TCF bleaching of wheat straw pulp using ozone and xylanase. Part A: paper quality assessment M.B. Roncero * , A.L. Torres 1 , J.F. Colom 2 , T. Vidal 3 Department of Textile and Paper Engineering, E.T.S.E.I. Terrassa, Polytechnical University of Catalonia, Colon 11, Terrassa 08222, Spain Received 18 April 2002; received in revised form 16 September 2002; accepted 16 September 2002 Abstract The XOAZRP TCF sequence was applied to bleach wheat straw pulp. Following each bleaching stage, the properties of the pulp (viz. kappa number, standard viscosity, borohydride viscosity and brightness) and of the resulting effluents were determined. The performance of the reagents was analyzed through the studies of xylanase treatment and crystallinity and scanning electron micro- scopy of the pulps. Finally, the pulp was refined at 1000 revolutions in a PFI mill and the mechanical properties of the resulting paperweredeterminedandcomparedwiththoseofpaperfromaeucalyptuspulp.Despiteitsshortcomings,wheatstrawpulpcanbe effectively bleached with the proposed TCF sequence. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Straw pulp; Eucalyptus; Bleaching; TCF; Ozone; Xylanase; Paper; COD; Colour; Cristallinity; XRD; SEM 1. Introduction Agriculturalfibreshavebeenusedtomakepaperever since it was invented. The paper industry started to use wood as a raw material a little over a century ago. This is indeed the preferential raw material for this purpose on account of its low cost, wide availability, little con- tent in non-fibrous materials and ease of processing, and alsoofthefactthatitprovideshighlyuniformpulp.The demand for paper has risen significantly in recent years, so much so that the Food and Agriculture Organization (FAO) has predicted an increase in the worldwide use of paper and cardboard from the 210 million tons of 1988 to about 350 million tons by 2010 (Giovannozzi-Ser- manni et al., 1997). This steady increase in paper de- mand is gradually leading to a worldwide shortage of wood fibre supplies. The current annual production of pulp cannot meet the increasing demand, which con- tinues to grow at a dramatic rate (Sabharwal and Young, 1996; Jim enez et al., 1997a). The overall worldwide production of cereal straw is estimatedtoexceed2900milliontonseachyear.Mostof this residue is burnt, thereby losing energy and causing significant pollution which is illegal in some countries. This raw material therefore possesses a high economic and environmental potential. In 1970, pulp from non- woody fibres accounted for only 6.7% of the overall worldwide production figure. By 1993, the proportion had risen to 10.6% and, some time in the future, it will predictably double that of pulp made from woody ma- terials (Atchinson, 1995; Giovannozzi-Sermanni et al., 1997). Agricultural fibres thus constitute an alternative to wood as a raw material for making pulp on account of their high growth rate and adaptability to various soil types. Spain produces more than 16 million tons of major agricultural residues each year. With a yield of 40–50%, this mass would provide more than four times the amount of paper currently obtained from wood fi- bres in this country. One of the chief problems posed by this type of raw material is the low quality of the resulting paper in re- lation to wood pulp. This is largely the result of its high content in non-fibrous material. Thus, wheat straw typically contains about 50% of fibre, the remainder Bioresource Technology 87 (2003) 305–314 * Corresponding author. Tel.: +34-93-7398288; fax: +34-93- 7398101. E-mail addresses: roncero@etp.upc.es (M.B. Roncero), tor- res@etp.upc.es (A.L. Torres), colom@etp.upc.es (J.F. Colom), tvi- dal@etp.upc.es (T. Vidal). 1 Tel.: +34-93-7398196; fax: +34-93-7398101. 2 Tel.: +34-93-7398172; fax: +34-93-7398101. 3 Tel.: +34-93-7398180; fax: +34-93-7398101. 0960-8524/03/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S0960-8524(02)00224-9