THE SUPPLY OF CORN STOVER IN THE MIDWESTERN UNITED STATES

1. THE SUPPLY OF CORN STOVER IN THE MIDWESTERN UNITED STATES Richard G. Nelson1, Marie E. Walsh2, and John Sheehan3 1Kansas State University 2University of Tennessee 3National Renewable Energy Laboratory

2. Background • U.S. heavily dependent upon fossil fuels • Consumes 98 Quads of primary energy annually (86% from fossil fuels)(year 2002) • 39 percent of primary energy use from petroleum (64% is imported). • 24 percent of primary energy use from natural gas • 23 percent of primary energy use from coal • Annual GHG emissions projected to increase from 1559 (year 2002) to 2237 mMTce by 2025 • Biomass resources, such as corn stover, can be used to produce electricity, transportation fuels, and chemicals while providing energy, economic, and environmental benefits

3. Project Objectives • Develop and apply a methodology to estimate quantities (dt/ac/yr) of crop residue that must be left on the field by individual soil type, crop rotation, and tillage practice to keep rain/wind erosion at or below the tolerable soil loss level (T) • Estimate crop residue supply curves for a continuous corn rotation (weighted by tillage practice) for 10 Midwestern states (IA, IL, IN, MN, WI, NE, MO, OH, KS, and SD)

4. Agricultural Crop Residue Retention/Removal Analysis Residue Required for Erosion Control is a Function of: 1. Type of Erosion (wind/rain) 2. Field operations (tillage scenarios, maintenance, etc.) • Soil Type 4. Climate (rainfall, temperature, retained moisture) 5. Physical field characteristics (% slope, soil erodibility) 6. Crop and cropping rotation 7. Tolerable Soil Loss, T

5. Remaining Residue Methodology • Identify physical characteristics (soil erodibility, percent slope, etc.) of all cropland soils in each county • Apply the Revised Universal Soil Loss Equation (RUSLE) and Wind Erosion eQuation (WEQ) to each soil type to estimate the quantity of residue that must remain on the field throughout the year as a function of three tillage scenarios (CT, MT, and NT) such that T is not exceeded • Calculate county-level quantities of corn stover (dt/ac) that must remain using an acreage-weighted approach

6. Removable Residue Methodology • County-level quantities of corn stover (dt/ac) that can be removed by tillage practice are the quantity produced (grain yields times residue factors) minus the higher of the rain/wind erosion quantities that must remain • Total county-level quantities of corn stover that can be removed (dt) are estimated as: removable quantities by tillage type * total corn acres * percent of corn acres in each tillage type

7. State Average Corn Stover Quantities CT is conventional tillage; MT is mulch till/reduced till; NT is no-till. Source: Nelson 2004.

8. Corn Stover Collection Cost Methodology • Corn stover harvested as large round bales • Collection costs include mowing/raking/ baling, picking up, and transport to field edge • Equipment cost methodology (fuel/lube, repairs, capital, insurance/housing, labor, etc.) and operating parameters from AAEA and ASAE • Costs vary as a function of corn stover quantity (dt/ac)

9. Corn Stover Collection Costs 40.00 35.00 30.00 Corn Stover Collection Costs ($/dt) 25.00 20.00 15.00 1 2 3 4 1.2 1.4 1.6 1.8 2.2 2.4 2.6 2.8 3.2 3.4 3.6 3.8 Corn Stover Quantity (dt/ac) Corn Stover Collection Costs as a Function of Removable Quantity

10. Corn Stover Supply Curves Source: Walsh 2004. Unpublished Analysis

11. On-Going Analysis • Erosion analyses completed for several crops (corn, soybeans, wheat, rye, barley, oats, rice) and rotations (e.g., continuous, corn-soybean, wheat-fallow, etc.) by soil type and tillage practice for continental U.S. • Soil carbon needs analysis underway • Incorporation of available quantities and collection cost estimates into dynamic agricultural sector model already modified to include energy crops (POLYSYS) to estimate integrated biomass supply curves