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

The effect of harvesting age of Eucalyptus camaldulensis on wood, pulp and paper-making 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 basic density at breast height increased with increasing tree age. Holocellulose, lignin and ash contents were not affected; the pentosan content decreased while extractive content increased with increasing tree age. Older trees had longer and coarser fibres. The vessel area was constant from 4- to 6-growth rings and then increased from 6- to 8-growth rings, while the parenchyma area was constant. Consequently, fibre area increased from 6- to 8-growth rings. The 4- to 6-year-old trees gave better pulp quality than the 8-year-old in terms of higher pulp yield, lower Kappa number, better bleachability, and brighter and stronger pulps.