Comparing Two Different Approaches in Modeling Small Diameter Energy Wood Drying in Logwood Piles

Moisture management is a key element to improving the cost-efficiency of energy wood supply, through the whole supply chain. Numerous studies of natural drying of forest biomass have been carried out based on traditional sampling of piles or weighing. The latest methodology for monitoring moisture changes has been continuous weighing of biomass in racks built on load cells. The aim of this study was to develop accurate drying models in Austria and Finland for small diameter logs and test the exchangeability of the developed models between countries. Overall drying periods were December 2009 to February 2011 for Austria and March 2012 to June 2013 for Finland. Moisture content dropped from 50.1% to 32.2% (Austria) and from 62.2% to 38.6% (Finland) during the drying periods. Drying performance was evaluated for the period April to October. Two different types of models were developed and the results were cross validated. It proved to be possible to fit satisfactory accurate drying models within the target deviation of ± 5% using both approaches. Whereas the Austrian approach is based on a more basic set of variables, the Finnish approach combines the variables within one. Both approaches are justified depending on the available data.