FEBRUARY 2008

Cotton industry recycles cotton byproducts and waste
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Seeds from the cotton plant that are separated from the lint at the gin mill represent a valuable commodity that is very recyclable.

Byproducts from the cotton fiber ginning process, including seed, linters, burs and oil, are being developed into value-added products for feed, food, erosion control, electronics and other industries.

The cotton industry has committed itself to such recycling efforts by dedicating millions of dollars each year to researching and developing new markets for such cotton end-products.

“Each year, U.S. cotton gins produce more than 2 million tons of cotton gin waste, representing a significant disposal problem for the ginning industry,” says Tom Wedegaertner, director of cottonseed research and marketing for Cotton Incorporated. “A significant recycling development, and a notable value-add success story, has been the creation of cotton-based erosion control products.”

Cotton-based erosion control products are the first of their kind in the erosion control industry, he says.

GeoSkin™ Cotton Hydromulch, developed as an alternative to wood and paper mulch products, was followed by the introduction of its premium counterpart, HydraCX2™ Cotton Hydromulch (formerly Cotton Fiber Matrix), for use on steep terrain.

In both products, the naturally porous cotton fiber matrix contours to uneven surfaces to control erosion and establish grass on construction sites.

Wedegaertner adds that the use of ground cotton gin waste as a substitute for wood products in composite resins, particle boards and thermal plastic decking boards is being investigated, as well.

“Ground cotton carpel (bur) has unique physical and chemical properties that give it a unique advantage over wood products in these applications,” he says.

“A key benefit of this product, from an environmental standpoint, is that the cotton product effectively soaks up styrene emissions and greatly reduces the volatile styrene that is emitted via the manufacturing process.” Cotton gins produce about 2 to 2.5 million tons of cotton byproducts annually.

“We are just now starting to find value for that waste stream so that it isn’t a disposal problem, but rather that it has value and people are going to buy it and make it into something.”

Between 33 and 40 percent of the seeds are used to produce cottonseed oil, with the remainder being sold to dairy farmers as a feedstock for their herds.

“The oil is used by restaurants, for the production of snack foods and other food products and for a variety of industrial purposes,” says Wedegaertner.

But before the oil can be squeezed out, the linters (the fuzz coating the seed) must be cut off the seed.

“This is pure cellulose, used for value-added items such as cellulose acetate,” says Wedegaertner. “Every single screen on a flat panel LCD television is made from cellulose acetate. Linters are the purest form of cellulose of any plant material on the planet. They are 99.7 percent pure.

“They are also used for cellulose gums,” he adds. “If you look on the label of a bottle of pancake syrup, you’ll see cellulose gums listed on the ingredients. Cellulose is also used for products such as photographic and x-ray film – a cellulose type of derivative.” There are many products that include edible and industrial thickeners made from cotton cellulose, including toothpaste.

“Cotton is and has been grown as a food crop,” says Wedegaertner. “The original cooking oil 100 years ago was cottonseed oil. The brand name Crisco®, originally developed by Proctor & Gamble, is short for crystallized cottonseed oil.”

Bill Norman, vice president for Technical Services at the National Cotton Council (NCC), has also been a major voice for recycling efforts in the cotton industry.

“Cotton is a natural product, and it is biodegradable,” he says, “so it can be recycled into any number of waste-type products.”

In addition to films, Norman stresses that cotton cellulose can be used for the production of fine quality papers and currency, and for industrial grade films to bind products, including food such as processed meats and other products.

The shift to selling the majority of seed to dairy farmers as a feedstock began in the 1970s.

“We’ve gone from almost 100 percent processed seed to about one third,” says Norman. “That has taken away some of the utilization of byproducts from our seed, and with the movement of much of our textile industry offshore, particularly in the last seven to eight years, our raw cotton is now being shipped overseas to mills and coming back to the United States as a finished product.”

If the material cannot be recycled, it can also be used as a fuel source for a mill should there be a steam requirement. When the lint is separated from the seed and cleaned, the waste that is generated, known in the industry as mote, is collected. “Motes can be processed as textile material for lower-grade fabric yarn that still has a textile value – it’s all a matter of integration,” says Norman. “They can be used for products such as mop yarn and very basic products that are usually made from lower grade waste fibers.”

While many textile manufacturers have moved their operations outside the United States, several of the remaining mills are adjacent to gin mills.

“If it is a vertically integrated mill, once the cotton is spun into yarn,” says Norman, “it will be sent next door to either a weaving or knitting facility to produce cloth.”

The waste from the spinning process – either short fibers or other materials, is known as foss. Furthermore, the waste that is generated via a card during the combing process which arranges the fibers is referred to as comber noil. It is a fiber that contains bits of plant material that can either be re-entrained to manufacture a lower-grade product in the mill or will be baled for sale to another mill that could use that material, which is usually combined with a similar type of mote.

“It’s all about what is the end product,” says Norman. “If it is not available for textile grade use, it can then go into the cellulose pulp market. Because it is pure cellulose, there are several companies around the world that use it.”

Once the cotton is sent to the knitting and weaving mills, there is very little leftover material.

“Hopefully this is the case because the bulk of the expense of that process is the raw material,” says Norman, “so every percentage that you can utilize directly affects the bottom line and our mills are very efficient in utilizing all the product.

Cotton production in the U.S. has remained strong, with 22 million bales produced in 2006 and 23 million in 2005. In essence, as long as cotton is grown in such large volumes annually, it is a renewable resource that manufacturers and recyclers can rely upon.

Norman stresses that gin mills and knitting and weaving mills, be they domestic or foreign, take recycling seriously.

“For a textile mill to be competitive,” he says, “their percent utilization of raw material has to be extremely high. If there is any waste that finds its way into a landfill, it’s because someone didn’t sell it. There are uses for every bit of waste if you so choose. The textile markets are so competitive that every penny that can be obtained in the form of product or byproduct is very important.”

But Norman notes that the cotton industry is not seeking government legislation or tax credits and grants for recycling.

“Because the tradition has been to recycle in the first place, there is not much that a grant could do,” he says. “The industry, from the farm gate to the spinning and textile mills, has been a long-time recycler and utilizer of waste products.”