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Abstract

Suppression of prairie fires enabled Eastern Red Cedar (ERC) to invade and thrive on more than 12 million infested acres previously dominated by native grasses. Feedstock procurement for a biorefinery designed to use ERC biomass, would be unique relative to energy crop production systems such as switchgrass that can be expected to harvest feedstock produced on the same unit of land each year. Density of ERC is heterogeneous. After cutting, ERC does not regrow and after ERC is removed landowners could be expected to take measures such as prescribed fire to control it. A mixed integer mathematical programming model is constructed to determine the cost to obtain the rights to harvest, harvest, and deliver a specified quantity of ERC biomass each year, for a period of 20 years, to a biorefinery location. The optimal strategy depends critically on several assumptions including the proportion of ERC biomass under contract enabling ERC harvest once during the 20 years; ERC growth rate; ERC density; discount rate; harvest and transportation cost; and quantity of biomass required per day. Optimal harvest strategy, optimal biorefinery location, and maximum daily biorefinery capacity, are sensitive to tree density and the proportion of ERC biomass in the region from which ERC can be removed. The expected cost of delivered biomass ranges from $41 to $92 per ton depending on the assumption of proportion of ERC biomass under contract, quantity of biomass required at the biorefinery, harvest cost, growth rate of unharvested trees under contract, and discount rate.

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