*2.1. Sample Preparation Steps*

While Norway spruce was selected for this study because of its availability and suitability as a feedstock for heat and power production, pea starch was chosen for its cost-e ffectiveness and suitability as an additive in pelleting processes. Whereas the pea starch was an industrial secondary starch obtained in powder form from Lyckeby, Kristianstad, Sweden, Norway spruce was obtained in the form of logs from a local sawmill in Karlstad, Sweden and was cut into chips. The two raw materials, upon procurement in their pure form, were placed in small plastic bags and stored at room temperature. Prior to pelleting, the materials were dried in an oven at 50 ◦C for 24 h. Because starch was obtained in powder form, it did not require milling, but was sieved to a particle size of 0.3 mm, according to American Society for Testing and Materials (ASTM) standards (D 2013-72). Norway spruce was milled to a particle size of <1 mm using a Wiley mill and also sieved to obtain a final particle size equal to that of pea starch. Appropriate quantities of each sample were separately weighed and mixed with water to obtain a final moisture content of 10% (wet basis). This was because moisture is often required during pelleting to reduce friction and to avoid blocking of the pellet press die; under these circumstances, however, adding the right amount of water is very vital, as material moisture content must not exceed 10% for pellets made from woody biomass, and a maximum moisture content of 15% for pellets made from grass [6,28]. Preceding these steps and soon after procurement, milling, and sieving, the initial moisture contents of the two samples (Norway spruce and pea starch) were determined according to

standards [29]. The determination of moisture content was done on a wet basis by weighing the two samples and placing them in an oven at 105 ◦C for 24 h and weighing again to determine final weight.
