Proceedings available at: http://www.extension.org/67633 The concept of utilizing feedlot manure in an anaerobic digester to power an ethanol plant, which then produces feed for cattle, has been called a closed loop system. In this system inputs are minimized and outputs are used by another component. This research looked at differences in manure quality within this system. Trial 1 considered incorporating distillers grains into the cattle diet and the effects on methane potential of the manure. For this system to be utilized by the feedlot industry in Nebraska, the manure collected for anaerobic digestion must be collected from soil-based open feedlot pens which account for over 95% of the feedlot cattle raised in Nebraska. Trial 2 addressed the methane potential of open-lot feedlot manure and its feasibility for anaerobic digestion.

1. Anaerobic Digestion of Finishing
Cattle Manure
A.K. Watson, S.C. Fernando, G.E. Erickson, T.J. Klopfenstein
University of Nebraska, Lincoln, NE

2. Integrated BioRefinery
Feedlot Ethanol Plant
Anaerobic Digester
Distillers Grains
Manure
Crop
Production
Grain

3. Integrated BioRefinery
Feedlot Ethanol Plant
Anaerobic Digester
Distillers Grains
Manure
Crop
Production
Grain

4. Integrated BioRefinery
Feedlot Ethanol Plant
Anaerobic Digester
Distillers Grains
Manure
Crop
Production
Grain

5. Objectives
Trial 1
• Impact of cattle diet on manure quality
Trial 2
• Impact of cattle housing and ash contamination

6. Materials and Methods
• Seven, 1 L digesters
– Turnover every 20 days (sample
and feed 1/20th every day)
– 9% DM
– 37° C
– pH 7.00 (sodium hydroxide)
– Anaerobic conditions, constant
flow of N2 gas

7. 0.00
0.05
0.10
0.15
0.20
0.25
0.30
30 35 40 45 50 55 60 65
Methaneproduction,L/gOMfed
C
3 d
9 d
18 d
37 C
20 d RT
Mesophilic Thermophilic
Varel et al. 1980. Effect of temperature and retention time on methane production from
beef cattle waste. Applied and Environmental Microbiology 40:217-222.

8. Materials and Methods
• Methane Production
– Methane Detector
• RKI instruments
– Concentration & flow rate
= methane production
• DM and OM degradation
– Feed 9.0% DM
– Measure DM and OM of
effluent

9. Impact of Diet
• Control Cattle
– 82.5% DRC
– 5% Molasses
– 7.5% Alfalfa
– 5% Supplement
• 0.986% urea
• WDGS Cattle
– 47.5% DRC
– 40% WDGS
– 7.5% Alfalfa
– 5% Supplement

10. Impact of Diet
• Complete collection in cement gutter
– 4 steers on each diet
– 3 d
– Manure slurry analyzed and weighed into individual
feeding allotments
• Switchback design
– 7 digesters
– Digesters on trt for 42 d (2 complete turnovers)
– Measurements made last 5 d

11. Cattle Performance
0.150
0.155
0.160
0.165
0.170
0.175
0 10 20 30 40 50
G:F
Corn DGS Inclusion, % of diet DM
Bremer et al. 2011. Effect of distillers grains moisture and inclusion level in livestock
diets on greenhouse gas emissions in the corn-ethanol-livestock life cycle. Prof. Anim.
Sci. 27:449-455.
Linear Quad
WDGS < 0.01 < 0.01
MDGS < 0.01 0.05
DDGS < 0.01 0.45

12. Digestibility
0
20
40
60
80
100
0 40
TotalTractDigestibility,%
Corn WDGS Inclusion, % of diet DM
Corrigan et al. 2009. Effect of corn processing method and corn wet distillers grains plus
solubles inclusion level in finishing steers. J. Anim. Sci. 87:3351-3362.
P-value
Starch 0.92
OM 0.05
DM 0.08
NDF 0.72

13. Digestibility
0.0
0.5
1.0
1.5
2.0
2.5
0
20
40
60
80
100
0 15 30 45 60
FecalOM,kg/d
TotalTractDigestibility,%
Corn/Sorghum WDGS Inclusion, % of diet DM
Luebbe et al. 2012. Wet distillers grains plus solubles concentration in steam-flaked-
corn-based diets: Effects on feedlot cattle performance, carcass characteristics, nutrient
digestibility, and ruminal fermentation characteristics. J. Anim. Sci. 90:1589-1602.
Linear Quad
Starch < 0.01 < 0.01
OM < 0.01 0.99
NDF < 0.01 0.89
Fecal OM 0.04 0.32

14. Impact of Diet
% of DM CONT
Manure
CONT
Effluent
WDGS
Manure
WDGS
Effluent
Total N 3.95a 6.93d 3.79a 6.02c
P 1.88a 4.40c 2.64b 4.82d
S 0.45a 0.83c 0.51b 0.75c
Mg 0.48a 1.08c 0.65b 1.19c
a,b,c,d Means within a row without a common superscript differ (P<0.05).

15. Impact of Diet
• Two 6-week periods (switchback design)
CONT WDGS SEM P-value
DMD 42.7 44.9 1.1 0.05
OMD 51.0 52.9 1.1 0.10

16. Impact of Diet
• Two 6-week periods (switchback design)
CONT WDGS SEM P-value
Methane,
L/d
0.551 0.634 0.05 0.10
Methane,
L/g OM fed
0.116 0.137 0.01 0.05

17. Impact of Diet
CONT WDGS SEM P-value
OMD 51.0 52.9 1.1 0.10
Methane,
L/g OM fed
0.116 0.137 0.01 0.05
Methane,
L/g OM
degraded
0.237 0.261 0.03 0.44

18. • Samples taken from digesters on each
treatment at 4 time points
• Started with 100,000 sequences and 10,000
OTUs
– Data analyzed represents 3,500 OTUs
– Ribosomal Database Project (Michigan State
University)
Microbial Community Analysis
Effluent
Sample
DNA PCR
454
Sequencing
Diversity
Identity

19. Effluent Samples-Eubacteria at Phylum Level
Fibrobacteres
Firmicutes
Tenericutes
Actinobacteria
Synergistetes
Chloroflexi
Bacteriodetes
Proteobacteria
Verrucomicrobia
Unclassified
WDGS
CONT

20. Thermoprotei
Thermoplasmata
Methanomicrobia
Methanobacteria
WDGS
CONT
Effluent Samples-Archaea at Class Level

21. Microbial Community Analysis
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4
PC2(15.5%-Bacteria,14.0%-Archaea)
PC1 (23.6% - Bacteria, 53.9% - Archaea)
Bacteria-WDGS Bacteria-CONT
Archaea-WDGS Archaea-CONT

22. Species Diversity
• Eubacteria populations
– WDGS 177 OTUs common to all 4 samples
– CONT 47 OTUs common to all 4 samples
• Homova P < 0.001
• Amova P < 0.001
• Archaea populations
– WDGS 137 OTUs common to all 4 samples
– CONT 87 OTUs common to all 4 samples
• Homova P = 0.019
• Amova P < 0.001

23. Impact of Housing
• Open lot manure quality affected by
– Cattle ration
– Environmental conditions
• season
– Animal stocking density
– Pen cleaning frequency
– Distance from the feed bunk

24. Feedlot Pen Surface
0
5
10
15
20
25
0 5 10 15 20 25 30
Depth,cm
Organic Matter, %
Organic Layer
Interface Layer
Soil Layer
Mielke et al. 1974. Soil profile conditions of cattle feedlots. J. Environ.
Quality 3:14-17.

25. Feedlot Pen Surface
0
5
10
15
20
25
0 5 10 15 20 25 30
Depth,cm
Organic Matter, %
Organic Layer
Interface Layer
Soil Layer
Mielke et al. 1974. Soil profile conditions of cattle feedlots. J. Environ.
Quality 3:14-17.

26. Impact of Housing
• Complete confinement
manure, 88% OM (CONF)
• Open feedlot manure, 26% OM
(FDLT)
• One 6-week period
– 3 digesters on CONF
– 4 digesters on FDLT (3 failed due
to ash buildup)

27. Impact of Housing
CONF FDLT SEM P-value
OMD, % 46.7 24.8 3.11 < 0.01
Methane,
L/d
0.478 0.229 0.07 < 0.01
Methane,
L/g OM fed
0.103 0.189 0.03 0.01
• 4 remaining digesters

28. Next Steps
• New design
– 45 L, ash removal
• Varying levels of ash contamination
– “Pure” manure 80% OM
– Soil surface of pen 10% OM
– Stockpiled 20% OM
– Fresh 25% OM
– Cement pad 50% OM
Frequency and area of pen cleaning

29. Summary
• Feeding WDGS to cattle
– Improves cattle performance
– Decreases digestibility in cattle
– Enhances digestibility and methane production
• Changes in OM composition of manure
• Changes in microbial community
• Open lot manure can be used as anaerobic digester
feedstock if ash buildup is avoided
– 95% of feedlot cattle in open lot soil based pens

30. Questions??
Himark BioGas
Vegreville, AB, Canada