feeding distillers grains and reduced sulfur emissions

Dan Miller, Mindy Spiehs, andBryan Woodbury

USDA-ARS, Lincoln & Clay Center, NE

Reduced sulfur emissions and feeding distillers byproducts

Why Study Reduced Sulfur in Cattle Feedlots?

• Reduced sulfur gases very smelly• H2S (rotten eggs)• Methyl sulfides (even worse!)

• H2S reporting issue (not in feedlots)• ATSDR 30 & 70 ppb• H2S levels very low

Koelsch et al, 2004

How is TRS related to distillers byproducts?

• Wet distillers grains with solubles (WDGS)• Depleted in starch• Enriched in CP, oil, P and S• Sulfate due to sulfuric acid use• Fed at high levels (up to 50%)

Sulfate,Amino Acids

H2S,

Methyl SulfidesRumen Bacteria

Research Questions

Q: How does diet

effect sulfur emissions?

Q: Where are cattle

feedlot pen ‘hot spots’?

Q: Sulfur sources:

manure or soil?

WDGS Study #1

• 160 steer calves, 10 per pen• Concrete floor• Four levels WDGS (0, 20, 40, 60% on

DM basis)• Pens cleaned 3-4 weeks• Collect manure composite for each pen

at monthly intervals• Measure H2S content of manure• Determine relative TRS emission

Feeding >20% WDGS increases H2S content in the manure.

Manure Composition

WDGS in diet (% DM basis)

Constituent 0% 20% 40% 60% SEM

Total S (mg/g DM) 5.1a 8.7b 11.7c 14.2d 0.3

H2S-S (mg/g DM)

1.57a 3.07a 8.85b 16.41c 0.88

Varel et al., JEQ 2008

Measuring Relative TRS Emission

• Fresh manure sample (consistent surface area)

• Air flow 1 L/min (internal fan to mix)• Sample airstream for total reduced S (TRS)

Three highest values averaged & background subtracted

TRS Emission ProfilePen 3 (40% WDGS) 8/20/07

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8 10 12

Gas sample

H2S

, pp

m

Manure Added

Manure Removed

• Feeding >20% wet distillers increases H2S emission.

• Similar result for large-scale feedlot?

WDGS Study #1WDGS Study #1

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0 20 40 60

Percentage Wet Distillers Grains

To

tal

Red

uce

d S

ulf

ur,

pp

m8/20/2007

9/24/2007

10/22/2007

a aa a

b

b

b

c

a a

b

c

WDGS Study #2a(During Production)

• Eight pens• Working feedlot (concrete & soil)• Two levels WDGS (0 & 40% on DM

basis)• Collect manure composite (feed

bunk area) for each pen at roughly monthly intervals

• Determine relative H2S emission

Study #2 Relative TRS Emission

• 0.7 to 2.5-fold increase for WDGS • Low moisture content on 5/5 and 6/16

2008 Feedlot Study

0.00

0.10

0.20

0.30

0.40

0.50

0.60

4/14 5/5 6/2 6/16

Date

H2S

, pp

m0%

40%

P = 0.001

P = 0.079

P = 0.002

P = 0.088

WDGS Study #2b(Post Production—Lingering

Effects?)

• Four pens (2 WDGS, 2 DRC)• Utilize EC to select 20 sites per pen

Represent entire surfaceClassified sites as ‘Mound’ or ‘Edge’

• Measure H2S flux with chambers• Collected soil samples for analysis

Moisture contentOrganic matter content

Comparing Field Emissions

Analysis of Results—Pen Average

Source Pr > F

Diet 0.037

Site 0.008

Diet*Site 0.407

Mound

Edge

DRC 8a 14.5b

WDGS 11.5a 21.0c

WDGS Study #3Multi-year, pen emission

• Ten pens (5 per diet treatment)• Twelve sites per pen (mound vs.

edge)• Two levels WDGS (0 & 40% on DM

basis)• Determine relative TRS emission

from the soil over two production cycles

WDGS Study #3Relative TRS emission

• WDGS flux 0.3 to 4-fold higher on 5 of 7 dates.

WDGS Study #3Edge versus Mound

• Larger relative emission in control diet.

• WDGS consistent but not significant

Diet Mound EdgeWDGS 3.35 5.56Control 2.21A 2.99B

T-test 0.001 0.028

Research Questions

Q: Diet? Q: Location?Q: Source?

A: 40% WDGS

increases TRS.

A: Pen edges more important

than mound

A: Manure strongest source.

Future Directions• What mechanism for soil emission?

• Degasing or sulfate reduction in the soil?

• Does this matter at the fence line?• What about low S WDGS?

Questions?