cornstover

When the lignocellulosic biofuels industry reaches maturity and many types of biomass sources become economically viable, management of multiple feedstock supplies – that vary in their yields, density (tons per unit area), harvest window, storage and seasonal costs, storage losses, transport distance to the production plant – will become increasingly important for the success of individual enterprises. The manager’s feedstock procurement problem is modeled as a multi-period sequence problem to account for dynamic management over time. The case is illustrated with a hypothetical 53 million annual US gallon cellulosic ethanol plant located in south west Kansas that requires approximately 700,000 metric dry tons of biomass. The problem is framed over 40 quarters (10 years), where the production manager minimizes cumulative costs by choosing the land acreage that has to be contracted with for corn stover collection, or dedicated energy production and the amount of biomass stored for off-season. The sensitivity of feedstock costs to changes in yield patterns, harvesting and transport costs, seasonal costs and the extent of area available for feedstock procurement are studied. The outputs of the model include expected feedstock cost and optimal mix of feedstocks used by the cellulosic ethanol plant every year. The problem is coded and solved using GAMS software. The analysis demonstrates how the feedstock choice affects the resulting raw material cost for cellulosic ethanol production, and how the optimal combination varies with two types of feedstocks (annual and perennial).

This presentation summarizes findings of a life cycle analysis of the energy and environmental impacts of converting corn stove (the residue from corn harvesting) to ethanol.

The harvest of corn stover or herbaceous crops as feedstocks for bioenergy purposes has been shown to have significant benefits from energy and climate change perspectives. There is a potential, however, to adversely impact water and soil quality, especially in Midwestern states where the biomass feedstock production would predominantly occur. The overall goal of this research is to provide a thorough and mechanistic understanding of the relationship between stover and/or herbaceous crop production management practices and resulting range of impacts on soil and water quality, with a focus on Eastern Iowa. The production of these bioenergy crops is compared to corn and corn-soybean rotations on eight different soils representative of the region. The APEX model, which predicts crop, water, nutrient, carbon and soil flows within an integrated agricultural and hydrological system, provides a means to quantify sustainability metrics and is used to generate sufficient data to provide a greater understanding of the particular variables that affect water and soil quality than previously possible. The sustainability metrics include total nutrient emissions to ground and surface water, total soil losses due to wind and water erosion, and cumulative soil carbon losses, all normalized to acreage and crop production. As expected, the results clearly show the superiority of switchgrass from a soil and water quality perspective. They also show, however, that compared to corn-soybean rotations with conventional tillage, soil and water quality degradation can be reduced at the same time stover is collected under certain soil types and no-till agricultural practices.