Blending hydrochar improves hydrophobic properties of corn stover pellets

Inadequate weather resistance and hydrophilic nature of biomass pellets are two major concerns for transportation, storage, and conversion. This study investigates how hydrophobicity of air classified corn stover pellets can be increased by blending corn stover with hydrochar. Hydrochar was prepared by hydrothermal carbonization (HTC) of waste corn stover at 260 degrees C for 30 min of residence time. Pellets were prepared from various blends of corn stover and hydrochar ranging from 0 to 50 wt. % hydrochar, and hydrophobic nature of the blend pellets was characterized by equilibrium moisture content (EMC) and contact angle measurement. The results show that hydrochar can significantly improve the hydrophobicity by reducing EMC by 25-40% at relative humidity > 50% and resulting in a higher contact angle (from 53 degrees to 83 degrees) indicating lower wettability. Further investigation of the surface morphology of the blend pellets after moisture uptake showed that blend pellet disintegration can be attenuated significantly with the increase of hydrochar composition. Moreover, the mass and energy densities of the pellets were increased by 4-22% and 17-73%, respectively, with the addition of hydrochar.