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  Making Pulp from Wood

Woodpulp currently represents 44% on average of the fibre used to manufacture paper and board worldwide, of which 11% is home produced. None of these mills uses mature fully grown trees, but rather small dimension timber, (which is no use to other commercial users such as furniture makers and builders), saw mill waste and forest thinning.

In the past the industry used softwoods such as spruce, pine, fir, larch and cedar almost exclusively, but hardwoods such as birch and aspen are gaining in popularity. Fast growing eucalyptus have been successfully cultivated in Northern Spain, Portugal and Brazil and provide the papermaker with very high quality pulp. Softwoods provide long strong cellulose fibres and are used to produce papers where strength is a requirement, for example, packaging papers. The shorter hardwood fibres provide bulk, smoothness and opacity and are used to produce fluting medium and printings and writings.

Trees vary enormously in the time they take to reach full size. Much depends on climate and the soil, but these figures give a rough comparison:

Tree Type Life Expectancy (years)
Willow 25 - 35 years
Sitka spruce 50 years
Douglas fir 55 - 60 years
Scots pine 70 - 80 years
Norway spruce 70 - 75 years
Oak >100 years (not used for papermaking)

Oak trees usually live 200 - 300 years, but some have been known to live for more than 1,000

When a tree trunk or thick branch is cut across, a series of dark rings can be seen. These are annual rings which result for the seasonal growth. Each ring represents one year's growth. The grain in timber is caused by the annual rings which show when a log is cut. Teak, mahogany, oak, beech and elm have attractive grain and are used for furniture making (rather than papermaking).

Woodpulp comes from trees from managed forests where more trees are planted than harvested to ensure that demand for timber products will never outstrip supply. The forest industry has become more aware over recent years that it has a responsibility, not only to ensure the economic viability of its operations, but also to ensure that the requirements of local communities are catered for. Greater care is taken to ensure that logged areas blend in more readily with the landscape.

Certain pulp characteristics depend on the process used to reduce the wood to its component fibres. There are three main ones:

Mechanical or ground wood




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