Datos

Bioresource Technology 97 (2006) 535–544

Alkaline pulping of some eucalypts from Sudan
P. Khristova
a

a,*

, O. Kordsachia b, R. Patt b, S. Dafaalla

a

University of Khartoum, People’s Hall 11113, P.O. Box 6272, Khartoum, Sudan
b
Institute of Wood Chemistry, 21031 Hamburg, Germany

Received 25 August 2004; received in revised form 20 January 2005; accepted 11 April 2005Available online 2 June 2005

Abstract
Four eucalypts (Eucalyptus camaldulensis, Eucalyptus microtheca, Eucalyptus tereticornis and Eucalyptus citriodora) grown in
Sudan were examined for their suitability for pulping and papermaking with different alkaline methods. Their physical, morphological and chemical characteristics are reported. The pulping trials with E. citriodora and E. tereticornis werecarried out using the
kraft-AQ, soda-AQ, modified AS/AQ (ASA), ASAM and kraft methods. For the other two species, only the ASAM and the kraft
process were applied. ASAM pulping gave the best results in terms of yield, degree of delignification, mechanical and optical pulp
properties. The best pulps, obtained in kraft and ASAM cooking of E. citriodora, were bleached to 88% ISO brightness in atotally
chlorine free bleaching sequence (OQ1O/PQ2P). The bleached pulps, especially the ASAM pulp, showed good papermaking properties and would be suitable for manufacture of writing and printing grades of paper.
Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: Eucalyptus camaldulensis, Eucalyptus citriodora, Eucalyptus microtheca, Eucalyptus tereticornis; Kraft, kraft-AQ, soda-AQ, ASA, ASAMpulping; TCF bleaching; Pulp evaluation

1. Introduction
Eucalypts have become a major worldwide source of
papermaking fibres and other important wood products
in tropical, subtropical and some temperate regions.
This evergreen species owes its popularity as a pulpwood to its fast growth rate, the high yield of wood substance per unit area in plantations and to the excellent
pulp grades withunique combination of physical and
optical properties (Kordsachia et al., 1992).
However, out of nearly 600 known species, less than a
dozen are in commercial use for pulp production. These
species, most frequently found in plantations in the
different regions of the world, may not always be favourable with regard to fibre quality and wood composition
as well as natural evolution and ease ofhybridization.

*

Corresponding author. Tel.: +249 183229960.
E-mail address: pkhristova@hotmail.com (P. Khristova).

0960-8524/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.biortech.2005.04.006

Other Eucalyptus species may have adequate or even
better genetic and growth characteristics under distinct
climatic conditions and may be suitable for pulpproduction as well.
Since 1965 some Eucalyptus species, originating
from Australia, have been planted in different parts of
Sudan (Badi et al., 1989). Pulping with kraft, HTS and
soda-AQ processes of some of the most successfully
introduced, Eucalyptus tereticornis, Eucalyptus camaldulensis, Eucalyptus microtheca and Eucalyptus paniculata (Khristova et al., 1997; Khristova, 2000), have
indicatedtheir suitability for pulping with acceptable
yields and pulp strength properties. In different pulping
studies carried out in Malawi, India, Brazil and Congo,
Eucalyptus citriodora, which is also planted in Gabel
Marra–Western Sudan, was used as raw material. In
conventional pulping, slightly below average yields and
strength properties of the pulps were attained, except
for tear index. Allin all, the pulp quality could not fully
match the standard of good eucalypts kraft market

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pulps (Foelkel et al., 1975; Soloman, 1960; Gupta and
Prasad, 1961; Palmer et al., 1989).
The aim of the present work was to use young trees,
to avoid higher extractive and lignin contents, in comparative pulping with the...