Abstract

Clones of Eucalyptus globulus Labill. (5- to 7-year-old), from a common geographic area, were evaluated for chemical pulping easiness. Significant variations were observed in the pulp yield and specific wood consumption to produce pulps with similar kappa numbers, as well as in the strength properties of the resulting kraft pulps. Comprehensive lignin analyses were undertaken in an attempt to rationalize the observed differences in these clones' pulping performance. While lignin content did not correlate with pulp yield, the data reported here provides evidence of the influence of lignin features on the pulping response of different eucalyptus clones. Significant correlations were observed between pulp yield and specific wood consumption and the content of syringyl-type arylglycerol-β-aryl structures (β-O-4 linkages). Furthermore, eucalyptus woods with a greater content of uncondensed β-O-4 linkages were found to require more PFI revolutions to obtain pulps with a given drainability. In contrast, no relationship between pulping efficiency and the other lignin structural features evaluated was apparent, including syringyl/guaiacyl ratio (S/G), total aliphatic and phenolic hydroxyl groups, syringyl and guaiacyl units bearing free phenolic hydroxyls, and the erythro-to-threo ratio of β-O-4 structures. These findings support the use of the content of syringyl-type arylglycerol-β-aryl structures as a selection parameter in clonal breeding programs for pulpwood production. © 2008 American Chemical Society.