By W. Stanley Anthony, Supervisory Agricultural Engineer, Cotton Ginning Research Unit, Agricultural, Research Service, U. S. Department of Agriculture, Stoneville, MS

ABSTRACT

Short fiber content in ginned lint can be dramatically reduced with technology developed by the Cotton Ginning Research Laboratory (CGRL) of the USDA and others. These dramatic improvements in short fiber are sufficient to meet current textile industry demands. Many years of ginning research have consistently demonstrated the impact of each ginning machine on the fiber quality parameters of numerous varieties of cotton as measured by the existing cotton classification system as well as other parameters that are very important to the textile industry. The impact of the moisture content while ginning and cleaning cotton has also consistently illustrated its effect on fiber qualities. A computerized gin process control system (CGPCS) is now available to utilize this information to optimize drying and cleaning. Farmer profits are also increased over $20 per bale. New lint cleaning technology has also been developed to reduce fiber damage and fiber loss during gin processing, and to increase farmer profits.

INTRODUCTION

Textile mill concerns with the quality of cotton fiber produced in the United States include fiber quality factors such as short fibers, neps, seed-coat fragments, and fine trash. These factors are not included in the existing classification system for cotton. Adequate knowledge is now available to improve these quality factors should the industry provide clear communication of its interest in resolving these quality issues through the market process.

Research by the CGRL at Stoneville established the basic ginning and cleaning characteristics of many of the cotton varieties currently grown in the United States and has also established their fiber quality characteristics after ginning and cleaning as shown in Table 1 (2, 22). Some varieties contain twice as many short fibers as others. Consideration must also be given, however, to yields and market value to ensure acceptable farmer profits. No variety consistently exhibits the best levels of short fiber content and maximum farmer profits. Thus, acceptable compromises must be considered. For one study of cotton varieties which is consistent with the results from numerous others, short fiber content by weight based on the Peyer AL101 instrument ranged from 4.9% to 11.5% (22). These varieties were all produced under common cultural practices and ginned identically.

In another study comparing the impact of moisture and cleaning machinery at the gin, both had a major influence on short fiber. Low moisture content during gin processing increased short fiber content over 50% (Table 2). Different machine treatments impacted short fiber content by 55%. For the same study, strength was reduced from 29.8 to 27.7 grams per tex by processing at low moisture (Table 3).

Armed with a full spectrum of knowledge concerning the response of fiber quality characteristics to gin machinery and moisture, varieties that exhibit the most favorable characteristics can be selected for planting. After the varieties are selected, good production practices must be followed to ensure that the highest quality fiber is available for harvesting. Since fiber degradation begins in the field, moisture during harvesting and storage must be controlled within acceptable levels. Recently patented USDA sensors to measure the moisture content during harvesting and moduling can be used to minimize fiber degradation (19, 25).

These same moisture sensors can be coupled with adequate software and instrumentation to accurately control cotton moisture content during the drying process (24). The response of cotton to various combinations of gin cleaning machinery and drying is well documented in terms of current manual and High Volume Instrument (HVI) classification (3, 9, 10). Sound relationships also exist for short fiber content. Thus, these parameters that are of major concern to segments of the textile processing industry can also be optimized. Research has consistently shown a 25% to 75% reduction in short fiber content when the drying and cleaning processes are properly controlled (3, 10). Intelligent processing of cotton at the gin can control the negative impact on fiber quality and optimize monetary returns. This technique provides a method to influence the fiber quality characteristics desired by the marketing and/or textile industry. For example, this means that for a given cotton short fiber content by weight can be reduced from levels of 12% to levels of 6%. By selecting certain varieties and ensuring that fiber quality is maintained before ginning, and using optimum gin treatments, short fiber content can be reduced to levels less than 5%.

Integration of the knowledge of the response of cotton to various gin cleaning and drying treatments is accomplished with an intelligent process control system developed by the CGRL (1, 11, 14, 16, 20). The system integrates varietal characteristics with the operational and performance characteristics of gin machinery and the market price schedule for cotton as well as the requirements of the textile industry, and makes the optimum decision in order to satisfy the requirements of all parties. These technologies provide the basis for a quantum leap in ginning and subsequent improvement in fiber quality characteristics. Simply put, this technology allows ginners to modify the cleaning sequence and drying level for cotton based upon its needs. The ginning treatment can be changed every few seconds in an automated fashion without interrupting or interfering with the ginning process.

The patented CGPCS includes automated mechanisms to collect samples of cotton throughout the gin process and evaluate the fiber quality characteristics of those samples (4, 5, 6, 7, 8). Components of the CGPCS also include 1) the capability to automatically redirect the flow of cotton in a ginning system to use or not use various cleaning machines, 2) computer software to optimize the processing of cotton based upon analysis every three seconds, and 3) the capability to automatically calibrate electronic sensors such as those commonly used to measure color and trash (12, 18).

The stickiness of cotton caused by entomological sugars can also be measured continuously online during the ginning process, thereby providing an indication of the stickiness of cotton as well as an indication of the level of mediation required during gin processing to reduce potential problems at the textile mill; this technology is also covered by a USDA patent (15, 17).

Experiences at commercial gins have indicated average savings in excess of $20 per bale for the farmer (20, 21). Experience at the textile mill level with processing this "gently ginned" cotton indicates that the textile industry has far more to gain than the cotton farming segment of the industry (23, 26). When these technologies are fully implemented in the U. S., farmer profits can be increased by over $400 million annually based on a 20 million bale crop. Additional profits for the U.S. textile industry will equal or exceed that amount.

 Much of the spindle-harvested cotton in the United States can be processed optimally with the computerized process control system; however, the initial condition of some of the cotton will still require extreme drying and cleaning in order to meet current marketing requirements and not penalize the cotton farmer excessively. The same is true to a lesser extent for stripper-harvested cotton which has as much as five times more foreign matter initially and requires more cleaning than spindle-harvested cotton.

 Several of these technologies are licensed to Zellweger Uster for implementation in the cotton industry. In addition to the technologies licensed exclusively or non-exclusively to Zellweger Uster, other patents are awaiting the licensing process.

 For instance, the saw-type lint cleaner which is currently required to comb, blend, and clean cotton fiber after it is separated from the cottonseed is a major contributor to short fiber content. An improved lint cleaning machine has been developed at the CGRL and is currently in the patenting process (13) and should be available to the cotton industry in 1999. This new device will reduce short fiber content and will decrease fiber loss relative to the conventional saw-type lint cleaner by 50% or about 10 pounds per bale. Comparisons of two versions of the experimental lint cleaner with other cleaning equipment such as the air-jet and saw-type lint cleaners suggest improvement in AFIS short fiber content by 25% (Table 4). Textile industry experience with fiber produced from this cleaning device has been exceptionally good (26, 27).

Other USDA developments such as the belt dryer, stick machine, and coupled gin-lint cleaner are also capable of improving fiber quality (28).

In summary, implementation of these technologies by the ginning industry simply requires support of the textile industry in the marketing process.

Table 1. Performance of 37 cultivars in the Early Maturing Cotton Cultivar Test at Stoneville, MS, in 1994 that includes length distribution, neps, and seed-coat fragment means for Bosket very fine sandy loam, Field 11¹.

¹ Gin sequence included tower dryer, cylinder cleaner, stick machine, tower dryer, cylinder cleaner, gin stand, and two lint cleaners

² Short fiber content, %, as determined by a Peyer AL101

³ Neps per gram based on the Advanced Fiber Information System

⁴ Per 3 grams of ginned lint

 Table 2. Short fiber content by weight, AFIS neps, and manual seed-coat fragments as a function of moisture and cleaning machinery for a cotton variety at the gin (1996 data)¹.

¹ Means within each variable not followed by the same lowercase letter are significantly different at the 5% level as judged by Duncan's Multiple Range Test

² Based on Peyer AL101

³ Manual procedure

⁴ Based on Advanced Fiber Information System

⁵ Includes extractor-feeder

⁶ Includes extractor-feeder and gin stand.

⁷ LC = Lint cleaner

⁸ Standard = dryer, cylinder cleaner, dryer, stick machine, Trashmaster, extractor-feeder/gin stand and two lint cleaners

Table 3. Moisture and machine main effect means for the High Volume Instrument (HVI) measurements and foreign matter¹.

¹ Means within each variable not followed by the same lowercase letter are significantly different at the 5% level as judged by Duncan's Multiple Range Test.

² Includes extractor-feeder

³ Includes extractor-feeder and gin stand

⁴ LC = Lint cleaner

⁵ Standard = dryer, cylinder cleaner, dryer, stick machine, Trashmaster, extractor-feeder/gin stand and two lint cleaners

⁶ Presented as thirty-seconds of an inch

 Table 4. Means for short fiber content by weight and neps for cleaning and moisture treatments based on Advanced fiber Information System (AFIS) and Peyer.

¹ CC=cylinder cleaner, SM=stick machine, LC=lint cleaner, 1ELC=experiment lint cleaner, 2ELC=another experimental lint cleaner

² Each treatment includes extractor-feeder and gin stand

³ Per 3 grams of ginned lint

⁴ Data point is questionable

 REFERENCES