Update of Distillers Grains Displacement Ratios 

for Corn Ethanol Life-Cycle Analysis 

Salil Arora, May Wu, and Michael Wang 

Center for Transportation Research 

Energy System Division 

Argonne National Laboratory 

September 2008 
Contents 

Acknowledgments..................................................................................................................... iv 

1 Introduction ......................................................................................................................... 1 

2 Coproducts from Corn Ethanol Dry Milling Plants ............................................................ 2 

2.1 Update of Displacement Ratios of Distillers Grains .................................................. 2 

2.1.1 Step 1: Characterize U.S. DGS Production, Feed Composition, and 

Animal Performance ....................................................................................... 2 

2.1.2 Step 2: Characterize U.S. Distillers Grains Consumption by 

Animal Type ................................................................................................... 8 

2.1.3 Step 3: Characterize Life Cycle of Animals ................................................... 9 

2.1.4 Step 4: Results — Displacement Ratio of Distillers Grains ........................... 10 

2.1.5 Methane Emission Savings from Enteric Fermentation Reduction of Cattle Fed 

with DGS ........................................................................................................ 12 

2.1.6 Impact of 2007 Energy Independence and Security Act on 

DGS Displacement Ratio ............................................................................... 13 

2.1.7 Animal Production Effects of Addition of DGS to Animal Feed Market ...... 13 

 

3 References ........................................................................................................................... 14 

ii 
Tables 

1 Coproduct Displacement Ratios ......................................................................................... 1 

2 Major Components of Corn and DDGS.............................................................................. 2 

3 Annual U.S. Distillers Grains Production ........................................................................... 3 

4 U.S. Distillers Grains Consumption by Animal Type ........................................................ 4 

5 U.S. DGS Exports ............................................................................................................... 4 

6 Feed Composition and Animal Performance for Beef Cattle with 

DDGS Inclusion .................................................................................................................. 5 

7 Feed Composition and Animal Performance for Beef Cattle with 

WDGS Inclusion ................................................................................................................. 6 

8 Ingredient Content of Feed for Dairy Cattle ....................................................................... 7 

9 Milk Yield and Composition for Cows Fed Control Diet and Diets Containing 

10% DDGS, 20% DDGS, 10% WDGS, and 20% WDGS ................................................. 7 

10 Growth Performance for Swine with DDGS Inclusion ...................................................... 8 

11 Coproducts Fed by Animal Type — Distillers Dried Grains with 

Solubles ............................................................................................................................... 9 

12 Life Cycle of Beef Cattle .................................................................................................... 10 

13 Life Cycle of Dairy Cattle................................................................................................... 10 

14 Distillers Grains Displacement Ratio by Animal Type ...................................................... 11 

15 Distillers Grains Displacement Ratio .................................................................................. 11 

16 Greenhouse Gas Savings due to Reduced Enteric Fermentation ........................................ 12 

17 DGS Market Growth ........................................................................................................... 13 

18 Distillers Grains Displacement Ratio .................................................................................. 13 

iii 
iv 

Acknowledgments 

This work was sponsored by Office of Biomass Program in the U.S. Department of Energy’s 

Office of Energy Efficiency and Renewable Energy. The authors sincerely thank following 

individuals for their feedback to this effort: Terry Klopfenstein of University of Nebraska, Larry 

Berger of University of Illinois at Urbana-Champaign, David Schingoethe of South Dakota State 

University, Gerald Shurson of University of Minnesota, Joel Spencer of JBS United, Charlie 

Staff of Distillers Grains Technology Council, and Sean Broderick of CHS, Inc. Argonne 

National Laboratory is a U.S. Department of Energy laboratory managed by UChicago Argonne, 

LLC, under Contract No. DE-AC02-06CH11357. 
1 Introduction 

Production of corn-based ethanol (either by wet milling or by dry milling) yields the following 

coproducts: distillers grains with solubles (DGS), corn gluten meal (CGM), corn gluten feed 

(CGF), and corn oil. Of these coproducts, all except corn oil can replace conventional animal 

feeds, such as corn, soybean meal, and urea. 

Displacement ratios of corn-ethanol coproducts including 

DGS, CGM, and CGF were last updated in 1998 at a 

workshop at Argonne National Laboratory on the basis of 

input from a group of experts on animal feeds, including 

Prof. Klopfenstein (University of Nebraska, Lincoln), 

Prof. Berger (University of Illinois, Urbana-Champaign), 

Mr. Madson (Rapheal Katzen International Associates, 

Inc.), and Prof. Trenkle (Iowa State University) (Wang 

1999). Table 1 presents current dry milling coproduct 

displacement ratios being used in the GREET model. 

TABLE 1 Coproduct 

Displacement Ratios (lb of 

displaced product per lb of 

coproduct)a

Coproduct Ratio 

DGS 

Corn 1.077 

Soybean meal 0.823 

a

 Source: Wang 1999 

The current effort focuses on updating displacement ratios of dry milling corn-ethanol 

coproducts used in the animal feed industry. Because of the increased availability and use of 

these coproducts as animal feeds, more information is available on how these coproducts replace 

conventional animal feeds. To glean this information, it is also important to understand how 

industry selects feed. 

Because of the wide variety of available feeds, animal nutritionists use commercial software 

(such as Brill FormulationTM) for feed formulation. The software recommends feed for the 

animal on the basis of the nutritional characteristics, availability, and price of various animal 

feeds, as well as on the nutritional requirements of the animal (Corn Refiners Association 2006). 

Therefore, feed formulation considers both the economic and the nutritional characteristics of 

feed products. 

1 
2 Coproducts from Corn Ethanol Dry Milling Plants 

Distillers grains are the only coproduct from the corn ethanol dry milling process. Current U.S. 

industrial average DDGS yield is 5.4 bone-dry lb/undenatured gal EtOH. Generally, distillers 

grains are combined with condensed distillers solubles to form DGS, which are sold either as dry 

DGS (DDGS) or wet DGS (WDGS). A comparison of chemical composition of corn 

(NRC 1998) and DDGS (University of Minnesota 2008) is presented in Table 2. 

TABLE 2 Major Components of Corn and DDGS (dry matter 

basis) 

Item Corn graina DDGSb

Dry matter (%) 85.5 89.3 

Crude protein (%) 8.3 30.8 

Fat (%) 3.9 11.1 

a

 Source: NRC 1998 and White & Johnson 2003 

b

 Source: University of Minnesota 2008 

2.1 Update of Displacement Ratios of Distillers Grains 

The methodology to update displacement ratios for DGS consists of the following four steps: 

1. Characterize U.S. DGS production, recommended feed composition, and 

animal performance, with inclusion of distillers grains; 

2. Characterize U.S. distillers grains consumption by animal type; 

3. Characterize life cycle of various animals, to compare animal performance 

with or without distillers grains; and 

4. Calculate the displacement ratio of distillers grains by using these data. 

2.1.1 Step 1: Characterize U.S. DGS Production, Feed Composition, and Animal Performance 

The Renewable Fuels Association (RFA) and the U.S. Grains Council regularly track annual 

U.S. distillers grains production, consumption, and exports, and the current displacement ratio 

update relies on this information. Feed composition for conventional animal feeds and distillers 

grains-based diets was determined on the basis of (1) information gathered from the literature 

review of the recent animal feeding studies and (2) follow-up discussions with experts in animal 

science. A recent National Agricultural Statistics Service-U.S. Department of Agriculture 

(NASS-USDA) survey (discussed in Step 2) has reported distillers grains use by animal type, 

2 
and, on the basis of this survey, only beef, dairy, and swine diets are characterized for this 

update. 

2.1.1.1 Annual U.S. DGS Production, Consumption, and Exports 

Distillers grains production 

As reported on the Renewable Fuels Association (RFA) website (RFA 2008), a typical dry mill 

ethanol plant can produce as much as 2.8 gallons of denatured ethanol (2.72 gallons of undenatured ethanol1

) and more than 16 pounds of distillers grains from a bushel of corn. The RFA 

website also reports historic distillers grains production, and this information is listed in Table 3. 

TABLE 3 Annual U.S. Distillers Grains Productiona

Year 

DGS Production 

(million metric tons)b

DGS Production (million 

bushels of corn 

equivalent)c

DGS Production (protein 

equivalent-million bushels 

of corn)d

1999 2.3 91 336 

2000 2.7 106 394 

2001 3.1 122 453 

2002 3.6 142 526 

2003 5.8 228 847 

2004 7.3 287 1,066 

2005 9.0 354 1,315 

2006 12.0 472 1,753 

2007 14.6 575 2,133 

a

 Source: RFA 2008 

b

 As received basis, i.e. dry matter content of 89.3% 

c

 1 bushel of corn = 56 lb 

d

 Assuming average protein content for DGS and corn to be 30.8 and 8.3% 

U.S. distillers grains consumption 

Distillers grains consumption data, especially by animal type, are important for calculating 

displacement ratio of distillers grains as animal feed, because distillers grains replace varying 

amounts of conventional feed for different animals, as discussed above. 

CHS, Inc., one of the major marketers of distillers grains in the United States, provided the 

following information (Broderick 2008) regarding distillers grains consumption (Table 4). The 

RFA website (RFA 2008) also reports this information, but the animal distribution is slightly 

different from that obtained directly through CHS. 

 

1

 Assuming addition of 4.7% denaturant by volume 

3 
TABLE 4 U.S. Distillers Grains Consumption by Animal 

Type 

Animal Type CHS CHS/RFA 

CHS/RFA 

(excluding 

Poultry) 

Dairy 44% 42% 44.2% 

Beef 42% 42% 44.2% 

Swine 9% 11% 11.6% 

Poultry 5% 5% 

Additionally, the RFA website (RFA 2008) also reports that 64% of the distillers grains are 

consumed as DDGS, and the remaining 36% in the wet form as WDGS. 

For the current displacement ratio update, consumption data reported by the RFA were used, 

while poultry consumption was excluded because feed composition and performance data 

available for poultry were insufficient. 

U.S. distillers grains exports 

U.S. DGS exports roughly account for 15% of the annual U.S. production. The market for DGS 

has diversified from the European Union as the main market to Mexico, Southeast Asia, Canada, 

and Taiwan as significant customers, as shown in Table 5. All of the DGS exports are consumed 

in the animal feeding industry, and for the current displacement ratio update, it was assumed that 

all export markets have an animal distribution similar to that of the United States (Table 4). 

TABLE 5 U.S. DGS Exports (1,000 metric tons)a

Country/Region 2005/2006b 2006/2007b 

Mexico 281 608 

European Union 481 204 

Southeast Asia 168 262 

Canada 114 189

Taiwan 73 126 

Other 114 390 

Total 1,229 1,779 

a

 Source: U.S. Grains Council 2007 Annual Report 

b

 Sept. – Aug., marketing year 

4 
2.1.1.2 DGS Inclusion in Feed and Animal Performance 

Beef cattle 

A 2008 review (Klopfenstein et al. 2008a) of the use of distillers by-products as beef cattle feed 

conducts a meta-analysis of nine experiments for wet distillers grains plus solubles (WDGS) and 

five experiments for dry distillers grains plus solubles (DDGS). This meta-analysis, based on the 

optimal Gain:Feed2 (G:F) value, recommends a 30–40% inclusion rate for WDGS and a 20% 

inclusion rate for DDGS. On the basis of this publication and additional information about feed 

composition received from Prof. Klopfenstein (2008b), feed composition and animal 

performance at various inclusion rates for DDGS and WDGS are presented in Table 6 and 

Table 7. As per Prof. Klopfenstein, urea is removed from the supplement portion of feed, when 

more than 15% distillers grains are included in the diet. 

The animal performance data presented in Table 6 and Table 7 clearly show significantly higher 

average daily gain3

 (ADG, kg/d) when distillers grains are fed, in comparison with the control 

diet. 

TABLE 6 Feed Composition and Animal Performance for Beef Cattle with 

DDGS Inclusiona 

Parameter 

DDGS inclusion Rate (%) 

Control 10 20 30 40 

---------------------------------(% of Dry Matter)------------------------------ 

Corn 87.5 77.5 67.5 57.5 47.5 

Hay 7.5 7.5 7.5 7.5 7.5 

Supplementb 5 5 5 5 5 

Ureac 1.3 0.5 0 0 0 

DDGS 0 10 20 30 40 

DMI (kg/d) 10.17 10.40 10.53 10.56 10.49 

ADG (kg/d) 1.56 1.65 1.69 1.70 1.66 

G:F 0.152 0.160 0.159 0.155 0.152 

a

 Sources: Klopfenstein et al. 2008a, Klopfenstein 2008b 

b

 Contains vitamins, minerals, and feed additives. 

c

 Included in the supplement, replacing the carrier (such as corn). 

 

2

 G:F is a ratio of ADG to dry matter intake (DMI). It evaluates the effectiveness of diet on animal performance. 3

 Average daily gain (ADG) is a performance parameter that measures weight gain per day by animal. 

5 
TABLE 7 Feed Composition and Animal Performance for Beef Cattle with WDGS 

Inclusiona

Parameter 

WDGS inclusion Rate (%) 

Control 10 20 30 40 50 

-----------------------------------(% of Dry Matter) --------------------------------- 

Corn 87.5 77.5 67.5 57.5 47.5 37.5 

Hay 7.5 7.5 7.5 7.5 7.5 7.5 

Supplementb 5 5 5 5 5 5 

Ureac 1.3 0.5 0 0 0 0 

WDGS 0 10 20 30 40 50 

DMI (kg/d) 10.12 10.31 10.33 10.20 9.90 9.44 

ADG (kg/d) 1.57 1.68 1.74 1.76 1.73 1.66 

G:F 0.155 0.162 0.168 0.172 0.174 0.175 

a

 Sources: Klopfenstein et al. 2008a, Klopfenstein 2008b 

b

 Contains vitamins, minerals, and feed additives. 

c

 Included in the supplement, replacing the carrier (such as corn). 

Dairy cattle: 

A 2006 publication by Anderson et al. (2006) evaluates the effects of feeding dried or wet 

distillers grains with solubles on the lactation performance of dairy cows. This study considers 

DDGS/WDGS inclusion rates of 10% and 20% of diet dry matter and compares the milk 

production and composition for these diets with the control diet (corn + soybean meal). The 

ingredient content of these diets is described in Table 8. From this table, the amount of corn and 

soybean meal being displaced at 10% and 20% inclusion of distillers grains can be calculated. 

The comparison of milk production and composition presents significantly higher milk yields for 

distillers grains with solubles (DGS) -fed cows vs. the control (CON) diet, whereas the 

percentage of fat percentage is significantly higher for WDGS than that for DDGS and CON. 

The protein percentages are similar for CON and DGS diets. Both the milk fat yield and protein 

yield are significantly higher for DGS-based diets than the CON diet. This comparison is 

summarized in Table 9. 

6 
TABLE 8 Ingredient Content of Feed for Dairy Cattlea

Control 

10% 

DDGS 

20% 

DDGS 

10% 

WDGS 

20% 

WDGS 

Item -------------------------------------- (% of DM) --------------------------------- 

Corn silage 25 25 25 25 25 

Alfalfa hay 25 25 25 25 25 

Corn, ground 35.6 31.3 26.7 31.3 26.7 

Soybean meal, 44% CP 12.5 7 1.6 7 1.6 

DDGS 0 10 20 0 0 

WDGS 0 0 0 10 20 

Salt 0.53 0.53 0.53 0.53 0.53 

Magnesium oxide 0.05 0.05 0.05 0.05 0.05 

Limestone 0.82 0.82 0.82 0.82 0.82 

Dicalcium phosphate 0.22 0 0 0 0 

Dairy Micro premixb 0.25 0.25 0.25 0.25 0.25 

Vitamin E premix 0.07 0.07 0.07 0.07 0.07 

a

 Source: Anderson et al. 2006 

b

 10% Mg; 2.6% Zn; 1.7 ppm Mn; 4,640 ppm Fe; 4,712 ppm Cu; 396 ppm I; 119 ppm Co; 140 ppm Se; 

2,640,000 IU/kg vitamin A; 528,000 IU/kg vitamin D3; and 10,560 IU/kg vitamin E 

Table 9 Milk Yield and Composition for Cows Fed Control Diet and Diets 

Containing 10% DDGS, 20% DDGS, 10% WDGS, and 20% WDGSa

Diet 

Item Control 10% DDGS 20% DDGS 10% WDGS 20% WDGS 

DMI (kg/d) 23.4 22.8 22.5 23 21.9 

Milk (kg/d) 39.8 40.9 42.5 42.5 43.5 

Fat (%) 3.23 3.16 3.28 3.55 3.4 

Fat (kg/d) 1.28 1.32 1.39 1.44 1.43 

Protein (%) 3.05 3.01 3.02 3.11 3.06 

Protein (kg/d) 1.2 1.22 1.29 1.29 1.33 

ECMb

 (kg/d) 38.4 39.6 41.3 41.7 42 

Feed efficiencyc 1.7 1.79 1.87 1.84 1.92 

a

 Source: Anderson et al. 2006 

b

 ECM = Energy corrected milk 

c

 Feed efficiency = (ECM/DMI) 

7 
Swine 

Feed composition for swine was based on feedback received from Prof. Shurson (2008), who 

recommended DDGS inclusion at 10% in grower swine feed (and, as a “rule of thumb,” in a 

1,000-kg batch of grower swine feed). He also recommended that 100 kg of DDGS and 1.5 kg of 

limestone replace 89 kg of corn, 9.5 kg of soybean meal (46% CP), and 3 kg of dicalcium 

phosphate (CaHPO4). 

The information about feed composition from Prof. Shurson agrees with the feeding 

recommendations (Shurson and Spiehs 2002) published on the University of Minnesota DDGS 

website (www.ddgs.umn.edu), but it differs from the feed composition used by Whitney et al. 

(2006) in their study. The experimental swine grower feed used by Whitney et al. contains 

soybean oil in addition to DDGS, corn, and soybean meal. The difference in feed composition 

can be attributed to the lower quality of DDGS used in this study — the experimental feed had a 

crude protein (CP) content of 23.9%, as compared to the average protein content of 30% for the 

current commercially available DDGS. 

Data on animal growth reported by Whitney et al. present similar G:F and ADG values for the 

control and 10% DDGS diets, which indicates equivalent performance for a 10% DDGS diet 

compared to a control diet. A recent follow-up study by Spencer (2008) also reported similar G:F 

and ADG values for a corn-soybean meal control diet and a 15% DDGS diet. The growth 

performance data from both studies are summarized in Table 10. 

TABLE 10 Growth Performance for Swine with DDGS Inclusion 

Whitney et al. 2006a Spencer 2008 

Parameter 

Control 

diet 

10% DDGS 

inclusion 

Control 

diet 

15% DDGS 

inclusion 

30% DDGS 

inclusion 

P value (DDGS 

vs. control) 

ADG (kg/d) 0.862 0.859 0.912 0.921 0.907 0.67 

G:F 0.36 0.36 0.40 0.40 0.39 0.16 

a

 P value was determined for 10%, 20%, and 30% DDGS inclusion rates vs. control. However, growth performance at the 10% 

inclusion rate was statistically insignificant compared to control. 

2.1.2 Step 2: Characterize U.S. Distillers Grains Consumption by Animal Type 

A 2007 NASS-USDA ethanol coproducts survey has been used to select distillers grains 

inclusion rate (by animal type) for this update. Results from this survey are summarized below. 

The NASS-USDA survey (NASS-USDA 2007) was conducted in 2007 by the Nebraska Corn 

Development, Utilization & Marketing Board. The board contacted 9,400 livestock operations in 

Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, 

South Dakota, and Wisconsin regarding use of ethanol co-products in their animal feeding 

operations. The survey gathered information on dairy cattle, cattle on feed, beef cattle (cow/calf), 

and hogs. 

8 
This survey addressed the use of ethanol co-products from dry milling, as well as wet milling. 

For dry milling co-products, the survey reported use of DDGS, as well as condensed distillers 

solubles (CDS), distillers dried grains no solubles (DDG), and distillers wet grains. However, use 

of wet distillers grains with solubles (WDGS) was not reported in this survey. DDGS data from 

this survey are presented in Table 11. 

TABLE 11 Coproducts Fed by Animal Typea — Distillers Dried Grains with Solubles (DDGS) 

Item 

Operations 

Who Use This 

Type (%) 

Average Peak 

Inventoryb

(Head) 

Moisture Content 

in DDGS 

 (wt%, dry basis) 

Inclusion 

Rate (%) 

Average Amount 

Fed per Animal per 

Year (kg) 

Dairy Cattle 22 272 11 8 455 

Cattle on feedc 14 1,590 15 23 416 

Beef Cattle 13 344 12 22 180 

Hogs 37 27,708 12 10 27 

a

 Source: NASS – USDA 2007 

b

 2007 refers to average peak inventory of operations that fed particular coproduct during 2006. 

c

 Cattle on feed refers to beef cattle in commercial feedlots. 

The inclusion rates reported by the NASS-USDA survey approximately agree with the 

recommended DDGS inclusion rates specified in step 1 for beef cattle (20%) and swine (10%). 

For dairy cattle, this survey reports 8% DDGS inclusion; therefore, a scenario of 10% DDGS 

inclusion in Anderson et al. (2006) was selected for dairy cattle. 

For WDGS, a recommended inclusion rate of 40% for beef cattle was selected, while a 10% 

inclusion rate for dairy cattle was selected. 

2.1.3 Step 3: Characterize Life Cycle of Animals 

The impact of feeding distillers grains on animal performance was discussed in step 1 of this 

update. For beef and dairy cattle, feeding distillers grains clearly leads to improved animal 

performance in terms of faster weight gain for beef cattle and increased milk production for dairy 

cattle. However, swine growth performance remains unchanged, with similar G:F and weight 

gain values (Whitney et al. 2006, Spencer 2008; see Table 10). 

To quantify the difference in animal performance for beef and dairy cattle as a result of feeding 

distillers grains, the life cycle of beef and dairy cattle must be characterized. This 

characterization was based on feedback from experts in animal science. 

9 
2.1.3.1 Beef Cattle 

On the basis of feedback from Prof. Berger (2008), feeding 

distillers grains begins at an average body weight of 227 kg 

(500 lb), when cattle are moved into feedlots, at which point 

the feed is switched from grass/hay to a higher-energy and 

protein-based diet. Feeding distillers grains continues until the 

cattle are slaughtered at an average body weight of 590 kg 

(1,300 lb). This information is summarized in Table 12. 

TABLE 12 Life Cycle of Beef 

Cattle 

Initial weight (kg) 227 

Final weight (kg) 590 

Weight gain (kg) 363 

2.1.3.2 Dairy Cattle 

Dairy cattle performance is measured in terms of 

milk production. An average dairy cow over a 

lifetime of 4–5 years has 2.8 lactation periods, with 

each lactation lasting 10 months 

(Schingoethe 2008, Blayney 2008). Note that these 

numbers are for commercial dairy operations, for which the focus is on increased daily milk 

production. For non-commercial operations, dairy cows have more lactation periods but lower 

daily milk production. This information is summarized in Table 13. 

TABLE 13 Life Cycle of Dairy Cattle 

Average lactation periods/cow 2.8 

Lactation period (months) 10 

Total lifecycle lactation time (days) 840 

2.1.4 Step 4: Results — Displacement Ratio of Distillers Grains 

After characterizing animal performance, U.S. distillers grains production and consumption, and 

life cycle of animals, the displacement ratio of distillers grains was calculated in the following 

steps: 

a. Determine lifetime dry matter intake (DMI) for animals fed a conventional 

diet and a recommended distillers grains-based diet, aiming for equivalent 

animal performance (i.e., equal lifetime weight gain for beef cattle and equal 

lifetime milk production for dairy cattle); 

b. Determine lifetime conventional feed displacement, which includes direct 

replacement due to distillers grains inclusion and feed savings due to 

improved animal performance; 

c. Determine distillers grains displacement ratio for each animal type on the 

basis of lifetime distillers consumption, lifetime conventional feed 

displacement, and market share of DDGS and WDGS (RFA 2008); and 

d. Calculate overall displacement ratio as a sum of displacement ratio by animal 

type weighted over the market fraction for each animal (as specified in 

Table 4). 

10 
The displacement ratio for each animal type calculated by following steps 4a–d are presented in 

Table 14. 

Table 14 Distillers Grains Displacement Ratio by Animal Type 

Inclusion Rate, by Animal Type 

Beef Cattle Dairy Cattle Swinea

Parameter 

20% 

DDGS 

40% 

WDGS 

10% 

DDGS 

10% 

WDGS 

10% 

DDGS 

Lifetime DDGS/WDGS consumption (kg) 452 831 1864 1809 – 

Lifetime corn displacement (kg) 520 1060 1266 1491 – 

Lifetime SBMb

 displacement (kg) – – 1152 1191 – 

Lifetime urea displacement (kg) 30 30 – – – 

Normalized corn displacement (kg/kg 

distillers grains) 1.151 1.276 0.679 0.824 – 

Normalized SBM displacement (kg/kg 

distillers grains) – – 0.618 0.658 – 

Normalized urea displacement (kg/kg 

distillers grains) 0.067 0.037 – – – 

DDGS/WDGS market share (%) 64 36 64 36 100 

Corn displacement (kg/kg distillers grains) 1.196 0.731 0.890 

SBM displacement (kg/kg distillers grains) – 0.633 0.095 

Urea displacement (kg/kg distillers grains) 0.056 – – 

a

 Lifetime DDGS consumption for swine was not calculated because no difference in animal performance was found when fed 

distillers grains compared to control feed (see Table 10). 

b

 SBM = Soybean meal 

Final distillers grains displacement ratio results are presented below in Table 15. These results 

indicate that 1 kg of distiller grains displace 1.271 kg of conventional feed ingredients, thus 

signifying improved animal performance obtained by feeding distillers grains. 

Table 15 Distillers Grains Displacement Ratio 

Parameter Beef Dairy Swine 

Overall Ratio (kg/kg 

distillers grains) 

Market share (%) 44.2 44.2 11.6 100 

Corn 1.196 0.731 0.890 0.955 

Soybean meal – 0.633 0.095 0.291 

Urea 0.056 – – 0.025 

11 
2.1.5 Methane Emission Savings from Enteric Fermentation Reduction of Cattle Fed with DGS 

Methane (CH4) emissions due to enteric fermentation in animals are a significant source of 

greenhouse gas emissions, accounting for 28% of the total agriculture related greenhouse gas 

emissions in United States (EPA 2008). CH4 emissions from beef and dairy cattle represent 71 

percent and 24 percent of total CH4 emissions from enteric fermentation, respectively. Since 

feeding distillers grains improves animal performance for beef and dairy cattle, these animals 

remain in commercial feedlots for a shorter period (over their entire lifecycle, see section 2.1.3) 

compared to animals on conventional diet. Therefore, CH4 emissions over the lifecycle of 

animals fed with distillers grains are lower compared to those fed with conventional diets. 

University of Nebraska’s BESS model has first quantified these savings over the entire life cycle 

of corn ethanol production (Liska et al. 2008). 

For this study, greenhouse gas savings were calculated based on EPA emission factors for enteric 

fermentation. The calculated CH4 savings as CO2 equivalent are presented in Table 16. As the 

table shows, the reduction in CH4 emissions from enteric fermentation of animals by DGS is 

about 3,381 grams of CO2e per million Btu of ethanol produced, or 258 grams per gallon of 

ethanol produced. 

Table 16 Greenhouse Gas Savings due to Reduced Enteric Fermentation 

Animal Type Market Share (%) Emission Factor (kg 

CH4/head/year) 

CH4 Savings as CO2 Equivalent 

(g/million Btu EtOH) 

Dairy 44.2 130.26 5,244 

Beef 44.2 33.75 2,402 

Swinea 11.6 1.5 0 

Total 100 – 3,381 

a

 No greenhouse gas savings for swine because animal performance remains same when being fed with distillers grains (Whitney et 

al. 2006, Spencer 2008; see Table 10). 

12 
2.1.6 Impact of 2007 Energy Independence and Security Act on DGS Displacement Ratio 

The Energy Independence and Security Act (EISA) of 

2007 mandates the production of 15 billion gallons of 

corn-based ethanol by 2015, which will result in the 

production of more than twice the amount of DGS 

produced in 2007. This comparison and underlying 

assumptions are presented in Table 17. 

TABLE 17 DGS Market Growth 

Year 

U.S. Ethanol 

Production 

(billion gal 

per year) 

DGS Production 

(bone-dry 

million metric 

tons)a

2007b,c 6.5 12.7 

2015d,e 15 30.5 

a

 DGS yield is 5.1 bone-dry lb/gal of denatured 

ethanol (Source: RFA 2008). 

b

 2007 ethanol production volume obtained from 

RFA website. 

c

 2007 share of dry mill EtOH is 84% (Source: Staff 

2008). 

d

 2015 ethanol production volume estimated on the 

basis of the EISA 2007. 

e

 2015 share of dry mill EtOH is 87.5% (Source: 

GREET 1.8b, 2008). 

The theoretical maximum U.S. market size for 

distillers grains has been estimated at 40.3 million 

metric tons by Cooper (2006), assuming maximum 

inclusion rates of 40% for dairy, 40% for beef, 20% 

for swine, and 10% for poultry at 100% market 

penetration. This estimate clearly suggests that 

U.S. DGS markets approach saturation at 15 billion 

gallons of corn ethanol production, while DGS exports 

are assumed to remain fixed at 15%. 

In the current update, the impact of 15 billion gallons 

of corn ethanol on the DGS displacement ratio was 

estimated by assuming inclusion rates of 20% 

DDGS/40% WDGS for beef, 20% DDGS/20% 

WDGS for dairy, and 30% for swine. At these 

inclusion rates with 80% market penetration, 

maximum U.S. DGS consumption in 2015 was 

estimated at 23.4 million metric tons. The remaining 

7 million metric tons of DGS are assumed to be exported, and the export markets are assumed to 

have animal distribution similar to that in the United States. The updated DGS displacement ratio 

results are presented in Table 18. These results do not differ significantly from the current results 

for displacement ratio. 

TABLE 18 Distillers Grains 

Displacement Ratio (2015 Scenario) 

Feed Type 

Ratio (kg/kg distillers 

grains) 

Corn 0.947 

Soybean meal 0.303 

Urea 0.025 

2.1.7 Animal Production Effects of Addition of DGS to Animal Feed Market 

In 1998, the USDA simulated corn ethanol production and associated DGS production (See 

Wang 1999). The USDA simulations concluded that supply of DGS from corn ethanol 

production would result in decreased prices of animal feeds in the U.S. animal feed market, 

which would induce additional new meat and milk production in the U.S. The USDA simulations 

indicated an increase of 15.1% in new meat and milk production. This implies that 84.9% of the 

total DGS production will displace conventional animal feeds. However, the recent trends have 

shown that supply of DGS to the animal feed market does not cause decrease in animal feed 

prices, thus not inducing additional meat and milk production. For this reason, we have revised 

the GREET model to assume that all, not 84.9%, DGS production would be for displacement of 

conventional animal feeds. 

13 
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