Pulp and paper

Wood chips and exports

Woodchips are a by-product of harvesting operations where parts of trees or even whole trees are too low quality for sawlogs. These trees and part trees often need to be removed to allow young seedlings to grow properly in regenerated areas. The trees and part trees often need to be removed to allow young seedlings to grow properly in regenerated areas. The woodchips are used to produce pulp and high quality paper. However, the volume of native timber woodchips exported for papermaking has fallen sharply because of the reduced levels of harvesting. There is also an increased availability of high quality pulpwood from plantations.

The short fibres of eucalypt species make them very suitable for the production of chemical pulp for high quality paper manufacture, using the Kraft process. Western Australia had exported a 2:1 marri / karri woodchip mix to Japan since the mid 1970s. Contrary to public perception, woodchip logs are low quality and below sawlog requirements, with the main requirement being that no charcoal is allowed.

Marri is difficult to mill because of the high occurrence of kino (gum) veins, and provided a high percentage of residue logs. Forest thinnings of both species have been used for woodchip production, as well as tops of trees harvested for sawlogs and sawmill residue. Efficient utilisation includes revenue from residues, both forest and sawmill. Karri gives a higher yield of pulp than does marri.

Tasmanian blue gum (Eucalyptus globulus subsp globulus) is an excellent species for woodchip production, has been planted extensively in the State since the mid 1990s by both Government and private companies. Significant volumes of blue gum are becoming available, and consequently in late 2000 Marubeni Pty Ltd, the licensed exporter, stopped taking marri. Alternative markets must be found for the species.

The transition to a plantation based woodchip industry for paper-making is accelerating. It is expected that plantation woodchip exports will increase from 50 000 tonnes in 2000 to
750 000 tones in 2002.

A new plantation woodchip mill in Albany will contribute to the growth of a plantation based woodchip industry for Western Australia. The mill commenced operating in late 2001 and will reach full capacity of one million tonnes per year by 2005-2006.

It should be noted that the silvicultural and management requirements for growing blue gum for woodchips are different to those for growing sawlogs, and it is difficult for a forest grower to change direction from woodchip logs to sawlogs after the first few years.

Pulp and paper production

Australia exports large quantities of woodchips for pulp and paper manufacture, mainly to Japan. However, we are major importers of paper, mainly softwood fibre based from New Zealand and Finland. It would be an advantage for Western Australia to produce its own high quality paper using WA-grown eucalypts and chemical pulps.

How is paper made? Briefly, mechanical or chemical pulps are produced. Mechanical pulps are ground wood and recoveries are high because cellulose, hemicellulose, lignin (i.e. the cement binding the cells and in the cell wall) and extractives are not separated. Chemical pulping involves removing most lignin to separate the fibres, and then bleaching the residual lignin and the extractives to give the required brightness of paper. There are various modified methods that produce different qualities of pulp.

Softwoods (conifers) have long fibres and are generally used for newsprint and packaging, while hardwoods (Angiosperms or flowering plants) have small short fibres and are better used for high quality printing paper.