Kenaf [etymology: Persian], Hibiscus cannabinus, is a plant in the Malvaceae family. Hibiscus cannabinus is in the genus Hibiscus and is probably native to southern Asia, though its exact natural origin is unknown. The name also applies to the fibre obtained from this plant. Kenaf is one of the allied fibres of jute and shows similar characteristics.
It is an annual or biennial herbaceous plant (rarely a short-lived perennial) growing to 1.5-3.5 m tall with a woody base. The stems are 1–2 cm diameter, often but not always branched. The leaves are 10–15 cm long, variable in shape, with leaves near the base of the stems being deeply lobed with 3-7 lobes, while leaves near the top of the stem are shallowly lobed or unlobed lanceolate. The flowers are 8–15 cm diameter, white, yellow, or purple; when white or yellow, the centre is still dark purple. The fruit is a capsule 2 cm diameter, containing several seeds.
The fibres in kenaf are found in the bast (bark) and core (wood). The bast constitutes 40% of the plant. These fibres are long (2 – 6 mm) and slender. The cell wall is thick (6.3 µm). The core is about 60% of the plant and has thick (ø 38 µm) but short (0.5 mm) and thin walled (3 µm) fibres. Since the paper pulp is produced from the whole stem, the fibre distribution is bimodal. The pulp quality is similar to hardwood.
Kenaf is cultivated for its fibre in India, Bangladesh, United States of America, Indonesia, Malaysia, South Africa, Viet Nam, Thailand, parts of Africa, and to a small extent in southeast Europe. The stems produce two types of fibre, a coarser fibre in the outer layer (bast fibre), and a finer fibre in the core. It matures in 100 to 200 days. Kenaf was grown in Egypt over 3000 years ago. The kenaf leaves were consumed in human and animal diets, the bast fibre was used for bags, cordage, and the sails for Egyptian boats. This crop was not introduced into southern Europe until the early 1900s. Today, principal farming areas are China, India, and it is also grown in many other countries such as the US, Mexico and Senegal.
The main uses of kenaf fibre have been rope, twine, coarse cloth (similar to that made from jute), and paper. In California, Texas, Louisiana and Mississippi 3,200 acres (13 km²) of kenaf were grown in 1992, most of which was used for animal bedding and feed.
Uses of kenaf fibre include engineered wood, insulation, clothing-grade cloth, soil-less potting mixes, animal bedding, packing material, and material that absorbs oil and liquids. It is also useful as cut bast fibre for blending with resins for plastic composites, as a drilling fluid loss preventative for oil drilling muds, for a seeded hydromulch for erosion control. Kenaf can be made into various types of environmental mats, such as seeded grass mats for instant lawns and moldable mats for manufactured parts and containers. Panasonic has set up a plant in Malaysia to manufacture kenaf fibre boards and export them to Japan.
Additionally, as part of its overall effort to make vehicles more sustainable, Ford is making the material inside the door – known as the bolster – in part from kenaf. The first implementation of kenaf within a Ford vehicle will be in the 2013 Ford Escape.
The use of kenaf is anticipated to offset 300,000 pounds of oil-based resin per year in North America and reduces the weight of the door bolsters by 25 percent. Weight savings translate into fuel savings for drivers.
Kenaf seed oil
Kenaf seeds yield an edible vegetable oil. The kenaf seed oil is also used for cosmetics, industrial lubricants and for biofuel production. Kenaf oil is high in omega polyunsaturated fatty acids (PUFAs) which are now known to help in keeping humans healthy. Kenaf seed oil contains a high percentage of linoleic acid (Omega-6) a polyunsaturated fatty acid (PUFA). Linoleic acid (C18:2) is the dominant PUFA, followed by oleic acid (C18:1). Alpha-linolenic acid (C18:3) is present in 2 to 4 percent. The PUFAs are essential fatty acids for normal growth and health. Furthermore, they are important for reducing cholesterol and heart diseases.
Kenaf Seed oil is 20.4% of the total seed weight which is similar to cotton seed. Kenaf Edible Seed Oil Contains:
• Palmitic acid: 19.1%
• Oleic acid: 28.0% (Omega-9)
• Linoleic acid: 45% (Omega-6)
• Stearic acid: 3.0%
• Alpha-linolenic acid: 3% (Omega-3)
The most common process to make kenaf paper is using soda pulping before processing the obtained pulp in a paper machine.
The use of kenaf in paper production offers various environmental advantages over producing paper from trees. In 1960, the USDA surveyed more than 500 plants and selected kenaf as the most promising source of tree-free newsprint. In 1970, kenaf newsprint produced in the International Paper Company's mill in Pine Bluff, Arkansas, was successfully used by six U.S. newspapers. Printing and writing paper made from the fibrous kenaf plant has been offered in the United States since 1992. Again in 1987, a Canadian mill produced 13 rolls of kenaf newsprint which were used by four U.S. newspapers to print experimental issues. They found that kenaf newsprint made for stronger, brighter and cleaner pages than standard pine paper with less detriment to the environment. Due partly to kenaf fibres being naturally whiter than tree pulp, less bleaching is required to create a brighter sheet of paper. Hydrogen peroxide, an environmentally-safe bleaching agent that does not create dioxin, has been used with much success in the bleaching of kenaf.
Various reports suggest that the energy requirements for producing pulp from kenaf are about 20 percent less than those for wood pulp, mostly due to the lower lignin content of kenaf. Many of the facilities that now process Southern pine for paper use can be converted to accommodate kenaf.
An area of 1-acre (4,000 m2) of kenaf produces 5 to 8 tons of raw plant bast and core fibre in a single growing season. In contrast, 1-acre (4,000 m2) of forest (in the US) produces approximately 1.5 to 3.5 tons of usable fibre per year. It is estimated that growing kenaf on 5,000 acres (20 km²) can produce enough pulp to supply a paper plant having a capacity of 200 tons per day. Over 20 years, 1-acre (4,000 m2) of farmland can produce 10 to 20 times the amount of fiber that 1-acre (4,000 m2) of Southern pine can produce.
As one of the world's important natural fibres, kenaf is covered by the International Year of Natural Fibres 2009. The first novel to be published using 100% kenaf paper was The Land of Debris and the Home of Alfredo by Kenn Amdahl (1997, Clearwater Publishing Company).
David Brower, former Executive Director of the Sierra Club, in chapter 8 of his semi-autobiographical environmental book "Let the Mountains Talk, Let the Rivers Run: A Call to Save the Earth" (1995, Harper Collins), titled "Forest Revolution," advocated for kenaf paper use and explained its many advantages over wood pulp. The first edition of the book was printed on kenaf paper.
Pesticide and fertilizer use in kenaf crops
Kenaf is considered a hardy plant that requires a minimum of fertilizers, pesticides and water in comparison to conventional row crops.