The low bulk density and low flowability of lignocellulosic biomass feedstock have been regarded widely as major barriers for a sustainable and efficient supply system. Densification of biomass is a viable option to increase the bulk (and inherent energy) density and flowability of feedstock, leading to improved efficiency of the supply system. The energy consumption of feedstock densification is one of the key variables that determines the efficiency of the feedstock supply. This paper investigates the energy consumption of herbaceous feedstock compression in relation to particle physical properties, preheating, and binding agents, such as steep water and thin stillage, both byproducts of corn ethanol production. The results indicate that the specific energy consumption for mini-bale densification was a function of the particle size, moisture content, and feedstock type. During pelletization, where all pellets were exposed to an identical maximum pressure, preheating temperature, particle size, and moisture content played a significant role in improving the energy efficiency and pellet density. Both binding agents increased the energy requirement for pelletization but yielded more durable pellets.