Gin trash, or as it is called now, cotton gin byproducts, at one time represented a problem to be disposed of, a fire hazard on the gin yard, or an eyesore at the end of ginning season.

As the saying goes, one man’s trash can be another man’s treasure. In recent years, researchers have taken a closer look at gin waste and have found some valuable properties in the burrs, sticks and stems left over after the ginning process.

This series looks at some of the ongoing work that adds value to gin trash.

Cotton gin byproduct (CGB) has not quite lived up to its potential as an eco-friendly, sustainable derivative of the cotton ginning process. But that potential is real.

“I'm a believer in it. I'm optimistic,” says Greg Holt, research leader, USDA-ARS Cotton Production and Processing Research Unit in Lubbock, Texas.  “Someone smarter than I am will figure this out. It could be soon, the market and the technology coming together at the right time.”

Cotton gin waste has been a useful byproduct for decades, and researchers have looked into numerous, value-added uses for the burrs, stems, leaves and other organic materials left over after the ginning process.

“We've extruded it, pelletized it for fuel in stoves and boilers; we have made composites, hydro-mulch, other erosion control products (it works very well in that), and a substrate for growing mycelium to make one-use packaging as a polystyrene replacement,” Holt says.

Related:Research adding value to gin cotton byproducts

Other uses include MDF (medium-density fiberboards) and other building products used as acoustic materials for sound dampening, among other applications.

Those products, however worthwhile, remained primarily in niche markets or as temporary replacements for something else.

“Overall, it's been hit and miss,” Holt says. “We've had successes that showed promise briefly and then went away. We haven’t found a universal, lasting, overall solution.”

Feed and mulch

CGB as livestock feed has been a consistent byproduct, usually as a replacement during a feed shortage.

“The hydro-mulch was good,” Holt says. “One company manufactured it for 10 or 12 years, but it was like any other new product. You had to train people who were used to dealing with wood and paper. Cotton-based hydro-mulch looked different, even though it performed better, but the market was more about appearance than performance.”

Using plastic module wrap as a substitute for plastic filler suffered a similar fate. “We could get about 30% replacement of the plastic with used module wrap but somebody had to be patient with it. It's not like taking one material out and putting this one in. Systems and people are set up to run a certain way, and when something changes, equipment has to be set up again. Anything  associated with change is always a challenge.”

Related:There's treasure in gin trash

Coming back

Products and processes researchers were looking at some 20 years ago, Holt says, are coming back and could be the catalyst for a more robust market for CGB.

Researchers are looking at processing CGB for eco-friendly soil amendments, biochar, for instance. Holt explains that biochar is created by a thermal chemical process in the absence of oxygen that turns gin waste into a carbon material that acts as a soil amendment and improves moisture retention capacity. Biochar does not break down immediately.

“It’s a process of carbon capture that will be more valuable if carbon credits and funding become viable,” Holt says.

Equipment cost

The big hurdle for processing CGB into biochar, he adds, has been the cost of equipment. Gin owners already have significant investments in equipment and adding the cost of another machine to convert CGB would be prohibitive.

He sees promise in a new model — mobile machinery.  

“This is a different model that seems very attractive,” he says. “I don't know if it will come to fruition; it is in a prototype stage, and I think it's viable.”

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He explains that one company, Applied Carbon, manufactures reactors for pyrolysis, a thermo-chemical process that creates biochar.

“Applied Carbon is testing portable units to transport to gin yards. A gin would not have to invest in a pyrolysis unit, which is not a small endeavor.”

He adds that this company’s model would offer something like a short-term lease.  “They bring the portable unit on site to process the gin’s CGB. Then the machinery moves to another site.

“A cotton gin could process its own CGB and produce biochar for its own growers/customers. They benefit by processing it at the gin and hauling it to their fields to improve the soil.

Interest is high

“We’ve seen a lot of interest in this model,” Holt says.

“The idea that something could pull on site, you don't own it, you're paying a fee for use, and growers benefit from the byproduct is compelling. Cotton growers get an added benefit from their own product.

“I like that model, and I think the gins that have heard about it have started inquiring.
“But the devil's always in the details,” he says. “If the model performs as we hope, everybody's happy. Maybe this gets us over the hurdle. I'm hoping it works.”

Other opportunities

Holt adds that other products and applications could still prove beneficial. The hydro-mulch, for instance, was successful until the housing market dropped, the company was sold and started processing more traditional wood and paper mulches.

Other processes have shown promise but faced challenges in the marketplace. Holt says any successful product must be cost-effective. In some cases, it takes as much or more energy to produce a product than can be justified.

Holt says CGB's challenges include transportation, storage, competitiveness with established materials, and market adaptability.

Wood substitutes, for instance, offer beneficial characteristics but, in outdoor applications, are subject to water retention and swelling.

Acceptance

Acceptance of new products and the training necessary to produce and handle them also pose obstacles to adoption.

Transportation is an issue. An additional advantage to the mobile reactors is location, Holt says.

“There is a uniqueness associated with CGB compared to other agricultural products in that it's harvested in the field and brought to a central location.”

Holt is optimistic because technology and markets keep changing. “If researchers keep adapting to that, I don't doubt that eventually somebody will land on a solution,” he says.

CGB, he contends, can be a valuable product. “It's an organic material that offers a lot of sustainable opportunities. We just need to find a universal home for it rather than a niche market.”