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van Gelder, W.M.J., F.P. Cuperus, J.T.P. Derksen, B.G. Muuse, and J.E.G. van Dam. 1993. Characterization and processing research for increased industrial applicability of new and traditional crops: A European perspective. p. 38-45. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.

Characterization and Processing Research for Increased Industrial Applicability of New and Traditional Crops: A European Perspective

W.M.J. van Gelder, F.P. Cuperus, J.T.P. Derksen, B.G. Muuse, and J.E.G. van Dam

  1. EC SURPLUS POLICY
    1. History
    2. EC Price System
    3. Reducing the Surpluses
    4. Research Programs within the EC
    5. New Crops
  2. EXPLOITING ADVANTAGEOUS PROPERTIES OF CROPS FOR INDUSTRIAL APPLICATION
    1. Agrofibers for Composites and Construction Materials
    2. Primary Production and Processing of Oils from New Seed Crops
  3. SUMMARY
  4. REFERENCES
  5. Table 1
  6. Table 2
  7. Table 3
  8. Fig. 1
  9. Fig. 2
  10. Fig. 3
The surpluses of agricultural commodities have generated an increasingly growing interest in novel applications of agricultural produce. As crops are currently grown almost entirely for food and feed applications, a basic element of the policy within the European Community (EC) is increasing the use of traditional crops, and developing new crops for industrial applications (Rexen 1991). An encompassing R&D strategy is needed for achieving this goal.

R&D must be market oriented and the most promising technologies and products, selected after thorough evaluation for market potentials, should be commercialized. In research programs the entire production chain should be studied including primary production, harvesting, storage and processing technologies, product development and evaluation, marketing studies and economics.

Hence, a multidisciplinary approach is needed and both the public and private sector must participate. Introduction of agricultural commodities as industrial raw products is often hampered because the current raw materials used by industry are inexpensive, readily available and of acceptable quality. Thus, the specific advantageous properties of agricultural raw materials must be identified and exploited. Process technologies enabling exploitation of such preferential properties need also to be developed.

This paper presents a brief description of the background of the EC-surplus situation and of proposed measures for surplus reduction, especially by non-food applications of crops. This includes relevant R&D programs within the EC in general and in the Netherlands in particular. Some examples of research on new/industrial crops directed to exploiting preferential properties for technical applications are presented in more detail.

EC SURPLUS POLICY

History

After World War II, the agricultural production capacity in Europe was mainly employed to produce food and feed. After the EC had been founded, the agricultural policy of the community was to increase agricultural productivity to provide a reasonable and stable income for farmers and to ensure a stable food supply to consumers at reasonable prices. An important aim was to achieve a good balance between production and the market. In the 1960s and 1970s, this policy proved very successful. Afterwards, the EC-countries appeared unable to slow down increases in productivity, in order to keep supply and demand in balance. Moreover, as a result of its success in producing commodities for food and feed applications, agriculture had neglected entirely the opportunities of raw material production for the non-food industry, although agricultural products had been used for non-food applications for a long time. Among the traditional applications were natural fibers for ropes, cords, and textile, starch and proteins for glues, natural pigments for dyes, medicinal plants for pharmaceutics, and vegetable oils and fats for paints, linoleum, soaps, lubricants, and fuels. Due to their increasing prices, many of these raw materials became replaced by mineral- or petrochemical-based materials produced by the chemical industry. In addition, the chemical industry developed superior technologies and products after the second world war, while agriculture was focussing on producing commodities for food and feed.

EC Price System

The EC guarantees farmers a minimum price for their products--which is often (much) higher than the world-market price--even in the situation of excess production and within the frame-work of open-end intervention. As a result, the subsidies the EC has to pay to her farmers have now become an intolerable burden. Moreover, important trade-partners of the EC strongly object to the EC price system. For these reasons, the EC is changing the policy which will affect many farmers, especially the small family farms, resulting in a dramatic loss of income. As this situation leads to enormous political problems, the EC and its individual member-states are diligently looking for solutions for the surplus problem.

Reducing the Surpluses

A number of options for reducing the surpluses in the EC have been proposed: set-aside programs (laying agricultural areas fallow); increased land for recreation and nature preservation; afforestation; planting "fast-growing wood," such as popular and spruce, for pulp and paper production; and biological feedstocks for industry. Set-aside programs and afforestation have already been put into practice and much attention is being directed to finding industrial market-outlets for agricultural (annual) crops, especially for non-food/non-feed applications. On the longer term, diversifying agriculture to produce industrial feedstocks could reduce on a structural base the excess production and strengthen the agricultural economy. However, for many potential applications, agricultural raw materials must compete with mineral products which are often, but not always, cheaper and sometimes superior. Advantages of agricultural raw materials that can contribute to achieving a durable society will appear very important on the longer term. Compared to fossil raw materials those of agriculture are renewable, environmental friendly, and enable gradually growing to a closed carbon-dioxide cycle.

Although plants contain many unique valuable components that cannot, or only at very high costs, be produced by the chemical industry, it will be very difficult to introduce plant materials as replacement for current synthetic products. This is largely due to the relative primitiveness of many agricultural non-food processing technologies. Little investments have been made in this area in the last five decades, while the chemical industry invested billions of dollars in R&D. Thus, for the development of the raw products for industry based on agricultural materials new processing technologies have often to be developed.

In the proposed strategy, cooperation is essential between agriculture as the raw material supplier, the agricultural research field, and industry. As little is known on the specific characteristics of agricultural materials for modern technical applications, it is difficult to compare characteristics of most plant materials with the technical specifications demanded by industries. For this reason, the EC-countries direct much agricultural R&D effort in the coming years to characterize potential raw materials. In cooperation with industry, non-food process technologies and intermediate and consumer products will be developed. As the agricultural sellers market has changed into a buyers market, agriculture can only profit from the interesting opportunities that exist at the expense of very large investments in R&D.

Research Programs within the EC

EC programs. The EC Directorates General VI (Agriculture) and XII (Science, Research and Development) at Brussels, initiate and support research on creating new market-outlets for agricultural crops. Important programs which are (partly) directed to this field are: ECLAIR and FLAIR (Agro-industrial Technologies), total budget 105 million ECU (equivalent to US$ 130 million), 1988-1993; CAMAR (Adapting Agriculture to the New Situation and Market Policy), total budget 55 million ECU (US$ 68 million), 1989-1993; AIR (Agricultural and Agro-industrial Research), total budget 330 million ECU (US$ 410 million), 1991-1994; and a number of smaller programs and demonstration projects or studies.

Recently, the non-food uses have been assigned a key-area for EC-research (Rexen 1991). Especially within ECLAIR, CAMAR, and AIR, much emphasis is put to this area. To obtain support from the EC AIR-program, research projects must show a strategic approach and be market oriented. This means that the entire production chain must be represented in the project including pilot plants on a near reality scale for economic evaluation and participation of the industry. Additional conditions are amongst others, that processes and products to be developed must be "environmental and energy friendly" (Rexen 1991).

National research programs. In a number of EC countries, e.g. Germany, France, and The Netherlands, substantial research programs on increasing the non-food applicability of agricultural crops are or have been initiated. In The Netherlands, the research programs are initiated by the Ministry of Agriculture, Nature Management and Fisheries, some of them in cooperation with the Ministry of Economic Affairs. The total budget that has been allocated until now exceeds the equivalent to US$ 30 million. The Dutch programs focus on (increased) industrial application of carbohydrates, oils, fibers, and secondary metabolites from arable crops and proteins from plant and animal origin.

In addition to organizing and/or subsidizing these programs, in 1989, the Agrotechnological Research Institute (ATO-DLO) was founded in Wageningen, by the Ministry of Agriculture, Nature Management and Fisheries of the Netherlands. ATO-DLO consists of seven research divisions and now has 270 employees. The division Industrial Crops, Products and Process Technologies employs over 65 research workers involved in research on new and traditional crops for industrial utilization. The topics concur in general with those of the ministries. Research programs are multidisciplinary between scientists trained in plant physiology, organic chemistry, and biochemistry, biotechnology, processing technology, polymer and materials science, (molecular) physics, and the development of appropriate agrologistic systems.

In several programs, the entire production chain is studied including crop harvesting, storage, extraction, pre-processing, processing, product evaluation, and economics. Cooperation with plant breeders and agronomists is critical for improving the yield potential of the desired raw material. Close contacts/cooperation with chemical or non-food processing industries exist for developing economically feasible applications for agricultural raw materials.

Important topics within each research program are: (1) characterization of the agricultural raw material from an industrial perspective; (2) development of extraction, preprocessing, and processing techniques that can be applied by industries willing to use agricultural raw materials as an alternative to current raw materials; (3) development of required (bio)reactor systems; and (4) development of intermediate and/or other products.

New Crops

In addition to developing new applications for traditional crops, four groups of new crops are under evaluation:

Fiber crops. Fiber hemp (Cannabis sativa L.), fiber flax (Linum usitatissimum L.) and elephant grass (Miscanthus sinensis L.) are being studied for chemical, physical, and morphological characteristics that determine fiber quality. The relationship between fiber quality and harvesting date and processing conditions are under evaluation. Process technologies and products are being developed. Applications include fibers for reinforced composites, building and construction materials, and geotextiles (see hereafter) and pulp and cellulose for the paper industry.

Oilseed crops. The oil content and triglyceride and fatty acid compositions of a large number of oil seed crops and the yield of the desired fatty acids in relation to sowing and harvesting dates are being evaluated. Advanced techniques are being developed for enzymatic hydrolysis of specific fatty acids such as labile fatty acids or technical fatty acids on the 1,3 positions of the triglycerides. Development of bioreactor and enzymatic transesterification technologies for modification of triglycerides of new oil crops is in progress.

Carbohydrate crops. Inulin, a linear ß2-1 polyfructoside from root chicory (Cichorium intybus L.) and Jerusalem artichoke (Helianthus tuberosus L.), showing a degree of polymerization of DP 3 to DP > 70, is used as a sweetener after hydrolysis. Applications which exploit the polymeric nature of inulins are a novel approach and deserve much attention. The 3-D molecular structure of inulin is being studied and selective oxidation and cross-linking techniques are studied for valorization of the inulins.

Protein crops. The proteins of new or underutilized crops such as faba beans (Vicia faba L.), peas (Pisum sativum L.), lupins (Lupinus albus L.), and quinoa (Chenopodium quinoa Willd) are being isolated and characterized. The physical properties are being evaluated such as solubility, viscosity, elasticity, gel-forming, foaming and emulsifying properties, and coating characteristics. Chemical and enzymatic modification procedures are being developed for use by the food and non-food processing industries.

EXPLOITING ADVANTAGEOUS PROPERTIES OF CROPS FOR INDUSTRIAL APPLICATION

Some examples of research at ATO-DLO are presented below. These include studies on characterization and exploitation of specific properties of arable crops including development of necessary processing technologies; research in the application of agrofibers from "new" crops in composite and construction materials; and the primary production and processing of technical oils from new oil seed crops.

Agrofibers for Composites and Construction Materials

Crops such as fiber flax and fiber hemp are very interesting for diversifying agriculture as they require less pesticides and fertilizers than potato and sugar beet, which are the most important crops in The Netherlands. In order to introduce such agrofiber crops into the rotation scheme or to increase their area, novel non-textile applications must be developed. Potential and interesting applications of agrofibers are: agrofiber reinforced synthetic composite materials (thermoplastics and thermoset resins); fiber and particle boards; asbestos replacement in cement boards; insulating fiber mats (thermal and acoustic); filter materials; geotextiles.

Development of such innovative products is encouraging as the industry is interested in certain specific properties of these fibers. For instance, agrofibers show some advantages in the reinforcement of composites over glass fibers which are currently used. The low wear factor, low brittleness and low irritation factor are of interest to operator and production equipment, the high elasticity modulus and the low brittleness allow the composite to be moulded after the production process, which is usually not feasible with glass-fiber reinforced composites. Biodegradability and incinerability of agrofibers enables easy disposal of wastes or used-up composites; glass-fiber reinforced composites are more and more causing problems in this respect. Agrofibers may be price-competitive with glass-fiber. The prices of short and long flax fibers and hemp bast fibers vary between 0.2 and 3 US$/kg, the price of E-glass-fiber is 3 to 4 US$/kg. This shows that a margin for improvement/modification of the agrofibers may even exist.

Multidisciplinary (basic) research that is carried out in order to realize the novel applications includes the following topics:

  1. Characterization of quality parameters from an industrial perspective. Agrofibers must meet the technical specifications demanded by industries. Standardized quality assessments are needed for enabling a guaranteed supply of constant quality and uniform batches of raw materials (Kessler et al. 1988). Important technical parameters for processing and end-use appear to be aspect ratio, tensile strength, and elasticity modulus (Table 1). The processing and compounding conditions are dependent on compatibility of fibers with the matrix, moisture content, and thermal stability. Among the performance demands of end products are durability (UV, chemical, and wear resistance), insulating capacity, dyeability and color fastness. These quality characteristics are dependent on the gross chemical composition (Table 2), especially the lignin content, and on the structures of the agrofibers, especially the crystallinity of the cellulose, and can be adapted to a certain extent, to meet the industrial demands.
  2. Identification of preferences for different agrofiber crops is essential for estimating market potentials. For instance, aspect ratio (L/D) of fibers is important for final product quality of fiber reinforced composite materials. Table 1 shows that natural fibers from different crops vary strongly in their aspect ratios. Fiber flax and hemp show favorable ratios and are the more interesting fibers for advanced composites.
  3. Physical and/or chemical modification of agrofibers. The performance of the fibers must sometimes be improved; examples include durability, water resistance, or compatibility with the synthetic (often hydrophobic) matrix. For efficiently developing modification methods, detailed studies on the chemical compositions and the structures have to be conducted. Table 3 shows the carbohydrate composition of fiber flax and fiber hemp. The glucose originates almost entirely from cellulose and the other monosaccharides from hemicellulose. Studies on the structure of the lignocellulose complex and the crystallinity of the cellulose are in progress.
  4. Development or adaptation of process technologies for manufacturing agrofiber-reinforced products are carried out in close cooperation with industries; the latter are responsible for the economics and the marketing.

Primary Production and Processing of Oils from New Seed Crops

Yield potential of desired fatty acids. Crambe abyssinica Hochst, Euphorbia lagascae Spreng., Limnanthes alba Benth., and Calendula officinalis L. are potential new oilseed crops for which an increasing industrial interest exists (Haumann 1991; Hirsinger 1989; Sonntag 1991; Purdy and Craig 1987; Burg and Kleiman 1991). The oils contain valuable fatty acids and possess a number of other interesting chemical and physical properties (Muuse et al. 1992). However, as very little information was available on the optimization of the yield from these crops of the unusual primary fatty acids, studies were undertaken on the effect of sowing and harvesting dates on the yield of the primary fatty acids of these new oilseeds. For each new oilseed crop, three sowing dates with one month intervals were chosen starting at the end of March 1990 (Fig. 1). Seeds were harvested at early, medium, and late stages of seed development (expressed as thermal time after start of flowering) and analyzed for fatty acid composition and oil content.

Within each sowing date, only slight differences were found in the contents of the primary fatty acids with respect to harvest time (Fig. 2). This means that fatty acid yield is not dependent on harvest time. On the contrary, when thermal times after start of flowering were compared, differences of up to 20% in seed fatty acid content were observed between the various sowing dates. The date of sowing is much more critical than the date of harvest to maximize primary fatty acid yield. The relatively low effect of harvest date on primary fatty acid yield is agronomically important for growing these crops in climatologically unstable countries such as The Netherlands. Consequently, the yield of seeds can be considered as an important and easy harvest criterion.

Dedicated down-stream processing of specific fatty acids. The seed oil of Dimorphotheca pluvalis L. contains over 60% of the interesting, but highly reactive, dimorphophecolic acid (C 18:2, 9-OH) (Muuse et al. 1992). This fatty acid can be used in the production of polymers and coatings. Conventional production of fatty acids (by Colgate-Emery or Twitchell processes) will lead to impure products and/or a high degree of degradation and loss of reactive groups, especially in case of the labile dimorphecolic acid. Therefore, a method is needed to specifically and mildly isolate the desired fatty acid from the oil. Since the fatty acid was shown to be primarily located on the [[alpha]]-positions of the triglycerides, the use of bioreactors containing immobilized 1,3-specific lipases will show many advantages in processing such new industrial oils (Derksen et al. 1991; Muuse et al. 1992). A prudent choice of membrane in bioreactor construction may enable simultaneous hydrolysis of triglycerides and extraction of the desired reaction products, thus promoting favorable reaction kinetics as well as easy down-stream processing.

Fig. 2 schematically shows a membrane bioreactor system dedicated to processing Dimorphoteca oil. In the membrane module, Rhizopus javanicus lipase is immobilized on the lumen side of hydrophilic cellulose hollow-fibers, separating a water phase from an organic phase, as described by Pronk et al. (1988). Dilute Dimorphotheca oil (20% in hexane) is recirculated through the lumen of the reactor at 25°C. Triglycerides and liberated fatty acids mono-, and diglycerides were quantified (Muuse et al. 1992) by high-temperature capillary gas chromatography using octacosane and triheptadecanoin as internal standards. Dimorphecolic acid is liberated upon hydrolysis of Dimorphoteca oil in this membrane bioreactor system (Fig. 3). The initial reaction rate is high, but after 5 h the reaction rate decreases and hydrolysis runs at an equilibrium. As the lipases are immobilized onto the membrane and can remain active during a considerable period of time (reaction periods of over 300 h have been realized) multiple reuse of the enzyme is allowed.

The results show that lipases with 1,3-positional specificity can be employed for the production at mild conditions of unstable oxygenated fatty acids from new oil seed crops in pure form. Therefore, research is in progress to simultaneously hydrolyse the oil and recover the liberated dimorphecolic acid, thereby driving the hydrolysis reaction to completion. Such a system enables continuous processing of Dimorphoteca oil.

SUMMARY

The surpluses of agricultural commodities have generated a strongly growing interest in increasing the use of traditional crops and developing new crops for industrial applications. The EC has initiated large research programs directed to increasing the application of agricultural feedstocks in the (non-food) industry. In the Netherlands, the scope of research programs in this field includes the application of carbohydrates, oils, fibers, proteins, and secondary metabolites from arable crops. Strategies for finding and realizing new market-outlets for agriculture must include characterizing and exploiting the preferential properties of traditional and new industrial crops. Advantageous technical characteristics are being explored for fiber crops (flax and hemp) and new oilseed crops Crambe abyssinica, Euphorbia lagascae, Limnanthes alba, and Calendula officinalis, and new processing technologies are being developed.

REFERENCES

Table 1. Dimensions and physical properties of technical and individual (ultimate cells) fibers from fiber flax, fiber hemp, jute, and sisal.

Characteristic Fiber flax Fiber hemp Jute Sisal
Length (mm) 200-1400 1000-3000 1500-3600 600-100
Diameter (mm) 0.4-062 --- 0.03-0.14 0.1-0.46
Cell length [L](mm) 4-77 5-55 0.8-6 0.8-8
Cell width [D](mm) 0.005-0.076 0.01-0.051 0.005-0.025 0.007-0.047
Aspect ratio [L/D] 1000-2500 1000-1600 65-380 50-500
Specific gravity (kg/m3) 1500 1500 1500 1450
Tensile strength (GN/m2)z 1.0 0.7 1.0 0.53
Elasticity modules (GN/m2) 60 32 59 36
Break elongation (%) 2.5 2.2 1.5 2.0
zGN/m2 = Giga Newton/m2 standard expression according to SI

Table 2. Gross chemical composition of fibers from fiber flax, fiber hemp, jute, sisal.

Composition (% w/w)
Fiber Cellulose Hemicellulose Pectin Lignin Fats, wax
Flax 65-80 15-20 2-5 1-3 2-3
Hemp bast 60-75 12-18 --- 1-4 2-4
Jute 64 12-16 1 12 0.4
Sisal 60-70 12-16 1 10 0.3

Table 3. Carbohydrate composition of fibers from fiber flax (retted) and fiber hemp.

Composition (% w/w)
Fiber Arabinose Xylose Mannose Galactose Rhamnose Glucose
Flax 0.9 1.0 3.8 2.5 0.7 71.9
Hemp 0.7 1.5 2.3 1.7 0.4 66.7


Fig. 1. Effect of sowing and harvest time on the yield of major (technical) fatty acids (% of dry seed weight) of four new oilseed crops: Crambe abyssinica, Euphorbia lagascae, Limnanthes alba, and Calendula officinalis. Time of seed development expressed as thermal time after start of flowering in degree (C) days.

Fig. 2. Laboratory-scale hollow-fiber membrane bioreactor. Lipase (500 mg) immobilized on 1 m2 of cellulose hollow-fiber membrane. Reaction temperature 25°C.
Fig. 3. Production of dimorphecolic acid (mol/mol triglyceride) from Dimorphoteca oil by enzymatic hydrolysis in a membrane bioreactor using Rhizopus javanicus lipase.
Last update September 5, 1997 aw