Impact of amylose and amylopectin content in starch on wood pellet production

In the production of wood fuel pellets, starch is frequently used as an additive to enhance bonding and durability. This study investigated the effectiveness of four different kinds of starches as additives, each at a concentration of 5% (dry basis), when combined with sawdust from Scots pine (Pinus sylvestris). The starches tested included plain wheat flour, hydrothermally treated wheat starch, wheat starch with amylose-like properties, and nearly pure amylopectin obtained from waxy rice flour. All pellets were produced at a die temperature of 100 °C using a Single Pellet Press, with varying moisture contents of 5%, 8%, 11%, and 14% (wet basis). The pellets were evaluated for compression work, back pressure, physical density, hardness, and moisture content. Additionally, chemical bonding was assessed using FT-IR spectroscopy. Compression energy was found to be influenced by moisture content, irrespective of starch utilization, and it decreased with increasing moisture levels, especially between 5 to 8% (wb). The inclusion of starch led to notably higher pellet hardness, with amylose yielding the hardest pellets, 34±3 kg when the moisture content was 11%. Based on this study, it is recommended to use hydrothermally treated wheat flour, as it consistently produced high-quality pellets.