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Development of Feedstock Quality Specifications for Optimizing Biofuels Conversion Processes

Judy K. Partin, Materials Characterization, Idaho National Laboratory, 1765 N Yellowstone Highway, PO Box 1625, Idaho Falls, ID 83415-2211, Garold L. Gresham, Interfacial Chemistry, Idaho National Laboratory, 1765 N Yellowstone Highway, PO Box 1625, Idaho Falls, ID 83415-2208, and Peter A. Pryfogle, Biofuels and Renewable Energy, Idaho National Laboratory, 1765 N Yellowstone Highway, PO Box 1625, Idaho Falls, ID 83415-2203.

The DOE/USDA Billion Ton Technical Feasibility Study identified 1.3 tons per year of biomass feedstock that could potentially be used for biofuel conversion in the United States. One difficulty in the commercialization of this resource is that, unlike other major commodities, it is comprised of numerous smaller resources that have a variety of physical and chemical attributes. These attributes include material density and recalcitrance, carbohydrate, BTU, and lignin content, water activity, and the presence of various organic and inorganic compounds, or contaminants. Various collection, preprocessing, pretreatment, and storage operations may alter these properties in ways that impact the value of the feedstock for biochemical and thermochemical conversion processes. For example, harvesting could be managed to reduce moisture, influence carbohydrate and lignin content, or gather particular material fractions of the biomass. Wet storage and ensiling processes may present avenues for collecting soluble compounds, including sugars, salts, and other inorganic contaminates, or for reducing the recalcitrance of the biomass through pretreatment. Preprocessing operations, such as grinding and screening, could be used to reduce and select particle size distributions, resulting in higher material densities. In addition to increasing the biomass quality, these operations also present opportunities for reducing the handling, transportation, and storage costs of the feedstocks.

This paper describes on-going research directed at identifying the key feedstock attributes that impact conversion efficiencies, understanding how these properties can be changed during the feedstock assembly operations, and applying screening techniques to establish and track material quality through these operations. The goal of this work is to determine the quality factors for biomass feedstocks that could be used to select, value, and screen materials for use in specific conversion processes. In addition to minimizing problems associated with feedstock variability during conversion, this capability could also assist in addressing sustainability issues by determining which material fractions are the most valuable as residues.