Current issue: 55(5)
Under compilation: 56(1)
The article is a review on the wood procurement and cost of pulpwood in the Finnish mechanical and chemical pulp industry in 1922‒1926, based on statistics collected from the members of the Central Association of the Finnish Woodworking Industries (now Finnish Forest Industries), and the series Statistics of Industry and Foreign Trade. Wood trade is carried out by three types of sale: standing sales where the buyer of the wood takes care of fellings and transport (55% of the volume), contracts for the delivery of pulpwood (45% of the volume), and fellings in the own forests of the industry. Norway spruce (Picea abies (L.) H. Karst.) was the most important tree species, and was used almost exclusively especially in the mechanical pulp mills. According to the study, the demand of pulpwood increased markedly during the period. The stumpage prices did, however, not increase accordingly until in 1926. It is assumed that also the supply of wood was high after the World War I.
The PDF includes a summary in English.
The main source of data was the official industrial statistics in 1911‒1929. The data was complemented with information from other sources, and the figures converted to solid volumes under bark. The wood consumption of wood manufacturing industry in the period varied strongly, being lowest in 1918 (2.2 million m3) and highest in 1927 (18.1 million m3). The wood consumption dropped during the World War I.
The wood manufacturing industry in Finland concentrated on sawmilling industry which has used annually 70‒80% of the wood consumed in the whole wood manufacturing industry. Other sectors of industry using wood were plywood industry, wood-wool industry, spool factories, match industry, mechanical pulpwood industry and pulp industry.
The PDF includes a summary in German.
In the first part of the study, the selected wood and fiber properties were investigated in terms of their occurrence and variation in wood, as well as their relevance for thermomechanical pulping process and related end-products. It was concluded that the most important factors were the fiber dimensions, juvenile wood content, and in some cases, the content of heartwood being associated with extremely dry wood with low permeability in spruce. The following pulpwood assortments of which pulping potential was assumed to vary were formed: wood from regeneration cuttings, first-thinnings wood, and sawmill chips.
In the experimental part of the study, the average wood and fibre characteristics and their variation were determined for the raw material groups. Subsequently, each assortment – equalling about 1,500 m3 roundwood – was pulped separately for 24 h period. The properties of obtained newsgrade thermomechanical pulps were then determined.
Thermomechanical pulping (TMP) from sawmill chips had the highest proportion of long fibres, smallest proportion of fines, and had generally the coarsest and longest fibers. TMP from first-thinned wood was the opposite, whereas that from regeneration cuttings fell in between these two. High proportion of dry heartwood in wood originating from regeneration cuttings produced a slightly elevated shives content. However, no differences were found in pulp specific energy consumption. The obtained pulp tear index was clearly the best in TMP made from sawmill chips and poorest in pulp from first-thinned wood, which had generally inferior strength properties. No big differences in any of the strength properties were found between pulp from sawmill residual wood and regeneration cuttings. Pulp optical properties were superior in TMP from first-thinnings. No noticeable differences were found in sheet density, bulk, air permeance or roughness between the three pulps.
The most important wood quality factors were the fibre length, fibre cross-sectional dimensions and percentage juvenile wood. Differences found in the quality of TMP assortments suggest that they could be segregated and pulped separately to obtain specific product characteristics and to minimize unnecessary variation in the raw material and pulp quality.