopic 0.005-1.0 mM

Nowadays a worldwide focus is on renewable fuels, and ethanol has been considered an interesting option to replace petroleum derivate gasoline. It has been reported that the United States, France, Switzerland, Austra­lia, Canada, China, Russia, India, South Africa, and the European Com­munity are considering gasoline ethanol blends as fuel options. Recently, Brazilian government funds have been awarded to laboratories in univer­sities and research centers in different regions of the country, and a strict control of the physicochemical characteristics of the gasohol blend and hydrated fuel alcohol for combustion machines is necessary to prevent adulteration (1,2).

Among the physicochemical methodologies developed to identify chemicals, biosensors have been studied in the last 10 yr as analytical instruments that can be applied in clinical, food, and environmental analy­ses. Biosensors to be used as analytical instruments should present some important technical characteristics, such as low response time, high selec­tivity, relatively long lifetime, stability under the analytical conditions, and reproducibility of the measurements (3). Biosensors, which have many advantages, can be miniaturized and/or introduced in on-line pro­ceedings as analytical instruments to detect chemical concentrations with a very rapid response. Recently, increased applications of integrated biosensors and flow injection analysis (FIA) systems in monitoring and controlling biochemical processes have been reported (4-6). Table 1 lists various enzymatic ethanol biosensors published in recent literature. Amperometric, spectrophotometric, thermometric, and X-ray photoelec­tron spectroscopic methods were used to detect ethanol samples using free and immobilized enzyme systems. Alcohol dehydrogenase and NAD+/NADH, alcohol dehydrogenase and diaphorase, alcohol oxidase (AOD) and catalase, or horseradish peroxidase (HRP), have usually been applied in ethanol biosensors, as shown in Table 1.

To improve the quality control process of gasohol and hydrated etha­nol, an automated FIA system was developed using AOD and HRP enzymes, and addition of 4-aminophenazone and phenol. A colorimetric detection method was used in two different methods of analysis, with free (4) and immobilized enzymes. Both systems have shown good results when compared with established methods such as gas chromatography (GC) and high-performance liquid chromatography (HPLC) (4,7).

Pipeline transport of truck-delivered wood chips is only economical at large capacities and medium to long distances. For a one-way pipeline, the minimum economic capacity is >0.5 million dry t/yr. For a two-way pipeline, the minimum economic capacity is >1.25 million dry t/yr. At 2 million dry t/yr, the minimum economical distance for a one-way pipe­line without carrier fluid return is 75 km, and for a two-way pipeline with carrier fluid return is 470 km.

Furthermore, water transport of mixed hardwood and softwood chips causes an increase in moisture level to 65% or greater, which so degrades the LHV of the biomass that it cannot be economical for any process, such as direct combustion, that produces water vapor from water contained in the biomass. The impact on straw is greater, in that moisture levels are so high that the LHV is negative. Pipeline transport of biomass water slurries can only be utilized when produced water is removed as a liquid, such as from supercritical water gasification.

Finally, oil transport of mixed hardwood and softwood chips gives a fuel that is more than 30% oil by mass and is two-thirds oil and one-third wood on a thermal basis.

Acknowledgments

We gratefully acknowledge the Poole family and Bud Kushnir, whose financial support made this research possible. Sean Sanders of Syncrude Canada provided insight into pump size and pressure drop in the slurry pipeline and also provided heavy gas oil for the experiments. Mark Coolen, woodlands operations superintendent for Millar Western Forest Products, provided wood chips for the experiments and valuable discussions. David Williams, Chief Estimator for Bantrel (an affiliate of Bechtel), provided valuable comments concerning capital cost estimation of pipeline. Vic Lieffers and Pak Chow of the University of Alberta helped carry out the experiments. All conclusions and opinions are solely the authors and have not been reviewed or endorsed by any other party.

References

1. Kumar, A., Cameron, J. B., and Flynn, P. C. (2003), Biomass Bioenergy 24(6), 445-464.

2. Cameron, J., Kumar, A., and Flynn, P. C. (2002), in Proceedings of the 12th European Biomass Conference for Energy, Industry and Climate Protection, vol. 1, June 17-21, Amsterdam, The Netherlands, pp. 123-126.

3. Favreau, J. F. E. (1992), Technical report no. TR-105, Forest Engineering Research Institute of Canada, Canada.

4. Brebner, A. (1964), Can. J. Chem. Eng. 42, 139-142.

5. Elliott, D. R. (1960), Pulp Paper Mag. Canada 61, 170-175.

6. Wasp, E. J., Aude, T. C., Thompson, T. L., and Bailey, C. D. (1967), Tappi 50 (7), 313-318.

7. Hunt, W. A. (1976), in Proceedings of Hydrotransport 4,1976:4th International Conference on the Hydraulic Transport of Solids in Pipes, BHRA Fluid Engineering, Cranfield, UK,

pp. 1-18.

8. Liu, H., Noble, J., Zuniga, R., and Wu, J. (1995), Report no. 95-1, Capsule Pipeline Research Center (CPRC), University of Missouri, Columbia.

9. Jenkins, B. M., Bakker, R. R., and Wei, J. B. (1996), Biomass Bioenergy 10(4), 177-200.

10. Yoshida, Y., Dowaki, K., Matsumura, Y., Matsuhashi, R., Li, D., Ishitani, H. and Komiyama, H. (2003), Biomass Bioenergy 25(3), 257-272.

11. Werther, J., Saenger, M., Haetge, E.-U., Ogada, T., and Siagi, Z. (2000), Prog. Energy Combust. Sci. 26, 1-27.

12. Antal, M. J., Jr., Allen, S. G., Schulman, D. and Xu, X. (2000), Ind. Eng. Chem. Res. 39(11), 819-824.

13. Matsumura, Y., Xu, X., and Antal, M. J., Jr. (1997), Carbon 35(6), 819-824.

14. Matsumura, Y., Minowa, T., Xu, X., Nuessle, F. W., Adschiri, T., and Antal, M. J., Jr. (1997), in Developments in Thermochemical Biomass Conversion, Bridgwater A. V. M. and Boocock, D. G. B., eds., Blackie Academic and Professional, London, UK, pp. 864-877.

15. RS Means Company. (2000), in Heavy Construction Data—14th Annual Edition, Chan­dler, H. M., et al., eds.

16. Peters, M. S. and Timmerhaus, K. D. (1991), Plant Design and Economics for Chemical Engineers, 4th Ed., McGraw-Hill, New York, NY.

Copyright © 2004 by Humana Press Inc.

All rights of any nature whatsoever reserved. 0273-2289/04/113/0041-0054/$25.00

During 1991 to 2000, field corn was planted on about 400,000 acres in California. About half of that area was harvested for silage for the dairy industry each year, while the other half was harvested for grain. The aver­age grain yield was about 4.6 t of grain/acre. In our analysis, we assume that the grain production from 200,000 acres will be available for use in ethanol production.

Between 1991 and 2000, the average market price for California field corn was $108/t. That price is consistent with current prices and is used in our study. With current technology, 89 gal of ethanol can be produced/ton of corn (3). Hence, we use an average feedstock cost of $1.21/gal of ethanol produced using California-grown corn.

The search for a crop that can be grown as an energy fuel begins by finding fast-growing plants that develop a significant xylem ring in their stem. Growth capacity can be estimated from several measurable factors. First is the size or weight of the individual dried-down stalk. Second is the field density at which it can be planted (stalks/ft2. Third is the density of the material itself (kg/m3). As each plant species is introduced in the following sections, the physical characteristics of the plant are given to make the growth capacity estimation.

Although one important criterion for an energy crop will be the bulk of burnable mass that can be harvested, per acre, there will be other factors as well. For instance, it may be important for a plant to "dry down" quickly, so it can be taken immediately from field to burner. It may be important that the burnable portion of the plant be easily cut and handled with con­ventional harvest equipment. It may be important that the plant cause no ill effects to the local population where it is grown and to the workers who harvest it. The type of seed and their dormancy period may be an impor­tant consideration. Does it keep for periods of time without rotting? There are some political implications for some of the candidate plants, for they may have been categorized as "invasive plants" or more seriously placed on a list of "noxious plants." Their introduction into certain geographic regions may be forbidden. Therefore as each plant species is introduced next, general information is provided that may be significant in evaluating its potential (7).

New England Aster (Asteraceae novae-angliae) (Fig. 2)

New England Aster is a wildflower that has such a beautiful and hardy purple-violet flower that it has been domesticated and offered to gardeners as an autumn flower. Although it is a perennial, a multitude of seeds are dried from the flower and scattered each year. The stem has extended branches primary at its top and grows to a height of 2 m. Mostly it grows in a single stalk, but certain types grow as bushes and others grow in several stalk clusters.

Seeds are available commercially and there is sufficient experience with the cultivation of New England Aster to suggest the best planting time, germination rate, and compatible herbicides. Suited for full sun to partial shade, it is a vigorous plant when grown in wet to mildly wet soil, either fertile clay or loam and preferably slightly acid. Flowers bloom from early September through early November. The stalk dies in the middle of October and is reasonably dried by the first of December.

Stem construction consists of a waxy epidermis with xylem cylinder and spongy pith with a "pinhole" tube at the center. The xylem/pith radius ratio (XPR) is about 0.46 and typical stem diameter is 0.95 cm. Typical stalk weight is 26 g, height is 130 cm, and cultivation density is 72/m2. The density of the aster woody material (xylem) was determined to be 474 kg/ m3, which is similar to that of a light hardwood (lighter than pine).

New England Aster is probably the latest maturing of the SSPs. This could be an important factor in extending the harvest season.

Kinghead Ambrosia (Asteracea Ambrosia trifida) (Fig 3)

Kinghead Ambrosia is a wildflower, but the flower color is green, and therefore it is not recognizable in the field as such. Definitely considered a "weed" by farmers and woodsmen alike, it lines ditch banks and invades cornfields with equal vigor. It is a floodplain species but does well also in moderately wet fields. The plant height is amazingly impressive, easily exceeding 3 m and sometimes reaching 5 m.

Kinghead Ambrosia is an annual but drops sufficient seed (up to 275/ plant) to ensure its steady existence. Pollination occurs in mid-July. Pollen is very small and easily windborne, making it an allergen for humans, although not as serious as its related Common Ambrosia. Seeds are 0.3 to

0. 5 mm long, with a woody hull bearing blunt ridges that end in several short, thick spines at the tip. They germinate after a cold, moist dormant period. The stem has extended branches primarily at its top and grows thick enough to make a canopy to maximize its absorption of solar radia­tion. The stalk dies in late September or early October and dries down quickly (typically 2 wk).

Stem construction consists of a porous epidermis (not waxy), which probably is the cause of its quick drydown. The xylem cylinder has an XPR of 0.23, and a typical stalk diameter of 1.6 cm. Xylem material has a density of about 240 kg/m3, which makes it one of the lightest materials of all the SSPs introduced here. The pith is a solid spongy inner core that rots after about 2 mo of drydown.

Kinghead Ambrosia was suggested as an energy fuel more than 10 yr ago (6). Yields on the order of 2.5 t/acre were quoted. In the analysis done here, I find this number a gross understatement and project yields of 13.4 t/acre without adaptation or modification of the plant as it currently exists.

Kinghead Ambrosia is the largest plant on the list of SSPs, in both height and stem diameter. Although this corresponds to a great bulk of material from this plant, it does not generate a tremendous weight because of its relatively low density. However, the pollen from this plant is very small and easily airborne, causing allergies in humans. Before this plant could be cultivated commercially, it probably would need some alteration.

We have examined reserve pool prices and quantities for the years 1992 through 2001 to determine when the opportunity of selling raisins for etha­nol production might have generated greater net revenues for raisin grow­ers. We work with the assumption that 5000 t of raisins will be sold from the reserve pool every month (M. Pello, personal communication, 3/6/03). At this rate, the expected reserve pool of 60,000 t would be sold within 1 yr. The raisin marketing order requires that all raisins in the reserve pool be sold or discharged from the pool within 18 mo. This characteristic of the marketing order provides an economic incentive for developing viable market alterna­tives, particularly in years when production greatly exceeds the amount of raisins that can be sold in the food market. In addition, food market prices can be influenced substantially by large annual harvests and by maintaining large, nonmarketable reserve pools.

Based on an ethanol price of $1.20/gal, the fixed and variable ethanol production costs of $0.529/gal (this includes the credit of $0.06/gal for the coproduct), and an ethanol yield of 98 gal/t of raisins, we determined that ethanol producers could afford to pay up to $66/t of raisins sold for use in producing ethanol. Hence, the empirical information we use includes the following: PF is the price of raisins in the food marked; PE is the price of raisins for ethanol production, $66/t; and c is the storage cost, $11.00/t, per month.

+ The average prices of raisins sold from reserves ($/t) during the years considered in this analysis are as follows: 1991: $238; 1992: $281; 1993: $192; 1994: $152; 1995: $432; 1996: zero; 1997: $357; 1998: none; 1999: zero; 2000: $250. In 1996 and 1999, farmers received no credit for raisins sold from reserves, while in 1998, the crop was reduced by weather con­ditions, and no raisins were held in reserve (M. Pello, personal communication, 3/6/03).

We determined the month, m, according to Eq. 3, in which c = $11/t, per month, PE = $66/t, and QFm = 5,000 t/mo. We determined the return to raisins in the ethanol market based on a price of $1.20/gal ethanol, associ­ated ethanol production costs of $0.529, and an ethanol yield from raisins of 98 gal/t.

Results of Analysis

Based on the net revenue maximizing strategy, we conclude that between 1992 and 2001, the raisin industry would have benefited from an ethanol industry in 6 out of 10 yr. The additional net revenue in the ben­eficial years ranges from $0.689 million dollars in 1992 to $6.686 million in 2000 (Table 5). Preliminary market information from the 2002 harvest suggests that similar benefits might have been generated in that year.