Coir (coconut fiber) usage has become very common among professionals in various industries due to its versatility. In comparision to the remarkable reputation coir has established in the horticultural and agricultural industry, coir is relatively new to the landscape architectural and erosion control industries. Recognition of coir in the erosion control and landscape architectural industries has come from the fact that it is an abundant, renewable natural resource with an extremely low decomposition rate and a high strength compared to other natural fibers. In traditional erosion control blanket applications, coir blankets are well known for superior performance compared to other organic blankets. In most of these applications, long-term tensile strength in the blankets is not a critical design criterion. The rapid growth of environmentally concerned Landscape Architects and design engineers with their innovative designs has increased coir use in the erosion control industry. These designs incorporate coir products as structural components in the construction. This design expects woven coir blanket to provide resistance to shear stresses developed by the high velocity water flow since installation to development of mature vegetation. Therefore, high strength retention or slow rate of degradation of coir products in field applications fulfills the design expectations in these types of bioengineering designs.

It is normal for engineers and Landscape Architects to look for more information relative to their design criteria. Because of this need, there is a growing concern regarding durability and strength retention in field applications of coir erosion control products. The intent of this article is to discuss the contributing factors for strength retention and durability of coir in field applications and to encourage the use of coir products in the landscape architectural industry.

Coir is typically processed from ripe coconut husks which are dark brown in color and have been retted in freshwater for at least six months. The retting process of coconut husks acts as a curing process for fiber in coconut husks. Curing in freshwater increases resistance to UV (ultraviolet) degradation and also increases the flexibility of processed fiber without causing deterioration. During traditional processing, coconut fiber from cured husks is separated by skilled labor into grades depending on the length of fiber. The longer and stronger fibers are called bristle coir, and the shorter and thinner fibers are called mattress coir. Coir processed from ripe husks cured in freshwater appears dark brown in color.

When the ripe coconut husk is dry, it serves as an excellent firewood. As a result in countries with a high population density, most of the ripe brown coconut husks are used for firewood and the coconut husks available for processing coir are unripe green husks. Unripe green coconut husks are usually soaked in brine to make the coir processing easier. An economical way to soak coconut husks in brine is to use lagoons. Coir processed from lagoon-cured green husks is light brown or white in color. This coir is referred to as white coir. Salt in lagoon water makes it easier to process unripe green coconut husks. Needless to say, fibers in coir processed from unripe, green coconut husks are not fully mature compared to fibers coming from ripe brown coconut husks. Lagoon-cured brown coconut husks also produce white coir. Salt in lagoon water acts as a bleaching agent that can weaken coir used in field applications. White coir is, therefore, much weaker than brown bristle coir processed from ripe brown husks.

High demand for coir has led to new coir processing methods which may produce a weaker product than the traditional freshwater-curing process. Mass-scale coir manufacturers recently implemented coconut husk defibering machines. These machines can separate fiber from uncured or partially-cured husks or unripe green husks or ripe brown husks. Advantages of these defibering machines to the coir producer include reduced expense and faster production rates since skilled labor is not required and the six-month curing time is reduced or eliminated. Some of these mass-scale coir manufacturers go further and soak unripe green husks in a bacterial solution and process for white coir within 72 hours of curing. These machines do not separate fiber into bristle coir and mattress coir, but rather yield a mixture of long and short (strong and weak) fibers. A quick way to produce white colored coir for decorative coir products is chemical bleaching of the coir. In chemical bleaching, brown or light-brown colored coir is treated with chemicals to remove the brown color. Chemical bleaching may have some negative effects on the strength and durability of coir. On the other hand, coir from the ripe husk is well known as a natural fiber and the rich brown color is more attractive than a white color for erosion control applications. Most importantly, addition of chemicals to natural coir may create a potentially hazardous situation in many environmentally sensitive applications. There are four types of processed coir; Landscape Architects should understand that the coir processing method has a direct link to the appearance of the processed coir.

Experience with coir in the agricultural industry has shown that only the traditional brown bristle coir which is processed from ripe brown coconut husks cured for at least six months in freshwater has performed well in applications where durability and strength retention are critical for satisfactory field performances. With these facts of coir in mind, Landscape Architects are now beginning to consider the material's advantages to the landscape industry. Landscape Architect Dean Wilson of the King County Department of Transportation explains that the advantages of coir include, "Cost advantage and availability. We've used other products that are hard to install. Coir provides superior strength than some of the geotextiles that are available today." President George Junkin of American Land Concepts agrees, "Coir logs, in addition to erosion control, provide structural stability for a period until the roots get established, whereas other methods don't provide that."

The most common question today in soil bioengineered erosion control landscape designs regarding coir product usage involves the rate of degradation and strength retention of coir products in field applications. This issue is basic to total quality control where high quality raw materials and production standards build high quality into the final product. It is time for erosion control and landscape architectural industry professionals to look into the findings of other industries such as horticulture and agriculture for their valuable experience with coir. Such experience will guide the landscape architectural and erosion control industries in making better use of coir products, and also will help to identify problems and failures in coir products without blaming the entire coir industry. It is also profitable for industry professionals to learn the real facts about coir instead of accepting unfounded or untrue information published solely for purposes of marketing coir products. Most importantly, understanding the contributing factors to coir durability and degradation will help to develop industry standards for high quality coir products. In today's environmentally sensitive soil erosion control and landscaping designs-- when a slow rate of decomposition and a high retention of strength is important in field applications-- it is wise for Landscape Architects to look for the brown bristle coir raw material in coir products. lasn