Ind. Eng. Chem. Prod. Res. Dev. W 0 Q , 19, 489-496
Acknowledgment This paper was orginally presented at the 11th Central Regional Meeting of the American Chemical Society, Columbus, Ohio, on May 9,1979, at the Chemical Economics Section, chaired by E. S. Lipinsky. Appendix Cost Differences Resulting from Different Processes. The cost figures in Table V are calculated for total plants operating with modern distillery and wet-milling processes using prices of early May, 1979. It is assumed that fermentation and distillation processes are the same, so that the cost differences are the result of differences in the processes for milling the corn and producing the byproducts. This Appendix is intended to enlarge on the practical differences by examining the background of the costs and how the total product cost varies with changes in the costs and values of the different cost elements. The major assumptions used in these calculations are shown in Table VI and the calculations in Table VII. This significant cost differences between a distillery process using enzyme hydrolysis and a modified wetmilling process also using enzyme hydrolysis are the following. 1. Raw Material Cost. Over the past several years, the net corn cost per gallon of alcohol has been from 13 to 196/gal lower using the wet-milling process, with an average advantage of 15.9&/gal. 2. Capital Investment. For a plant producing 33 million gal of fuel alcohol per year, the investment would be higher for the wet-milling process to the extent of about $9.3 million. This translates into a higher cost of 4.2@/gal for depreciation, maintenance, and insurance. 3. Byproduct Drying. Less fresh water is used in the wet-milling process so that there is nearly 50 lb of water
480
less to be removed per gallon of alcohol. This results in using a total of 14.8 lb of steam less per gallon. The monetary difference depends upon the cost of fuel, type of system, energy-saving installations, etc. At different costs of steam, the savings are Steam,
$/lo00Ib 2.50 3.50 5.00 7.50
savings, dlgd 3.8 5.3 7.5 11.2
4. Power. The webmilling process uses about 0.41 kWh of power per gallon of alcohol, primarily in steeping, byproduct washing, and oil expelling. At different power rates, the added cost is 2.5 3.5 5.0 7.5
1.0 1.4 2.0 3.1
5. Operating Labor. Wet-milling may require up to two more operators per shift of 16800 man-hours per year. At 33 million gallons per year, the additional cost per gallon is, at different labor rates !j /k
dleal
4.00 6.00 8.00 10.00
0.2 0.3 0.4 0.5
Received f o r review June 20, 1979 Accepted June 9, 1980
Multi-Use Botanochemical Crops, an Economic Analysis and Feasibility Study Russell A. Buchanan, Fellx H. Otey,’ and 0. Earle Hamerstrand Northern Regional Research Center, Agricultural Research, Science and Education Adminlstratlon, U S . Department of Agriculture, Peoria, Illinois 6 1604
Dwindling reserves and increasing costs of petroleum have brought the realization that agricultural production of substitutes may be both feasible and the best long-term alternative. Multi-use oil- and hydrocarbon-producing (botanochemical)crops, specially designed for an adaptive agricultural system, appear to offer potential for combining the production of both food and industrial raw materials with increased overall productivity. Processing methods are being developed for extraction of prlmary botanochemicals, Le., soluble polyphenols, wholegiant oils, and isoprene polymers that could serve as chemical feedstocks. The extractive-free residues are promising raw materials for papermaking fibers, animal feeds, fermentation substrates, chemical feedstocks, fuels, and soil amendments. Preliminary cost assessments of crop production, collection, and processing compared wlth projected produce values suggest that a new and radically different agricultural system would be economically attractive.
Introduction New crops specially designed for “integrated adaptive agricultural systems” (Lipinsky, 1978a) offer much promise and have been designated “multi-use botanochemical crops” (Figure 1). A scenario has been developed for their
introduction into the U.S.agricultural scene (Buchanan and Otey, 1979). Besides the major social and economic achievement of allowing agricultural production of fuels and industrial feedstocks without necessarily decreasing food production,
This article not subject to U.S. Copyright. Published 1980 by the American Chemical Society
490
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 4, 1980
4
filler material
IndUSial POdUctS
Figure 1. One optional multi-use botanochemical processing scheme, raw materials and products.
multi-use botanochemical systems offer additional important advantages over other biomass utilization schemes. Greater economy and higher efficiency can be achieved by co-development of new crops and new integrated handling, processing, and marketing systems than can be achieved just by making better use of conventional crop residues. Expensive chemical conversion of plant products can be minimized by selecting crops capable of directly producing valuable energy-rich feedstocks. Since leafy residues from extraction of energy-rich materials contain most of the plant protein, they can potentially be used as feed and food products. Woody stem-residues are attractive lignocellulose sources for conversion to fuel alcohols or for isolating pure cellulose. Some of the potential botanochemical crops produce long bast fibers desirable for making premium grades of paper. Practical economics of “wastes for fuels” and other near-term biomass utilization options are being proven. Feasibility assessments have been made for various energy plantation ideas. However, it is particularly difficult to assess the economics of multi-use botanochemical systems, because they represent a radical change from US.agricultural and industrial trends. In this paper, cost considerations are discussed that relate to botanochemical crops in mainstream U S . agriculture and are perceived as being important enough to warrant their consideration at the conceptual stage. The format and logic used, which are illustrated with only a few hypothetical herbaceous, woody, and gutta crops, are intended for use as guidelines for researchers in the renewable resources field. Adjustments in numbers, processing costs, requirements for return on investment, and other parameters, can be readily made for other botanochemical crops of specific interest. Further, this paper updates our scenario (Buchanan and Otey, 1979) by taking recent political decisions, economic developments, and research advances into account. Social Constraints The energy plantation idea has been analyzed in considerable detail (Szego and Kemp, 1973; Goldstein, 1976). Lipinsky (1978b) has analyzed arid-land crop systems and concluded that they should be modeled after silviculture, probably operating as large plantations. Apparently the US.rubber industry is moving toward guayule plantations. One petrochemical company with an interest in gopher plant (Euphorbia Zathyris, Diamond Shamrock, 1978) and a company with an interest in pine chemicals (Goodyear, 1979) may eventually develop plantations. There is an important role for large company-operated plantations
where arid and stressed lands are to be operated with maximum efficiency in a silviculture mode. However, the botanochemical crops, considered here, could be grown on productive cultivated soils and integrated well into mainstream US.agriculture without disruption of its highly efficient, highly mechanized family farm system. Economic strain on the family farm system has already produced serious social problems that may be contributing to a trend toward corporate ownership of large tracts of farmland, which some view with apprehension. Furthermore, there is strong public sentiment for dispersed small-scale energy and basic materials production, i.e., farm, local, or regional self-sufficiency especially in energy (Bayh, 1979). Even though large-scale, high-technology processing of produce from large plantations may offer an economic advantage, we believe social constraints probably will dictate conventional family farm production of botanochemical crops.
Crop Options and Yields Crop Species. The multi-use concept requires plant breeders and agronomists to deal with a variety of new crops, each yielding several different producta with varying economic value. In screening plant species as potential crops, a rating system was employed that emphasized potential economy of plant production, total biomass yield, and oil and hydrocarbon contents (Buchanan and Otey, 1979). About 40 species have thus far been identified as having potential for development as crops. Screening of wild plant species continues. In our original scenario, potential rubber crops were considered. Since then, the decision has been made to develop guayule as the U.S. source of natural rubber for polymer use (Public Law 95-592, 1978). The domestic rubber market can potentially be entirely supplied by guayule grown in the southwest. However, several potential botanochemical crop species produce low-molecular-weight soluble rubbers (Swanson et al., 1979) that would be valuable as a hydrocarbon component of whole-plant oils. Certain perennial grasses produce gutta (trans-1,4polyisoprene, Buchanan et al., 1979). It could be feasible to develop one of these grasses as a crop for producing gutta either for polymer use or for producing an oil containing gutta as hydrocarbon. Plant scientists are engaged in making selections from among candidate species, but, except for guayule, they have made no final selections of species for developing botanochemical crops. Yield Specifications. Based on analysis of wild plant species, projected specifications for three types of botanochemical crops were developed by projecting increases in both dry matter yield and botanochemical content during domestication (Table I). The new crops are projected to be more productive of oil and protein than soybeans or alfalfa, respectively. The term “projected specifications” was chosen to imply that these are requirements, or goals, for plant breeders and agronomists to meet in successful development of new botanochemical crops. There are wild species in the herbaceous perennial and woody perennial categories that require only modest improvement to meet the specifications of Table I. Components specifications for protein and polyphenol were found in several wild species. HOWever, a slight increase in total dry matter, a twofold increase in whole-plant oil, and a several-fold increase in gutta yield would be required over those identified in wild species. The options presented in Table I include a herbaceous perennial oil crop. Genera considered in developing this
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 4, 1980 401
Table I. Projected Specifications for Yield and Composition of Three Types of Botanochemical Crops" perennial grass gutta herbaceous perennial woody perennial oil crop crop crop compn, component total dry matter crude protein (total)e gutta whole-plant oil polyphenol leaf meal (> 20% protein)e bast fiber residue e
yield,
compn,
yield,
compn,
yield,
% dry basis lb/(acre-year) % dry basis lb/(acre-year) % dry basis lb/(acre-year)
100 (9)
_--
141 7 32 6 41
16000 (1440)
11000
10000 (600)
(1100) 1320 880 770
-__
--_
2240 1120 5120 960 6560
1000
1800 1000
_--
___
---
6200
8030
" Yields are based on harvesting and using entire aerial plant, dry weight basis, Based on anticipated production provided by improved genetics and to-be-developed cultural practices (Buchanan and Duke, 1979). See text for candidate species. Assumes a coppice crop grown on a 2-year cycle to produce 1 0 tonlacre of dry matter. See text for candidate species. See text. Would require considerable improvement over wild species. e Protein does not extract but is retained in leaf and residue. f Assumes low-molecular-weight rubber would not be recovered as a separate product but would instead constitute 20-40% of the whole-plant oil by weight. specification include Asclepias, Cacalia, Campanula, Euphorbia, Silphium, Solidago, Sonchus, and Vernonia (Buchanan and Otey, 1979). Several of these genera would give, by direct hexane extraction, a whole-plant oil containing about 20 wt % of low-molecular-weight natural rubber. Values for extractive-free leaf meal and bast fiber were from an estimate for common milkweed (Asclepias syriaca, Buchanan and Duke, 1979). The woody perennial, very short rotation, oil and polyphenol crop specification (Table I) is based on Acer saccharinum, Lonicera tatarica, Rhus glabra, or Sassafras albidium. Except for L. tatarica, these species would give whole-plant oils not containing rubber. The yield of leaf meal for this type of crop was estimated as 10 wt % for plants grown on a 2-year cycle. It might be feasible to grow these crops on 1-year or alternating 1-and 2-year cycles (very short rotation) to increase leaf content. In this type of plant, the highest oil content is found in new growth and leaves, so the very short rotation would be desirable for better botanochemical yield and the produce could be handled like forage. The perennial grass gutta crop specification was based on Elymus canadensis. The projected gutta content of this crop may be unrealistic, since the highest content observed in small test plots (sown with wild seed) was 2.8% of dry matter. Although it is obvious that the value of botanochemical products may depend strongly on their specific composition, all the respective products have been treated as being equal in value regardless of which plant species they were derived from. Attempts are being made to select species and develop crops that cost less to produce than conventional forages. Preferably, botanochemical crops should not require nitrogen fertilizer. Ceanothus americanus is the only nitrogen-fixing species with any botanochemical potential that we have found. An alternative may be intercropping with nitrogen-fixing forages or some other low-energy crop production scheme. Logistics and Processing Scale Logistics. If social constraints operate as expected to cause integration of botanochemical crops into the family farm system, then transportation costs become a powerful economic constraint on the scale of botanochemical processing. Most potential botanochemical crops will require seasonal harvesting and removal from the field, but processing must be a year-round activity. Probably the crops will be field-dried and baled, then stored on the farm in covered stacks. The transport from farm to processing site
Table 11. Estimated Costs for Baling, Handling, Storing, and Transporting Botanochemical Crops, from Windrow to Processing Planta ~~
~
~~
estimated costs $/ton
$/acre
baling,Con-farm handling, and transport stacking and outdoor storage loading and transport to processing site, 15 miles
14-19
112-152
total
17-26
1-3.5 2-3.5
8-28 16-28 136-208
Assumes crops handled like conventional forages, see text, Based on 1977 costs (Miles, 1977) adjusted for inflation to 1979. Standard 3 wire bale, 16 x 22 x 46 in., 10-14 lb/ft3. a
must be scheduled to provide a dependable supply at the through-put rate. Baling and on-farm storage can best be regarded as crop production costs, whereas transport from farm to processing site likely will be handled by contract carriers. The scheduling problem can be solved through contractual agreements between the processor and the producer and carrier, respectively. Quality standards (grades) for the baled and stored produce will have to be established. Logistics and costs for such a system have been treated (Miles, 1977) and provide a good basis for calculations (Table 11). Collection, storage, and transport are projected as major cost items in multi-use botanochemical crop systems. Processing Scale. Transport costs for baled wholeplant produce may not entirely preclude the collection and shipment of whole-plant produce to large-scale central processing facilities, but transport further than 15 miles would cost about $0.09 per additional ton-mile (Miles, 1977). Thus, botanochemical plants probably will be dispersed throughout the crop region and situated to handle produce grown within about 15 miles. Although the proportion of cropland devoted to the new crop would depend on the interaction of many variables, plant-scale calculations are based on one-eighth the region's land so that a processing plant would be sized for produce from about 60 000 acres. Yield data from Table I were used to calculate processing scale. Each facility would process from about 300 to 500 thousand tons per year of whole-plant produce. Productivity. Some speculative choices between alternative products have been made, but Table I11 serves to illustrate the potential productivity of botanochemical crop systems. Table 111assumes (see also Figure 1)that
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Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 4, 1980
Table 111. Botanochemical Processing Scale and Product Outputa
product feedstock, wholeplant produce primary products: gutta oil polyphenol leaf meal (20% protein) bast fiber residue products from residue hydrolysis lignin SCP product fuel ethanol
herbaperennial ceous woody grass perennial perennial gutta oil crop, oil crop, crop, l o 3ton/ lo3 ton/ l o 3 ton/ year year year 480
300
-__
___
67.2 33.6 154
30.0 54.0
33 0 39.6 26.4 23.1
30.0
---
55.8 49.7 44.6
48.2 64.3 57.8
28.8 196 39.2 52.3 47.0
a Based on the projected specifications of Table I, and 60 000 acres of crop. Products if residue is saccharified to produce sugars for fermentation to fuel ethanol. There are several other optional uses for the residue. Single cell protein (SCP) product from yeast or other organism.
the least valuable woody residues from botanochemical processing would be saccharified and used as fermentation substrate for fuel alcohol production. Yields of hydrolysis lignin were calculated as 20% of the herbaceous and grass residues and 30% of the woody plant residue. Ethanol and single-cell protein (SCP) product were calculated as 240 tons (74000 gal) of anhydrous ethanol and 267 tons of SCP, respectively, per 1000 tons of residue based on Gulf Oil Chemicals Co. experience with residues of similar cellulose contents (Emert and Katzen, 1979). As indicated in Figure 1, fuel alcohol production would probably be based on combined botanochemical and conventional crop residues. Thus, total alcohol production at a given facility is likely to be at least twice that available from extractive-freeresidues alone, and alcohol production probably will actually be the major activity at a botanochemical processing facility, in terms of both quantity and value. The combined production of oils and alcohol from an individual botanochemical plant is almost insignificant when compared to US. annual consumption of liquid fuels. However, the chemical intermediates produced in only a few plants of the size considered above would be able to totally supply U.S. raw materials for such products as fatty acids, fatty alcohols, sterols, vegetable waxes, tannins (polyphenols), and terpenes. The domestic consumption of gutta is only about 2600 tons at a price of about $l/lb;
but gutta’s use would be much greater if it were available at a low enough price to compete with synthetic plastics. Feedstock Costs For the 1978 crop year, the national average gross returns to the farmer from corn and soybeans delivered at the grain elevator were about $214/acre and $194/acre, respectively (USDA,1979a,b). This gross return represented total amounts paid to farmers for production and handling as well as some storage and transport costa. Gross returns from crops less expensive to grow (forages, for example) were much lower. Thus, U.S. farmers probably would produce botanochemical crops for a gross annual return of less than $200/acre for the air-dry crop in the windrow. This provides a basis for estimating botanochemical feedstock costa (Table IV). Cost ranges of Table IV are very broad, which reflects uncertainties in the estimation. Comparable estimates by other authors range from $30/ton for Oregon grass straw (Miles, 1977) to $90.40/ton for guayule grown on irrigated land in Arizona (Wright, 1979). Since the intention is to develop crops for low-cost production, it is probably conservative to take the median as a best cost estimate. Hence, the best estimated costs for feedstocks (Table IV), which were used for subsequent cost calculations, represent a $200/(acre-year) return to the farmer as the windrow value for the herbaceous perennial oil crop and the perennial grass, plus an average of the listed costs in getting the crops from windrow to processing site. A $300/(acre-2 years) was used as windrow price for the woody perennial oil crop. Surprisingly, these calculations suggest that, with efficient handling and utilization technology, the feedstock could be produced at a cost about equal to ita net fuel value or $52.50 per ton (based on a current average energy value for fuel at $3.50 (MM BTU). Process Solvent extraction appears to be the most reasonable method for winning botanochemicals. The initial investigative approach at our research center is to form whole-plant produce into coherent flakes or other shaped particles and then solvent extract using equipment designed for extraction of soybean oil (Becker, 1978; Buchanan and Otey, 1979). The process for gutta requires a two-stage extraction, whereas oil production involves only a single extraction. Gutta. A block diagram for the continuous two-stage solvent extraction of grass gutta is shown in Figure 2. This process is essentially the same as one envisioned for guayule (Nivert et al., 1978) except that there is an added operation, the separation of resin into oil and polyphenol fractions. Baled produce is opened and fed to a series of flaking rolls to form a substrate for solvent extraction. The flakes are conveyed to a countercurrent percolation extractor
Table IV. Feedstock Costs for Botanochemical Processing herbaceous perennial cost item oil crop, $/ton crop production: $100/(acre-year) gross return $200/(acre-year) gross return $300/(acre-year)gross return on-farm collection, handling, storage, Table I1 loading and tranwort to processing site,-Table I1 total, cost range best estimate cost a
Assumes 2-year growth cycle.
woody perennial oil crop,a $/ton
perennial grass gutta crop, $/ton
12.5 25.0 37.5 15-22.5
20.0 40.0 60.0 15-22.5
18.2 36.4 54.5 15-22.5
2-3.5
2-3.5
2-3.5
29.5-63.5 46.5
37-86 51.5b
$300/acre total gross return or $150/(acre-year).
35.2-80.5 57.9
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 4, 1980 493 Grass Gutta Whole Plant Produce
Water
hexane
Acetone
Hexane
+-Residue Orying
Recovered acetone Polyphenol
ReCQVertd hexane t
Polymer Oyr+-
Gutta
Recovered hexane
Figure 2. Process for extracting gutta and other botanochemicals from whole-plant produce. Oil Whole Plant Produce
011 R e c o v e r y
Recovered hexane Oil -
R e c o v e l e d ethanol [Polyphenol R e C Q v e r Y c
'xt~::~:~:ree
-
--C
Polyphenol -
Fuel AICohOl Production (see t e x t 1
Figure 3. Process for extracting botanochemicals from whole-plant produce.
where the resin is extracted with dry acetone. Deresinated flakes need not be completely desolventized before extraction with hexane. The resin is separated into polyphenol and oil fractions, respectively, by adding a small amount of water to the acetone extract and partitioning between aqueous acetone and hexane solvents. The solvents are stripped from oil and polyphenol and recycled. Deresinated flake are conveyed to a countercurrent immersion extractor and contacted with hexane to extract gutta; antioxidant is introduced with the solvent. After extraction, the flaked residue is desolventized and dried to give the extractive-free residue that would be the basis for fuel alcohol production. The gutta solution is sent to stripping columns, where the polymer is coagulated and the solvent is recovered. Coagulated polymer is washed, dried, and packaged. All processing steps are standard operations that may be taken from either the soybean extraction industry or synthetic rubber manufacture. Whole-Plant Oils. A block diagram showing operations involved in processing oil-bearing produce is shown in Figure 3. This process is simpler and costs less than the one for gutta crops. No second-stage extraction and polymer recovery operations are involved. Acetone, ethanol, or methanol are suitable solvents for extraction of whole-plant produce that does not contain rubber. If low-molecular-weight rubber is to be included as a hydrocarbon component of a whole-plant oil, as with an Asclepias for example, mixed hexane-ethanol or hexane acetone solvent is required for total extraction of polyphenol, oil, or rubber. If, on the other hand, polyphenols were too low in price to make their recovery worthwhile, whole-plant oil with a rubber component could be extracted using hexane alone and the resin partitioning step omitted. Both quality and quantity of polyphenol can be
Table V. Costs of Grass Gutta Processinga capitol investment in plant and $54 million facilities required feedstock, best estimate value, $19.1 million/year Table IV processing cost $31.4 million/year $8.1 million/year return o n investment (ROI)of 15%/year $58.6 million/year total cost a For a plant handling the produce from about 60000 acres/year, see Table 111. Based on an estimate for processing 300000 tons/year of guayule shrub of 10% rubber content, Nivert e t al. (1978).
adapted to market demands by choice of solvent and adjustment of extraction conditions. The mechanical separations of bast fiber and leaf are important steps in the process, which may feasibly be accomplished by various methods and at various stages of processing. In Figure 3, the mechanical separation is shown preceding extraction and followed by separate processing of leaf and stem. In some candidate genera (Solidago,for example), nearly all the botanochemicals are contained in the leaves, and extraction of stems might be unnecessary. For most species, it would probably be better to extract the whole plant, then use air classification or some other method to separate the residue into components (compare Figure 1). Processing Costs The economic analysis of botanochemical crop systems resolves into the problem of determining whether value added by processing is sufficient to pay expenses and show a profit. Since process development is just beginning, there is not a good basis for calculating processing costs. Thus, crude estimates are the best that can be employed. Costs for farm production and transport are comparatively well known and inelastic. Gutta Process. The process for solvent extraction of gutta will probably be only slightly modified from one described for extracting guayule rubber (Nivert et al., 1978),so that the guayule estimate may be used for gutta. The guayule estimate is applied to gutta by using the figures for 10% polymer content; adding utility costs based on $0.05/kWh power, $4.00/1000 lb of steam, and $0.80/1000 gal of water; adding S;l.OO/lOO lb of gutta for antioxidant and other chemical costs; and subtracting guayule feedstock costs (Table V). Extraction costs of Table V are very high, about $O.O6/lb of whole plant processed or $0.50/lb of gutta produced. Research and development efforts are underway at our laboratory and elsewhere to improve the overall economics for extraction of rubber and gutta from whole-plant produce. Oil Process. Processing the two oil crops would be very similar to solvent extraction of soybean oil (Becker, 1978). Even the mechanical separation has a counterpart in soybean dehulling. Over the past several years, it appears that industry has processed soybeans for $O.Ol/lb or less including return on investment (ROI), based on the prices of soybeans, crude soybean oil, and soybean meal. Since the process envisioned here (Figure 3) is so similar, the cost should be similar on the basis of dry matter processed. On an oil basis, it might be expected that the cost for extracting whole-plant oils would be twice that for soybean oil, because whole-plant produce has only about half the oil content of soybean. Calculated processing costs at four levesl based on the soybean processing industry's experience are given (Table VI).
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Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 4, 1980
Table VI. Annual Costs of Whole-Plant Oil Crop Processing"
cost levels,b d/lb
total processing cost, $ million
total processing and feedstocks cost, $ million
A. Herbaceous Perennial Oil Crop, Feedstock CostC$22.3 million/year 0.8 7.7 30.0 1.0 9.6 31.9 1.5d 14.4 36.7 2.0 19.2 41.5
52.5 I
0.0 0
B. Woody Perennial Oil Crop, Feedstock CostC$15.5 million/year 0.8 4.8 20.3 1.0 6.0 21.5 1.5d 9.0 24.5 2.0 12.0 27.5
I
20
40 Extractivehe
I 1 60
I
80
Residue,
100
$/ton
Figure 4. Effect of the price of extractive-free residue on profitability: A, herbaceous perennial oil crop; B, woody perennial oil crop; C, grass gutta crop.
Plant for handling the produce of 60000 acre/year, see Table 111. Cost levels are based on a processing cost of ld/lb estimated from past experience of the soybean industry (see text). Best estimate values, Table IV. Cost level used in subsequent calculations of profitability index.
Value of Botanochemical Products Markets and Value. Botanochemical products from the first few production units on-stream could be marketed as chemical intermediates. However, U S . agriculture easily has the capacity to saturate such markets, and botanochemicals would eventually have to be sold as basic raw materials or as fuels. Thus,the price range considered here is for the unlimited long-term market that would develop as botanochemicals became a major US. agricultural commodity. Using actual current prices or conservatively estimated prices, the total value of producta from plants of size given in Table I11 are presented in Table VII. In the following discussion, the economics of botanochemicals are expressed as the ratio of total product value to total production costs where costs include a ROI (compare Tables V and VI with Table VII). Thus, a value to cost ratio (profitability index) of 1indicates a satisfactory profitability. The following figures show the effect of varying individual product prices while coproduct prices remain at the level give in Table VII. Woody Residue. The lowest value extractive-free woody residues are potentially useful as lignocellulosic raw
0 4 t
0
,
I
40
ly3
I
120 160 leal Protein Meal. Siton
80
1
200
Figure 5. Influence of the value of leaf protein meal on profitabiliw. A, herbaceous perennial oil crop; B, woody perennial oil crop.
materials for conversion to fuel alcohol. As noted above, alcohol production could actually be the major activity at a botanochemical plant, but it is discussed here just as a possible market for the residue. Some believe that the economics of alcohol fuel production from lignocellulosic residues is favorable (Emert and Katzen, 1979). Other competitive uses for the residues are solid fuels, paper- and board-making, conversion to animal feeds, and combined production of furfural and ethanol. Because the residue is the largest volume product, the profitability is strongly affected by its value (Figure 4). Leaf Meal. Table VI1 reveals the surprisingly large impact that extractive-free leaf protein meal could have on processing economics (Figure 5 ) . Recovery of protein for feed and food uses is vital from both social and economic points of view. A good market would exist for the leaf meal and alcohol byproduct feeds because extensive botanochemical production would decrease the crop av-
Table VII. Value of Botanochemical Products per Processing Planta
product item
cost basisb
primary products: gutta oil polyphenol leaf meal (> 20% protein) bast fiber residue total
polypropylene value, $0.30/lb petroleum value, $22/barrel(300 lb) fuel value, 9500 Btu/lb, $3.50/MM BtuC alfalfa pellet value, $103/ton papermaking fiber, $3OO/ton fuel value, 7500 Btu/lb, $3.50/MM BtuC
products from residue: hydrolysis lignin SCP product fuel ethanol total value added in conversion of residue
fuel value, 9000 Btu/lb, $3.50/MM BtuC distiller's dried solubles with grain value, $130/ton $1.3O/gal($O.l99/lb)
Based on 60000 crop acres; see Table I11 for product quantities in tons/year. site value.
herbaceous woody grass gutta, oil, $ mil- oil, $ mil- $ million/ lionlyear lion/year year
___
-_-
9.9 2.2 15.9 8.6 10.3 46.9
4.4 3.6 3.1
9.8 20.9
12.7 41.9
2.5 6.7
3.5 6.5
3.0 8.4
18.7 27.9 17.6
17.8 27.8 18.0
23.0 34.4 21.7
___
May-June 1979 prices.
23.8 3.9 1.5
.--
___
Estimated on-
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 4, 1980 495 1 2.0 -
2.0 1.6
1
0.4 0.70
0.30 I
0.0
l
0.20
I l l 0.60 0.m
l
0.40
0 4 t
I
1.00
1.20
0''
Gutta. Silb.
Figure 6. Effect of gutta price on profitability of a grass gutta crop system.
Oy73
I
I
005
020
010 015 Whole Plant 011, S i l h
Figure 8. Effect of oil price on profitability: A, herbaceous perennial oil crop; B, woody perennial oil crop; C, grass gutta crop. Table VIII. Costs and Returns for Botanochemical Processing on a Cents per Pound of Total Product Basis
o,4
1
t
Fuel value, at '3.50iMM BTU 0 033 I
Current average
0 16 II
1
1
feedstock processinga total cost, #/lb
woody herbaceous perenniperennial a1 oil oil crop, crop, #/lb 4Ilb A. Costs 2.325 2.575 1.5 1.5 4.075 3.825
-
-
grass gutta crop, dllb 2.895 5.985 8.880
B. Returns gutta oil polyphenol leaf meal bast fiber residue total return, d/lb
___
1.03 0.23 1.66 0.90 1.07 4.89
--0.73 0.60' 0.52
-_1.63 - 3.48
3.6 0.59 0.23
___
_-1.92 6.35
a Processing costs include ROI, compare Tables V and VI. b Minimum price of gutta for profitability is about 51.2#/lb (6.144 returnllb of total product); see Table VI1 and Figure 6. Minimum price of polyphenol for profitability of this crop is 6.64dllb (1.20#/lb of total product return); see Table VI1 and Figures 7 and 8.
terms of costs and returns per pound of total product. These data illustrate that any of the botanochemicals can potentially be produced at reasonable prices even if all co-products are marketed at relatively low prices as basic raw materials or fuels. Conclusions It appears highly feasible for US. agriculture to produce both a crude petroleum substitute and fuel alcohol in an integrated system that also produces feed, food, and fiber. This accomplishment requires the development of new crops that are productive of both biomass and botanochemicals and the development of low-cost processes for extraction of the energy-rich materials. Projected yield specifications for feasible crops have been developed. A preliminary economic analysis shows that a highly profitable botanochemical industry could be based on a leafy herbaceous perennial crop that would be grown, harvested, and handled like a conventional forage. If market development were done concurrently, it could also be profitable to develop specialty botanochemical crops for polyphenols and gutta. Probably a low-cost botanochemical extraction process can be adapted from conventional oil seed processing by slightly modifying methods and/or equipment. Botanochemical extraction can be profitable even up to a cost of more than 1.5 times the cost of soybean oil extraction, on a dry feed weight basis. When crop species meeting the above yield specifications are developed and extraction processes that are about as
Ind. Eng. Chem. Prod. Res. Dev. 1980, 19, 496-501
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low in cost as soybean oil extraction are designed, it should be feasible to produce whole-pIant oils at a cost below the import price of crude petroleum. L i t e r a t u r e Cited Bayh, B., US. Senator, Dinner Speech, ME-American Biomass Energy Workshop, Purdue University, Lafayette, Ind., May 21, 1979. Becker, W. J. Am. Oil Chem. Soc. 1078,55(1 I),754. Bmhanan, R. A.; Duke, J. A. “Potential MuRCUse Botanochemicai Crops”, in CRC Handbook of Biosoiar Resources”, Vol. 11, “Photosynthetic Resources”, Lipinsky, E. S.; McClure, T. A., Ed.; CRC Press Inc.; West Palm Beach, Fla., 1979. Buchanan, R. A.; Otey, F. H. “MuRCUse OIL and HydrocarborrProducingCrops in Adaptive Systems f w Food, Material and Energy Production, in “Roc.Int. Symp. Lanea: A Vast Resource of the American Deserts”, Camposlopez, E.; Mabry, T. J., Ed.; Consejo Naclonal de Ciencla y Technologla, D.F. Mexico; 1979. Buchanan, R. A.; Swanson, C. L.; Weisleder, D.; Cull, 1. M. Phytochemistry
M k , T. R. "Logistics of Energy Resources and Residues”, In “Fuels and Energy from Renewable Resources”, Tlliman, D. A,; Sarkanen. K. V.; Anderson, L. L., Ed.; Academic Press: New York, 1977. Nivert, J. J.; Glymph, E. M.;Snyder, C. E. “Preliminary Economlc Anaiysis of Guayule Rubber Productlon”, in Guayule Reencuentro en el Deslerto. Proc. Int. Symp., Saltilk, Aug 1977;Consejo Nacionai de Ciencia y Technokgia, Mexico, D.F., 1978. Public Law 95-592,95th Congress, Nov 4,1978;Congressbnal Record, 124 (92STAT.) 2529-2534 (1978). Szego, 0. C.; Kemp, C. C. CHEMTECH 1073, 275. Swanson, C. L.; Buchanan, R. A.; Otey, F. H. J. Appl. Pow.Sci. 1070,23(3),
743. USDA, ESCS Crop Reporting Board. Field Crops: Production,MspositiOn, Value 1077-1978. CrPr l(79)(1979a). USDA, ESCS Crop Reportlng Board. Crop Production 1978. Annual Summary: Acreage, Yleid, Production. CrPr 2-l(79)(1979b). W m t , N. G. “Estimated Costs of Producing Guayule in Central Arizona”, Office of Arid Land Studles, University of Arizona: Tucson, A r k , 1979.
1070, 18(6),1069. Diamond Shamrock Corp. Chem. Eng. News 1078,56(44),21. Emert, G. H.; Katzen, R. “Chemicals from Biomass by Improved Enzyme Technology, presented at the Symposium on Blomass as a Non-FossIl Fuel Source, Division Of Petroleum Chemistry, Joint Meeting of the American Chemical Society and chemical Society of Japan, W u , HawaH, Apr 1-6,
1979. Goidstein, I. S. Chem. Eng. News 1976,54(50),4. Goodyear Tire and Rubber Co. Rubber WorM Ig70, 179(4). 21. Lipinsky, E. S. Science 1078a. 199,644. Lipinsky. E. S.;Kresovich, S. “Fuels from Biomass Systems for Arid Land Environments”, presented at International Arid Lands Conference on Piant Resources, Lubbock, Texas, Oct 10, 1978b.
Received for review February 4,1980 Accepted July 14, 1980 Presented at the 11th Central Regional Meeting, American Chemical Society, in the Chemical Economics symposium, Fuels and Chemical Feedstocks from Renewable Resources, Columbus, Ohio, May 7-9,1979. Mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S.Department of Agriculture over other firms or similar products not mentioned.
111. Developments in Dyeing and Finishing G. 0. Phillips and H. Tonami, Chairmen ACSKSJ Chemical Congress, Honolulu, Hawaii, April 1979 (Continued from March and June 1980 issues)
Wool as a Biological Composite Structure Helmut Zahn, Josef Fohles, Magdalene Nlenhaus, Annette Schwan, and Manfred Spel Deutsches Wollforschungsinstirot an der Technlschen Hochschule Aachen, 5 100 Aachen, West Germany
Wool is a multicomponent fiber and fulfills the conditions of a composite structure. The three main components are cuticle, cell membrane complex, and cortex. Cuticle cells and cell membrane complexes have been Isolated and analyzed. The exocuticle displays a quite unusual amino acid composition, namely the simuttaneous presence of cystine cross-links and isopeptie cross-links. An explanation for this unusual result is given. Our investigation of the membranes has confirmed Swift’s findings that it is resistant to proteolytic enzymes which can probably be explained by the special arrangement of the lipid and protein layers in the cell membrane complex. X-ray investigations of chemically modified, solvent treated, and stretched keratins have shown that the intermicrofibrillar matrix displays a certain degree of order. The X-ray swelling of the matrix-rich human hair is lower than the swelling of the matrix-poorer keratins mohair and porcupine quill. This fact shows that the original hypothesis of preferential matrix swelling is no longer valid.
Introduction
Wool belongs to the family of keratins, which form the main bulk of the horny layer of the epidermis and of epidermal appendages such as hair, nails, claws, scales, and feathers. Keratins are typically durable, insoluble, and unreactive toward the natural environment (Fraser et al., 1972). Wool is a multicomponent fiber (Zahn, 1977) and consists of about 170 different protein molecules with a molecular weight distribution from a few thousand up to 100000. It is very important to know that these 170 various proteins are not randomly distributed in the fiber 0196-4321/80/1219-0496$01.00/0
as in a polyblend but are constituents of very definite morphological components of wool. Wool consists of the three main morphological components cuticle, cortex, and cell membrane complex, which consist of further subcomponents. Our present knowledge about the microscopic and micellar architecture of the wool fibers is represented by the Sikorski model (Dobb et al., 1961) (cf. Figure 1). This model gives a good overview of the single components and clearly shows that wool fulfi-like many other biological structures-the criteria of a composite structure. Wool even displays a manifold composite 0 1980 American Chemical Society
