Swedish Sawmills Research Articles

Macroscopic X-ray computed tomography aided numerical modelling of moisture flow in sawn timber

Mathematical models are essential for the development of schedules for the air-circulation drying of timber in Swedish sawmills, but earlier models have been shown to be conservative leading to longer drying times than necessary. In the current study, macroscopic (macro) X-ray computed tomography (CT) has been used in both the development and validation of a finite element (FE) model, to enable the macro-CT aided FE modelling of the nonlinear transient moisture flow in wood. The model uses more advanced theory than has previously been used in Swedish sawmills, by incorporating a surface emission coefficient to simulate the surface resistance to moisture flow. A single piece of Norway spruce [Picea abies (L.) Karst.] timber was subjected to that part of a traditional kiln-drying schedule, which is associated with diffusion-driven moisture transport. The incorporation of macro-CT data into the FE model resulted in a more realistic representation of the board’s geometry, the initial moisture state, and the definition of material parameters. It also led to a better simulation of flow speed and moisture gradient, especially the asymmetric MC development within the cross section throughout the drying process.

Sawmilling in Sweden: Past, present and future

With 62% of her land covered with forest, Sweden is the world’s second largest combined exporter of paper, pulp and sawn wood products. Modern industrial sawmilling of Sweden started from the mid-19th Century after British import was made liberal, and Norwegian exporters faced short supplies of raw materials and Canadian producers were more expensive. During the same time, Sweden also developed industries and technology making it more competitive. However, after 20th century, sawmilling in Sweden started to adopt ‘integrated forest firm approach’ where many small and locals sawmills were forced out of the business because of numerous war-crises and oil-crises that occurred. In recent decades production and exports from Sweden is in increasing trend. This increasing trend is the result of some specific strategies undertaken by Swedish sawmilling sectors viz. transforming market channel, transforming product value adding strategy and transforming service value adding strategy. Currently, Swedish sawmills can be categorized into nine groups based on their value addition strategy and technology they use. These sawmills face competition from other materials and countries, low efficient transfer of technology and knowledge transfer, presence of small scale sawmilling, and some sawmills are in risk as they lack of product diversification and have specialized production. Future of the sawmilling in Sweden is expected to be growing. However, they have to encourage the use of wood, transfer skill and knowledge, increase the size of the firm, further diversify the products, and also improve technology and mechanization. DOI: http://dx.doi.org/10.3126/init.v5i0.10260 The Initiation 2013 Vol.5; 110-120

Integrated production of semi-finished components in sawmills, part II: Management of internal operations

Recently, several Swedish sawmills have taken over production of components from customers in the furniture, joinery and house-manufacturing industries. The purpose of this study was to identify key factors in management of internal operations for sawmills with this strategy. A multiple case study design, based on face-to-face interviews with Swedish sawmill practitioners and on various forms of secondary data, produced comprehensive research information. Starting integrated production of components is a demanding strategy for sawmills. It requires deep knowledge about the customer and qualified skills in advanced further-processing of sawn wood. The complexity of quality management, production planning and cost calculation increases, and investments in processing equipment and customer relations reduce strategic flexibility. The diverging material flow complicates sawmills' possibilities to economize on scale, and they must instead economize on other factors, such as scope, combined operations and internal control. New tools for production follow-up and control, for production planning, for analysis of product profitability and for strategic partnership analysis are requested by practitioners. But, even if new analysis tools would facilitate better analysis and management of operations, the willingness and ability to innovate and learn among the personnel emerges as a key factor for success.

Industrial Sawing of Pinus sylvestris L.: Power Consumption

The wood industry continues to strive to reduce production costs and increase productivity to remain competitive. Knowledge of the effect of wood cutting parameters on power consumption could increase energy efficiency, reducing operating costs and increasing profitability. Measuring power consumption also provides information about other variables, such as tool edge wear, occurrence of catastrophic failures, and other parameters that affect the quality of the sawn boards and the momentary efficiency of the breakdown process. In this work, power consumption during sawing of Pinus sylvestris L. using a double arbor circular saw was investigated. Both climb-sawing and counter-sawing were considered. The experiments were carried out under normal production circumstances in two Swedish sawmills. The relationship between cutting parameters and theoretical power consumption was investigated. The experimental power consumption increased by 11 to 35% during an 8-h shift, mainly due to an increase in the tooth radius. Additionally, this study showed that climb-sawing consumed more power than counter-sawing.

Improved energy efficiency in sawmill drying system

The worldwide use of biomass has increased drastically during the last decade. At Swedish sawmills about half of the entering timber becomes lumber, with the remainder considered as by-product (biomass). A significant part of this biomass is used for internal heat production, mainly for forced drying of lumber in drying kilns. Large heat losses in kilns arise due to difficulties in recovering evaporative heat in moist air at low temperatures. This paper addresses the impact of available state-of-the-art technologies of heat recycling on the most common drying schemes used in Swedish sawmills. Simulations of different technologies were performed on an hourly basis to compare the heat and electricity demand with the different technologies. This was executed for a total sawmill and finally to the national level to assess the potential effects upon energy efficiency and biomass consumption. Since some techniques produce a surplus of heat the comparison has to include the whole sawmill. The impact on a national level shows the potential of the different investigated techniques. The results show that if air heat exchangers were introduced across all sawmills in Sweden, the heat demand would decrease by 0.3TWh/year. The mechanical heat pump technology would decrease the heat demand by 5.6TWh/year and would also produce a surplus for external heat sinks, though electricity demand would increase by 1TWh/year. The open absorption system decreases the heat demand by 3.4TWh/year on a national level, though at the same time there is a moderate increase in electricity demand of 0.05TWh/year. Introducing actual energy prices in Sweden gives an annual profit (investment cost excluded) on national level for the open absorption system of almost 580million SEK. For the mechanical heat pump technology the profit is 204million SEK and for the traditional heat exchanger the profit is significant lower. It has been found that a widespread implementation of available energy recovery technologies across Swedish sawmills would result in substantial savings of biomass for other purposes in the society.

Integrated production of semi-finished components in sawmills, part I: External interactions

In a changing business landscape, where globalization and new customer requirements create new business opportunities, some Swedish sawmills have taken over the production of components from their industrial customers. In light of the emerging network-centric perspective on business, sawmill managers' perceptions about component customers' operational requirements, customer interaction processes, and their sawmills' offerings are researched and discussed in this article. A multiple case study design, based on face-to-face interviews with Swedish sawmill managers and on various forms of secondary data, produced comprehensive information about sawmills' interaction processes with component purchasing customers. Thematic data coding facilitated the assessment of the research information in relation to the conceptual and empirical findings of previous research. The findings of the study indicate that more process orientation in housing-, joinery-, and furniture-manufacturing implies an opportunity for sawmills to make service-based offerings including not only physical goods, but also administrative services, logistics, and expert advice. The results of the study confirm the network-centric perspective on business where value is created through the interaction between firms. However, noteworthy barriers in the form of process-, culture-, as well as socially related factors at customer firms must be considered.

Surplus biomass through energy efficient kilns

The use of biomass in the European Union has increased since the middle of the 1990s, mostly because of high subsidies and CO 2 emission regulation through the Kyoto protocol. The sawmills are huge biomass suppliers to the market; out of the Swedish annual lumber production of 16.4 Mm 3, 95% is produced by medium to large-volume sawmills with a lumber quotient of 47%. The remaining part is produced as biomass. An essential part (12%) of the entering timber is used for supply of heat in their production processes, mostly in the substantial drying process. The drying process is the most time and heat consuming process in the sawmill. This study was undertaken to determine the sawmills’ national use of energy and potential magnitude of improvements. If the drying process can be made more effective, sawmills’ own use of biomass can be decreased and allow a considerably larger supply to the biomass market through processed or unprocessed biomass, heat or electricity production. The national electricity and heat usage when drying the lumber have been analysed by theoretical evaluation and experimental validation at a batch kiln. The main conclusion is that the heat consumption for drying lumber among the Swedish sawmills is 4.9 TW h/year, and with available state-of-the-art techniques it is possible to decrease the national heat consumption by approximately 2.9 TW h. This additional amount of energy corresponds to the market’s desire for larger energy supply.

Automatic counting of annual rings on Pinus sylvestris end faces in sawmill industry

Abstract The quality of wood can be analyzed using annual ring width. At Swedish sawmills, this is performed using manual inspection for grading purpose. Here a completely automatic method for counting the number of annual rings on log end faces is described and evaluated. The method is applied and tested using images from Pinus sylvestris end faces acquired in online sawmill production with a camera mounted above a conveyor belt. Completely untreated end faces were captured, as well as newly sawn ones. The proposed method includes preprocessing, pith detection and counting the number of rings in two regions of the end face. A new method to remove marks from uneven sawing is presented as a part of the preprocessing steps. The evaluation shows that the suggested automatic method performs as well as the manual measurements that are the method used for measuring today.

Increased Yield in Sawmills by Applying Alternate Rotation and Lateral Positioning

Modern sawmills are increasingly like process industries, running continuously with very large volumes flowing through the process every second. This fact makes it vital for every company to utilize its equipment and raw material as effectively as possible to maximize yield and value. The objective of this simulated breakdown study was to analyze the potential to increase volume yield in Swedish sawmills. While the commonly used horns-down position performs well on an average basis, the results show that the optimal rotation position for an individual log is most often found at another position. Results from extended simulations show that the average volume yield can be increased further by applying the optimal combination of rotation and parallel positioning in cant and deal saw. An increase in average volume yield by 4.5 percentage points (8.6%) would enable a typical Swedish sawmill to produce a further 17,300 m3 of boards per year and thereby increase potential annual income by US$3.7 million per year. This optimization concept requires a preevaluation of every log in order to define the optimal combination of settings. Some of these procedures must be performed online within a split second to accommodate production speed demands. Modern technology such as industrial x-ray in combination with traceability methods, multivariate models, breakdown simulation software, and high-performance computers enables evaluation and optimization of every log online at full production speed. Sawing machines will need development in order to be able to perform optimization online without loss of production capacity.

Wood drying process: impact on Scots pine lumber durability

There are indications that the drying process may have negative effects on the natural durability of wood. The impact of various drying processes on the durability of Scots pine lumber has been evaluated with mass loss in a decay test with brown rot fungus, Coniophora puteana, as measure of the decay resistance of sapwood and inner and outer heartwood. Drying with or without steam conditioning was performed in six different series: air drying, kiln drying at temperature ranges commonly used in Swedish sawmills at 70°C and 90°C with two different regulation principles, and one high-temperature drying at 110°C. Durability varied considerably both between and within boards. Sapwood showed considerable less durability than heartwood. No difference in durability was found between inner heartwood and outer heartwood. Air-dried heartwood showed the highest durability compared to other drying series. The lowest durability in sapwood and heartwood was found for series dried at the 90°C temperature level with high material temperature early in drying. The interpretation is that the duration of high material temperature at high moisture content (MC) is the critical combination for decay resistance in heartwood. Steam conditioning after drying decreased durability in sapwood.

Improved ecoeffectiveness of interior hardwood products in the house-building industry as a way to promote sustainable forestry

Sawn hardwood is required by the market to be homogeneous, even in texture and colour, but the products produced by Swedish hardwood sawmills exhibit a wide variation in characteristics. This makes it difficult for hardwood sawmills to find profitable markets for all their products. By developing new products with other properties for the building industry it may be possible to utilize hardwood more efficiently and increase the prices. This would result in higher ecoeffectiveness (defined as value in relation to environmental impact) of the forest-related business system by giving an incentive to grow deciduous forests, which leads to richer biological diversity. Diversity is fundamental to achieving sustainable forestry. At the same time, other less ecoefficient materials in buildings may be replaced. Exploring the requirements of the customers is essential before developing new products, in order to maximize the value of a product. In this study, the requirements of interior hardwood products in the Swedish house-building industry were studied in interviews and through questionnaires. The most important requirements, ranked higher than price, are delivery on time, shape stability, packaged products, rapid delivery and accurate moisture content. The results make it possible to focus on critical factors to gain market shares for hardwood as an ecoeffective building material.

The Fingerprint Method: Using Over-bark and Under-bark Log Measurement Data Generated by Three-dimensional Log Scanners in Combination with Radiofrequency Identification Tags to Achieve Traceability in the Log Yard at the Sawmill

In the forestry–wood chain the concept and the technologies of traceability are in a mature development phase. Important advances in marking and reading techniques have been made in different parts along the forestry–wood chain. For Swedish sawmills the most critical information gap is located between the log sorting station and the saw intake, where the forest log batch identity disappears and the logs are mixed according to different sorting criteria. This study utilizes radiofrequency identification tags for automatic log marking/reading to develop a traceability system for logs, which is free of marking/reading, between the log sorting station and the saw intake, i.e. the fingerprint method. The originality of the fingerprint approach rests on the hypothesis that logs are separate entities with individual features. The results show that the log parameters and the search algorithm developed, combined with the negative influence of the measurement uncertainty due to bark thickness and bark damage, made it possible to achieve an individual separation for 57% of the tested logs.

Identification of Value-adding Strategies in the Swedish Sawn Wood Industry

Swedish sawmills are increasing their application of value-adding processes in sawn wood production. This study identified the most common value-adding combinations used by the Swedish sawmills. Data were obtained from a survey of Swedish sawmills in 1995 and from industry statistics. Nine different groupings of sawmills with regard to the level and types of value-adding technologies were identified by cluster analysis. The largest group added value only to marginal quantities of their production. Eight other groups that applied different combinations of value-adding processes were identified. Drying and planing were important elements in several strategies. Adding value to the sawn wood is not a homogeneous strategy; instead it includes several ways to focus production on different products and customer groups. Advanced value-adding processes often generated a higher unit profit margin than the production of commodity sawn wood.

Production strategies in the Swedish softwood sawmilling industry

The strategic production decisions to improve profits for sawmills can be described in three main dimensions. More value-added production increases unit revenues, larger volumes reduce fixed costs per produced unit, and improved productivity reduces unit costs. Using data about the Swedish sawmills and cluster analysis, six groups of sawmills were defined with these strategy dimensions. Characteristics of each strategy are presented concerning ownership, location, technology, and economic indicators. The results indicate that different groups of Swedish sawmills employ different production strategies, which are reflected both in the dimensions, value-added shares, size, productivity, and by other technical and economic characteristics of the sawmills. The relationships between production strategy and profitability is also analysed and discussed.

Adoption of value-adding processes in Swedish sawmills

Adding value to lumber by processing it after sawing and standard drying is one means for the sawmilling industry to increase market shares in competition with other materials, e.g. glass, steel, concrete, aluminium, and plastics. In this study the adoption patterns of value-adding processes used in Swedish softwood sawmills were analysed based on production data from 1995. About 90% of the sawmills applied a value-adding process after initial sawing and drying, and 72% of the sawmills applied two or more processes. The total share of processed sawnwood was about 40%. Important dimensions of value-adding processes are: extra drying and production of blanks for doors/windows and for furniture; surface-treatment, mainly planing, which is sometimes associated with preservation and painting; length trimming and pallet production; extra drying and production of edge-glued panels and laminated beams; and stress grading and production of building components. The association of different value-adding dimensions with location, ownership and production characteristics were investigated. The total share of value-added production were higher for private sawmills than for mills owned by forest companies or by forest owners’ associations, and it was higher for mills in southern Sweden than for sawmills in other parts of the country. Value-added share does not clearly correlate with mill size or with the dominating tree species being sawn.

Inhalation fever and respiratory symptoms in the trimming department of Swedish sawmills.

Mold dust exposure in the trimming departments of sawmills may cause inhalation fever as well as allergic alveolitis. Responses to questionnaires sent to 2,052 workers from trimming departments of 233 Swedish sawmills showed that one of five workers experienced work-related febrile attacks. A single case of allergic alveolitis was found.

Trade unions in the Swedish sawmills

Abstract Although the sawmill industry occupied a strategic position during the industrialisation of Sweden, it has on the whole been the subject of remarkably little research. A number of monographs by Harald Wiik, Ernst Söderlund, Karl-Gusraf Hildebrand, Thore Hammarland and the present reviewer deal with production, exports, working conditions and trade unions, but special studies have been rare. Within the last few years this has begun to change, resulting from the launch of the Urnef Economic History Institute's project, Skogsindustrier oeh bondesamhällen i Norrland (Forest Industries and Peasant Communities in Norrland). The present work is the project's first completed study.

Use of chlorophenols as fungicides in sawmills.

Several commercial formulations of chlorophenols used as fungicides in sawmills were found to contain impurities, some of which are known to be much more toxic than the main products. The most frequent impurities were chlorinated phenoxyphenols, chlorinated diphenyl ethers, chlorinated dibenzofurans, and chlorinated dibenzodioxins. Samples of wood dust from several positions in two Swedish sawmills were analyzed. The results suggest that the impurities in the chlorophenol formulations are enriched in the work environment in relation to the chlorophenols themselves, probably because of the low volatility and high chemical stability of the impurities. The effect of various methods of fungicide application on the work environment is discussed.