Euphytica 140: 1–6, 2004.
C 2004 Kluwer Academic Publishers. Printed in the Netherlands.

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Hemp as a raw material for industrial applications Paolo Ranalli1,∗ & Gianpietro Venturi2 1

Research Institute for Industrial Crops, Via di Corticella 133, 40128 Bologna, Italy; 2Department of Agroenvironmental Science and Technology, viale Fanin 44, 40127 Bologna, Italy; (∗ author for correspondence: e-mail: [email protected])

Key words: crop improvement, end-products, fibre, germplasm resources, multi-use crop

Summary Developed countries need to promote alternatives to crops produced in excess (such as cereals), and cultivation with limited environmental impact. Hemp (Cannabis sativa L.) is a potentially profitable crop, fitting into sustainable farming systems. Interest in “new” fibre crops is in fact increasing, to find alternatives to a high-input crop such as cotton, or to relieve the pressure of the paper industry on remaining natural forests. Besides, innovative applications are provided by hemp in renewable raw materials (oils from seeds and essential oils or secondary metabolites from inflorescences for food, cosmetic or pharmaceutical industry; straw and hurds for the building industry and for energy production). The development of more specialized hemp plants, needs a better understanding and control of metabolism. Since the renewed interest for this crop is increasing all over the world, it is important to update the knowledge on this crop, to understand whether it is a really sustainable, alternative and economically rewarding crop, and what contribution plant breeding, agronomical practice, and processing techniques are making, or could further make, to improve the relevant traits. The symposium “Hemp: perspectives for advanced utilization”, held in Bologna (Italy) on March 2004, was an opportunity to update the research carried out in different fields.

Between tradition and innovation Historically, the cultivation of Cannabis sativa L. (hemp) initiated in China around 2700 BC, where its properties as a medicinal plant were for the first time discovered. Cultivation then spread across Asia and Europe, arriving in Europe about 2000–2200 years ago, by that time it had become widely cultivated as had so many uses (Figure 1). Hemp fibres were found to be durable and were used in clothing, sailmaking and papermaking. Notably, the first copies of the Bible were made of hemp paper. Oils from hemp seeds were used for a wide range of purposes, from cooking to cosmetics, and extracts of hemp were used to treat a wide range of ailments. This widespread industrial use of hemp continued until the middle of 20th century, when cheap and plentiful imported cotton and jute made hemp uncompetitive.

In the history of hemp utilization, times of splendour were often followed by periods of crisis, resulting in initiatives to step away from tradition and call for innovation. Alternate periods of war and peace and the consequential shift in hemp demand and hemp prices, caused transitions from good to bad periods. However, modernisation was gradual and continual, and always modest, in order to avoid an inversion onto a downward slope. So what becomes obvious is the need to link the process of innovation to tradition. From tradition two aspects should be stressed – one positive and one negative. The first regards the excellent quality of raw materials, and the second the intensive hand labour and high cost of work, necessary to obtain a good quality end product. It is therefore easy to understand what innovation should be! For product innovation tradition can be recalled upon. Hemp, has an optimum image because the young

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Figure 1. Hemp cultivation has a long tradition in many european countries. These pictures, shot in the early decades of XXth century in italian Northern planes around Bologna, illustrate some of the steps in the hemp post-harvest processing: (a) in order to have stem bundles of homogeneous height, long or large stems could be pulled out; (b) stem bundles of homogeneous characteristics were grouped together; (c) the tops of the stem bundles were usually topped (cimatura), to increase homogeneity; (d) stem bundles were submerged in ponds for the retting.

generations has not impressed in the memory the intensive, laborious work done in poor conditions that hemp once demanded. Now hemp is considered as a clean, environmentally friendly activity. This aspect should be considered and can possibly be the winning card for all hemp products. Finally, in many cases tradition and innovation cannot be separated. Traditional processes and techniques built on centuries of experience tend to meet objectives of interest, often without knowing the relationship between cause and effect. Only the necessary action and the obtained result were known. Innovation instead must and can be based on the knowledge of the mechanism through which the end product is obtained (Venturi, 2004).

A multi-use crop Hemp provides many opportunities, i.e. weed control, pest and disease resistance, pesticide elimination without disadvantages, soil improvement by means of crop rotation. These agricultural benefits make hemp a suitable crop for both conventional and organic farming procedures, able to provide high biomass production with low inputs (Ranalli, 1999). Dry matter yields up to 15 tonnes have been reported under semi-arid conditions like those prevailing in Mediterranean areas; requiring 250–400 mm of water, hemp consumes much less than other conventional crops (including maize, sugar beet, alfalfa, etc.). Seeds may have a content of oil as high as 35%, to be used for fuel and as a source

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Figure 2. Steps in the early development of hemp fibre processing. (a) in 1861, the first “scavezzatrice” was produced by farmer Bernagozzi from Bologna, and consisted of a wheel of mallets, (b) a further development was achieved substituting the wheels with a couple of cylinders, with the “scavezzatrice” incorporated between them; (c) the next step of development was the creation of a machine combining the two processes of “scavezzatura” and “gramolatura,” by using a series of pairs of grooved cylinders that were made of different materials, and had different diameters, numbers of teeth, and speed of rotation.

of epoxy fatty acids for plastics and other industrial products. The oil-extracted meal is used as feed for livestock or as fertilizer. The leaves of the plant are left on-site as natural nitrogen to replenish the soil. The stalks are harvested and have their high-quality bast fibers removed for specialized textile use; the remaining hurds are used as a biomass feedstock for cellulosic applications (Figure 2). The most important aspect is that for each of these destinations there now exists knowledge and techniques that were not even thinkable a few years ago. This means that each end product can be obtained at a lower cost using technologies that are safer and more environmentally friendly, and the product characteristics can reflect the demands of the consumers who are then willing to pay higher prices. Besides, hemp has the capacity to grow fast (i.e. no need for early herbicide treatments), to remove significant quantities of heavy metals from the soil (bioremediation), to develop a long tap root, up to

2.5 m (preventing soil erosion), and to increase the yield of the succeeding crop in rotation cycle up to 10–15%. Can Cannabis provide a support to sustainable agriculture? We believe the answer is yes, because hemp promotes environmental-friendly agricultural methods (through improvement of rotation) which might secure a long-term land management strategy; a strategy that might be even more significantly improved, if hemp was used as a key bioremediation crop to restore unproductive land into agricultural use. An international symposium, held in Bologna in March 5–6, 2004, entitled: “Hemp: Perspectives for Advanced Utilization”, focused on the state of art of hemp research. The putative role of hemp as a multiuse crop for Southern Europe and the innovative application provided by hemp in renewable raw materials have been discussed. In the symposium the two most important destinations of hemp were stressed. The first is the use of

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Figure 3. The strategy to cut the stems in two portions.

hemp fibre for biocomposites, a destination that would require a large amount of material and has no particular demand for the quality of raw material. Industrial sectors in which these applications of hemp can be developed are the automobile industry, building materials, defence against erosion and cultivation of valuable crops (Karus, 2004). In all these applications hemp has to compete not only with synthetic materials, but also with all the other fibres that are suitable for these same applications. A second major destination for hemp is for textiles (Ranalli et al., 1999). This sector requires smaller amounts of raw material than that for biocomposites, and puts demands on the quality of the fibre. If the quality needed for producing clothes and apparel is attained however, the fibre has a very high added value.

Hemp for the textile industry However, fibre extraction has always been the main utilization for hemp. Fibres were used as a basic raw material for the production of rope, canvas and clothing (Ranalli et al., 1999). In Europe, hemp reached the maximum cultivated area in the past three centuries. Decline occurred after World War II for several reasons: high-labour cost, introduction of synthetic fibres, association of the plant with illegal narcotics, and the large scale production of cotton.

In the last decade there has been a revived interest in hemp as a renewable resources. In Europe, cultivated areas increased from 2762 ha in 1989 to a peak of 41,682 ha in 1998. Following the 1998 peak, there was a sharp decrease due to reduced subsidies and the introduction of new and stricter European rules for the allocation of subsidies: a minimum threshold in straw yield was required, as well as the liability to demonstrate a processing contract in order to get the subsidies. Consequently, the widespread use of hemp fibres for technical applications, as for example in the automotive or paper industry, did not produce a similar increase in cultivated areas. The main reason was the discrepancy between production costs and the performance of the final product. This discrepancy is no longer compensated for by EC financial support and market competition in the world for raw materials used for technical applications is mainly based on price rather than on quality. Therefore, fibre production in countries with high-labour costs, such as in Europe, can only be profitable if it is aimed at a market producing high added-value products such as textiles or for other specific technical uses. In recent years, several European research projects have been carried out, and others are in progress, to develop new production methods, new processing approaches and, conclusively, to update the entire production chain.

5 If hemp has to play an important role in the textile sector again, it needs to overcome a series of technical constraints, involving the entire sequence of production and utilization: mechanical harvesting, water retting, scutching arrangement (Ranalli, 1999). Up to now, research was done in these fields and a relevant know-how has been reached. In particular, research started in order to develop prototypes able to harvest the hemp plants when they reach heights of 2–4 m, and to cut stems in sections 1.2-m long during harvesting (Figure 3). The aim is to adapt the hemp plant to flax processing equipment, particularly to the scutching machine arrangements. This short-term strategy, provides the possibility to process hemp fibres in factories using the existing flax machines, without requirements for extensive new developments and financing. Moreover, stem fragmentation optimizes the retting process, adapting it to the different plant sections, being the plant composition different along the stem. The retting procedure is of crucial importance in the processing of long bast fibres (flax, hemp, kenaf), affecting the final quality of the fibre. Beside, the different sections of the stem could be aimed at different end uses depending on the different fibre characteristics and content. As an alternative, in Italy the “Canapa Italia Consortium” (www.canapaitalia.com) promoted the procedure called “baby canapa”: intensive sowing (100–120 kg of seeds per ha), followed, when the hemp stems are 1.2-m tall, by spraying with desiccants, generally glyphosate, in order to stop their growth. From that moment, the stems undergo the same initial flax processing methods: pulling, dew retting, drying, storing and scutching. Then, the scutched material can be sent to a spinning factory to be converted into yarn. The advantages of this procedure are clear: plant height is tailored to be processed by the same equipment used for flax. However, the disadvantages are also relevant: the high-cultivation costs, low-straw yield (between 30 and 50% of conventional hemp), the use of chemicals, the poor quality of the fibre and its unevenness due to plant immaturity, as well as the dew retting process which, at Italy’s latitudes, generally is not uniform along the stem and does not lead to a good quality of the fibre (Di Candilo et al., 2000; Liberalato, 2003). Regarding fibre quality, the dominant parameters required in textile applications are fibre strength, fineness and refinability. In order to introduce hemp into the high-quality clothing sector, it is necessary to obtain a degree of fineness allowing the spinning of yarns between Nm 20 and Nm 40. The finer the fibre, the wider its application in clothing and industrial textiles. It is

necessary, therefore, to develop hemp varieties with a smaller fibre diameter. Hemp improvement The performance of hemp in assuring products of the whole plant and end-products relies on insights gained in different fields: agronomy; germplasm recovering and restoration in stable conditions (Forapani et al., 2001); identification of genes underlying the expression of the most relevant traits (de Meijer et al., 2003); integration of conventional and molecular techniques in breeding schemes for the development of new dioecious and monoecious varieties (Mandolino & Ranalli, 2002); harvesting, logistic and processing of the straw (harvesting, post-harvest treatment, decortication and retting); retting procedures (traditional water retting takes much time and is labour intensive, facilities have been created which make retting more predictable, reproducible and less expensive) (Di Candilo et al., 2000); design application (yarn and fabrics produced need to be transformed into high-value, modern end-products). All these fields of research and applications have been highlighted during the symposium on hemp held in Bologna last March. The symposium gathered the main experts of the different fields of hemp research and industrial applications. The basic rationale that supported hemp research in the different fields was the quality improvement of the raw material which affects the quality obtained in each of the successive phases and in the end products. The factors that influence both quality and quantity of the product are numerous: climate, soil conditions, genetic material, sowing time, harvest time, sowing density, addition of nitrogen, and irrigation (Ranalli, 1999). Research has given, and continues to give, new knowledge and new indications that enable the gradual improvement of the quality and quantity of hemp produced. Harvesting and the successive phases certainly require further innovation; the slow development of the mechanisation of the harvesting phase is in fact indicated as one of the causes of the decline of hemp. The total post-harvest processes requires 60–70 days of work per hectare and so mechanisation has the principal aim to reduce the amount of time needed. In this sense the results of developments in mechanisation have been satisfactory. Process innovation should involve all the steps of the production chain. In the first place the genetic improvement of hemp, with its different aims, that can

6 benefit from the continuous development of biotechnology. At present, hemp breeding is facing these objectives: increasing content of fiber and improving its quality, obtaining plants with high efficiency of biomass per hectare, reduction to a minimum of the
9 THC content in plants, obtaining early forms with high yields of seed and good oil quality, maximal stabilization of monoeciousness. Advances have been made in these fields; the effects should be evaluated as a function of the intended end-use, taking into account the harvesting and primary processing techniques. Innovation will therefore have to consider each of the successive phases of the production chain, and should therefore be approached as a multidisciplinary issue. However, the main aspects under consideration should always be quality and environmental impact. As a consequence, research about the plant’s physiology, and the relationships between genotypes, phytotechnique and the environment, is a priority. Also important for innovation is the availability of analytical techniques, able to evaluate the relevant qualitative parameters objectively, rapidly, and at low cost. Relevant qualitative parameters diverge with the end-use of hemp, but apart from the end-use, research involves actors from each successive phase of the production chain. Finally, a relevant aspect of innovation, though not a technical or scientific issue, is the addition of value along the production chain, all the way from raw material to the end-product. Until now the added value has not been enjoyed by the farmers, but by the downstream actors in the production chain. Maybe the best thing to do, in order to re-launch the cultivation of hemp, is to increase the participation of the hemp farmers in the earliest phases of processing, giving them the possibility to get a larger quota of the added value.

Conclusions 1. Since hemp is a multi-use crop, the development of plants for specialized productivity needs an enhanced understanding of metabolic control both in terms of molecular and genetic mechanisms in order to promote a remodelling of metabolic pathways. 2. The progress of the process relies on an interdisciplinary approach in which different disciplines must be organized simultaneously. The symposium provided the opportunity to update research according to the different tasks.

3. A competitive, innovative, and sustainable hemp production depends on innovative varieties, developed by integrating the latest advances in different fields of genomic, proteomic and metabolomic areas. 4. The development and introduction of cultivars suitable for particular trends in hemp use will improve the efficiency and quality of raw material and reduce production costs. 5. The future textile applications for hemp fibres are promising and almost achieved. It will, of course, be necessary for the different subjects of the agroindustrial production chain, which are farmers, fibre producers and product manufacturers, to make a co-ordinated effort to overcome the remaining limitations associated with hemp fibres when used in textile production. 6. The promotion of hemp and other no-food crops for the production of renewable raw materials could provide a significant opportunity to improve diversification in EU agriculture. This special issue, born as a result of the contributions of many speakers who participated in the symposium on hemp last March in Bologna, will try to focus the state of the art of research, innovation and production for all the above mentioned steps and issues. References Di Candilo M., P. Ranalli, C. Bozzi, B. Focher & G. Mastromei, 2000. Preliminary results of test facing with the controlled retting of hemp. Ind Crops Products 11: 197–203. Di Candilo M., P. Ranalli, M. Diozzi & P. Zonda, 2000. Canapa da fibra: Modalit`a colturali a confronto. L’Informatore Agrario 16: 75–79. Forapani S., A. Carboni, C. Paoletti, V.M.C. Moliterni, P. Ranalli & G. Mandolino, 2001. Comparison of Hemp Varieties Using Random Amplified Polymorphic DNA Markers. Crop Sci 42: 1682–1689. Liberalato D., 2003. Prospect of hemp utilization in the European textile industry. Agroindustria 2/3: 147–148. Mandolino G. & P. Ranalli, 2002. The applications of molecular markers in genetics and breeding of hemp. J Ind Hemp 7: 7–23. Meijer E.P.M. de, M. Bagatta, A. Carboni, P. Crucitti, V.M.C. Moliterni, P. Ranalli & G. Mandolino, 2003. The inheritance of chemical phenotype in Cannabis sativa L. Genetics 163: 335–346. Ranalli P., 1999. Advances in Hemp Research. The Haworth Press, Binghamton, New York (U.S.A.), 272 pp. Ranalli P., M. Di Candilo, G. Mandolino, G. Grassi & A. Carboni, 1999. Hemp for sustainable agricultural systems. Agro-FoodIndustry Hi-Tech. 2(10): 33–38. Venturi G., 2004. Le colture da fibra: Alcune nuove destinazioni d’uso del prodotto. Agroindustria 1: 51–55.