The state of the art in woody biomass comminution and sorting in Northern Europe

Abstract

This review provides a survey of the literature on methods for comminuting and sorting woody biomass. The reported methods were classified according to their basic operating principles: methods of comminution were separated based on whether they use sharp, semi-sharp or blunt tools; methods of discrimination were classified according to the parameters they use. The identified methods of comminution differ significantly in terms of productivity and energy use. The differences between individual biocomponents with respect to the parameters used for discrimination (such as solid density, or particle size and shape) are often rather small and species dependent, which makes it difficult to efficiently sort woody biomass from mixed species. Other parameters (e.g. optical and near-infrared properties) can be used as inputs for active sorting on larger scales. Several methods for tree processing and chip sorting that were originally developed for pulp-chip production now see little use because they are not considered cost-effective. However, the economic importance of fuel products has increased substantially in recent years. Fuel can be produced using material with a higher bark content than is tolerated in pulp chips, so it may be worth re-evaluating some of the methods that were previously discarded. Examples include tree-processing machines such as drums and cradles for partial foliage removal, processes such as delimbing and debarking (which facilitate downstream sorting of the comminuted material), and screens and wind classifiers for processes such as separating fines (often ash-rich) from comminuted material. The available data on the performance, required investment, and operating costs for these methods are incomplete and often not comparable. This issue must be addressed to facilitate the development of optimized fuel supply chains.

Performance of a small and a medium sized professional chippers and the impact of storage time on Scots pine (Pinus sylvestris) stem wood chips characteristics

“…Moreover, grinders offer a rather coarse product that is unsuitable for use in some smaller plants (Hakkila 1989;Strelher 2000;Rinne 2010;Eriksson et al 2013). Currently, roadside chipping is the dominant chipping system in Finland and Sweden as well as in other European countries (Junginger et al 2005;Stampfer and Kanzian 2006;Kärhä 2011;Eriksson et al 2013;Holzleitner et al 2013;Rottensteiner et al 2013;Routa et al 2013;Wolfsmayr and Rauch 2014;Eliasson et al 2015). Large disc chippers or drum chippers are used on terminals for chipping large-sized stemwood, while drum chippers dominate the chipping of logging residues and small trees on landings in Finland (Kärhä 2011).…”

“…1989; Rinne 2010; Spinelli et al 2011c;Spinelli et al 2012;Eriksson et al 2013). Drum and disk chippers are the primarily technology used, whereas cone-screw chippers are rarely used (Hakkila 1989;Eriksson et al 2013;Wolfsmayr and Rauch 2014).…”

“…Drum and disk chippers are the primarily technology used, whereas cone-screw chippers are rarely used (Hakkila 1989;Eriksson et al 2013;Wolfsmayr and Rauch 2014). The grinders are more consistent against interruptions caused by impurities.…”

The cost competitiveness of conifer stumps in the procurement of forest chips for fuel in Southern and Northern Finland

“…Systems based on comminution at the landing increase the payload of trucks, since the comminuted material is less bulky, and thereby reduce transport costs (Eriksson et al 2014a;Eriksson et al 2014b). Screening also reduces the amount of fine material contaminants at the source and increases the quality of the produced fuel (Eriksson et al 2013;Dukes et al 2013;Laitila and Nuutinen 2015). Thanks to screening, an ash content of 0.4-2.3% for ground stumps has been reported, while the wood-matter losses have been rather nominal (Laitila and Nuutinen 2015).…”

“…Handling, transportation, and screening of stump material tends to lower the contaminant content (Korpinen et al 2007;Laitila et al 2008;Athanassiadis et al 2011;Anerud and Jirjis 2011;Palander et al 2011;Anerud 2012;Kärhä 2012;Fogdestam et al 2012;Dukes et al 2013;Anerud et al 2013;Nuutinen et al 2013;Eriksson et al 2013;Eriksson et al 2014a;Eriksson et al 2014b;Berg 2014;Laitila and Nuutinen 2015). When stumps are ground directly to an acceptable fuel fraction at the landing, the amount of upgrading vibration is the lowest and the ash content of ground stump material is the highest.…”