Rural Industries Research & Development Corporation

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Introduction

These crops are grown specifically for fibre production but there are a number of other crops from which useful plant fibres are produced as a by-product. These include the cereal straws of wheat, sorghum and rice, bagasse (the residual fibrous residue left after the extraction of sugar from sugar cane) and the straw from linseed crops. All these materials are used for the production of building boards and paper.

In this chapter we discuss the potential for the plant fibre crops, other than cotton, jute and abaca. Cotton has been excluded as it is now a major established crop in Australia. Of the other major fibre crops in world trade jute and abaca appear to have limited potential for production in Australia. Jute requires deep fertile alluvial soils and hot humid conditions and there appear to be only limited areas in Australia where it could be grown in competition with current crops. Abaca could be grown where bananas are grown but production of abaca fibre is very labour intensive and difficult to mechanise. Also, cyclones would pose a serious threat to production.

The world production of plant fibre crops for textile use has steadily declined during the past five decades. This is the combined result of advances in cotton production, the development of synthetic fibres, such as nylon and polypropylene, and a decline in the use of sacks for agricultural produce. However, a new use is emerging for some of the plant fibre crops. All the traditional fibre crops can be pulped to make a range of papers comparable in quality with those produced from wood. With the decline in forest resources around the world and an increasing demand for paper, non-wood fibre crops could well be used for this purpose.
 

Markets and marketing issues

In 1994-95 Australia imported 191, 000 tonnes of chemical pulp and 1.3 million tonnes of paper and paper board with a total value of about $1.5 billion. At the present time all Australian pulp and paper is made from wood, particularly hardwoods. Currently, about 8% of the world’s production of pulp is produced from non-wood materials, including cereal straws, bamboo, bagasse and fibre crops such as kenaf, industrial hemp and sunn hemp.

In Australia the pulp and paper industry has shown little interest in the use of non-wood fibre crops as a feedstock for paper making. However, non-wood fibres are widely used for paper making in India and China and the Japanese pulp and paper industry has recently said that it wishes to produce 10% of its 15 million tonnes from non-wood materials by the year 2000.

Work in the USA has shown a wide range of uses for the bark and core fractions of kenaf, one of the most promising of the stem fibre crops. For the bast fibre the end-uses include paper, textiles, non-woven earth mats and as a fibreglass substitute. For the core the end-uses include animal bedding, kitty and chicken litter, oil-absorbent mats, particle board (acoustic tiles) and as a component in potting mixes. Similar end-uses could be expected for the other bast fibre crops.

Sisal and henequen are the source of leaf fibres which were traditionally used for twines but are now being used to make high-strength reinforcing pulps which can be used to strengthen recycled paper and paper bags, such as cement bags.

The fibres of jute, kenaf, roselle, sunn hemp, industrial hemp, ramie and flax are present in the bark fraction of the stem and are referred to as bast fibres. The bast fibre crops appear to offer the best prospects for commercial production in Australia with pulp and paper production as the principal end-use. However, other end-uses could be established as subsidiary niche markets. Local or export markets would need to be established for pulp and paper production and it seems likely that the initial development would require an overseas pulp and paper producer. Initially, the enterprise might start by exporting the raw product for processing, but later it should be possible to establish a local pulping facility.

Ramie produces a premium fibre that is used in fine linen and other clothing fabrics. If production and fibre extraction could be fully mechanised there could be a good niche market for the fibre for textile production with any waste fibres being used for high-quality specialty papers.

Production requirements

Kenaf, roselle and ramie are not particularly demanding in their soil requirements and could be grown on a range of soils under dryland or irrigated conditions in the semi-arid areas of NSW, Queensland and the Northern Territory. Sunn hemp could also be grown in these areas but grows best on well-drained, alluvial soils with a sandy loam or loamy texture. Sisal and henequen are cactus-like plants capable of growing on a wide range of soils in the semi-arid tropics and sub-tropics. However, they require a well-drained soil and will not tolerate waterlogged conditions.

The growing of hemp is illegal in all Australian States and imports of seed and hemp products are controlled under the Commonwealth Customs Act 1901. Australia is signatory to a number of United Nations Treaties which refer to international drug controls. Hemp is banned because the leaves of the plant contain the psychotropic drug tetrahydrocannibinol (THC). Industrial hemp is a form of hemp which has been selected to contain less than 0.35% of THC on a dry weight basis. The State Governments in Tasmania, South Australia, Victoria, Western Australia and New South Wales have in recent years all granted licences for experimental sowing of industrial hemp using seed of low-THC varieties imported from Europe. The Queensland Government has recently announced that it will also issue licences for experimental sowing of low-THC industrial hemp. The results of the hemp trials conducted to date in Australia have generally been disappointing as most varieties have given low yields because of early flowering.

Varieties

Kenaf is considered to be the most promising of the bast fibre crops for the production of paper pulp and a large collection of varieties is held in storage at the Australian Tropical Crops Genetic Resource Centre, QDPI Research Station, Biloela, Queensland. Studies to date have shown that cv. Guatemala 4 is well suited to conditions in northern Australia with Everglades 71 well suited to growing conditions in temperate Australia.

Since production of industrial hemp can only be done under licence and varietal trials have been limited, there are no varieties which can be recommended.

Agronomy

Industrial hemp: Hemp is adapted to mild temperate climates with an annual rainfall of at least 700 mm. It is intolerant of waterlogging and grows best on a well drained clay loam or silt loam where pH is neutral or slightly alkaline. The crop is sensitive to drought and requires ample water especially during the first six weeks of growth. The optimum temperature range for growth is 14ºC to 17ºC but the crop will survive short periods of frost. Plant population affects both fibre yield and quality and the optimum plant population appears to be about 900,000 plants per hectare. Sowing date is crucial and should be chosen to maximise the rate and duration of vegetative growth; trials conducted in southern Australia suggest an optimum sowing date of about mid-September.

Good weed control is necessary, especially in the early stages of growth but unfortunately no herbicides are registered In Australia for use with hemp. As hemp produces a large quantity of biomass it has a correspondingly large requirement for nutrients. While the actual requirement will depend on soil nutrient content and the expected biomass yields, European studies suggest that application rates of N, P and K should be about 100-130, 35-50 and 110-140 kilograms per hectare respectively

Sunn hemp: Sunn hemp grows best in the tropics and sub-tropics on well drained alluvial soils with a sandy loam or loamy texture. The optimum plant population is considered to be about 500,000 plants per hectare with 30 cm between rows and 6 cm between plants. This would require a sowing rate of about 25 kg/ha. Cultural requirements are similar to those for kenaf and roselle.

Flax: Flax and linseed are the same species but differ in growth habit. Seed flax can be grown under a fairly wide range of conditions but fibre flax needs abundant moisture and cool weather during the growing season. It grows best on well drained loams and clay loams. It is intolerant of salinity and soil pH should be between 5 and 7. Fibre flax requires a clean, smooth, firm seedbed. It is a temperate crop and is sown as soon as possible in the spring. The seed is drilled to a depth of about 2 cm and, depending on the variety, 80 to 110 kilograms per hectare are required. Good weed control is essential as the seed is small and early growth is slow. The crop does not have a high requirement for nutrients but the root system of flax is not extensive and so an adequate level of easily assimilable nutrients is needed.

Ramie: Ramie requires a warm, humid climate with annual rainfall or irrigation of at least 1000 mm spread fairly evenly over the year. While sensitive to waterlogging, ramie is tolerant of soil type but prefers slightly acid conditions with pH in the range of 5.5 to 6.5. Ramie is a perennial having a useful life of 7 to 20 years. It is usually propagated from rhizomes or stem cuttings planted every 30 to 50 cm in rows that are 70 to 80 cm apart. Ramie is usually harvested by hand two or three times per year but under good growing conditions up to six harvests are possible. The highest yield is usually attained in the third and fourth years and maintained until the about the sixth year. For high production a high application rate of plant nutrients is required, particularly of N, P and K. The return of the tops and waste material can substantially reduce the need for added nutrients.

Sisal and henequen: These two species have similar cultural requirements. They are both fleshy perennials with a productive life of 6 to 20 years. The plants consist of a short, thick stem carrying a rosette of long fleshy leaves which are straight and pointed. Both species are stoloniferous and produce shoots from the stolons, known as suckers, which can be used for propagation. However, propagation is usually by means of bulbils which are small buds that develop in the axils of the flower stalk after flowering. The suckers or bulbils are grown on in nurseries until they are about 50 to 70 cm high and are then planted about 1 metre apart in rows 3 to 4 metres apart. Planting is usually done in advance of the seasonal rains when the soil is dry. Rooting is shallow and most roots are concentrated in the upper 40 cm of soil. Permeable sandy loam soils containing some lime are preferred but both species will grow on well drained clay soils. Nutrient requirements will depend on the level of soil fertility and the yield of the crop. Both crops have a high requirement for calcium, nitrogen, potassium and magnesium.

Pest and disease control

In hemp trials conducted in southern Australia there have been few problems with disease but some problems were experienced with lucerne flea, Helicoverpa spp and black beetle. Both sisal and henequen appear to be free of disease and insect pest problems. Ramie is reported to be subject to a number of pest and disease problems in China, the main producer of ramie fibre. However, no problems were experienced in the limited trials conducted in Queensland.

Harvesting, post-harvesting 
treatment and processing

A feature of the stem material of all bast fibre crops is that it consists of two components: bark and core. The bark, which usually comprises about 30 to 40% by weight of the dry stems, contains the long fibres that are used for the production of textiles and high quality paper. The core also contains fibres but these are short and can only be used for low strength pulps and papers. For some types of paper, such as newsprint, both the bark and the core material can be pulped together. For others, it is preferable either to use only the long bast fibre or to pulp the bark and core fractions separately and then blend the pulps back in varying proportions.

Where textile fibre is being produced from kenaf, roselle and sunn hemp the stems are cut at the base, bundled and, after a short period of field drying to allow shedding of the leaves, placed in water for several weeks. During this process, which is known as retting, microbes decompose the non-fibrous material surrounding the fibre bundles so that the fibre bundles can be loosened for extraction. This process is labour intensive and leads to serious contamination of waterways. Attempts to fully mechanise the process have not been completely successful and are generally expensive, making the final fibre non-competitive with cotton and synthetics.

The quality of flax fibre is very dependent on the timing of harvesting, which is generally done when two-thirds of the stem has turned yellow and the leaves have shed. This is usually about one month after the appearance of the first flowers. The plants are generally pulled by hand and allowed to dry in the field. They can also be dew-retted in the field where humidity is high or can be water-retted in ponds. After retting, the plants are dried and the fibre is separated at special scutching mills.

Both sisal and henequen are usually grown in developing countries where labour is cheap and they are harvested by hand. Sisal has a terminal spine which is removed during harvesting. Henequen has marginal spines which make manual harvesting more difficult than with sisal. The rosette pattern of growth makes it difficult to mechanise harvesting. The first harvest is usually done when leaves 60 cm or more in length begin to touch the ground. Harvesting is done at intervals of 10 to 12 months with 20 to 25 leaves being left on the plants after each cut. For paper-making the fibres of sisal and henequen are extracted by first cutting the leaves transversely into pieces about 50 mm long and then passing them through a hammer mill. The fibres are then separated from the juice and residual cell material and dried.

Potential use of non-wood 
plant fibres in Australia

Flax offers the greatest potential as a textile fibre and its fibres have a well-established reputation for length, fineness and durability. Australia imports small quantities of flax for blending with cotton for furnishing fabrics, sheets and canvas, and for making horse rugs. Flax is still commercially grown and processed in Western Europe into fine apparel and linen, although the industry there suffers from a lack of investment in research and development and of modern processing equipment.

Ramie is also suitable for apparel applications and has been imported into Australia in blends with cotton for jeans fabric. It has also been blended with wool for the production of coarse woven fabrics.

The best potential for industrial hemp appears to be for textile fibre and it could find successful markets in applications similar to flax. In prepared form it would attract a price of about $3500/t and preliminary price calculations suggest that it would be profitable to grow and process in Australia at this price. Hemp has similar textile processing requirements and physical characteristics to flax although the hemp fibre is shorter and coarser than flax, making it less versatile. The market for hemp and flax textile fibre in Australia is relatively small, probably less than 300 tonnes per year. If a hemp textile processing facility was set up in Australia, it should be an industry focused on the export market. As the initial quantities of hemp fibre for textile use in Australia are likely to be small, textile fibre production should probably be secondary to its use for the production of paper pulp or building products. Alternatively, hemp fibre could be grown in Australia under contract for export overseas.

Pulp and paper. The process of pulping involves the reduction of the lignocellulosic material to individual fibres while paper making encompasses the various stages of forming the pulp into a sheet of paper or paper board. Conventional pulping comprises three main categories; chemical, semi-chemical and mechanical. The first uses chemicals to dissolve the lignin that binds the individual fibres together while the third uses mechanical forces to separate the fibres. Semi-chemical processes use a combination of chemical and mechanical processes. Chemical processes are used to produce high quality pulps while mechanical processes are used to produce the lower quality pulps, such as those used to make newsprint.

A feature of all the traditional non-wood fibre crops is that the extracted fibres can all be used to produce high quality, high strength paper and paper pulps. The pulps can be blended with lower quality pulps to improve their strength characteristics or they can be used alone to produce high value papers such as banknotes, film and insulating papers. Work undertaken in the USA in the 1950s and 1960s demonstrated that the whole stems or the separated bark of the fibre crop kenaf could be used to make a range of paper products that had characteristics comparable with those produced from wood fibres. Both the stem material and the extracted fibres are now being used to produce pulp and paper in the USA, Thailand, India and China.

Preliminary assessments of the costs of growing kenaf in northern Australia suggest that it could be produced and marketed for pulping at prices competitive with those currently being paid for hardwood chips being exported from Australia to Japan. Similar assessments for the production of industrial hemp in southern Australia suggest that its potential as a feedstock for the production of paper and particle board is low. Woodchips are currently available at one-third to one-half the price of hemp when prices are compared on the basis of the cost per unit mass of fibre. The advantages which hemp may have because of its longer and stronger fibre are outweighed by the need to cut the fibre to a length of about 2.5 mm to prevent clumping of the fibres during pulping and the almost negligible value of the core material.

Building products. Plant fibres are currently used in the USA as a substitute for wood chips in the production of particle board. They can also be used for insulation in houses. When there was a scare some years ago that rock wool was unhealthy because the particles of the glass fibres could lodge in the lungs, there was some interest in developing a cellulosic fibre insulation batt as an alternative to fibreglass batts. However, a fibrous batt is effective only if its constituent fibres are very thin and evenly dispersed – an expensive process which is likely to make such batts non-competitive with fibreglass batts.

Sisal is used to a small extent as a reinforcing fibre in plaster-boards and decorative plaster shapes in the building industry but cheaper, chopped glass-fibre matting is replacing it. However, some users continue to prefer sisal as they consider it to be easier to handle and less health threatening than fibreglass.

Other end-uses. Sisal tow is currently being imported into Australia at about AUS$500/t in the form of fibres one to two metres long for the manufacture of twine or rope. Tow is the fibre removed during the combing and brushing of the extracted fibre. However, the use of sisal for rope and twine is steadily being replaced by polypropylene and nylon. Small niche markets exist for sisal twine under eco-friendly farming systems but the declining demand can be expected to be met increasingly by imports of the finished product. Sisal is used to a limited extent as mattress and upholstery stuffing and here it competes with recycled textile waste fibre.

Australia imports jute ‘caddy’ at about AUS$300/t for use in carpet underlays or in soil matting for weed and erosion control and revegetation. Jute caddy consists of the short waste jute fibres collected during the processing of the longer fibres to yarns. Jute carpet underlays compete with recycled rubber and foam products and are preferred in industrial applications. Increasing interest in environmental restoration can be expected to lead to an increasing demand for soil matting but prices are very low and soil mats compete with a range of bark products and hydro- and straw mulch applications.

Kenaf bast fibres are comparable with those of jute and both are too coarse to be used for apparel. However, they are used widely for sacking and carpet backing. Kenaf fibre could be used in soil mats in semi-processed form but this is an extremely low-value application, competing with mulch.

The potential of industrial hemp to substitute for sisal and jute is small because, although suitable, it would be considerably more expensive after taking into account growing and preparation costs and the likely level of waste.

The use of hemp as a substitute for glass fibre as a reinforcing material is unlikely to be cost-effective and its non-uniform characteristics would be a disadvantage. All non-wood fibres vary because of climate, differences between individual plants and the preparatory processing. These variations make the development of rigorous strength standards difficult. The use of hemp as a filler compound in plastic products is also unlikely to be cost-effective, unless there is a need for recyclable plastics, in which case hemp would have to compete with cotton fibre and recycled cotton fibres, which are considerably cheaper.

Economics of production and processing 
of non-wood fibres for pulp and paper production

If the raw stem material was being exported for pulping it would need to be compressed into a bale, briquette or pellet to facilitate transport and movement into or from a ship or mill. The costs of producing the pellets etc, transporting them to a port and loading them onto the ship would need to be such that the total cost of the product was cost-competitive with wood chips which are currently being exported from Australia at about AUS$130 per dry tonne.

Key contacts

Dr Stuart de Jong
Planning and Managing Projects Pty Ltd
Suite 15, Level 2
56-62 Chandos St
St Leonards, NSW 2065
Phone: (02) 9439 6545
Fax: (02) 9439 7597
(Expertise in textile use of non-wood fibres).

Key references

Hazard, W.H., Norman, K.L.. Wood, I.M. and Garside, A. L. (Eds) 1988 Kenaf production in the Burdekin River Irrigation Area Queensland Department of Primary Industries, Information Series Q188022.

Kirschbaum. M. U. F (Ed) 1990 Proceedings of Workshop ‘Development of a kenaf industry in Australia’, Brisbane 6–7 February 1990. Bureau of Rural Resources Proceedings No. 9. Bureau of Rural Resources, Canberra.

Wood, I. M. W. (1997) Fibre Crops: New opportunities for Australian agriculture Queensland Department of Primary Industries, Brisbane, Information Series Q197023

Wood, I.M. and Stewart, G.A. (Eds) 1981 Proceedings of Conference ‘Kenaf as a potential source of pulp in Australia’ Brisbane 28-29 May, CSIRO Division of Tropical Crops and Pastures, Brisbane and CSIRO Division of Chemical Technology Melbourne.

*About the authors