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Fuel or feed, cotton waste may have good value

A perennial dilemma for the ginning industry has been disposal of the cotton waste that's generated. From burning to dumping on fields to enhance organic matter to turning it into compost/mulch, the waste has been mostly a problem for which nobody had a widely acceptable solution — particularly one with commercial value.

Researchers at the USDA Agricultural Research Service Cropping Systems Laboratory at Lubbock, Texas, with funding assistance from Cotton Incorporated, are looking at innovative uses of gin waste that might turn it into commercially viable products.

Don Comis reports in the April Agricultural Research magazine that the scientists are evaluating a process to turn the waste into pellets that can be used as fuel for heating purposes and for animal feed. The pellets, tested last winter in two commercially available stoves, burned as well as commercial products made from sawdust/wood chips or wheat straw, according to agricultural engineer Greg Holt. Data are still being analyzed to determine if the gin waste pellets burn as cleanly as the other products.

By adding a little cottonseed oil to the pellets, he noted, the heating value was increased to about 9,000 BTUs per pound of pellets — more heat output than from most wood pellets.

Holt and his colleagues say the COBY (cotton byproducts) process uses a hot, gelatinized starch solution that acts as a glue to hold the cotton waste ingredients together, and a lubricant to smooth the mixture's flow through the extrusion equipment that makes the pellets. The process also cooks, sterilizes, and improves nutrient availability of the mixture, as well as killing any weed seeds or fungi that might be in the waste.

The COBY system is “very flexible,” Holt says, and “you can easily tailor-make products, adding things like molasses, cottonseed, various grain meals, and protein supplements.” Animal feeding trials were started this spring at Texas Tech University, Lubbock.

The pellets are made with a commercially available mill, which presses the gin trash and other ingredients into pellets about 0.25 inch wide and 0.5 to 1 inch long. Three types of pellets have been made with the COBY system: a low-starch mix, a high-starch mix, and a low-starch/low-cottonseed oil blend. The waste was obtained from ARS gins at Stoneville, Miss., and Lubbock, and Holt notes that the composition of the waste varies from one growing region to another — some has more woody material, such as plant stems. “We've studying how this affects the heating efficiency,” he says.

The Pellet Fuels Institute reports 57 firms making bagged pellet fuel, with 730,000 tons sold during the 2000-01 heating season. That represented a 14 percent increase over the previous winter.

The researchers are also looking at using loose, non-pelletized, cooked waste as a mulch for flower beds and other landscaping purposes.

“By creating value-added products,” Holt says, “we hope to improve the marketability of cotton byproducts, turning them from waste into a commodity that can increase ginning income and potentially create jobs in rural areas.” Several gins are considering jointly building a plant to process and sell waste.

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