The present study has evaluated the effect of moisture content at the inlet of the compression die, the use of additives, the compression die and the raw material composition to the blends of poplar and pine on the pellet production process to obtain pellet with ENPlus quality according to EN 14961-2 [5]. It has been observed that the ash content is the most restrictive parameter to select the proportion of raw material for blends to obtain pellets with the highest ENPlus quality. The use of blends of poplar and pine as raw material allows increasing the poplar pellet quality, even making unnecessary the use of additive to get pellet with ENPlus A2 or ENPlus A1 quality. An increase of pine percentage in the blend makes necessary higher compression die to make pellets with thehighest quality because softwood needs higher compression die that hardwood to be compressed. The increase in moisture content at the inlet of the compression die reduces both the energy consumption of the pellet press and the die temperature, which are indicative of improved pelletization process. This is an indication of improved pelletization process. In addition, higher moisture content at the inlet increases the pellet moisture, but it must be controlled to obtain pellet with moisture content below 10 wt.%. Pellets ENPlus A1 were obtained when the pine percentage to the blendwas below5wt.% d.b. and pellets ENPlus A2 were obtained when the pine content in the blend was between 25 and 45wt.% d.b. Poplar pellet could not be classified as ENPlus
category because the bulk density obtainedwas belowtheminimumEN 14961-2 limit.
The addition of 1 or 2 wt.% d.b. of lignosulfonate to poplar improved the pelletization process, as inferred from the lower electric intensity and die temperature, and higher durability and density of the pellets was obtained. Nevertheless, the pellet produced was not classified as ENPlus B because again the bulk density obtained was below the minimum and the sulfur and ash contents were increased over the maximum EN 14962–1 limit.