Physical characterization of commercial woodchips on the Italian energy market

The Authors set out to determine the particle-size distribution, the fiber and bark content, and the heating value of a wide sample of wood chips, collected from 60 commercial biomass terminals active in Northern Italy. This sample was meant to represent a cross-section of the Italian fuel chip market, and focused on four main feedstock types: sawmill residues, logging residues, small trees and short rotation coppice (SRC). Overall, the Authors collected 300 samples, each weighing approximately 1 kg. Particle-size distribution was determined with an automatic screening device on 210 samples, according to European Standard CEN/TS 15149-1. All samples were also manually separated into the following main components: fiber, bark, twigs, leaves, dust and other. The higher heating value (HHV) was determined on 56 one-gram subsamples using an adiabatic bomb calorimeter. Sawmill residues and small trees offered the best quality, with high fiber content (85-90%) and favorable particle-size distribution. On the contrary, both logging residues and SRC presented a high bark content (>= 20%) and occasionally a mediocre particle-size distribution, being often too rich in fines (>= 10%). These problems were especially serious with fuel derived from 1-year old SRC sprouts. There is a need for reducing the supply cost of small trees, and improving the quality of SRC biomass.