Cost and profit impacts of modifying stover harvest operations to improve feedstock quality
Biomass quality attributes, and the potential tractability of those attributes, are key to a successful biomass feedstock supply chain, in addition to quantity and price. 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, harvest costs are 2–3 per ton cheaper for three–pass versus two–pass systems wherever residue retention coefficients are less than 0.5, and per ton 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 rather than 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 of the order of 9–25 per ton to make up for the per acre lost revenue. Here, when solving for the least–cost supply, agronomic simulations suggest about 2/3 of stover is harvested with a three–pass system.