*1.1. Biomass Variability*

Due to the diversity in the supply of available biomass, biorefineries are expected to receive varied feedstocks with different physical properties and chemical compositions. Biomass obtained from different regions, weather patterns, harvesting, handling and storage conditions, and crop varieties increases this variability factor even further. To address these variability issues, biorefineries need either to re-engineer their processes for each feedstock or to design systems with extreme tolerance, which can have a significant impact on the overall cost. One of the major limitations in using biomass at large scale is variability in the physical and chemical properties of the biomass and the seasonal and geographic availability of the biomass [6]. The variability in biomass physical and chemical properties limit its commercial-scale applications [7]. For example, biomass moisture variability influences grinder throughput and particle size distribution, which in turn causes inconsistent mass and heat transfer in conversion. Particle size variability creates feed-handling and conversion issues. For example, larger particle sizes (such as chips and coarsely ground herbaceous biomass) plug bins and augers and do not fully cook in digesters, thereby plugging downstream equipment. Fine particles influence ash composition, thus causing fire, explosion, and health hazards, plugging of weep holes in digesters, and creating inconsistent mass and heat transfer during biochemical and thermochemical conversion.
