Keith L. Edmisten, Cotton Extension
North Carolina State University
United States textile industry losses due to contaminated cotton in 1996 were estimated at $5 million. In the past several years, concerns have arisen regarding contaminants in cotton. Current bale marking techniques have made it easier to trace contamination problems to the source and could result in reluctance of buyers to purchase cotton in areas where contamination has occurred. By understanding the seriousness, the causes, and what can be done to minimize the problem, relationships between growers, ginners and textile manufactures can be restored and maintained.
Figure 1. Potential contamination cost of 1 bale of cotton as it progresses through the various stages of processing. National Cotton Council (1990)
Figure 1 shows she seriousness of the problem. The cost incurred due to contaminants in one bale of cotton increases exponentially as the cotton progresses to the finished goods stage. Early detection results in relatively low costs at laydown ($350)whereas if contaminants are not detected early the increase in dollars lost is much higher at the finished goods stage ($350,000).
Several contaminants have been identified and ranked in order of importance by the National Cotton Council of America. They reported that fifty percent of contaminants found in cotton were plastic. These included plastic bags (Figure 2), module covers, tie downs used to secure module covers (Figure 2), and irrigation ditch liners. The most frequently found item was Wal-Mart shopping bags. Twenty-five percent of the contaminated cotton was caused by apparel fibers such as hats, gloves, t-shirts, and cleaning rags. Fifteen percent of the contamination in cotton was rubber that most often originated from doffers moistener pads. This rubber causes tainting of finished goods. Grease and oil accounts for approximately five percent of the contamination. Grease can accumulate on picker bars and break off and stain cotton and excessive use of oils can cause sticky cotton. The last five percent of contaminant comes from various sources including discoloration due to marking modules or bails and residues of barks, grasses, and plant parts. All of these contaminants listed above can result in reduced spinning quality and inferior finished goods (Figure 3)
Figure 1. Loose tie down strings on modules and plastic bags not picked up at harvest are both commonly the cause of contaminated cotton. Source-Cotton Incorporated.
Figure 2. If not detected early, the presence of contamination in raw cotton will lead to cotton of poor spinning quality and inferior finished products. Source- Cotton Incorporated.
Simple measures can be taken to reduce the levels of contamination found in North Carolina Cotton. One of the simplest is walking your fields and removing debris prior to harvest. This is of particular importance where fields are close to highways where trash may be thrown out of car windows. It is also of particularly important to check fields for debris when storms with high winds may have blown debris into fields. Several ways to avoid cotton contaminated with plastic is to replace old plastic tie downs and ropes with newer cotton types or at least make sure they are in good condition, and make an extra effort to remove all covers and tie downs before the cotton reaches the suction or module feeder. Keeping all hats, gloves, and cleaning rags away from gins and seed cotton can help avoid contamination due to apparel fibers. Problems with contamination due to rubber can be minimized by adjusting the spindle to doffer clearance to the manufacturers recommendations and by replacing old worn doffers with new non-contaminating parts. Manufacturer recommendations should also be followed regarding the levels of oil to be used. Picker heads should be cleaned weekly during the harvest period and motor and diesel oil should never be used in the moistening system. Other practices that will reduce levels of contamination in NC cotton are using non-contaminating markers on bales and avoiding any production practices that can produce excess bark.
The cotton industry as a whole has a responsibility to lower contamination. High quality cotton will improve its competitiveness with manmade fibers and maintain its share of the market. Lastly, production of non-contaminated cotton will maintain relationships between growers, ginners, and textile companies.
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