Hibiscus cannabinus, which is commonly known as kenaf, is a annual or biennial herbaceous plant that is grown to heights of 12 to 18 feet in as little as 4 to 5 months. Kenaf can produce 5-10 tons of dry fiber and core per acre and typically does not require treatment with herbicides or pesticides. The kenaf plant is believed to have originated in Africa or Asia and has been cultivated for its fiber in India, Bangladesh, Thailand, and Egypt for thousands of years. Kenaf fiber, which is frequently referred to simply as “knaft,” has traditionally been used in manufacturing rope, twine, clothing, rugs, and paper. Today the kenaf plant is also being commercially cultivated in the Untied States.
The kenaf plant is comprised of two distinct types of different materials. These materials include an outer fiber and a core. The outer fiber is frequently referred to as simply the fiber and is sometimes called the bast or the bast fiber. The bast accounts for about one-third of the plant by weight. The core is a low density woody type material while the bast is a much lower density fluffy type fiber of high tensile strength. As harvested, the bast fibers tenaciously adhere to the core. In a typical harvested kenaf crop, the core is slightly tapered from bottom to top and has a small diameter at the top in the range of 0.25 inch to 0.5 inch.
The core and fibers have distinctly different uses and must be separated before they are suitable for these different uses. The core is useable as animal bedding, oil-absorbent material for oil spill cleanup, potting soil, kitty litter and particle board or other similar construction materials. The most promising high volume use of bast fibers is in paper manufacture. Another potential high volume use is in the manufacture of fiberboard used in automotive door panels and the like. The economics of using bast fibers in such high volume applications is attractive because the cost of the cultivated crop compares very favorably to the cost of timber which is the conventional source of fiber used in paper and fiberboard production.
U.S. Pat. No. 5,970,582 discloses a method of separating kenaf into its constituents of fiber and core comprising the steps of delivering lengths of kenaf onto a periphery of a saw cylinder comprising a multiplicity of spaced apart teeth; rotating the saw cylinder and snagging the fiber on the teeth, moving snagged lengths of kenaf into contact with a grate and delivering pieces of core through the grate thereby separating the core from the fiber; and removing the fiber from the saw cylinder.
As has been noted, kenaf core is an oil-absorbent material that is used for oil spill cleanup. For instance, U.S. Pat. No. 5,271,691 discloses using kenaf core particles for adsorbing oil spills on water and on dry surfaces. The kenaf used in the oil cleanup technique of U.S. Pat. No. 5,271,691 can be comprised entirely of core material. However, the teachings of this patent also indicate that mixtures containing 90% core and 10% bast can also be used. U.S. Pat. No. 5,271,691 further indicates that in floor sweeping applications that it is preferable to utilize a mixture containing 80% core material and 20% bast.
Particles or pellets of clay are also commonly used as an absorbent for spilled oil. Clay is relatively inexpensive and can be used to absorb oil that has been spilled onto the ground and other hard surfaces, such as concrete and asphalt. However, clay pellets cannot be used to cleanup oil that has been spilled on water. This is because clay is more dense than water and sinks rather than floating on the water's surface. Oil saturated clay pellets also tend to disintegrate in cleanup operations when attempts are made to recover them by sweeping. Thus, using clay as an absorbent for recovering spilled oil can be a messy procedure. Another drawback associated with using clay pellets as an absorbent in oil cleanup operations is that disposal of the oil saturated clay pellets also presents a disposal problem. For example, oil saturated clay pellets will not burn and there is no simple way to recover that oil from the pellets. Accordingly, the oil saturated pellets are typically discarded into a landfill which leads to other undesirable environmental issues.