Economics of Alternative Corn Stover Logistics Systems

Abstract

Eight different corn stover logistics systems were modeled for the purpose of evaluating their sensitivity to key system parameters to identify the lowest cost feedstock system. Reducing field operations and maintaining harvester productivity were vital to reducing harvest costs. Storage costs were lowest with systems that had low losses and transport costs were minimized when truck weight limit was attained. Deconstructing and size-reducing bales added considerably to processing costs compared to bulk system where size-reduction took place at harvest. For these reasons, bulk harvest and storage systems consistently provided lower cost feedstock than bale systems. Of the systems considered where the stover and grain were separated at harvest, the two-pass chopped, bulk system where moist stover was conserved by anaerobic storage and fermentation produced the lowest feedstock cost at $84/Mg, a difference of $26.7/Mg or 24% lower than the conventional three-pass LSB, covered storage scenario. Storage and transport costs made up a significant fraction of total costs with this bulk system, but these greater costs were offset by much lower harvest and processing costs compared to other systems. A sensitivity analysis showed that yield and the size of the processor had the most impact on feedstock cost. They do so, primarily by the impact on transportation distance, which was found to be the largest cost. A new approach was considered in which very mature corn grain and stover would be harvested, stored and shipped together. The grain and stover fractions would then be separated for further processing. The stover feedstock costs were 55% less than conventional stover harvest systems and 34% less than the lowest cost two-pass system. This system offers the best opportunity to significantly reduce corn stover feedstock costs.