Plastic contaminants in cotton have increased significantly in the last three or four years, says Tommy Valco, USDA Agricultural Research technology transfer coordinator at Stoneville, Miss.

But despite a general tendency to link the increase to the rapid and widespread adoption of the round module system, preliminary studies indicate very little of the plastic that makes it into spinning yarn, giving textile mills fits, is traced to the module covers, he says.

Rather, most of it comes from plastic grocery bags, black agricultural mulch used widely in vegetable production, and other sources.

“Plastic in the ginning process has become an increasing concern not only for ginners, but for marketing and textile processing,” he said at the summer meeting of the Southern Cotton Ginners Association at Biloxi, Miss.

“It’s  crucial that we do everything possible to keep plastic out of our cotton. U.S. cotton is some of the least contaminated in the world, and we want to do everything we can to keep it that way. We want everyone to be aware of the issue and the problems it causes in the marketing and processing of our cotton.”

 Adoption of the round module harvesting system “has accelerated much faster than many expected,” Valco says. “At many gins, 60 percent to 80 percent of the cotton that’s ginned is round modules, and this has required a lot of changes to the ginning system. Even in faraway Australia, as much as 95 percent of the cotton ginned is from round modules, and these systems are going into Brazil, China, and other cotton-producing regions.

“Like any new technology, there is a learning curve, just as when the original module-builder system was introduced in the early 1970s.”

Tests at the USDA Cotton Ginning Laboratory at Stoneville have shown, Valco says, that “the thicker the plastic, the more easily it is removed by gin equipment. The wrap on round modules is relatively thick and is more easily removed by the system. Even if some of it does get into the ginned bale, 99 times out of 100 it gets removed in the textile cleaning system at the mill. We see very little yarn with module wrap plastic, but plenty with fragments of black plastic agriculture mulch, grocery bags, etc.”

Rick Byler, research leader at the Stoneville ginning lab, says while “there aren’t a lot of data on this, the module wrap is less likely to be a problem getting into yarn at mills than plastic mulch or other kinds of plastic.

“A decent size piece of module wrap could very well get through the gin and end end up in the bale that goes to the mill,” he said at the joint annual meeting of the Delta Council Ginning and Cotton Quality Committee and the Southern Cotton Ginners Association.

“Mills are finding more of this in their bales, and they’re definitely complaining about it. But these large pieces are typically removed in their cleaning process and aren’t likely to get into the yarn. I’ve not seen any module wrap plastic I’m convinced made it into the final yarn.”

Round modules use a multi-part wrap, Byler notes. “One part of the wrap isn’t stuck to anything, and if you cut into it, that piece will be completely loose and will tend to go into the seed cotton pile. From there it can get into the module feeder, wrap around the beaters, and get beaten into little pieces, some of which can make it into the final bale.”

While there are automated systems to properly cut and remove the wrap from round modules, he says because of the cost and problems with misalignment, most gins are not using them, but rather are cutting the wrap manually.