A Method for Determining the Dry Weight of Pulpwood

The accuracy of the determination, of the dry weight of pulpwood when different measurement methods, are used, is considered. The solid volume method gives a coefficient of variation of 4 – 5 percent, and the stacked volume method gives a somewhat higher figure due to variations in the relative solid volume content. The corresponding figures for spruce and pine obtained by the green weight method are about 7 percent, and that for birch about 4 percent, if the timber is scaled just after cutting. A method for determining the dry weight of pulpwood directly is described. The pulpwood is weighed and samples, in form of chips, are taken from logs on either side of the truckload. The chips are weighed in the green condition, ovendried and weighed again in the ovendried condition. The dry matter percentage is calculated for each sample. The dry weight of the whole truckload is calculated from these figures. The coefficient of variation for the mean is about 5 percent, if chip samples are taken from 10 logs in the truckload. If samples are taken from all logs on both sides of a truckload, the mean will have a standard error of about 3.5 percent. In a delivery consisting of many truckloads it is not necessary to sample each load to obtain high accuracy. A necessary prerequisite to this method is that the trucks are loaded randomly so that logs on the sides of the truckload can be considered as random samples of the whole truckload. If, in winter time, the timber is covered with snow and ice, the method will, to some extent, adjust for the overestimated green weight of the pulpwood.

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