Kenaf
Kenaf plant
Kenaf (Hibiscus cannabinus ) is a tropical or subtropical plant of the mallow family that is grown for the production of the same fibers and oil.
- 5.1 kenaf fiber
- 5.2 Kenafsaat
- 6.1 Notes and references
- 6.2 Literature
- 6.3 External links
Features
Kenaf has a taproot. In close stand the plant grows unbranched three to four meters high. The stems are rauhaarig and stachelborstig. Depending on the variety they are green or reddish to purple. The leaves are stalked long and soft hairs. The nickname cannabinus ( hemp -like) can be attributed to the similarity of leaf shape with the hemp. Depending on the variety they are palmately lobed to entire.
The flowers sit individually in the upper leaf axils. They are large, white to yellowish with a dark red spot at the base. The flowers open before sunrise and wither already at noon of the same day. It weighs about self-fertilization. The fruit capsules are hairy edges and fine. They are surrounded by the hardened, spiny sepals. Skip to maturity, the capsules with five flaps and dismissed the 5 x 3 millimeter seeds. These are gray and black wedge-shaped - edged. They contain from 15 to 20% of a semi-drying oil.
The fiber content of the bark is in the flower-bearing part lower than the bottom. He is between 2.5 and 5%. The individual fibers are 1.5 to 11 mm in length (mean 2.4 millimeters ), with a diameter of 12 to 36 microns (mean 20 microns).
Kenaf is diploid with a chromosome number of 2n = 36
Occurrence
Kenaf comes from the Afro- Asian region, is not frost hardy in Central Europe and therefore only annual. However, without frost, the plant may also be perennial. The main growing areas are in India, China and Southeast Asia.
Cultivation
The most favorable conditions are at a temperature between 15 and 27 ° C, so that the potential growing area is of 45 ° north to 30 ° south latitude. During the growth period should fall precipitation in 2.5 to 4.5 months between 500 and 700 mm. As soil sandy loam and clay soils at pH values between 5 and 7 are optimal. In dry periods, the groundwater is sufficient, provided it is not deeper than 1.5 meters, otherwise irrigation is necessary. For fiber formation adequate intake of phosphorus and potassium needed. We recommend: phosphate 60 kg / ha, potassium 120 kg / ha, nitrogen first dose 20 to 30 kg / ha, second dose 50 to 60 kg / ha. Care is usually required only in the first three weeks after sowing. The vegetation period is 70 to 140 days.
For non standortgerechtem kenaf cultivation is sensitive to root rot and anthracnose ( Colletotrichum hibisci ). During growth, 1 ton kenaf binds about 1.5 tonnes of CO2 and thus has one of the highest CO2 absorption rates at all within the plant world.
The harvest takes place after the release of the first five to ten flowers. Immediately after the mowing of kenaf is debarked. The roasting takes eight to 12 days at water temperatures above 24 ° C.
Growing in Central Europe
Kenaf has higher heat demands than the corn thrives best on moderate weed-free soil and is somewhat sensitive to summer drought. He reached in four to five months a height of 3.5 to 4 m. Useful plant parts are stem, which - divided into long fibers and shives in (with short fibers) - similar to hemp. The total yield is about 8 t / ha at a fiber content of 20%. Due to the high climatic claims kenaf little chance in Germany, however, can be given.
The sowing of kenaf takes place in Central Europe in the period from mid-May to early June. The seed rate is 35 to 40 viable seeds per m2, the sowing depth at 3-4 cm. For a mechanical weeding a row spacing of 40-50 cm is required. The time required for the germination bottom temperature is 12 ° C, required for growth is a temperature of at least 16 ° C. Germination is rapid, youth development, however slowly, the elongation growth is in late July, early August. Because of the high temperature requirements kenaf is dependent competitive weak and in an efficient weed control. Weeds are to be controlled in the bud - to 2 -leaf stage, a mechanical control is possible from 15 cm plant height of kenaf. In favorable situations, and in good years a dose of 30 kg N per ha seems to be sufficient to soils with good N- mineralization. The most important disease of gray mold (Botrytis cinerea).
Production figures
Explicit figures for world production of kenaf do not exist. From the FAO kenaf is listed along with other juteähnlichen fiber plants in the category " kenaf and allied fibers" ( kenaf and similar fibers). The juteähnlichen and its use fiber plants is one example Roselle. The adjacent table shows the global production of fibers of the FAO category " kenaf and allied fibers" for the marketing year 2007/08.
Use
Kenaf fiber
When grown for fiber use kenaf, are the fiber yields from 1.8 to 2.5 tons per hectare, in the optimal case at 3.5 tons per hectare. The fiber is made from the bast of the stem, so the kenaf fiber is in a group of bast fibers. The fibers are similar to those of jute, but containing about 5% less lignin, which makes them less sensitive to light. The kenaf fiber consists of 44-57 wt - % of cellulose, 15-19 wt - % lignin, 22-23 wt - % pentosans and 2-5 wt - % ash.
Kenaf is traditionally used for the manufacture of ropes or blind cloth. Newer applications include building materials and the use as an absorbent or as feed or bedding material for livestock. Kenaf is also used for making paper. When attaching to Papierpulpeherstellung the yield is about 20 tons per hectare pulp. Even when fiber cultivation residues are used for pulp production, or they are used as fuel.
Kenaf fibers can also be used as reinforcing fibers for natural fiber reinforced plastics. Like many other natural fibers, kenaf has good mechanical properties at a low density. As kenaf is grown commercially, the fibers are also economically interesting. One of the first products produced with kenaf fibers is a mobile phone housing of the NEC Corporation of kenaffaserverstärktem PLA. When PLA is a biopolymer that kenaf reinforced material is completely biodegradable. By admixture of the kenaf fibers to the plastic to improve the heat resistance and the stiffness could be achieved. Also in connection with polypropylene can be produced natural fiber composites, the very good train and have flexural properties.
A growing area of application of kenaf fibers in the automotive industry; Pioneers of which company Toyota, which first began in 2000 Kenaf inner door lining in the model Toyota Celsior and now kenaf (eg on seat back ) in 27 models, mainly the upper class used for five different vehicle components.
Kenafsaat
When growing for oil or seed extraction yields are at 0.7 to 1.0 tonnes of seed per hectare. The oil of the Kenafsamen but it is used for industrial purposes as well as food.