Gin trash is about as useful as belly button lint and a lot more difficult to get rid of. And there is a lot to dispose of. The cotton industry generates as much as 3 million tons of gin waste a year. That figure varies with the size of the cotton crop.
Folks have tried to develop an economically viable product out of this mixture of stems, dirty lint, burrs and foreign matter for years with only limited economic success. Two of the most promising products — pellets enriched with appropriate nutrients for cattle feed, and, also in pellet form, fuel for wood-burning stoves — worked well but were not cost effective to replace other materials.
Now Greg Holt, an agricultural engineer at the USDA-ARS station in Lubbock, Texas, may have an answer: mulch.
Taking the raw gin trash and scattering it over a landscape offers little in the way of aesthetics or ability to hold soil in place, Holt says. But processed, colorized and mixed with another material (sudangrass seems to work nicely), gin waste can be sprayed onto a landscape, roadway or other bare area to help hold seed or soil in place.
“Gin waste with sudangrass covers as well as other mulches,” Holt says. The waste alone doesn't look as good, but with processing and sudangrass it is competitive in appearance and performance with other materials. It's also cost-competitive.
Holt says the cotton lint in the waste “clings to the soil and binds the other materials together. Hay alone doesn't cling as well.”
Holt has been looking for a useful product from gin waste since 1999. He's worked with the feed and fuel, but found that the feed was no better than other roughage and that pelletized fuel was no better than wood products.
“The process of turning gin trash into a mulch is not expensive. We use equipment for chopping, shredding, coloring and bagging, and we're still competitive with other mulch products. We can add it to grass seed to hold seed and soil in place and we also see value as erosion control.”
Holt says hydro-mulch material typically goes out at 1 pound of material to 2 gallons of water. With gin waste, that ratio is 1 pound per 1 gallon.
“Cotton absorbs and holds water,” Holt says. “That improves pumping ability. With an air sprayer, we can apply gin waste mulch at 1 pound of material with 1 ounce of water.”
In that system, the water mixes with the product at the end of the hose. “It's not in solution,” Holt says,” so the ability to mix it with water and spray is not a concern. But we're not limited to air application. This product can be used through either machine. In fact, it's already being used commercially as a hydro-mulch.”
Andy Ellis, who runs a commercial mulch operation out of Center, Ala., uses the product.
Holt says having a commercial applicator involved in early stages helps focus his research. “Industry helps us answer questions about coverage, pumping problems and such.”
“We also get a lot of input from Tom Wedergartner, director of agricultural research for Cotton Incorporated, which has provided key support for the project.
The mulch industry offers tremendous potential for mulch developed from cotton gin waste, Holt says. “It's a multi-million dollar industry that's under the green industry umbrella. We anticipate a lot of uses.”
Holt says processing is not particularly complicated, but quality control is necessary to prepare the proper texture, size, blend of gin waste and hay and sanitation.
“We do some sterilization — heat and steam — to kill weed seed. We want to provide a weed-free product. The mix is important, too. The hay provides eye appeal and the gin waste does the work, clinging to the soil particles.”
Tests have shown the gin waste mulch to be effective for erosion control. “On a 20-degree slope and rainfall at 4 and 9 inches per hour, the mulch did well,” he says.
Holt and associates are working with several machines to determine the best processing procedure. They use a commercial hammer mill, rotary cutters, a fiberizer, a shredder, colorizer and a vibrating conveyor. “We can segregate certain size materials. We also use a steam and dye process.”
Holt says the original work on adding value to gin waste took off following a 1998 survey of the Texas Cotton Ginners Association. The survey asked ginners to list their top 10 concerns. “Gin waste disposal was No. 2 on that list,” Holt says.
Gins generate considerable waste and then face the problem of getting rid of it. “We wanted to add value to a waste product,” Holt says. “Research focused on a process that could produce multiple products — feed, fuel, mulch and building materials, all processed with basically the same equipment. It's flexible manufacturing.”
He says building materials also offer potential. “We use a resin filler to make tile-like materials and some that resemble cinder block. We've seen interest go up and down for the products. We're also looking at termite-resistant building materials.
“We want to take a waste material and create a revenue stream,” he says. “Mulch looks promising.”