Recently, there have been significant R&D advances in dry herbaceous preprocessing that will enable the transition from the current state-of-technology bale-based system to a more cost-effective bulk feedstock system for biorefineries. However, additional advances are needed in three key areas: 1) preprocessing equipment capacity, 2) feedstock bulk density, and 3) feedstock quality. Equipment capacity and bulk density directly affect feedstock cost. Thus, they are important technical parameters to address, along with the interrelated effect on feedstock rheological properties. Furthermore, a key component of feedstock R&D is to extend preprocessing beyond size reduction to include value-added operations that improve feedstock quality for the biorefinery, such as fractionation and separation of higher-value components.

Specific research needed in this area includes:

• Developing preprocessing requirements for each feedstock type

• Understanding the relationship between biomass structure and composition for assess­ing quality-upgrade potential and developing equipment and methods to achieve these upgrades

• Understanding and controlling biomass tissue deconstruction in preprocessing and the relationships among grinder configuration, tissue fractions, tissue moisture, and grinder capacity to optimize grinder configuration for fractionation, capacity, and efficiency

• Increasing bulk densities by coupling the understanding of biomass deconstruction and rheological properties with innovative bulk compaction methods

• Understanding and controlling feedstock rheological properties resulting from prepro­cessing operations to provide a product that minimizes problems in transportation, han­dling, and queuing operations.