CONVERSION OF COTTON PLANT AND COTTON GIN RESIDUES TO FUELS BY THE EXTRUDER-FEEDER LIQUEFACTION PROCESS

Cotton is planted on a large scale in the USA, and is a major crop in Arizona. A large amount of cotton plant residue and cotton gin waste i s produced annually, and these present a disposal problem. This materi al is comprised of cotton stalks, along with the upper portion of the taproot, and cotton gin trash. Cotton plant residues are a greater pro blem in the warmer regions of the USA as they serve as an overwinterin g site for insect pests, and thus must be destroyed. Presently they ar e buried. Most field operations used to bury the residue are high ener gy consumers and tend to destroy soil structure, thereby increasing th e potential for erosion. This burial process is considered to be detri mental to the soil. One option to change the negative value of this bi omass to a positive one is to harvest the cotton plants and combine th em with other cotton wastes to produce a feedstock for liquefaction pu rposes. A process for harvesting and transporting the roots and stalks is being developed at the University of Arizona. In this paper we pro pose a combined harvesting/liquefaction system. This system would harv est and liquefy cotton wastes into oil and densified solid fuels with higher economic values. The extruder-feeder liquefaction process was d eveloped at the University of Arizona in the 1980s under the sponsorsh ip of the U.S. Department of Energy, with the goal to convert wood to a clean, 16 000 btu/lb liquid fuel. The process has been redirected to other organic wastes using additional processing to yield 'value-adde d' byproducts. Cotton wastes are good candidates for this process. By combining the harvesting and fuel processing operations, a negative va lue biomass would become a positive value biomass by (a) solving a dis posal problem, and (b) producing high value fuels. (C) 1996 Published by Elsevier Science Ltd.