The availability of corn and wheat crop residues was analyzed for each county in Ohio. Results showed that two clusters in western Ohio, each encompassing 17 counties with a collection radius of 50 miles, could provide feedstock for two ethanol plants at a capacity of 5,000 dry tons per day each. This calculation assumes that 35% of the corn stover and wheat straw per acre would be removed. These two plants could produce a total of 240 million gallons of ethanol per year.
This fact sheet illustrates the process of evaluating where such facilities might be feasible. Naturally, not every acre of corn or wheat residue in a county would be available, nor would every acre have 35% of the residue removed.
World oil prices are the major factor in the demand for ethanol in the U.S. Although low prices for gasoline reduce the demand for ethanol and other bio-based fuels, the long-range prospects are for higher prices; therefore, there is good market potential for these alternative fuels.
Approximately 30% of U.S. corn grain is used in ethanol production. Research is continuing on using crop residues (cellulose in corn fodder and wheat straw, for example) as another economical source of ethanol. Crop residues suitable for cellulosic ethanol production will likely be in high demand in the future.
Other regions of Ohio with fewer acres of corn and wheat could grow energy crops such as switchgrass and poplar trees, and could provide mixed feedstocks for a cellulosic ethanol plant. Wood waste and municipal solid waste could also be a feedstock.
Ohio corn production for grain in 2005 and 2006 was about 470 million bushels per year. Among Ohio crops, corn has the greatest potential for cellulosic ethanol production. Corn stover includes stalks, leaves, cobs, and husks and contains approximately 35% cellulose, 22% hemicellulose, and 18% lignin (EERE, 2007). Nationally, the amount of corn stover that can be sustainably collected is estimated to be 80–100 million dry tons per year (Kadam and McMillan, 2003).
Soybean is the second major crop in Ohio, with an annual average harvest of 209 million bushels, but the relatively small amount of residue rapidly degrades in the field and is not considered as a potential feedstock for ethanol production.
Wheat is the third major crop, with 62 million bushels produced per year in 2005 and 2006. Wheat straw contains approximately 33% cellulose, 23% hemicellulose, and 17% lignin and is the second best source among grain crops for cellulosic ethanol production.
OSU researchers studied the distribution of usable crop residues among Ohio counties and calculated amounts of wheat straw and corn stover for each Ohio county (Jeanty et al., 2004).
This fact sheet summarizes the availability of major crop residues (sustainable amount per square mile) in Ohio at the county level (Table 1). The sustainable amount of crop residue in each county was calculated based on the residue yield and a collection factor of 35%. Counties were clustered for the purpose of identifying potential feedstock supply areas for future cellulosic ethanol plants.
Sustainable Crop Residue
Crop residues play an important role in protecting the soil surface from water and wind erosion and in helping to maintain nutrient levels, so removing them comes at a cost. Currently in the U.S., most corn stover is tilled or left undisturbed on the field. Previous research has estimated that 20%–35% can be removed without unduly harming the soil (Nelson, 2002). A collection factor (percentage of crop residue removed from the field) of 35% was used in this study.
To estimate the crop residue available, the ratio of corn grain to corn stover was assumed to be 1:1. For wheat, the ratio of grain to straw was assumed to be 1:0.8. Average grain production in 2005 and 2006 was used in our calculations. Accurately estimating the amount of biomass available is essential to evaluate the collection cost for ethanol production.
Ethanol Production Potential
How much ethanol can be produced from a ton of corn stover or wheat straw? The amount varies depending on the composition of the crop residues and the ethanol production technologies.
The National Renewable Energy Laboratory (NREL, 2007) estimates the theoretical ethanol yield for corn stover at 113 gallons per dry ton for an average corn stover composition and assuming that both hexose and pentose sugars are fermented. For this analysis, we assumed an ethanol yield of 73 gallons per dry ton, which is about 64% of the theoretical yield. For wheat straw, we used an ethanol yield of 70 gallons per dry ton, based on a study by Kadam and McMillan (2003).
Table 1 summarizes the data for the 43 counties in Ohio with the greatest potential to support cellulosic ethanol production. The hydrolysis technologies assumed are either dilute acid hydrolysis or enzymatic hydrolysis. The fermentation process should be able to convert hexose and some of the pentose.
The total sustainable amount of corn stover and wheat straw in Ohio is estimated to be 4.6 and 0.7 million dry tons per year, respectively. The majority (85%, or 4.5 million tons) of these crop residues are located in 43 counties in northwestern and west central Ohio.
Figure 1 shows the amount of corn stover for each Ohio county. Figure 2 shows the total amount of corn stover and wheat straw by county.
The corn and wheat biomass availability of each county is distinguished with a different color based on the sustainable amount of crop residue per square mile of total area. Fulton County has the highest total biomass availability at 380 dry tons per square mile. The biomass availability in seven other counties (Henry, Crawford, Mercer, Darke, Van Wert, Wood, and Putnam) exceeds 300 dry tons per square mile.
Bioethanol Production Potential
Total bioethanol potential from crop residues in Ohio was estimated to be about 340 million gallons per year. The bioethanol potential from crop residues in the 43 northwestern and west central counties of Ohio was estimated to be about 300 million gallons per year, or about 85% of the total ethanol potential from crop residues in Ohio.
The delivery cost of biomass is the most important factor for the bioethanol producer. Nearly one-third of the biomass ethanol production costs is attributed to the costs of the feedstock, which includes handling costs and payments to the landowner/tenant. Perlack and Turhollow (2003) estimated that corn stover can be collected, stored, and transported to ethanol facilities for about $43–$60 per dry ton using conventional baling equipment. Transportation, collection, baling, and farmer payments accounted for over 90% of that total cost.
The scale of the bioethanol conversion facilities is relatively significant for the economy of bioethanol production. Generally, capital costs for ethanol plants increase by 60%–70% for each doubling of output capacity (Perlack and Turhollow, 2003). As plants increase in capacity, the cost saving from economies of scale will be offset somewhat by increased transportation costs associated with hauling feedstock greater distances. Consequently, determining the ideal location of an ethanol plant involves striking a balance between larger handling capacities and higher feedstock costs.
Based on considerations of economies of scale and biomass availability, the optimal locations of potential ethanol plants in Ohio were determined. Counties with high biomass availability were clustered to provide two ethanol plants with feedstock demands of 6,800 and 5,700 dry tons per day, respectively (Figure 3).
Cluster 1 consists of 17 counties: Crawford, Fulton, Henry, Van Wert, Wood, Putnam, Hardin, Wyandot, Hancock, Sandusky, Seneca, Paulding, Allen, Williams, Defiance, Ottawa, and Lucas. These 17 counties can sustainably produce almost 7,000 dry tons of residues per day, which can supply an ethanol plant with a capacity of 130 million gallons of ethanol per year. The equivalent collection radius for this ethanol plant was estimated to be 50 miles. The equivalent collection radius was calculated based on the total area of the counties in the cluster. The transportation cost for this cluster was estimated to be about $33.75 per ton. Naturally, the actual cost is affected by current fuel prices.
Cluster 2 consists of 17 counties: Mercer, Darke, Auglaize, Madison, Preble, Shelby, Fayette, Miami, Warren, Champaign, Clinton, Clark, Logan, Greene, Union, Montgomery, and Butler. These 17 counties can sustainably produce close to 6,000 dry tons of residues per day, which can supply an ethanol plant with a capacity of 110 million gallons of ethanol per year. The equivalent collection radius for this cluster was estimated to be 50 miles. The transportation cost for this cluster was estimated to be about $34.50 per ton.
These clusters of counties are examples of how to combine counties to provide feedstock for a potential ethanol plant. The location of any future ethanol plant should be determined using the biomass availability of each county.
Ohio counties with fewer crop acres might have other cel ulosic biomass such as wood waste or municipal solid waste. It is possible to provide mixed feedstock for a cellulosic ethanol plant in those areas.
A key to improving the economics of transporting the crop residue will be the development of a packing system that increases the density above that of a conventional baler. If the stover and straw were packed to a density of, say, double that of the current big square bales, then the feasible distance to the ethanol plant could be increased and the farmer might receive a higher return.
This analysis was supported by funding from The Ohio State University Department of Food, Agricultural, and Biological Engineering and the Ohio Agricultural Research and Development Center (OARDC). Dr. Harold Keener, Professor of Food, Agricultural, and Biological Engineering, and Mary Wicks, OARDC, assisted with the study. This publication was reviewed by Dr. Erdal Ozkan, Professor of Food, Agricultural, and Biological Engineering.
- EERE. 2007. Biomass feedstock composition and property database. Washington, D.C.: U.S. Department of Energy. Available at: afdc.energy.gov/biomass/progs/search1.cgi. Accessed November 20, 2007.
- Jeanty, P. M., D. Warren, and F. Hitzhusen. 2004. Assessing Ohio's biomass resources for energy potential using GIS. Report to the Ohio Department of Development.
- Kadam, K. L., and J. D. McMillan. 2003. Availability of corn stover as a sustainable feedstock for bioethanol production. Bioresour. Tech. 88(1): 17–25.
- Kerstetter, J.D., and J.K. Lyons. 2001. Logging and agricultural residue supply curves for the Pacific Northwest. Report prepared for the U.S. Department of Energy. Available at: pacificbiomass.org/documents/WA_AssessmentLoggingAndAgResidueSupplyCurveFinalReport.pdf. Accessed June 17, 2008.
- Nelson, R.G. 2002. Resource assessment and removal analysis for corn stover and wheat straw in the eastern and midwestern United States: Rainfall and wind-induced soil erosion methodology. Biomass Bioenergy 22(5): 349–363.
- NREL. 2007. Theoretical ethanol yield calculator. Washington, D.C.: U.S. Department of Energy. Available at: www.eere.energy.gov/biomass/ethanol_yield_calculator.html. Accessed November 30, 2007.
- Perlack, R.D., and A.F. Turhollow. 2003. Feedstock cost analysis of corn stover residues for further processing. Energy 28(14): 1395–1403.
Table 1. Biomass Availability and Ethanol Potential for the Top 43 Counties of Ohio.
(ranked by biomass/mi2)
|Corn Stover||Wheat Straw||Total|
Figure 1. Availability of Corn Stover in Ohio on a County Basis.
Figure 2. Availability of Crop Residues (Corn Stover and Wheat Straw) in Ohio on a County Basis.
Figure 3. Clusters of Counties for Ethanol Production in Ohio.
This fact sheet is based on Drs. Yebo Li and Harold Keener's publication titled "County level analysis of crop residues availability for fuel ethanol production in Ohio" published in Transactions of the ASABE 52(1): 313–318.