Open access publications in the SLU publication database

Abstract

Scaling pulpwood according to its weight for payment purposes is done in many places
around the world. In North America, pulpwood is commonly scaled according to its green weight, while in Central Europe the wood is commonly scaled according to its dry weight. In Sweden pulpwood is measured according to its volume.

This doctoral thesis aims to study the prerequisites for Sweden to weight scale its pulpwood. Historical observations of the green density plus meteorological data were used to create a model that predicted the green density of Norway spruce pulpwood that arrived at Braviken pulp and paper mill. By obtaining the weight of the wood and the prediction of green density, the volume could be obtained. To study the prerequisites for scaling wood according to its dry weight, the variation in moisture content was described within and between logs of Norway spruce. Further, dual energy X-ray absorptiometry was recognized and studied with respect to its potential to quickly and accurately determine the moisture content in wood samples. Different techniques for sampling roundwood to determine the moisture content were also studied.

The results of this thesis showed that the green density could be determined with similar precision as the volume measurement performed today. Moreover, it was shown that there was a large variation in the moisture content both within single discs and between logs of Norway spruce. It was shown that with dual energy X-ray absorptiometry, it was possible to determine the moisture content in chips of Scots pineand Norway spruce in good concurrence with the gravimetric method. The different techniques to sample roundwood showed similar results for a regular chainsaw and a modified chain sampler, but none of them worked totally satisfactorily and they both contained systemic errors.

The main benefits of weight scaling are that it is faster compared to volume measurement, it has potential to be less laborious while the new technique using X-ray absorptiometry to determine the moisture content in the wood provides the opportunity to sort arriving wood dependent on its moisture content.