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The British Wood Pulp Association

Woodpulp was first produced in the mid-19th century by grinding logs against a water lubricated, rotating stone-faced drum. The heat generated by grinding softens the lignin and the mechanised forces separate the fibres to form ‘groundwood pulp’ (sometimes called "wood free").

This process is still used today, especially for newsprint. In the last two decades or so, newer mechanical techniques using "refiners" have been developed. In a refiner, woodchips are subjected to intensive shearing forces between a rotating steel disc and a fixed plate. In subsequent modifications to this process, the woodchips are pre-softened by heat(Thermomechanical pulp - TMP) or by heat and a mild chemical treatment with sodium sulphite(Chemi-thermomechanical pulp -CTMP).

Mechanical pulping provides a good yield from the pulpwood of 90% or above, because it uses all the log except for the bark, but the energy requirement for refining is high and can only be partly compensated by using the bark as fuel. The investment costs for mechanical pulp mills are relatively low in comparison with other types of pulp mills. Mechanical pulp is well suited for "bulk" grades of paper, such as newsprint and packaging boards. It can be bleached with peroxide for use in higher value-added products. It has lower strength characteristics than softwood chemical pulps and, because it retains most of the lignin which reacts with ultra-violet light, can "yellow" when exposed to bright light.