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© 2008 Plant Management Network. Comparing the Feed, Fertilizer, and Fuel Value of Distiller’s Grains John A. Lory, Extension Associate Professor, Division of Plant Science; Raymond E. Massey, Extension Professor, Agricultural Economics; Charles D. Fulhage, Professor, Biological Systems Engineering; Marcia C. Shannon, Associate Professor and Ronald L. Belyea, Professor, Animal Science; and Joseph M. Zulovich, Extension Assistant Professor, Biological Systems Engineering, University of Missouri, Columbia 65211 Corresponding author: John A. Lory. LoryJ@missouri.edu Lory, J. A., Massey, R. E., Fulhage, C. D., Shannon, M. C., Belyea, R. L., and Zulovich, J. M. 2008. Comparing the feed, fertilizer, and fuel value of distiller’s grains. Online. Crop Management doi:10.1094/CM-2008-0428-01-RV. Abstract Continued rapid expansion of ethanol production by dry-grind plants will increase the amount of ethanol byproducts such as dried distillers grains with solubles (DDGS) and wet distiller’s grains with solubles. The objective of this review was to determine if continued expansion of ethanol production is likely to lead to significant amounts of ethanol byproducts being used as a fertilizer for crop production. Nutrient density in DDGS and wet distiller’s grains is similar to some forms of animal manure used as fertilizer. Plants with DDGS currently have the option of selling it as a feed, fertilizer, or energy source. Our analysis indicates that feed value currently exceeds the value of other uses of DDGS by at least $90/ton. The high feed value of DDGS and wet distiller’s grains with solubles makes it highly unlikely that these materials will be used as a fertilizer source. Introduction Ethanol production in the United States more than doubled from 1,770 to 4,855 million gallons between 2002 and 2006 (10). Rapid expansion of ethanol production continues with 131 existing plants, 72 new plants under construction, and 10 plants undergoing expansion in October 2007 (11). Production capacity is projected to nearly double from 7,023 to 13,475 million gallons upon completion of current projects. Most of the industry expansion has been in dry-grind plants that process corn into ethanol (8). In these plants corn is ground, mixed with water, and the resulting mash is treated with enzymes to convert starch to sugar and then processed with yeast to convert sugars to ethanol. Figure 1 summarizes the handling of stillage byproduct from fermentation. Dried distiller’s grains with solubles (DDGS) currently is the dominant byproduct, although wet distiller’s grains, condensed distiller’s solubles (syrup), and wet distiller’s grains with solubles can be sold from the plant.
Currently most byproducts are fed to animals. But nutrient concentration in some ethanol byproducts is similar to other waste materials utilized for a fertilizer (Table 1). High fertilizer prices are encouraging farmers to consider alternative nutrient sources for crops. This has led to questions by farmers about the economics of distiller’s grains as a fertilizer source for crops. The objective of this review was to determine if a surplus of ethanol byproducts will lead to significant amounts of ethanol byproducts being used directly as a fertilizer for crops. Table 1. Nutrient and dry matter characteristics of selected distiller’s byproducts, manure and fertilizer sources. All values are on a wet basis.
Nutrient Value of Distiller’s Grains The chemical equation for ethanol production from sugar is:
Table 2. Nutrient concentration in corn feed stock and dried distiller’s
The phosphorus and potassium concentrations in Table 2 are consistent with plants that generated 17 lbs of DDGS dry matter per bushel corn feedstock. There are reports that plant efficiency is increasing resulting in more ethanol being produced per unit of feedstock corn. This trend should result in higher concentrations of nutrients in the DDGS. Nutrient concentrations in DDGS are similar to or greater than byproducts that are routinely applied as fertilizers (Table 1). Nutrient density in DDGS is similar to poultry litter but substantially less than most commercial fertilizers. Lower nutrient density limits the distance a material can profitably be transported as a fertilizer. There is little data available measuring fertilizer nutrient availability of nutrients in DDGS. One report indicated nitrogen was greater than 50% available in a lab mineralization experiment (3). Another research report indicated that nitrogen in DDGS was less available than anhydrous ammonia and rates of application up to 3260 lb/acre did not have a negative impact on yield (5). There has been more work reported on nutrient availability as a feed. Phosphorus has been reported to be 77% and 59% available to animals (4,6) compared to 15% for the corn feed stock. A survey of 14 Midwest ethanol plants indicated that standardized true ileal crude protein digestibility in pigs ranged from 76 to 91% (12). A second study evaluating 10 sources of DDGS reported crude protein as 83% available in pigs (6). For comparison, state recommendations in the Midwest suggest the nitrogen in poultry litter is 45 to 60% available as a fertilizer in the year of application and phosphorus and potassium is 100% available (2). High fertilizer prices are substantially increasing the theoretical value of byproduct derived fertilizers such as DDGS, wet distiller’s grains with solubles and poultry litter (Fig. 2). The theoretical fertilizer value assumes that farmers are willing to pay the same price for nutrients in a byproduct fertilizer as commercial chemical fertilizers. In 2007 the theoretical fertilizer value of DDGS topped $35/ton and wet distiller’s grains with solubles was over $14/ton. Farmers typically are not willing to pay the theoretical fertilizer value for manure because manure nutrients can be more variable and less available than commercial fertilizers and the lower nutrient concentration in manure (Table 1) increases application costs. Similar concerns are likely to make the actual fertilizer value of DDGS and WDGS less than the theoretical fertilizer value.
Comparing Value for Alternative Uses of Distiller’s Grains Currently there are three potential uses for DDGS and wet distiller’s grains with solubles: as a feed for animals, as a fertilizer or as an energy source, either through direct combustion or cellulosic ethanol production. Market price of DDGS has been greater than corn grain since 1992 at Midwest Grains in Atchinson, KS and has been about one third the value of soybean meal (Fig. 3). A survey of 10 sources of DDGS (6) documented DDGS and corn have similar metabolizable energy (7,013 and 7,178 BTU/lb dry matter, respectively) and DDGS has nearly four times the crude protein concentration (32.2% and 8.3%. respectively). Full market value for the energy and protein content of DDGS in dairy and swine diets is substantially higher than what is paid for DDGS on the Kansas spot market (Fig. 4). The price paid for DDGS in October 2007 was ~$115/ton on the Kansas spot market, 55 to 80% of the theoretical value of energy, protein, and phosphorus in the diets considered (Fig. 4). This reduction in the price paid is analogous to farmer’s wanting to pay less than full fertilizer value for manure nutrients because of real or perceived limitations of manure as a fertilizer. In this case farmers apparently perceive the sources of energy and protein in traditional feedstuffs to have more value than energy and protein in DDGS. Farmers may attribute less value to DDGS as an energy and protein source because they perceive DDGS to be lower quality energy and protein source, because they perceive the feed value to vary more within a lot of feed, and/or because it has different handling qualities than corn.
Another potential use for ethanol byproducts is as a fuel for combustion. Table 3 compares energy content of a range of materials including wet distiller’s grains with solubles and DDGS. The lower energy value for wet distiller’s grains with solubles compared to DDGS reflects the high moisture content of these materials. The value of energy in a material is heavily dependent on form (Table 3). For example, society values energy in the form of a liquid (gasoline or ethanol) more than energy in the form of a gas (natural gas) or a solid (coal). If one assumes the energy value of corn and ethanol byproducts is equal to coal then the fuel value DDGS and wet distiller’s grains with solubles is similar to their theoretical fertilizer value (Table 3). After combustion, there would be some phosphorus and potassium fertilizer value to the ash to supplement its energy value. Table 3. Energy content and current value of selected energy sources. Energy value of corn, dried distiller’s grains (DDGS), and wet distiller’s grains (WDGS) is based on the assumption that the energy value is similar to coal.
x Based on Perry and Chilton (7) except for corn, DDGS, and WDGS which is based on Pedersen et al. (6). y Based on an E85 price of $2.24/gal. z Assumes energy value in corn and ethanol byproducts is similar to coal. Plants with DDGS currently have the option of selling it as a feed, fertilizer or energy source. Our analysis indicates that feed value currently exceeds the value of other uses of DDGS by at least $90/ton. For $90/ton it is possible to ship distiller’s grains considerable distances. A typical hopper style grain truck with high sides has capacity for 26 tons of DDGS. The USDA (13) estimated the cost of operating a grain hauling semi truck in December 2006 was $2.52 per loaded mile. This truck would have a range of over 900 miles to profitably haul DDGS as a feed compared to selling at the plant gate as a fertilizer. The expense of hauling by rail would be significantly lower increasing the profitable range for hauling DDGS. This implies that ethanol plants will have an economic incentive to move DDGS large distances as a feed before they would dispose of it as a fertilizer. Rising fuel prices will lower the distance to profitably haul DDGS as a feed but higher commodity prices plus the potential expense of distributing DDGS as a fertilizer could increase the breakeven hauling distance. US producers currently move corn grain worldwide. It is likely that any substantial drop in DDGS feed value in the US would quickly lead to the development of an infrastructure capable of moving large quantities of DDGS into world markets. Plants with wet distiller’s grains with solubles have the option to sell the material wet to local markets as a feed, fertilizer or fuel or dry the material for the DDGS market. In October 2007 the spot market price for wet distiller’s grains with solubles in Atchison, KS was close to $45/ton. If the plant chose to dry the wet distiller’s grains with solubles the value of the DDGS derived from ton of wet distiller’s grains with solubles is also ~$45. To dry a ton of wet distiller’s grains with solubles would require removing 1,100 lbs of water. Using a rotary drum dryer requires about 1,300 BTU per pound water to evaporate 1 lb water (8). It should cost ~$11 to dry a ton of wet distiller’s grains with solubles at current natural gas prices ($8.00/1000 cubic feet). In an earlier section we indicated that true fertilizer value of DDGS is likely significantly less than $14/ton. Most operations will find it profitable to invest in the fuel to dry wet distiller’s grains with solubles and sell it as DDGS before selling wet distiller’s grains with solubles as a fertilizer. Conclusions The high feed value of DDGS and wet distiller’s grains with solubles makes it highly unlikely that these materials will be used as a fertilizer source. The exceptions will be land application as a disposal method to get rid of damaged materials or in some specialty markets that may value an organic source of nutrients and other perceived attributes of land applying DDGS and wet distiller’s grains with solubles. Literature Cited 1. Clevenger, T. E., Singh, V., Belyea, R. L., Johnston, D. B., Tubleson, M. E., and Rausch, K. D. 2005. Element concentration in dry grind corn processing streams. Fourth Intn'l Starch Tech. Conf., June 5-8, 2005, Univ. of Illinois. 2. Joern, B. C., and Hess, P. 2007. Manure Nutrient Availability Calculator. Version 0.2.3.0. Online. Manure Management Planner Webpage, Department of Agronomy, Purdue Univ., West Lafayette, IN. 3. Moore, A., Alva, A., Collins, H., and Boydston, R. 2007. Transformations of nitrogen from biofuel products and animal manures amended to a sandy soil. Abstract #224-9, ASA-CSA-SSSA Annual Meetings Nov. 4-8, New Orleans, LA. 4. National Research Council. 1998. Nutrient Requirements of Swine, 10th Rev. Edn. Nat'l. Acad. P., Washington, DC. 5. Nelson, K., Meinhardt, C., and Smoot, R. 2006. Utility of DDGS as a fertilizer source and for weed suppression. In Greenley Memorial Research Center 2007 Field Day Report. Online. Greenly Memorial Res. Center, Agric. Exp. Station, Univ. of Missouri, Novelty, MO. 6. Pedersen, C., Boersma, M. G., and Stein, H. H. 2007. Digestibility of energy and phosphorus in ten samples of distillers dried grains with solubles fed to growing pigs. J. Anim. Sci. 85:1168-1176. 7. Perry, R., and Chilton, C. 1973. Chemical Engineer’s Handbook, Fifth Edn. McGraw-Hill, New York, NY. 8. Rausch, K. D., and Belyea, R. L. 2006. The future of coproducts from corn processing. Appl. Biochem. Biotechnol. 128:47-86. 9. Rausch, K. D., Belyea, R. L., Johnson, D. B., Clevenger, T. E., and Tumbleson, M. E. 2005. Protein in dry grind corn processing streams. Fourth International Starch Technology Conference, June 5-8, 2005, Univ. of Illinois. 12. Shurman, J. 2006. US DDGS comparison tables. Online. Dept. of Animal Sci., Univ. of Minnesota, St. Paul, MN. 13. USDA. 2007. Quarterly truck and ocean report. Online. Agricultural Marketing Service, USDA, Washington, DC. |
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