In addition, softwood tends to springback more than hardwood [13]. Thus, it is  
Figure 1: Illustration of the powder compression curve divided into particle rearrangement, fragmentation, elastic and plastic deformation and hardening. The figure has been modified from [PERSON], [PERSON] et al. [1]. important to understand why springback occurs. Even if there have been studies that correlate the springback effects of biomasses, there is a gap in the knowledge on which substances within a chemical composition in biomass have more or less of an impact. The diverse composition of biomass can be divided into two broad categories: macromolecular and low-molecular-weight substances. The macromolecular category includes lignin, polysaccharides, and proteins. Polysaccharides can be further divided into cellulose, hemicelluloses (mainly glucomannan and xylan), and other polysaccharides, such as pectin, starch, and galactan. The low-molecular-weight substances, including organic and inorganic substances, where organic substances include extractives (such as fat, wax, and tannin substances) and inorganic substances include ash substances [4; 14]. The chemical composition of biomass is well defined in the literature [14; 15; 16], where it can be seen that for hardwood, the main hemicellulose component is xylan, and for softwood, mannan is the main component. [PERSON] et al. studied the impact of polysaccharides (cellulose, hemicellulose, and other polysaccharides) lignin, protein, and extractives and found that there is a difference between how the substances behave during densification, particularly the difference within the hemicellulose's components--xylan and glucomannan [4; 17], where xylan is more affected by added water in comparison to mannan. However, the question of whether there is a variation between these substances, especially the hemicelluloses, in correlation to springback, has not been studied. [PERSON] et al. further showed that the flexible polysaccharides--xylan and pectin pellets--changed in terms of their color and structure during densification, especially when water was added [17]. There was also a difference between the hemicellulose components, xylan and glucomannan, correlated to these changes, where xylan changes in color from a light beige to a darker brown and glucomannan shows no color changes [17]. Pellets undergoing changes in color have also been seen when feedstock is steam-treated before pelletization [18; 19]. Using steam-treatment in a pellet process increases both the moisture, as well the temperature, and the fact that increased temperature can change color in wood has been seen in techniques other than pelletization. When wood is heat-treated on purpose to improve properties such as dimensional stability and durability against biodegradation, color changes occur homogeneously throughout the wood [20; 21; 22]. Even if these are two different techniques, steam-treatment of wood and pelletization, it is likely that theories behind color changes can be based on the same parameters, where one theory is that hemicelluloses play an important role. The darker tonality of heat-treated wood is often attributed to the formation of colored degradation products from hemicelluloses [23; 24; 25], where cellulose is less affected because of its semi-crystalline nature [20]. One explanation for the color changes is that the hemicelluloses are degraded to a greater extent than other cell wall components [22], due to the presence of the acetyl groups that are thermally labile in the hemicelluloses and lead to the formation of acetic acid and subsequent acid-catalyzed reactions [20]. The formation of oxidation products, such as quinones, is also stated as the reason for color changes [26; 27]. Heat treatment generally results in an increased proportion of lignin, which may be attributed to a relative decrease in carbohydrate proportion and also to hemicellulose dehydration and the subsequent condensation to form pseudo-lignin [21] that can result in color changes.