The journal Cleaner Engineering and Technology recently published a study by David Takal, Nathan Howell, Joshua Partheepan, and a team of researchers examining the transition of biochar production from laboratory settings to pilot-scale operations. Every year, the United States generates approximately 2.32 million metric tons of cotton gin waste, a bulky residue consisting of seeds, stems, and lint. For cotton gin owners, managing this waste is a costly and inconvenient burden. Converting this residue into biochar offers a promising solution by creating a value-added product that can improve soil health and capture carbon. However, a significant knowledge gap exists between well-controlled laboratory results and the realities of larger-scale production necessary for agricultural applications.

The findings of this study provide critical quantitative insights into the efficiency of scaling up. In controlled laboratory environments using a muffle furnace, the average biochar yield was 37.1%. When production was moved to a pilot-scale rotary kiln capable of processing 50 kilograms of biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More per hour, the average yield dropped to 25.8%. The researchers identified that the primary reason for this decrease was the unintended entry of air into the larger reactor, which caused some of the material to burn into ashAsh is the non-combustible inorganic residue that remains after organic matter, like wood or biomass, is completely burned. It consists mainly of minerals and is different from biochar, which is produced through incomplete combustion.   Ash Ash is the residue that remains after the complete More rather than carbonize. Despite this difference in yield, the stability of the biochar produced at both scales remained exceptionally high. By analyzing oxygen-to-carbon ratios, the team estimated that the biochar has a half-life of more than 1,000 years, making it an effective tool for long-term carbon sequestration.

Beyond carbon storage, the study highlights the biochar’s potential as a soil amendmentA soil amendment is any material added to the soil to enhance its physical or chemical properties, improving its suitability for plant growth. Biochar is considered a soil amendment as it can improve soil structure, water retention, nutrient availability, and microbial activity.   More. The material produced from cotton gin waste was found to be a rich source of water-extractable nutrients. Specifically, sulfur, magnesium, boron, and potassium showed high extraction fractions, ranging from 6% to 59%. In regions like the Texas High Plains, where soils are often alkaline, the application of this biochar could provide essential nutrients to crops, potentially reducing the need for synthetic fertilizers. The researchers noted that at a typical field application rate, the available sulfur from the biochar could meet or even exceed standard agricultural requirements. This represents a significant opportunity for farmers to lower input costs while improving the quality of their land.

From an economic perspective, the study provides a detailed technoeconomic analysis of producing biochar at different scales. At the pilot scale, the estimated cost of production was approximately 2.93 dollars per kilogram, or nearly 3,000 dollars per ton. While this price is currently on the higher end of the market, the researchers project that costs will decrease substantially as production reaches industrial scales. By utilizing process gases as a heat source and benefiting from economies of scale, the unit cost could drop by as much as 47% to 55%. This would bring the cost of cotton gin waste biochar to approximately 1,539 dollars per ton, making it much more competitive with other agricultural soil amendments and carbon credits.

The authors conclude that while the heterogeneous nature of cotton gin waste presents challenges for consistent production, the potential for large-scale utilization is clear. Future improvements in reactor design, such as using inert gases to prevent oxidation, will be vital to increasing biochar quality and yield at the industrial level. Furthermore, preprocessing steps like grinding or densifying the waste could help ensure more uniform heating and better particle flow in continuous-feed systems. By refining these processes, the cotton industry can transform a waste disposal problem into a sustainable business model that supports both the environment and the agricultural economy. This study serves as a foundational roadmap for moving biochar technology out of the lab and into the fields where it can have the greatest impact.

Source: Takal, D., Howell, N., Partheepan, J., Bhattacharia, S., Koziel, J. A., Brewer, C. E., Bednarz, C., & Guerrero, B. (2026). Lab- and pilot-scale biochar production from cotton gin waste. Cleaner Engineering and Technology, 101222.