The effect of whole tree chips in pulp and papermaking

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Virginia Polytechnic Institute and State University

For a variety of reasons, the need for increased utilization of the world's pulpwood resource has become an important subject of discussion in the 1970's. Whole tree chipping, or the use of all above-ground portions of trees, is a feasible method of achieving this goal. Many reports have been published in the field of pulping whole tree chips, and articles pertinent to softwood pulping are discussed in the literature review of the present study. Because a noticeable lack of information on mixed component pulping of southern pines was observed in the literature, the present study was designed to investigate the following topics:

  1. The chemical and biological differences between conventional chips and whole tree chips, and the nature of the variation in the composition of whole tree chips.

  2. The results of pulping mixed whole tree components in a laboratory digester.

  3. The nature of changes that could be expected to develop in a pulping system as the amount of whole tree chips was varied from 0 to 100% of chip input. Kraft pulping of loblolly pine (Pinus taeda, L) was chosen because it is the major pulping system and species in the southeastern U. S.

Unscreened whole tree chips are highly variable in their composition, and age and species have a large effect on the chip composition. Mixed component cooks do not appear to have the poor qualities predicted by individual component cooks. When yield and pulping conditions are held constant and the percent of WTC material is increased, fibrous yield decreases, kappa number rises and pulp color darkens. This may be a result of liquor chemical exhaustion and precipitation of lignin onto pulp fibers. These results indicate that in a mill operation, WTC material should be pulped with increased chemical and liquor volume.