Feedstock quality: A poorly understood but critical aspect for the development of a biorefining industry

The success of a future national-scale biofuel and biochemical industry will depend on a reliable supply of commodity biomass feedstock having multiple end uses to reduce supply risk and encourage investment. Commodity markets utilize grading systems to describe the suitability of a given lot of the commodity for a specified end use. Establishing a grading system for biomass is difficult because of the wide range of available conversion processes, as well as the myriad of different biomass types that will comprise the required billion tons of biomass. Mature biomass supply systems and quality metrics already exist for the agriculture, logging, food, and pulp and paper industries, which fosters assumptions that similar biomass quality indicators are also appropriate for conversion to biofuels/chemicals. In this presentation we consider feedstock quality requirements as they relate to different conversion processes and end uses.  At the highest level, physical characteristics and chemical composition are the most important indicators of a biomass source’s potential for conversion into biofuels. However, requirements for these quality indicators can be markedly different among conversion processes and additional compositional and structural requirements necessarily come into play. We consider feedstock attributes at physical (macro), structural (micro), and molecular scales and their relationships to quality requirements occurring in the feedstock supply chain, entering the biorefinery, and during conversion. Finally, we discuss ongoing work at INL on quality mitigation strategies that can be employed in distributed feedstock depots or inside the biorefinery gate to reduce feedstock supply risk and mobilize the billion tons.