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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Livestock Nutrient Management Research » Research » Publications at this Location » Publication #424308
Research Project: Strategies to Manage Feed Nutrients, Reduce Gas Emissions, and Promote Soil Health for Beef and Dairy Cattle Production Systems of the Southern Great Plains

Location: Livestock Nutrient Management Research

Title: Lab- and pilot-scale biochar production from cotton gin waste

Author
item TAKAL, DAVID - West Texas A & M University
item HOWELL, NATHAN - West Texas A & M University
item PARTHEEPAN, JOSHUA - West Texas A & M University
item BHATTACHARIA, SANJOY - Iowa State University
item Koziel, Jacek
item BREWER, CATHERINE - New Mexico State University
item BEDNARZ, CRAIG - West Texas A & M University
item GUERRERO, BRIDGET - West Texas A & M University

Submitted to: Cleaner Engineering and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2026
Publication Date: 5/5/2026
Citation: Takal, D., Howell, N., Partheepan, J., Bhattacharia, S., Koziel, J.A., Brewer, C., Bednarz, C., Guerrero, B. 2026. Lab- and pilot-scale biochar production from cotton gin waste. Cleaner Engineering and Technology. 32. Artic1e 101222. https://doi.org/10.1016/j.clet.2026.101222.
DOI: https://doi.org/10.1016/j.clet.2026.101222

Interpretive Summary: The U.S. is a leading exporter of cotton. Cotton production generates millions of tons of low-value residue called cotton gin waste (CGW). The CGW is made over a very large growing areas for about 2-3 months each year when the harvest is in. Researchers from USDA ARS (Bushland, Texas), West Texas A&M University, and New Mexico State University investigated new uses that could add value to the abundant and largely unused CGW. The scientists made a carbon-rich material from CGW called biochar for agricultural and environmental uses. They aimed to answer a question on how to scale up biochar production from the laboratory to something approaching an industrial scale. The answer was that one cannot move directly from a lab to an industrial scale. Besides the business risk involved in doing so, there are immense challenges because CGW is different from gin to gin and over time during cotton ginning. These challenges also include the projected environmental stability of the biochar added to soil, the energy cost, the high labor cost, the difficulty of process temperature control, and the need to adjust your well-optimized laboratory biochar-making recipe to work well at a different and larger scale and process configuration. The study concerns a question which is very necessary for the High Plains Area and also globally. Many stakeholders are looking for adding value to agricultural waste such as CGW.

Technical Abstract: As much as 2.32 x 10^6 metric tons of cotton gin waste (CGW) is generated in the U.S. annually. Technologies for utilization of CGW, including improved nutrient cycling via conversion to biochar, are of high interest to the agroindustry seeking answers regarding technoeconomic feasibility. Yet there is generally a gap between what is understood about CGW and similar crop residue biochar made in the lab as opposed to that which might be made at larger scales. The purpose of this work was to examine the quality and quantity of biochar made from CGW, at lab- and pilot-scale, taken directly from a working gin. We considered scaling up of CGW biochar production at 350-600 deg C. Specifically, we compared the reactor operation and the quality of biochar produced with a research-grade lab-scale muffle furnace to a less controlled pilot-scale rotary kiln. The average biochar yields were 37.1% ± 6.39% (mean ± s.d.) for the muffle furnace and 25.8% ± 8.99% for the rotary kiln, and these differences were significant (p < 0.05). We attribute many of the differences in yield and quality to unintended air entry into the rotary kiln. Porosity of the biochar was higher for the muffle furnace (0.929) compared to the rotary kiln (0.747). The estimated stability of all biochar was generally high (O/C < 0.2; >1,000-year half-life). The biochar nutrients most extractable by water were S, Mg, B, and K, with extraction fractions ranging from 6-59%. The technoeconomic potential of CGW biochar produced in the pilot-scale reactor was approximately $3,000/t; costs are expected to decrease substantially for a full-scale industrial process if a conservative economy of scale can be harnessed. More studies on increasing biochar production from lab to pilot scale are needed if biochar is to reach its potential for large-scale production and applications. Specifically, studies should focus on the unit cost of production and the consistency of biochar quality, since much of biochar’s ultimate value depends on the demonstration of specific properties for each application.