2.1. Biomaterials
Sawdust of Scots pine (Pinus sylvestris L.) and Norway spruce
(Picea abies Karst. (L.)) originating from latitude 57 and 64°N were
collected and delivered from four different sawmills in Sweden. About
18 tons of each biomaterial were transported to a biofuel pellet plant
in the beginning of June, where one half of each material was stacked
for a 140 day storage period during the summer. The second half was
immediately dried to about 15% moisture content, while the first half
was dried to the same moisture content at the end of storage. All
materials were then transported to a pilot pellet plant at the Biofuel
Technology Centre (BTC) at the Swedish University of Agricultural
Sciences (SLU) in Umeå where the pelletizing experiments were
conducted.
At the pilot plant each biomaterial was batch-wise dried to 9 and
12% moisture content, respectively according to the experimental
design using a drying wagon and ventilating warm air (see Fig. 1). The
piles of stored biomaterial were monitored during 140 days by
measuring the temperature continuously and collecting samples once
a month in which the content of fatty and resin acids was determined.