Metla has produced an information packed working paper on the drying of small energywood stems.
The working paper (number 186) is titled “Natural drying methods to promote fuel quality enhancement of small energywood stems”, and is available from Metla (Finnish Forest Research Institute). Drying of these stems in the forest can improve the quality of the fuel wood and make the supply chains more efficient. The research tested natural drying of the stem biomass, and how methods such as partial debarking, bark scarifying and covering the wood would affect the drying. Field trials were carried out in Finland, Scotland and Italy. The paper contains much information, and is well structured with good use of graphs and pictures.
The working paper consists of two parts:
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Part 1 – “Partial debarking of stemwood as part of the chain of production of forest chips and split firewood”.
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Part 2 – “Partial debarking and covering to promote drying of roundwood for energy in Finland, Scotland and Italy”.
The research found that with laboratory tests of birch, partial debarking and scarifying can be as effective as log splitting. Scarifying needs to take place along the entire stem. Partial debarking and scarifying can result in 10% lower moisture content than the control of stems with bark on. With pine, it was found that scarifying did not work as effectively.
With the field trials, it was discovered that covering was very important for drying when much rain is experienced. There were also notable differences between species, with species such as alder and sitka spruce drying faster than the pines. The drying season was proven to be essential to decrease moisture contents.
The authors of this article were Dominik Roser, Ari Erkkila, Blas Mola-Yudego, Lauri Sikanen, Robert Prinz, Antti Heikkinen, Heikki Kaipainen, Heikki Oravainen, Kari Hillebrand, Beatrice Emer and Kari Vaatainen. Source: www.metla.fi