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Cost and profit impacts of modifying stover harvest operations to improve feedstock quality

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Biofuels, Bioproducts and Biorefining
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In addition to quantity and price, biomass quality attributes, and the potential tractability of those attributes, is key to a successful biomass feedstock supply chain. Modifying harvest operations is one potential approach to managing biomass feedstock quality for corn stover. For example, eliminating raking from stover harvest operations is proposed as an approach to reduce ash content. However, changes in the stover harvest configuration cause changes in per-acre profits, per-ton costs, and available supply at specified prices. Here we evaluate sensitivity of profit, cost, and supply to conversion from a three-pass to a two-pass stover harvesting configuration as a means to reduce ash content. For all simulated yields, per-ton harvest costs are $2-$3 per ton cheaper for three-pass vs two-pass systems wherever residue retention coefficients are less than 0.5, and per tons costs for both systems increase dramatically where residue retention coefficients are greater than 0.7. Per-acre net returns are greater under all simulated yields wherever residue sustainability retention coefficients are less than 0.6. Under these conditions, farmers lose between $13 and $49 per acre by harvesting with a two-pass vs a three-pass system. Where competing with stover markets with less stringent quality specifications, meeting ash targets by harvesting with a two-pass system may require higher grower payments on the order of $9-$25 per ton to make up for the per-acre lost revenue. When solving for the least-cost supply, agronomic simulations suggest about 2/3 of stover is harvested with a three-pass system.