*2.3. The Pellet Production Process*

Pure and blended pellets were produced from Norway spruce and pea starch using a single pellet press available at the Department of Engineering and Chemical Sciences of Karlstad University in Sweden. Figure 1 presents the laboratory-scale pellet press set-up used in the pellet production process.

**Figure 1.** The single-unit pellet press set-up used in this study with labeled parts.

The press consisted of a cylindrical die made of hard steel, about 8 mm in diameter, with connected heating elements and thermal insulation. A temperature control unit was used to regulate die temperature from ambient conditions to a maximum temperature of 100 ◦C. The bottom end of the cylindrical die was closed with a removable plastic piston stopper. Compression force was mechanically applied with a piston pointing directly toward the top opening of the die filled with exactly 1 g each of the pure and blended samples of milled Norway spruce and pea starch. Piston movement was controlled by the entire pellet press system, and pressure was applied to the piston through a load cell whose maximum compression force was about 2000 kN. Before each use and when changing the raw materials, the die was rinsed several times with acetone and cleanly wiped with a paper towel. Each of the pure and blended samples was compressed at a velocity of 30 mm·min−<sup>1</sup> until a maximum pressure of 16 kN was reached. The holding time for every test was set at 10 s, which is in agreemen<sup>t</sup> with studies conducted by Nielsen et al. [30] and by Nguyen et al. [31]. The pellets were removed from the die by removing the stopper and mechanically pushing out the pellets, slowly, at a velocity of 5 mm·min−1. According to a previous study [7], the optimum pelleting conditions under which the pure and blended samples of Norway spruce pellet (NSP) and pea starch pellet (PSP) were produced at a laboratory scale are shown in Table 1.

**Table 1.** Optimum pelleting conditions under which pure and blended samples of Norway spruce pellet (NSP) and pea starch pellet (PSP) were produced [7].

