Energy balance of on-farm production and extraction of vegetable oil for fuel in the United States' inland northwest

Energy in Agriculture, 3 (1984) 155--166

155

Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

ENERGY BALANCE OF ON-FARM PRODUCTION AND EXTRACTION OF VEGETABLE OIL FOR FUEL IN THE UNITED STATES' INLAND NORTHWEST

CHRISTOPHER S. McINTOSH*, STEPHEN M. SMITH and RUSSELL V. WITHERS

Department of Agricultural Economics, University of Idaho, Moscow, ID 83843 (U.S.A.) *Present address: Department of Agricultural Economics, Texas A&M University, College Station, TX 77843, U.S.A. (Accepted 29 February 1984) ABSTRACT McIntosh, C.S., Smith, S.M. and Withers, R.V., 1984. Energy balance on on-farm production and extraction of vegetable oil for fuel in the United States' inland Northwest. Energy Agric., 3: 155--166. This paper (1) presents a comprehensive method for calculating the energy required to produce vegetable oil fuels on the farm and (2) determines the balance between energy inputs and outputs per area for vegetable oil produced from sunflower, safflower, and winter rape. The energy required for on-farm extraction of vegetable oils was estimated and the energy inputs apportioned between the oil and meal co-products, based on University of Idaho analysis of expeller-extracted materials. All three oilseeds yielded positive energy balances.

INTRODUCTION

The production, processing and preparation of food in the United States utilizes approximately 17% of the nation's annual fossil fuel consumption. Approximately 3% of the fuel consumed annually in the United States is used directly for agricultural production (Torgerson and Cooper, 1980). Rising prices and occasional unstable supplies have aroused interest in finding feasible, renewable alternatives to petroleum based fuels. The two promising biologically produced alternative fuels are ethanol and vegetable oils. Vegetable oils, unlike ethanol, can be substituted readily for diesel fuel, which is used increasingly in most energy-intensive operations in field crop production. The idea of using vegetable oils as fuel dates back to the Paris Exposition of 1900, when Rudolph Diesel used pea:nut oil to fuel one of his demonstration engines. Current research suggests that most vegetable oils can be used as direct replacements for diesel fuel in existing Research funded under United States Department of Agriculture, Science and Education Administration Grant No. 59-2161-1--6-040-0, and Hatch Project No. IDA00787.

0167-5826/84/$03.00

© 1984 Elsevier Science Publishers B.V.

156 engines with no modification, if operated for short periods of time only. Long-term endurance tests have indicated problems with engine gumming and carbon build-up. Research aimed at correcting these problems is underw a y (Peterson et al., 1982}. Vegetable oil fuels are not y e t acceptable because t h e y are more expensive than petroleum based fuels. McIntosh et al. (1982) estimated that the price of diesel would have to increase nearly threefold over current levels before it would be economically feasible to produce and extract vegetable oils on the farm for use as a fuel. This conclusion will be revised as prices of petroleum based products increase and production o f oilseeds and vegetable oil become more efficient. Another requirement for alternative fuels to be successful is the achievement o f a positive return to the energy used to produce the fuel. This means that the energy contained in the fuel must exceed the energy required to produce that product. This paper focuses on this energy balance aspect. One purpose is to present a comprehensive method for calculating the energy required to produce vegetable oil fuels on the farm. The second is to determine the energy inputs and returns per area for the production and onfarm extraction o f three vegetable oils in selected areas o f the inland Northwest of the United States. The calculation of input energies to determine energy balances for alternative fuels is subject to disagreement. Some believe that the calculation must include the solar energy which nurtures the plants in the field through the energy used to produce the final fuel product. Others limit the calculation to only that 'extra' energy required to produce the alternative fuel which would n o t otherwise have been used in the agricultural production process. The stages of production, and their accompanying energy requirements, which are deemed appropriate for inclusion will influence the final energy balance. The more energy inputs included, the lower will be the final energy balance and vice versa. The authors o f this paper have taken a conservative, or comprehensive approach, preferring to err on the side of including t o o many input energies, while attempting to remain reasonable. The energies required for the production and on-farm extraction of vegetable oils are derived from many sources. Those of primary importance include fossil fuels, electricity from nuclear energy, hydroelectric or coal fired generators, and solar. Solar energy as captured by plants through photosynthesis was considered a free good for the purposes of this study and was n o t included. Other forms of energy, which are available only at a real economic cost, may be classified as either direct or indirect inputs to the production process. Figure 1 depicts energy utilization in the production and use of vegetable otis. Direct energies include those which are consumed during the production and extraction of vegetable otis. The actual energy contained in diesel fuel, gasoline, fertilizers, chemicals, and electricity are examples of direct energy inputs. Indirect energies are those required in the manufacture and mainte-

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nance of direct inputs and durable items such as tractors and machinery. Examples of indirect energies include the energy used in producing the steel from which machinery and implements are fabricated, the energy required to refine crude oil into gasoline and diesel fuel, and the energy required to mine and process phosphate for fertilizers. Every stage of the production process utilizes b o t h direct and indirect energies required for production and on-farm extraction of vegetable oils.

I .......

~• ~-

Direct Energy F l o w Indirect Energy F l o w Product Flows

Fig. 1. Energy flow model for oilseed production and utilization. PRODUCTION DATA FOR OILSEEDS AND ON-FARM OIL EXTRACTION

Several oilseeds have been tested as possible alternative crops in the inland Northwest of the United States. Three of these crops appear to have potential for commercial crop production. These are sunflower, safflower, and winter rape. Production information for these crops was gathered b y means of personal interviews with growers. Representative production methods were determined from these data (see McIntosh, 1981). There are three basic methods of extracting oils from oil bearing seeds: mechanical or expeller extraction, direct solvent extraction, and pre-press solvent extraction. The latter two methods employ solvents as a means of separating the oil from the seed. The solvent must be distilled to recover the oil, which re quires extensive capital investment in distillation equipment, and the handling of highly volatile substances. The solvent extraction systems were considered inappropriate technology for on-farm operations because of the expenses and size required to attain needed efficiencies and because of increased and more highly skilled labor requirements. The technology for expeller extraction is simple. It is a continuous process using a screw press, consisting of a worm shaft rotating within a pressing cylinder or cage, which literally squeezes the oil from the seed. The seeds are usually conditioned by heating prior to extraction to facilitate the removal of oil from the seed fibers (Peterson et al., 1982). A small expeller extraction facility (e.g., 40 kg per h) could supply b e t w e e n 11.4 and 18.9 1 of vegetable

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oil per h o f operation, depending u p o n the t y p e and oil c o n t e n t of the seed being processed. A facility of this size could be assembled for less than $27 000 (Peterson et al., 1982; McIntosh et al., 1982).

Calculation of energy inputs After production data were compiled, each input was converted to an energy cost based on coefficients obtained from previous studies.

Machinery. Estimates of the energy costs per h associated with various pieces of farm machinery were calculated using procedures set forth b y Doering (1980). Doering used data from the steel and rubber industries to estimate the energy embodied in the steel and tires used in farm machinery. Data from farm machinery manufacturers were used to estimate the energy required to fabricate raw materials into various types of equipment. Doering also estimated the energy needed to supply spare parts and repairs. These factors were summed to obtain the total energy cost associated with each machine. A specific set of machinery was selected for the production of each crop, based on the interview data. Weights in kg were determined for each machine and an energy value in MJ h -1 calculated (Table I). These energy values were then divided b y typical machine life and multiplied b y the hours used on each crop to determine energy costs in MJ ha -1 year -1. Appendix A contains an example o f these calculations. TABLE I T o t a l e m b o d i e d , fabrication and repair parts energy (MJ h -l) for selected farm m a c h i n e r y Item

Weight (kg)

(MJ h- ~)

Wheel tractor Wheel tractor Crawler tractor Truck Pickup Pickup Hillside c o m b i n e Offset disk T a n d e m disk Chisel plow Field cultivator Rodweeder Harrow Cultivator Fertilizer spreader Sprayer Planter 6 row Grain drill

9 5 10 2 2 2 10 9 2 1 2 2

53.5 30.4 59.1 117.8 84.2 80.8 325.6 95.6 88.6 54.3 80.1 68.6 18.0 26.1 68.2 53.1 68.3 168.2

Source: see A p p e n d i x A.

782 311 364 955 227 136 977 965 727 680 488 130 560 809 1 016 815 1 064 2 658

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Fertilizers, seed, fuel, insecticides, herbicides. For converting fertilizer rates to energy costs the coefficients of Table II were used. Heichel (1980) evaluated four methods of determining the energy costs of propagating the seed used to produce agricultural crops. His results indicate t h a t the most accurate m e t h o d is to calculate a fossil energy budget for producing each seed crop. This is difficult because such data are available for very few species. The next most accurate m e t h o d relies upon the economic costs of seed or propagation materials to estimate the energy costs. This m e t h o d is based on the energy attributable to a dollar unit of gross national product. Heichel computes a dollar-to-energy transformation coefficient of 66.15 MJ per dollar. The energy costs associated with the seed for each crop are estimated based on this coefficient, and seeding rates and costs were determined from the on-farm interviews (see Appendix A for the calculation). T A B L E II C o e f f i c i e n t s ( M J kg -1 ) to c o n v e r t fertilizer rates t o e n e r g y costs N as a m m o n i u m n i t r a t e P as n o r m a l s u p e r p h o s p h a t e K as m u r i a t e o f p o t a s h

61.5 9.6 6.7

From Lockeretz (1980).

The fuel requirements for crop production were estimated from data in the Agricultural Engineers Yearbook -- the cultural practices using ASAE Engineering Practice EP391 and ASAE Data D230.3 (ASAE, 1980, pp. 239--250). The energy required to transport crops from farm storage to market locations was not included, since haul methods and distances were unknown. Since the focus here is on-farm production and use, this information is not relevant. To estimate the energy costs for fuel consumed during crop production, the coefficients of Table III were used. The amounts and types of herbicides and insecticides used in the production of oilseed crops were determined from the interviews. Energy costs were calculated from this information using a list of coefficients provided by Pimentel (1980a). T A B L E III C o e f f i c i e n t s (MJ 1-1) t o e s t i m a t e t h e e n e r g y costs for fuel c o n s u m e d d u r i n g c r o p p r o d u c tion Gasoline Diesel

42.3 47.8

F r o m C e r r i n k a , 1980.

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Transportation, labor, aircraft. Pimentel (1980b) estimated that each kg of farm supplies is transported an average distance of 640 km. Based on this assumption, a coefficient of 1.08 MJ kg-' was used to calculate the energy required to transport fuel, fertilizers and seed to the farm. For labor, Goering and Daugherty (1981) assumed that a farm worker consumes 2.28 MJ of energy per h. This coefficient was employed to convert hours of labor into energy costs. The energy costs associated with a 447 kW (600 hp) agricultural spray aircraft have been estimated to be 269 MJ h -1 (Johnson and Chancellor, 1980). This, and data obtained from R. Fountain (Fountain's Flying Service Inc., Moscow, ID, personal communication, 1982) were used to estimate the energy costs of aerial application of farm chemicals. Irrigation. Two examples of irrigated sunflower production were analyzed. The first employed a wheel line or side roll sprinkler system, and the second utilized a center pivot sprinkler system. Both areas required pumping of water from underground sources, resulting in a total dynamic head of approximately 137 m and 152 m, respectively. The energy embodied in the sprinkler systems and pumping requirements was estimated from actual production data using information provided by Batty and Keller (1980). Irrigation efficiencies of 65% and pumping efficiencies o f 78% were assumed for each area (Appendix A).

Oil recovery. The energy attributable to the oilseed press was calculated in the same manner as machinery. The press used in this project was a 'CeCoCo New Type 52' oil expeller. The electrical energy needed to operate the press system was determined during closely monitored operation (Peterson, 1982). An energy cost for labor was calculated based on 5 min of labor per h of press operation (Appendix A). Calculation o f energy outputs Average seed yields obtained by the growers interviewed and the percentage oil by weight contained in the seed (D.L. Auld, Department of Plant, TABLE IV Average oilseed yield (kg ha -1) Dryland North Idaho Sunflower South Idaho Sunflower North Idaho Safflower South Idaho Safflower North Idaho Winter Rape Irrigated Sunflower Power County, ID Adams County, WA

1120 1120 1008 1008 2017 2689 2801

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Soil and Entomological Sciences, University of Idaho, unpublished data, 1982) were used in calculating the energy yields of oilseed production. The average yields are listed in Table IV. To calculate the energy contained in the vegetable otis, the coefficients of Table V were used. A high-protein meal useable as livestock feed is obtained as a co-product of vegetable oil extraction. Expeller-extracted oilseed meals were evaluated for their energy content. The coefficients of Table VI were determined. TABLE V Coefficients (MJ 1-1) to calculate the energy in vegetable oils Sunflower oil Safflower oil Winter rape oil

36.4 36.5 36.3

From D.T. Driscoll, University of Idaho, Fuel characteristics of vegetable oils and vegetable oil--diesel mixture, unpublished data, 1980. TABLE VI Coefficients (MJ kg -1) to calculate the energy in expeller-extracted oilseed meals Sunflower meal Safflower meal Winter rape meal

21.3 20.6 22.4

From R.J. Katz, Department of Animal and Veterinary Sciences, University of Idaho, Moscow, ID, unpublished data, 1982.

APPORTIONING ENERGY INPUTS BETWEEN THE OIL AND MEAL

A key assumption in the calculation of the energy balance is that the coproduct high protein meal is used as a livestock feed. With this assumption, the energy required to produce the oilseed crop, the oil and the meal can be apportioned between the o u t p u t energies of the oil and meal. The input energies were apportioned between the oil and meal co-products based on the relative amounts of each obtained from the expeller output. The following example illustrates this process for the South Idaho dryland sunflower analysis: 100 kg o f sunflower seed yields approximately: 69 kg o f sunflower seed meal and 33.5 1 of sunflower oil 1 ha yields approximately: 1 120 kg of whole seed or 773 kg of meal and 375 1 o f oil

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Converting these figures to energy equivalents we obtain: Meal: 773 kg × 21.3 MJ kg -1 = 16 465 MJ Oil: 375 kg × 36.4 MJ kg -1 = 13 650 MJ Total

+

30 115 MJ

The percentage charged to oil = 13 650/30 115, or 45.3%. The energy inputs were apportioned on the basis of the energy content of the co-products. Extraction efficiencies o f 70% for sunflower, 71% for safflower, and 85% for winter rape were assumed, based on University o f Idaho data. ENERGY

BALANCE

RESULTS

Energy inputs and outputs were calculated for each of three oilseed crops produced in selected areas of the inland Pacific Northwest of the United States: sunflower, safflower and winter rape. This was done with the actual production data and methods of energy analysis presented above. The energy required for on-farm production and extraction o f vegetable oils was estimatTABLE VII Estimated energy inputs and outputs ( M J h a -~) for on-farm extracted vegetable oils in Idaho, dryland production Item

Sunflower North ID

Seed Fertilizer Herbicides Pesticides Machinery Diesel Gasoline Aircraft Gasoline a Labor Transportation Total input Oil recovery Total Yield (oil)

1 373 4 148 352 204 543 2 951 1 987 13 268 13 336 12 188 1 259 13 447 16 391

Percent charged to oil Ratio of output/input

Safflower South ID

North ID

Winter Rape South ID

North ID

1373 2602 352

2 043 4363 352

2 043 2 981 352

623 3 057 2137

600 2541 2 295

611 2940 1769

13 329 10486 1 049 11 535 13659

11 437 12 6 4 2 1 173 13 8 1 5 13 3 4 6

12 356 11064 957 12021 10918

204 638 2644 2118 25 536 11 429 11946 1 753 13 699 29 567

45.35

45.35

41.99

41.99

51.29

2.69

2.61

2.30

2.16

4.21

aGasoline for aircraftonly.

277 5044

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ed and the energy inputs apportioned between the co-products, oil and meal, based on University of Idaho analysis of expeller extracted materials. Tables VII and VIII show the balance between energy inputs and o u t p u t s for the three vegetable oil crops studied. T A B L E VIII Estimated energy inputs and o u t p u t s (MJ ha -1) for on-farm e x t r a c t e d sunflower oil in the Pacific Northwest, irrigated p r o d u c t i o n Item

P o w e r C o u n t y , ID 1 648 7 345 352

Adams C o u n t y , WA

Seed Fertilizer Herbicides Pesticides Machinery Diesel Gasoline Aircraft Gasoline a Defoliant Irrigation p u m p i n g Irrigation e q u i p m e n t Labor Transportation Total input Oil recovery Total Yield (oil)

12 219 b 1 115 b 22 752 31 187 2 518 33 705 32 781

1 422 8 295 352 819 751 3 558 4 033 25 536 251 16 293 c 1 077 c 20 596 38 028 2 624 40 652 34 149

Percent charged to oil R a t i o of o u t p u t / i n p u t

45.35 2.14

45.35 1.85

722 3 734 3 278

aGasoline for aircraft only. bWheel line irrigation. CCenter pivot irrigation.

All three oilseeds examined provided a positive return of oil energy outp u t to input ratios, based on the assumption that the meal is used as a livestock feed. Sunflower showed returns of 2.7 and 2.6, and safflower 2.3 and 2.2, respectively, for North and South Idaho dryland production. Irrigated sunflower had returns of 2.1 and 1.8, respectively, for Power County, ID and Adams County, WA. Winter rape was produced on dryland farms in North Idaho and achieved the most promising return ratio of 4.2 MJ o u t p u t for each MJ o f o u t p u t . If the assumption of the meal being used as a livestock feed is n o t tenable, the positive energy balances will be reduced considerably. The use of sunflower and safflower meal as a livestock feed is well-established, b u t the meal from the varieties of winter rape used in this study cannot be fed in the quantities normally used for high-protein supplement. This is because of a

164

high glucosinolate component. Certain varieties, primarily grown in Canada, yield meal which can be fed (Thomas et al., 1982). If the energy value o f the meal is assumed to be zero, sunflower and winter rape still produce positive ratios (1.2 for sunflower and 2.2 for winter rape), while the safflower ratios are 0.97 and 0.91. The meal can still be burned to provide direct energy, or used as fertilizer, thus adding to the energy balance. These energy values were not calculated. Fertilizers were the inputs with the highest energy use in dryland production due to the quantities o f nitrogen required. Diesel and gasoline for tractors, trucks, and combines ranked second and third by energy intensity among the inputs, followed by oil recovery and seed. Irrigation pumping was the largest consumer of energy for irrigated crop production, followed by fertilizer, diesel and gasoline. Although per ha yields were m u c h higher under irrigation, the increase in energy output was greatly overshadowed by the energies required for irrigation. Dryland production enjoys a distinct advantage in terms o f energy output per unit of input when irrigation requires pumping from deep wells, as was the case in these examples. The calculation of irrigation energy assumes electrical pumping, and that the electricity is generated from fossil fuels. This is appropriate since hydroelectric sources are almost fully exploited. Thus, any expansion of irrigation to produce oilseed crops would require more electricity, which likely would come from fossil fuel sources. This would also be a more costly energy. To improve these energy balances, attention should be focused on three major production inputs. The first is in conventional fuel use (diesel and gasoline), which consumes over 40% of the total energy used in the production of the seeds and oil. The second area is nitrogen fertilizers which make up almost one-third of the energy consumption. Genetic improvements in plants, particularly nitrogen-fixing legumes, could reduce the need for nitrogen. The third area is irrigation pumping. Improvements in irrigation and pumping efficiencies and selection of crop varieties with low consumptive irrigation requirements could improve this situation.

REFERENCES ASAE, 1980. Agricultural Engineers Yearbook. American Society of Agricultural Engineers, St. Joseph, MI. Batty, J.C. and Keller, J., 1980. Energy requirements for irrigation. In: Handbook of Energy Utilization in Agriculture. CRC Press, Boca Raton, FL, pp. 33--44. Cervinka, V., 1980. Fuel and energy efficiency. In: D. Pimentel (Editor), Handbook of Energy Utilization in Agriculture. CRC Press, Boca Raton, FL, pp. 15--21. Doering, O.C., 1980. Accounting for energy in farm machinery and buildings. In: Handbook of Energy Utilization in Agriculture. CRC Press, Boca Rat0n, FL, pp. 9--14. Goering, C.E. and Daugherty, M.J., 1981. Energy inputs and outputs of eleven vegetable oil fuels. ASAE Pap. 81-3586, American Society of Agricultural Engineers, St. Joseph, MI, 28 pp.

165 Heichel, G.H., 1980. Assessing the fossil energy costs of propagating agricultural crops. In: D. Pimentel (Editor), Handbook of Energy Utilization in Agriculture. CRC Press, Boca Raton, FL, pp. 27--33. Johnson, H. and Chancellor, W.J., 1980. Energy inputs and outputs for crop systems -cantaloupes. In: D. Pimentel (Editor), Handbook of Energy Utilization in Agriculture. CRC Press, Boca Raton, FL, pp. 209--217. Lockeretz, W., 1980. Energy inputs for nitrogen, phosphorus, and potash fertilizers. In: Handbook of Energy Utilization in Agriculture. CRC Press, Boca Raton, FL, pp. 23--24. McIntosh, C.S., 1981. An economic analysis of sunflower, safflower and winter rape production in the pacific northwest. M.S. Thesis, Department of Agricultural Economics, University of Idaho, Moscow, ID, 188 pp. McIntosh, C.S., Withers, R.S. and Smith, S.M., 1982. Costs of installing and operating small scale vegetable oil extraction plants; and economic analysis of producing and using vegetable oil as a fuel in the pacific northwest. In: The Potential of Vegetable Oil as an Alternative Source of Liquid Fuel for Agriculture in the Pacific Northwest. Misc. Ser. 73, College of Agriculture, University of Idaho, pp. 110--131. Peterson, C.L., 1982. Unpublished data. University of Idaho. Peterson, C.L., Wagner, G.L. and Hawley, K.N., 1982. Short term engine tests of farm extracted vegetable oil and vegetable oil-diesel fuel mixtures. In: The Potential of Vegetable Oil as an Alternative Source of Liquid Fuel for Agriculture in the Pacific Northwest. Misc. Ser. 73, College of Agriculture, University of Idaho, pp. 75--88. Pimentel, D., 1980a. Energy inputs for the production, formulation, packaging and transport of various pesticides. In: Handbook of Energy Utilization in Agriculture. CRC Press, Boca Raton, FL, pp. 45--48. Pimentel, D., 1980b. Energy used for transporting supplies to the farm. In: D. Pimentel (Editor), Handbook of Energy Utilization in Agriculture. CRC Press, Boca Raton, FL, p. 55. Thomas, V.M., Katz, R.J., Auld, D.A., Petersen, C.F. and Sauter, E.A., 1982. Potential feed value of farm extracted meal residue as a high protein animal feed. In: The Potential of Vegetable Oil as an Alternative Source of Liquid Fuel for Agriculture in the Pacific Northwest. Misc. Ser. 73, College of Agriculture, University of Idaho, pp. 132--142. Torgerson, D. and Cooper, H., 1980. Energy & U.S. Agriculture: 1974 and 1978. Stat. Bull. 632, Economics, Statistics & Cooperatives Service, U.S. Department of Agriculture, Washington, DC, 115 pp.

APPENDIX A Machinery energy The total energy associated with a particular piece of farm machinery is comprised of: (1) the energy embodied in the materials that make up the machine; (2) the energy used at the point of manufacture in the fabrication of the machine; and (3) the energy, both embodied and fabrication, contained in the repair parts and materials needed to maintain a machine throughout its useful life (Doering, 1980). The calculation of total energy was based on the weight of the machine (kg), and fabrication, embodied and total accumulated repair (TAR) energy coefficients presented by Doering. The following example illustrates this process for a 78 kW (105 hp) diesel, two-wheel drive tractor. The total weight was determined by averaging operating weights of four tractors of this size determined from Nebraska tractor test data. This average was 5 311 kg. The embodied energy is equal to the product of the weight and the embodied energy coefficient, 49.46 MJ kg -~. The result was 262 682 MJ. The fabrication

166 e n e r g y was d e t e r m i n e d b y e s t i m a t i n g t h e w e i g h t exclusive of tires (82.1% o f t h e t o t a l weight). T h i s was m u l t i p l i e d b y t h e f a b r i c a t i o n c o e f f i c i e n t 14.63 M J kg -~. T h e fabricat i o n e n e r g y is e q u a l to 0.821% x 5 3 1 1 k g x 1 4 . 6 3 M J k g - ~ = 6 3 7 9 1 M J . T h e r e p l a c e m e n t p a r t s e n e r g y was d e t e r m i n e d for t h e reliable life o f t h e t r a c t o r b y m u l t i p l y i n g t h e t o t a l o f e m b o d i e d a n d f a b r i c a t i o n energies b y t h e T A R n u m b e r , 0.891, a n d b y 0 . 3 3 3 , to a c c o u n t for p a r t s exclusive of l a b o r and m a i n t e n a n c e costs. T h e r e s u l t was 96 8 6 5 MJ. T h e t o t a l e m b o d i e d a n d f a b r i c a t i o n energy m u s t be a d j u s t e d t o t h e t r a c t o r ' s reliable life, e s t i m a t e d to be 82% o f its t o t a l life. This p r o d u c t was 267 7 0 8 MJ. T h e a d j u s t e d e m b o d i e d a n d f a b r i c a t i o n e n e r g y was a d d e d to t h e r e p a i r p a r t s energy, and this s u m ( 3 6 4 572 M J ) divided b y t h e h o u r s o f useful life (12 0 0 0 h) to d e t e r m i n e an energy c o e f f i c i e n t o f 30.4 M J h -1 ( T a b l e I). Seed energy

T h e e n e r g y c o n t a i n e d in t h e seed was c o m p u t e d f r o m seed cost a n d seeding rates. T h e following f o r m u l a was used: Seed price ($ kg -~ x 6 6 . 1 5 M J $-1 x seeding rate ( k g h a -~) = seed e n e r g y ( M J h a "1) Transp orta rio n

T h e t o t a l weight in kg was c a l c u l a t e d for t h e fertilizers, seed, a n d fuel n e e d e d for t h e p r o d u c t i o n o f each crop. Weights a s s u m e d for gasoline a n d diesel were 0.69 kg1-1 a n d 0.85 kg l- i, respectively. P u m p i n g energy

P u m p i n g energies were c a l c u l a t e d using t h e f o l l o w i n g f o r m u l a : ( T o t a l d y n a m i c h e a d ( m ) x 3 7 1 . 4 6 M J h a - ' m - ~ ) / ( p u m p i n g e f f i c i e n c y x irrigation efficiency) = p u m p i n g e n e r g y (MJ h a -~ m -1 o f w a t e r applied). This analysis a s s u m e d p u m p i n g efficiencies o f 78% a n d irrigation efficiencies o f 65%. Oil recovery

T h e e n e r g y r e q u i r e d for t h e expeller e x t r a c t i o n o f t h e v e g e t a b l e oils was c a l c u l a t e d b y s u m m i n g t h e e m b o d i e d f a b r i c a t i o n a n d repair p a r t s e n e r g y for t h e press a n d t h e electricity a n d l a b o r r e q u i r e d f o r its o p e r a t i o n . T h e following e x a m p l e illustrates this process for t h e S o u t h I d a h o d r y l a n d s u n f l o w e r analysis. T h e e l e c t r i c i t y r e q u i r e m e n t s were o b t a i n e d f r o m U n i v e r s i t y o f I d a h o data. A c o n v e r s i o n c o e f f i c i e n t o f 1 1 . 9 8 7 M J ( k W h ) -1 was used to a c c o u n t for t h e e n e r g y n e e d e d for g e n e r a t i o n a n d d i s t r i b u t i o n o f electricity. 1 h a yields 1 123 kg o f s u n f l o w e r seed Press c a p a c i t y = 4 4 . 5 5 k g h -~ o r 2 5 . 2 1 h h a ~ P o w e r r e q u i r e m e n t = 3 . 1 0 5 k W h h -1 E m b o d i e d , f a b r i c a t i o n a n d repair p a r t s e n e r g y = 4.21 M J h-1 L a b o r = 5 m i n p e r h of press o p e r a t i o n = 5 m i n / 6 0 rain = 0.08 Press: 25.21 h h a -I × 4.21 M J h -~ E l e c t r i c i t y : 3 . 1 0 5 k W h h -1 x 2 5 . 2 1 h h a -I × 1 1 . 9 8 7 M J ( k W h ) L a b o r : 0 . 0 8 x 2 5 . 2 1 h h a -1 × 2 . 2 8 M J h -1

-1

Total:

= 106.1 M J h a -1 = 9 3 8 . 3 M J h a -1 = 4.6 M J h a -1 1 0 4 9 . 0 M J h a -1