Effect of fiber natures on the formation of “solid bridge” for preparing wood sawdust derived biomass pellet fuel

• Sawdust was densified into biomass pellet biofuel in the presence of natural fiber.
• Natural fiber could be a substitute of wrapping paper fiber as “solid bridge”.
• Geometrical shape of natural fiber limited the formation of “solid bridge”.
• Hydrophilicity of the fiber determined the formation of “solid bridge”.

Four different types of fibers including rice straw, wheat straw, rubber leaf and nylon were added into wood sawdust to prepare renewable biomass pellets (BPs) at room temperature. The effects of these fiber natures on the physical properties of BPs were investigated by characterizing the elongation, particle density, abrasive resistance and impact resistant index. Experimental results showed that the addition of rice straw and rubber leaf possessed a positive effect on the physical properties of BPs while the addition of wheat straw and nylon had a negative effect. The positive effect of the former can be attributed to the strengthened bonds in the BPs by the intertwining action of a “solid bridge” between these linear hydrophilic fibers and wood sawdust. The negative effect of the latter is due to the repelling role between the hydrophobic fiber and hydrophilic wood sawdust to arrest the formation of their “solid bridge”. Therefore, the added fiber natures highly influenced the formation of a “solid bridge” that determined the physical properties of BPs derived from wood sawdust.