Combined production of sawn timber and firewood billets at a birch sawmill in Finland: A simulation approach

Abstract

Growing markets for chopped firewood have created alternative uses for the by-products of sawmills. Based on empirical data and simulated results, the potential of birch (Betula pendula Roth, Betula pubescens Ehrh.) from commercial thinnings for combined industrial production of sawn timber and firewood billets was investigated. In the simulations, different sawing patterns were used for logs intended to combine production of sawn timber and billets for chopped firewood (‘sawlogs’), and for logs intended only to firewood production (‘firewood logs’). Finally, economical feasibility analysis was done concerning the differences between the sawmills’ traditional business concept and the novel concept combining sawn wood and firewood production. The bucking results for the volume yield of different timber assortments varied only slightly between the different bucking options, i.e. the combinations of timber assortments. The main differences in the volumes of timber assortments were due to the stand type where the birch trees were sampled (planted, naturally regenerated, mixed birch–spruce). In the sawing procedure, the output of sawn timber varied between 24% and 42% of the log volume in the sawlogs, depending on the log diameter class. As the volume yield of sawn timber and firewood billets was counted together in the case of sawlogs, the log consumption was c. 1.75 m³ of roundwood per 1 m³ of sawn timber and firewood billets. In the case of the firewood logs, the log consumption rate was considerably lower, only c. 1.35. The economic calculations showed that using the firewood approach in sawing may increase the net added value of products by €1.9–5.4 m⁻³ of logs, depending on their diameter class. As a conclusion, parallel production of sawn timber and firewood from logs from the first and second commercial thinning of birch-dominated stands is a concept that could work as an alliance between a sawmiller and a firewood entrepreneur. The concept could be competitive compared with both traditional sawmilling and production of chopped firewood.

Keywords:

• Chopped firewood
• logs
• sawing
• side products
• thinning

Acknowledgements

Financial support from the National Technology Agency of Finland (Tekes), the Finnish Forest Research Institute (Metla), and the Employment and Economic Development Centre for South Savo is gratefully acknowledged. This study was jointly a part of the project ‘PILKEKONSEPTI—The Firewood Concept’ in the development programme ‘Small-Scale Production and Use of Wood Fuels, 2002–2006’ at Tekes, and a part of the research project ‘Diversification of Hardwood Utilization, 2003–2007’ at Metla. We express our gratitude to Jani Lehtimäki, Jukka Lehtimäki, Juha Metros and Veijo Salo from Metla for collecting the field data in the aforementioned projects.