CHARACTERISTICS OF PELLET FUEL FROM COTTON GIN BYPRODUCTS UTILIZING VARIOUS PROCESSING TREATMENTS

Authors: Holt, Gregory; BLODGETT, T - ALCOA, ROCKDALE, TX; Nakayama, Francis

Submitted to: Association for the Advancement of Industrial Crops Conference
Publication Type: Proceedings
Publication Acceptance Date: 7/16/2005
Publication Date: 9/17/2005
Citation: Holt, G.A., Blodgett, T.L., Nakayama, F.S. 2005. Characteristics of pellet fuel from cotton gin byproducts utilizing various processing treatments. In: Pascual-Villalobos, M.J., Nakayama, F.S., Bailey, C.A., Correal, E., Schloman, Jr., W.W., editors. Proceedings of 2005 Annual Meeting of the Association for the Advancement of Industrial Crops: International Conference on Industrial Crops and Rural Development, 17-21 September, 2005, Murcia, Spain. p. 89-104.

Interpretive Summary: Finding a use for cotton gin byproducts (gin waste) that can be implemented across the cottonbelt has been problematic. One potential application that had not been specifically addressed in past studies was making pellet fuel from the byproducts for use in residential pellet stoves. This study compared six cotton gin byproduct fuel pellets to a premium grade wood pellet that is commercially used in residential pellet stoves. The study was designed to compare emissions from burning gin waste pellets in a commercially available pellet stove with the stove adjusted and setup to burn wood pellets. The idea was to evaluate whether or not the emissions from burning the gin waste pellets would be within a respectable level of the wood pellets without major adjustments to the stove. Most of the gin waste fuel pellets were comparable to the wood pellets in heating value, pellet length, and bulk density. The one characteristic of the gin waste pellets that was significantly higher than the wood pellets was the ash content. The ash content of the gin waste pellets ranged from 4.9 to 9.8 percent compared to wood at 0.5 percent. Since the stove was not optimized to burn the gin waste pellets, the gaseous and particulate emissions were higher than they were for the wood pellets. Overall, byproducts from cotton gins can be utilized as a residential fuel that has economic potential but work remains in order reduce the ash content of the fuel and optimizing the combustion process to reduce emissions within levels that are similar to a premium grade wood pellet.

Technical Abstract: Agricultural plant wastes when properly processed into useful commodities can become an economic asset. It has been estimated that in the United States, there are over 2.04 million Mg of cotton byproducts generated each year. On average, the disposal of these byproducts costs the cotton gin approximately $1.65 (U.S.) per Mg. One means of changing a financial liability into a potential revenue generator is to process the byproducts into renewable, compact pellet-type fuel that can be used at the site or transported to the consumer. Furnace and water heaters that can burn pelletized plant materials have become popular and their safety, low pollution, and reasonable operational costs have been demonstrated. Also, the drastic increases in the price of liquified fuel and its uncertain supply place a premium for finding and using alternate, low-cost, cellulose-based fuels. The objectives of our study were to fabricate pellet fuel from cotton gin byproducts using various processing techniques, determine its physical properties, and measure the emissions when fired in a commercial pellet stove used for residential heating. Byproducts from two cotton gins were collected and processed into fuel pellets. Seven different treatments were evaluated. The treatments resulted from using different material streams from the ginning process as well as varying quantities of starch and/or crude cottonseed oil during the fuel pellet manufacturing process. The fuel pellet density from the various treatments ranged from 488 to 678 kg/m3. The various treatments were burned in a conventional pellet stove (four replications) and the gaseous and particulate emissions measured. The average calorific value of the pellets ranged from 17.9 to 20.9 MJ/kg (HHV). The ash content for the various treatments ranged from a low of 4.9 % to a high of 9.8 %. The sodium content indicated concentration ranges from 91 to 282 ppm depending on the treatment. The emissions from the cotton gin byproduct pellets were higher than for a premium grade wood pellet. The emissions measured during testing were: CO, NO, NO2, SO2, and particulates. The pellet stove was setup, as per the manufacturer’s recommendation, to burn wood pellets and was not adjusted for the cotton gin fuel pellets. By utilizing various additives and processing techniques cotton gin byproducts could be used in the manufacture of a pellet fuel that has economic potential. However, work remains in order to minimize the ash content and determine the optimal settings for maximizing combustion.