Integrated systems of producing beef and ethanol from fractionated maize silage

Biomass 7 (1985) 13-25

Integrated Systems of Producing Beef and Ethanol from Fractionated Maize Silage

D. Ganesh and D. N. Mowat* Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada, N1G 2Wl (Received: 8 March, 1984)

ABSTRACT Systems were designed, simulated and analyzed to assess the economic feasibility of producing ethanol from high-moisture grain, gradually separated from mature whole-plant maize silage. The residual stover fraction containing some grain fines was fed, along with ethanol production by-products (stillage or maize gluten feed), to growing steers. Three systems were compared. In the control, regular maize silage was fed to growing steers with extra maize harvested later and soM as grain for cash. In one alternative (system 2), the separated grain fraction was processed to ethanol and stillage at a local farmer-cooperative plant. In another alternative (system 3), the grain fraction was transferred to a regional industrial plant for wet milling to ethanol, corn gluten-feed and other products. System comparisons were based on estimating gross costs per farm during 1980 to 1982, minus credits for products such as grain maize (control)and ethanol (alternative systems). System 3 was the more attractive alternative. When ethanol was valued at wholesale prices for regular leaded gasoline, these costs were similar in 1981 and 1982 for System 3 and the control. Further refinements o f a separation unit, and detailed assessment o f the feeding value o f the stover fraction plus stillage or corn gluten feed, are warranted. Key words: simulation model, animal feed, fuel alcohol, maize silage. * To whom correspondence should be addressed. 13 Biomass 0144-4565/85/$03.30- © Elsevier Applied Science Publishers Ltd, England, 1985. Printed in Great Britain

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D. Ganesh, D. N. Mowat

INTRODUCTION The economic feasiblity of producing ethanol from grains such as maize can be greatly improved through efficient utilization of the by-products as feed. Two types of by-products are involved with maize - ethanol production by-products and stover. When grains are fermented to ethanol, approximately one-third of the dry matter (DM) remains, giving, in the case of maize, a by-product averaging 29% crude protein. 1 The main problem in economically utilizing ethanol production by-products relates to the high levels of moisture present. It has been estimated 2 that almost one-half of the energy input cost in ethanol production from maize is used for evaporating and drying the by-products. Thus, smaller-sized distillation plants in close proximity to livestock feeding would enable efficient utilization of the by-products in the wet form. The other by-product, maize stover, generally remains in the field. It is only minimally utilized because of harvest difficulties and cost, as well as low feeding value. However, a novel approach to increasing the utilization of maize stover has been proposed, involving harvesting and storing the mature whole plant as silage and gradually separating at feeding into grain and stover fractions? At 50-55% moisture in the whole plant, grain maize (at 30-35% moisture) is near maximum yield.4 The silage might be fractionated by a unit similar to that developed for small cereals by Wilton. s The stover fraction should be of high quality, due to its relatively early harvest 6, 7 plus the presence of some residual grain (fines). In addition to improving feeding value, this system would greatly reduce the difficulties and cost of harvesting stover. The high moisture (HM) grain fraction could be utilized for local ethanol production, with the ethanol production by-products providing an excellent source of protein for supplementing the maize stover fraction for feeding growing cattle. The objective of this study was to evaluate the incorporation of pending technology for separating mature whole plant maize silage into grain and stover fractions, in integrated systems of producing beef and ethanol. METHODS Systems were designed, simulated and analyzed to assess the economic feasibility, under conditions in southwestern Ontario, Canada, of pro-

Integrated production of food and fuel

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ducing ethanol from HM grain maize separated from the ensiled mature whole plant. The residual stover fraction containing some grain fines was fed, along with ethanol production by-products (stillage or wet maize gluten), to growing steers. Silage separation into grain and stover fractions was assumed to be accomplished by a unit adapted from one developed by Wilton s for whole plant small cereals. Common to each of the three systems compared was a total of 122 ha of maize and a 500-head growing cattle operation comprising one and a half lots per year. Cattle were fed from 200-386 kg liveweight over a 200-day feeding period. Diets were adjusted to at least 11% crude protein (CP) on a DM basis adequate for cattle gaining approximately 0.9 kg per day.8 The cattle daily DM intake was assumed equal for each system and determined from equations by Fox and Black.9 Separated stover feed value was estimated based on previous work. 6' 7, 10 In the control (system I), a conventional maize silage ration was fed to the steers, with excess maize harvested later as grain and sold as a cash crop. Whole plant maize silage yield was estimated at 11.8 t DM ha-1 following harvest and storage with 46% of total DM (5.4 t DM ha -1) as grain) ° For both alternatives (systems 2 and 3), most, if not all, of the maize was harvested as the mature, whole plant, then ensiled and gradually separated into the two fractions at feeding. The grain fraction was then transported off-farm to local plants for processing to ethanol. The processing plant for system 2 was assumed cooperatively owned by local farmers. Costs and analyses of different sized small-scale ethanol plants have been estimated in various US reports. TM 12 Based on these studies, a plant producing 3.8 million litres ethanol per year was chosen. Besides spreading out capital cost, operating cost and risk per farmer, a plant of this capacity would produce a purer quality product (anhydrous alcohol) as compared to on-farm stills. All stillage produced from the grain fraction was returned on-farm for feeding. The ethanol was assumed to be used locally and its evaluation was based on the price of gasoline. In system 3, a larger-scale processing plant involving wet-milling was chosen. Wet-milling plants frequently involve high capital expenditure and, combined with complex processes, make it difficult to fit this type of plant into a local cooperative. However, to ensure proper comparison with the other systems, costs were estimated for this plant assuming cooperative ownership. The plant selected was based on a US study 13 where approximately 237 500 t DM grain maize was processed annually to produce 102.4 million litres ethanol, 8500 t maize oil, 73 000 t DM

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D. Ganesh, D. N. Mowat

maize gluten feed and 13 000 t DM gluten meal. All the wet gluten feed, and whatever gluten meal was required to meet the supplemental protein needs, was transported back on-farm and fed with the stover fraction to cattle. System comparisons were based on estimating gross cost per farm in each system over a period of three years - 1980, 1981 and 1982. Credits for products such as grain maize (control) and ethanol (alternative systems) were deducted from gross cost. Gross cost consisted of production costs for 122 ha of maize and in the alternative systems for separation, grain fraction transportation and processing, stover fertilizer value and by-product feed transport and storage. Allocated cost for stover removal was evaluated only for nutrient loss and not for the value of stover in conserving soil or maintaining soil structure. Any additional buildings or machinery were assumed to be built, or purchased, in 1980. Depreciation costs for plants and equipment were calculated by the declining balance method. An average interest rate of 14% for 1980 was combined with an assumed equity interest rate of 10% for an average of 12%. Attempts were made to simulate, as much as possible, the cost structure of plants for Guelph Township, Ontario, Canada. Property and business taxes for Guelph Township, averaging 16% of the processing plant's capital and operating costs, were included.

RESULTS AND DISCUSSION Average DM intake of steers was calculated to be 7.0 kg day-~, or 1050 t for all steers over the full feeding period within each system. In the control system, adjustment of the diet to 11% CP on a DM basis resulted in an estimated 1006 t DM maize (whole plant) silage being fed to steers (Table 1). Land required for producing this feedstock was 85 ha. The remaining 37 ha harvested as grain for cash crop yielded approximately 2O0 t DM. Maize production costs increased markedly from 1980 to 1981, and slightly further between 1981 and 1982 (Table 2). However, in the control system, revenue from the grain cash crop decreased by 26% and 2% for these two time periods, respectively. The net result was that cost for the control system, after deducting the cash crop credit,

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In tegrated production of food and fuel TABLE 1 Annual Ingredient Intake of Diet in Each System (t DM)a

Ingredient Maize Maize stover fraction Soybean meal Stillage Maize gluten feed Maize gluten meal Urea a

System 1

System 2

System 3

1006.5 39.0 3.9

825.0 225.0 -

846.0 192.0 12.0 -

Feeding the equivalent of 500 steers for 300 days.

TABLE 2 System 1 Costs and Credit, per Farmers ($)

Bem Gross costs Feed Maize silage (production, 85 ha) Soybean meal Urea Grain maize (production, 37 ha) Total Credit Grain maize (199.8 t DM) Gross costs - credit

1980

1981

1982

52 991 13 728 1 238 24 556 92 513

67 446 14 235 1 238 31 128 114 047

71 330 12 909 1 238 33 573 119 050

35 764 56 749

26 473 87 574

25 974 93 076

increased 54% b e t w e e n 1980 and 1981, and 6% b e t w e e n 1981 and 1982. In s y s t e m s 2 and 3, the a m o u n t o f separated grain a f t e r harvest and storage was e s t i m a t e d at 4.75 t DM ha -1, or 88% o f the grain DM stored, a° S t o v e r c o n t a m i n a t i o n ( m a i n l y cobs) was e x p e c t e d to raise the grain f r a c t i o n yield to 4 . 8 6 t DM ha -1. The stover fraction f o r m e d the remain-

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D. Ganesh, D. N. Mowat

ing 6.94 t DM ha -1 of which 9.4% was assumed to be fragmented and crushed (unseparable) grain. Presence of this unseparable grain, plus evidence of some soluble nitrogen transfer from grain to stover during storage,1° elevated the protein content of the stover fraction to an estimated 7.9% on a DM basis. In system 2, estimated DM intake of the stover fraction was 5.50 kg per steer day -1, or 825 t for all steers during the feeding period. The land required to supply this feedstock was 119 ha, leaving 3 ha of maize to be utilized for grain cash crop. Grain fraction yield from 119 ha was an estimated 578 t DM, of which 565 t DM was pure grain. Assuming 4 5 6 litres ethanol and 374 kg DM stillage produced per t DM maize grain processed,11 ethanol yield was estimated at 257754 litres and stillage produced was 225 t DM, including the 13 t DM stover combination. Inclusion of cobs dropped protein content of stillage from 29-6% to 28.3% in DM.8 The stover fraction-stillage combination in system 2 produced a diet containing approximately 12.3% CP in DM, higher than the supposedly adequate level in control. Various costs and credits for system 2 are shown in Table 3. The separation unit was estimated at $15 000 with an expected lifetime of 10 years. The processing plant was cooperatively.owned by 15 farmers, with annual capital and operating costs spread amongst these individuals. Stillage feed cost was calculated for transporting the by-product from the plant in a 17 290 litre tanker and for storage in used stainless steel tanks. If ethanol was valued at the retail price, minus Ontario road taxes, for regular leaded gasoline of SCan0.201, $0.314 and $0.381 per litre for 1980, 1981 and 1982, respectively, costs after deducting credits gradually decreased in system 2 and became comparable to control in 1982. However, the ethanol produced would far exceed that required on-farm by these farmers. Therefore, much of the ethanol may need to be valued at the wholesale price of gasoline, resulting in costs minus credits much higher than control even in 1982. In system 3, stover fraction DM intake was estimated at 5.64 kg per day per steer, or 846 t DM for all steers over the feeding period. To supply this amount of stover, all 122 ha of maize were harvested and separated with a grain fraction yield of 593 t DM, of which 579.5 t DM was pure grain. Wet-milling of each t DM pure grain produced approximately 35.9 kg maize oil, 53.3 kg DM maize gluten meal, 306.6 kg DM gluten feed and 424 litres ethanolJ 3 Grain fraction processing therefore yielded 245 708 litres ethanol plus 192 t DM gluten feed, which included

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TABLE 3 System 2 Costs and Credits, per Farmer ($)a Bem

Gross costs Maize silage (production, 119 ha) Stillage Transport b Pumping and storage Separation Processing Grain maize (production, 3 ha) Fertilizer value of stover (34 ha) Total Credits Ethanol (275 754 litre) c Grain maize (16.2 t DM) Total Gross costs - credits

1980

1981

1982

75 295

95 397

100 815

17 124 3 936 3 684 54 305 1 991 309 156 644

18 837 3 78l 3 600 58 568 2 524 265 182 972

20 636 3 794 3 394 63 036 2 722 296 194 693

51 809 2 900 54 709 101 935

80 935 2 146 83 081 99 891

98 204 2 106 100 310 94 383

a Fifteen farmers in cooperative. b Includes cost of grain fraction transport from farm. c Valued at retail price of gasoline minus Ontario road taxes.

the 13.5 t DM stover contamination. This stover contamination lowered the protein content of the gluten feed from 25% 1 to approximately 23.5% on a DM basis. However, all the stover and gluten feed produced was still 12 t DM short o f the quantity theoretically consumed by the steers. Maize gluten meal supplied this amount, and with 60% CP 1 in the DM raised the protein content of the diet to 11-3%. The assumed equality of DM intake and rate o f gain for cattle fed all three diets may be questioned. Certainly more precise information is needed in this regard. However, feeding the stover without the grain fraction may avoid possible negative associative effects on digestibility} 4 Also, in vitro studies showed 15 that maize distillers condensed solubles enhanced both cellulose digestion and microbial protein synthesis. In reality, the wet-milling plant would be commercially operated rather than be part of a local cooperative. However, assuming coopera-

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D. Ganesh, D. N. Mowat

tive ownership for proper comparison with systems 1 and 2 , 4 1 7 farms would be required to supply enough separated maize grain to meet the plant's capacity of 102.4 million litre ethanol annually. Capital cost of the plant (built in 1980) was estimated at $38 million with operating costs averaging over $17 million per year from 1980 to 1982. Gross costs for this system were lower each year than for system 2 but higher than the control (Table 4). Even though wet-milling is more complex than traditional milling, processing costs were lower, possibly reflecting economies of scale. All gluten feed was assumed to be fed on-farm in the moist state, eliminating drying expenditure. The transport vehicle used for transferring the grain fraction was also used for trucking the moist gluten to the farm on the return trip. The moisture

TABLE 4

System 3 Costs and Credits, per Farmer ($)a Item

Gross costs Maize silage (production, 122 ha) Wet maize gluten feed Transport b Storage Maize gluten meal Separation Processing Fertilizer value of stover (37 ha) Total Credits Ethanol (245 708 litre) c Maize gluten meal (19.1 t DM)a Maize oil (20-8 t) Total Gross costs - credits

1980

1981

1982

77 287

97 887

103 441

7 568 233 5 042 3 834 43 812 337 137 113

8 331 199 4 877 3 750 46 220 289 161 553

9 841 173 4 629 3 544 48 594 322 170 544

49 387 8 179 27 461 85 027 53 086

77 152 7 911 27 461 112 524 49 029

93 615 7 510 27 461 128 586 41 958

a Equivalent of 417 farmers in cooperative. b Includes cost of grain fraction transport from farm. c Valued at retail price of gasoline minus Ontario road taxes. a Remaining gluten meal not fed.

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Integrated production of food and fuel

content o f the moist gluten feed was approximately 56%, 16 enabling much lower transportation and storage costs compared to stillage. Credits in system 3 a m o u n t e d to approximately $30000 more each year than in system 2. Gross costs after deducting credits decreased slightly over the three years and were much lower than the control in 1981 and 1982. In addition, these costs were very similar in 1981 and 1982 between system 3 and the control when ethanol was valued at wholesale prices for regular leaded gasoline. Another m e t h o d of evaluating the alternative systems was to calculate ethanol production costs after deducting the stillage and stover fraction credits (Tables 5 and 6). Stillage value, as calculated by the formulae o f David e t a l . , 11 was $211, $206 and $191 per t DM for 1980, 1981 and 1982, respectively. Estimated value of the stover fraction based on Petersen coefficients 17 and its grain content was $60, $42 and $59 per t DM for the three respective years. With system 2, ethanol production cost (after credits) per litre was higher than wholesale, but

TABLE 5

Cost per Litre of Ethanol Produced, System 2 ($) ~em

Production costs Feedstock Separation Transportation a Processing Fertilizer value of stover Total Credits Stillage (225 t DM) Maize stover fraction (825 t DM) Total Production costs - credits Total Per litre a Only for grain fraction.

1980

1981

1982

75 295 3 684 4 368 54 305 309 137 961

95 397 3 600 4 812 58 568 265 162 642

100 815 3 394 5 682 63 036 296 173 223

47 475 49 500 96 975

46 350 34 650 81 000

42 975 48 675 91 650

40 986 0.16

81 642 0.32

81 573 0.32

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D. Ganesh, D. N. Mowat

TABLE 6

Cost per Litre of Ethanol Produced, System 3 ($) Item

Production costs Feedstock Separation Transport a Processing Fertilizer value of stover Total Credits Maize oil (20.8 t) Maize gluten feed (192.0 t DM) Maize gluten meal (30.9 t DM) Maize stover fraction (846.0 t DM) Total Production costs - credits Total Per litre

1980

1981

1982

77 287 3 834 5 244 43 736 337 130 438

97 887 3 750 5 772 46 193 289 153 891

103 441 3 544 6 816 48 650 322 162 773

27 461 34 368 9 703 50 760 122 292

27 461 33 024 9 888 35 532 105 905

27 461 30 528 9 023 49 914 116 926

8 146 0.03

47 986 0.19

45 847 0.19

a Only for grain fraction.

lower than retail prices of regular leaded gasoline prices after Ontario Road Taxes were deducted. Government subsidies in the form of reduced business and property taxes would lower production cost of ethanol even further, possibly making it more competitive to the wholesale gasoline price. In system 3, moist maize gluten feed was evaluated, based on Petersen coefficients, to be worth $179, $172 and $ 1 5 9 p e r t D M for 1980, 1981 and 1982, respectively. The gluten meal was evaluated similarly at $3 14, $320 and $292 per t DM for the three consecutive years. With this system, ethanol production costs were quite competitive with wholesale prices of regular leaded gasoline. Keim 13 noted that a combined wet-milling and alcohol process produced ethanol at much lower cost than the modern distillery. Similar observations can be made when comparing ethanol production costs in systems 2 and 3 (Table 7). In

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Integrated production of food and fuel TABLE 7

Ethanol Production Cost Compaison ($ litre-1) ~em

Regular leaded gasoline Retail Retail - Ontario road taxesa Wholesale Diesel - Ontario road taxesa Ethanol System 2 System 3

1980

1981

1982

0.247 0.201 0-100 0.209

0-377 0.314 0.151 0.304

0.453 0.381 0-182 0.338

0.160 0.033

0.317 0.195

0.316 0.187

a Ontario farmers exempt from road taxes.

the future, advances in the wet-milling industry may allow this process to be conducted on a much smaller scale, so that it could be incorporated at a cooperative farmer level. As compared to conventional milling, the variability and quality of the products o f wet-milling may help to offset the fluctuation that ethanol prices undergo when based on the value o f gasoline, so that risk to the individual farmer in the cooperative would be reduced. In conclusion, this systems analysis study suggested that the integrated production o f beef and ethanol may be currently economical in Ontario, Canada, by incorporating novel technology for fractionating mature whole plant maize silage into grain and stover fractions. The grain fraction would be transferred to a regional, industrial plant for wet milling and production of ethanol, along with the products, maize oil and maize gluten meal. The ethanol production by-product, maize gluten feed, would return on-farm to supplement the other by-product, the stover fraction, to produce beef. Such an integrated system, involving efficient utilization o f by-products, would produce ethanol at prices competitive with wholesale gasoline. These results suggest that priority should be given towards refinement of a cheap, efficient separating unit. In addition, a detailed assessment of the feeding value o f a diet composed of the stover fraction and maize gluten feed is warranted, and also desirable to validate certain assumptions made in this study.

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D. Ganesh, D. N. Mowat ACKNOWLEDGEMENTS

This s t u d y was supported by the Ontario Ministry of Agriculture and F o o d , and Agriculture Canada.

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13. Keim, C. R. (1979). Economics of ethanol and D-glucose derived from corn.

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Proceedings 11th Central Regional Meeting American Chemical Society, Columbus, Ohio, 37-41. Byers, F. M., Matsushima, J. K. & Johnson, D. E. (1975). Associative effects on corn net energy values. Journal of Animal Science, 41,394. Beeson, W. M. & Chen, M. C. (1976). In vitro studies on the effect of screened and centrifuged processed corn distillers solubles on cellulose digestion and microbial synthesis of proteins. Proceedings Distillers Feed Research Council Conference, Cincinnati, Ohio, USA, 8-15. Macleod, G. K. & Droppo, T. D. (1983). Moist by-products of corn wet-milling for feeding to cattle. Proceedings Nutrition Conference for Feed Manufacturers, University of Guelph, Guelph, Ontario, 110-I 5. Cullison, A. E. (1982). Feeds and Feeding, 3rd Edition, Reston Publishing Company Inc., Reston, Virginia, USA.