Effect of harvesting age on the quality of bleached kraft pulp from Eucalyptus camaldulensis

The effect of harvesting age of Eucalyptus camaldulensis on wood, pulp and papermaking properties was studied. Bleached kraft pulp was prepared from 4, 6 and 8 year old trees, which came from the same clone and area located in eastern Thailand. The specific gravity at breast height increases with increasing tree age. Holocellulose, lignin and ash contents are not affected; the pentosan content decreased while extractive content increased with increasing tree age. Older trees give longer and coarser fibers. The vessel area is constant from 4- to 6-growth rings and then increases from 6- to 8-growth rings, while the parenchyma area is constant. Consequently, fiber area increases from 6- to 8-growth rings. The 4- to 6-year-old trees give better pulp quality than the 8 year-old with higher pulp yield, lower kappa number, better bleachability brighter and stronger pulps.