# 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. Di stillers 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 Indepe ndence 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 Pe rformance for Beef Cattle with DDGS Inclusion ................................................................................................................ .. 5

7 Feed Composition and Animal Pe rformance 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 Re duced 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 En ergy. The authors sincer ely thank following individuals for their feedback to this effort: Te rry Klopfenstein of University of Nebraska, Larry Berger of University of Illinois at Urbana-C hampaign, 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 repl ace conventional animal feeds, such as corn, soybean meal, and urea.

Displacement ratios of corn-e thanol coproducts including DGS, CGM, and CGF were la st updated in 1998 at a workshop at Argonne National La boratory 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 us ed 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. Becau se of the increased availability and use of these coproducts as animal feeds, more inform ation is available on how these coproducts replace conventional animal feeds. To glean this info rmation, it is also impor tant 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 formula tion. The software recommends feed for the animal on the basis of the nutritio nal 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 DG S, which are sold either as dry DGS (DDGS) or wet DGS (WDGS). A compar ison of chemical composition of corn (NRC 1998) and DDGS (University of Minneso ta 2008) is presented in Table 2.

TABLE 2 Major Components of Corn and DDGS (dry matter basis)

Item Corn grain a DDGS b

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 incl usion of distillers grains;

2. Characterize U.S. distillers gr ains consumption by animal type;

3. Characterize life cycle of various anim als, to compare animal performance with or without dist illers grains; and

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

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



### The Renewable Fuels Association (RFA) and th e U.S. Grains Council regularly track annual U.S. distillers grains production, consumption, a nd exports, and the current displacement ratio update relies on this information. Feed compositi on for conventional animal feeds and distillers grains-based diets was determined on the basis of (1) informati on 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 Statistic s Service-U.S. Department of Agriculture (NASS-USDA) survey (discussed in Step 2) has re ported distillers grai ns use by animal type,

2

### and, on the basis of this survey, only beef, da iry, 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 denatu red ethanol (2.72 gallons of undenatured ethanol 1 

### ) and more than 16 pounds of distillers grains from a bushel of corn. The RFA website also reports historic dist illers grains production, and this in formation is listed in Table 3.

TABLE 3 Annual U.S. Distillers Grains Production a

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 fo r 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 gr ains as animal feed, because di stillers grains replace varying amounts of conventional feed for diffe rent animals, as discussed above.

CHS, Inc., one of the major mark eters 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 repo rts this information, but the an imal distribution is slightly different from that obtai ned directly through CHS.

1 Assuming addition of 4.7% denaturant by volume



### 3TABLE 4 U.S. Distillers Grai ns 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, cons umption data reported by the RFA were used, while poultry consumption was excluded becaus e 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 customer s, 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 anim al distribution similar to that of the United States (Table 4).

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

Country/Region 2005/2006 b 2006/2007 b

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



### 42.1.1.2 DGS Inclusion in Feed and Animal Performance

Beef cattle



### A 2008 review (Klopfenstein et al. 2008a) of the use of distillers by-products as be ef cattle feed conducts a meta-analysis of nine experiments for we t distillers grains plus solubles (WDGS) and five experiments for dry distillers grains plus solubles (DDGS). This meta-analysis, based on the optimal Gain:Feed 2 

### (G:F) value, recommends a 30–40% in clusion 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. Klopfenstei n (2008b), feed composition and animal performance at various inclusion rates for DD GS and WDGS are presented in Table 6 and Table 7. As per Prof. Klopfenstein, urea is remo ved from the supplement portion of feed, when more than 15% distillers grai ns are included in the diet.

The animal performance data presented in Table 6 and Table 7 clearly show significantly higher average daily gain 3 

### (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 Inclusion a

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 Supplement b 5 5 5 5 5
Urea c 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, mi nerals, and feed additives.

c Included in the supplement, replaci ng the carrier (such as corn).

2 G:F is a ratio of ADG to dry matter in take (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.



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

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 Supplement b 5 5 5 5 5 5
Urea c 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, mi nerals, and feed additives.

c Included in the supplement, replaci ng the carrier (such as corn).

Dairy cattle:



### A 2006 publication by Anderson et al. (2006) eval uates 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 thes e 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% incl usion 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 simila r for CON and DGS diets. Both the milk fat yield and protein yield are significantly higher for DGS-based di ets than the CON diet. This comparison is summarized in Table 9.

6TABLE 8 Ingredient Content of Feed for Dairy Cattle a

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 premix b 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% WDGS a

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
ECM b (kg/d) 38.4 39.6 41.3 41.7 42 Feed efficiency c 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)



### 7Swine



### 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 s oybean meal (46% CP), and 3 kg of dicalcium phosphate (CaHPO 4 

### ).

The information about feed composition from Prof. Shurson agrees with the feeding recommendations (Shurson and Spiehs 2002) pub lished 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 experime ntal swine grower feed used by Whitney et al. contains soybean oil in addition to DDGS, corn, and soyb ean meal. The difference in feed composition can be attributed to the lower quality of DDGS used in this st udy — 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 performan ce 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 cont rol 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. 2006 a 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 in significant compared to control.

2.1.2 Step 2: Characterize U.S. Distille rs 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) wa s conducted in 2007 by the Nebraska Corn Development, Utilization & Marketing Board. Th e board contacted 9,400 lives tock operations in Illinois, Indiana, Iowa, Kansas, Michigan, Minn esota, Missouri, Nebras ka, North Dakota, Ohio, South Dakota, and Wisconsin regarding use of ethanol co-products in their animal feeding operations. The survey gathered information on dair y cattle, cattle on feed, beef cattle (cow/calf), and hogs.

8

### This survey addressed the use of ethanol co-pr oducts 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), distille rs 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 pres ented in Table 11.

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

Item Operations Who Use This Type (%) Average Peak Inventory b

(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 feed c 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 st ep 1 for beef cattle (2 0%) and swine (10%). For dairy cattle, this survey reports 8% DDGS inclusion; ther efore, 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 discusse d in step 1 of this update. For beef and dairy cattle, feeding distill ers 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 cy cle of beef and dairy cattle must be characterized. This characterization was based on feedback from experts in animal science.

92.1.3.1 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 dair y operations, for which the focu s is on increased daily milk production. For non-commercial operat ions, 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. di stillers grains producti on and consumption, and life cycle of animals, the displ acement 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 grai ns-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 displace ment ratio for each animal type on the basis of lifetime distillers cons umption, 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 cal culated by following steps 4a–d are presented in Table 14.

Table 14 Distillers Grains Disp lacement Ratio by Animal Type

Inclusion Rate, by Animal Type

Beef Cattle Dairy Cattle Swine a

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 SBM b 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 disp lacement (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 distille rs 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 bec ause 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 displacem ent 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 di stillers grains.

Table 15 Distillers Grai ns 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



### 112.1.5 Methane Emission Savings from Enteric Fe rmentation Reduction of Cattle Fed with DGS



### Methane (CH 4 

### ) 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). CH 4 

### emissions from beef and dairy cattle represent 71 percent and 24 percent of total CH 4 

### emissions from enteric fermentation, respectively. Since feeding distillers grains impr oves animal performance for beef and dairy cattle, these animals remain in commercial feedlots for a shorter peri od (over their entire lif ecycle, see section 2.1.3) compared to animals on conventional diet. Therefore, CH 4 

### emissions over the lifecycle of animals fed with distillers grains are lower co mpared to those fed with conventional diets. University of Nebraska’s BESS model has first qu antified these savings over the entire life cycle of corn ethanol production (Liska et al. 2008).

For this study, greenhouse gas sa vings were calculated based on EP A emission factors for enteric fermentation. The calculated CH 4 

### savings as CO 2 

### equivalent are presented in Table 16. As the table shows, the reduction in CH 4 

### emissions from enteric fermentation of animals by DGS is about 3,381 grams of CO 2 

### e 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
CH 4 /head/year) CH 4 Savings as CO 2 Equivalent (g/million Btu EtOH) Dairy 44.2 130.26 5,244
Beef 44.2 33.75 2,402
Swine a 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).



### 122.1.6 Impact of 2007 Energy Independence a nd 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, wh ich will result in the production of more than twice the amount of DGS produced in 2007. This co mparison 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

2007 b,c 6.5 12.7
2015 d,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 Addi tion of DGS to Animal Feed Market



### In 1998, the USDA simulated corn ethanol pr oduction and associated DGS production (See Wang 1999). The USDA simulations concluded th at 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 produc tion. This implies that 84.9% of the total DGS production will displace c onventional animal feeds. However, the recent trends have shown that supply of DGS to the animal feed ma rket does not cause decrease in animal feed prices, thus not inducin g 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

## 3 References

Anderson, J.L., et al., 2006, “Evaluation of Dried and Wet Distillers Grains Included at Two Concentrations in the Diets of Lactating Dairy Cows,” J. Dairy Sci. 89:3133–3142.

Berger, L., 2008, personal communication, University of Illinois at Urbana-Champaign, May.

Blayney, D., 2008, personal communication, ERS-USDA.

Broderick, S., 2008, personal communication, CHS Inc., MN, Feb. 18.

Cooper, G., 2006, “A Brief Encouraging Look at ‘Theoretical’ Distille rs Grains Markets,” Distillers Grains Quarterly, First Quarter.

Corn Refiners Association, 2006, Corn Wet Milled Feed Products, 4th edition. http://www.corn.org/Feed2006.pdf , accessed February 2008.

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