GENERAL RESEARCH Ethanol Pulping from Tagasaste (Chamaecytisus proliferus L.F. ssp palmensis). A New Promising Source for Cellulose Pulp M. J. Dı ´az,* ,† A. Alfaro, ‡ M. M. Garcı ´a, † M. E. Eugenio, § J. Ariza, † and F. Lo ´ pez † Chemical Engineering Department Facultad de Ciencias Experimentales Campus del Carmen, Universidad de Huelva, Avda, de las Fuerzas Armadas S/N, 21007 Huelva Spain, Forestry Science Department, Universidad de Huelva, Ctra, Huelva-Palos de la Frontera s/n, 21819 La Ra ´ bida, Palos de la Frontera, Huelva, Spain, and Environmental Science Department, Universidad Pablo de Olavide, Ctra, Utrera Km. 5, Sevilla, Spain The chemical characteristics of tagasaste trimming wood and eucalyptus wood are similar in ash, holocellulose, lignine, xylan, and acetyl groups. Then, tagasaste wood could be an adequate raw material for pulp and paper making. Therefore, the influence of independent variables in the pulp processing of tagasaste with ethanol-water mixtures (ethanol concentration, time, pulping temperature, wash temperature, and disintegrate temperature) on various properties of the pulp (yield, kappa number, viscosity, brightness, and stretch related properties of paper sheets) was studied to determine the best processing conditions to obtain quality pulp and paper sheets. Using medium to high (185-200 °C) pulping temperatures and ethanol concentration (60-80%), suitable physical characteristics of paper sheets and an acceptable yield, the kappa index, and viscosity could be obtained. Wash and disintegrate temperatures have an influence on all the dependent variables, especially on the yield and the tensile index. A high wash temperature and a disintegrate temperature must be used in order to ensure that the pulp and the resulting paper sheets will possess optimal properties. 1. Introduction Standard chemical pulping processes (kraft processes) are typically used for making pulp from agro-based fibers. 1 However, these processes are energy-intensive, require large capital investments, and contribute to air and water pollution. Technologies are currently in development that would reduce the environmental impact of kraft pulping. The problem of emission of volatile sulfur compounds and high chemical oxygen demand bleaching effluents is yet to be solved. Organosolv pulping circumvents the environmental problems related to sulfur emissions, and it has been found to be effective on several wood species with a broad range of organic solvents. 2 Organosolv pulping is a two-stage process involving hydrolysis and the re- moval of lignin with an organic solvent 3 and offers several potential advantages over conventional pulping techniques such as relatively low chemical and energy consumption coupled with low capital costs and low environmental impact due to the recirculation of ef- fluents and the replacement of chemical additives used in a conventional pulp mill. 2 Pulp recovery from organosolv pulping ranges be- tween 50 and 60% for hardwoods and 40 and 45% for softwoods. 4 Typical hardwood fiber recoveries compare favorably with those from kraft pulping. Little waste is produced by the process, and low alcohols are recovered easily by distillation, thus requiring a relatively low capital investment. However, fibers produced by the organosolv process are weaker than those recovered by the kraft process. Thus, the papers produced from the organosolv pulp are suitable for uses where strength is not the most important property. 5 Organosolv pulping uses several organic compounds as solvent to delignify the fiber by breaking off pieces of the lignin molecule to render it soluble. 6 A variety of organic solvents, including alcohols, ketones, glycols, esters, and organic acids had been used in organosolv pulping. However, economic reasons in terms of price and difficulties in solvent recovery have favored the use of low molecular weight alcohols. The use of ethanol is particularly attractive both ecologically and economically, since the ethanol solvent can be distilled and reused, leaving behind a powder rich in lignin and other organics, which can then be sold to make fertilizer or binding agents. Commercial viability of this technology will require that markets be developed for byproducts of the process. 6 Organosolv processes had been applied with varying success to hard and soft wood and also, to a lesser extent, to nonwood materials. Several nonwood materi- als have been studied by different authors. 7-11 The use of nonwoody faster-growing species for pa- permaking could have a great advantage in that they provide remediation for the environmental problems associated with deforestation. Tagasaste (Chamae- cytisus proliferus (L.F.) ssp palmensis) began to be * To whom correspondence should be addressed. Tel.: +34 959 01 99 90. Fax: +34 959 01 99 83. E-mail: dblanco@uhu.es. † Chemical Engineering Department Facultad de Ciencias Experimentales Campus del Carmen, Universidad de Huelva. ‡ Forestry Science Department, Universidad de Huelva. § Universidad Pablo de Olavide. 1875 Ind. Eng. Chem. Res. 2004, 43, 1875-1881 10.1021/ie030611a CCC: $27.50 © 2004 American Chemical Society Published on Web 03/18/2004