Setting Acceptable Odor Criteria Using Steady-state and Variable Weather

Data

Z. Yu1, H. Guo2, C. Lague3

1.Division of Environmental Engineering, University of Saskatchewan, Saskatoon, SK

2.Department of Agricultural and Bioresource Engineering, University of Saskatchewan, Saskatoon, SK

3.Faculty of Engineering, University of Ottawa, Ottawa, ON

Presentation outline

• Introduction• Objectives• Materials and Methods• Results and Discussions• Conclusions• Acknowledgement

Introduction• Livestock odor & Setback distance & Odor

dispersion model• Odor criteria

– odor concentration – odor occurrence frequency

• Different acceptable odor concentration– different odor intensity/strength perceptions for odor

concentrations– different weather data: steady-state or variable weather data– different odor occurrence frequencies

Objectives• Explore the odor dispersion under steady-state and variable

(hourly historical) weather conditions by CALPUFF model

• Identify the equivalent odor criteria (odor concentration and occurrence frequency) for determination of setback distance using these two weather conditions.

Materials and Methods• Swine farm• CALPUFF• Weather condition

– Steady state • F1, F3, E3, E5, D5, D8, C5• Prevailing wind (WNW)

– Variable• annual hourly

meteorological data (2003)Note: When using annual hourly meteorological data to study the actual occurrence and duration of the steady-state weather conditions, steady-state weather condition marked as stability with wind speed (F1, F3, etc.) represented the weather condition with certain stability class and the wind speed equal or less than certain value and any other conditions that are more stable than the indicated condition

Materials and Methods (Cont’d)

• Computation Assumptions and model setup

– Point sources for the barn and area source for manure storage

– Constant emission rates , the odor emitting height was 1.5 m for the barn and the manure storage cells located on ground level.

– The odor exit velocity was considered to be 0.05 m/s. The exhaust air temperature from the barn was 22oC.

– Ambient temperature of 20oC and mixing height of 1500 m . The wind direction was constant from WNW.

– The model simulation time period was set up long enough

– Deposition or chemical transformation were not considered.

– Receptors were arranged in grid format of 100 m from each other within 5 km from the farm. The receptor’s detection height was considered to be 1.5 m above the ground.

• Data analysis method

CDD: Critical Detection DistanceO.C: Odor ConcentrationO.F: Occurrence Frequency

Results and Discussion

• Odor dispersion under steady-state meteorological conditions

• Annual occurrence frequency and duration of steady-state weather condition

• Odor dispersion using annual hourly meteorological data

• Comparison of odor criteria under two weather conditions

Odor dispersion under steady-state meteorological conditions

• Critical detection distance

0

5

10

15

20

25

F1 F3 E3 E5 D5 D8 C5

Weather condition

• Odor concentration within 5 km

Annual occurrence frequency and duration of steady-state weather condition

1. Maximum Occurrence frequencies for weather conditions F1 and F3

appeared in WNW direction,

2. Maximum Occurrence frequencies of E3 and E5 in W direction and D5, D8 and C5 in SSE direction.

3. The annual occurrence Frequencies for F1 to C5 in WNW directions were 0.71%, 1.39%, 1.72%, 2.89%, 4.83%, 8.24% and 10.25%, respectively.

Annual occurrence frequency and duration of steady-state weather condition (Cont’d)

1. The stable conditions (F1 and F3) and slightly stable (E3 and E5) conditions seldom occurred at daytime.

2. Neutral conditions (D5 and D8) occurred mostly at nigh and slightly unstable condition (C5) occurred more often at night time than daytime,.

3. Long duration occurrences are mainly in winter season

4. long durations of the same weather conditions (or close to steady-state weather condition) were very rare.

5. For F1 to E5, the largest duration was 5 hours and occurred no more than 4 times in a year.

6. The largest duration is 11 hours for C5 which occurs twice

Odor dispersion using annual hourly meteorological data• Mean annual odor concentration

• Annual occurrence frequencies for various odor concentrations

-5 -4 -3 -2 -1 0 1 2 3 4 5-5

-4

-3

-2

-1

0

1

2

3

4

5

1

2

3

5

7

10

20

25

28

Kilom eters

Kilo

met

ers

1. maximum distances occur for various odor concentrations leeward of the prevailing winds in the NW and SE areas

2. If annual average odor concentrations of 1 to 10 OU are used as setback criteria, the maximum setback distance will be in the range of 0.8 to 2.5 km

Comparison of odor criteria under two weather conditions

Odour occurrence frequencies with certain concentration levels undervariable weather condition

0

10

20

30

40

0 10 20 30 40 50 60 70 80Odour concentration(OU)

Odo

ur o

ccur

renc

e fr

eque

ncie

s (%

)

0.5 Km

1 Km2 Km

3 Km4 Km

5 Km

Odour occurence frequencies with certain concentration levels understeady state weather condition

0

5

10

15

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300

Odour concentration(OU)

Odo

ur o

ccur

renc

e fr

eque

ncie

s (%

)

0.5 Km

1 Km

2 Km

3 Km

4 Km

5 Km

baxy

y

1

ln

bxay

y

ln1

ln

for variable weather condition

for steady state weather condition

Comparison of odor criteria under two weather conditions Cont’d

Odour cri teri a

0

5

10

15

20

25

30

35

40

0 10 20 30 40 50 60 70 80 90 100 110 120

Odour concent rat i on(OU)

Odou

r oc

cure

nce

freq

uenc

y (%

)

0. 5 Km (1)

1 Km(1)

2 Km(1)

3 Km(1)

4 Km(1)

5 km(1)

0. 5 Km(2)

1 Km(2)

2 Km(2)

3 Km(2)

4 Km(2)

5 Km(2)

0

5

10

15

20

25

30

35

40

0 10 20 30 40 50 60 70 80 90 100 110 120

6

12.5

7.2

Conclusions• Under steady-state weather conditions, the odor travels much farther under

stable weather condition and the travel distance decreases significantly with decrease of atmospheric stability.

• Using the annual hourly meteorological data and considering annual average odor

concentrations of 1 to 10 OU as acceptable odor concentration, the maximum setback distance will be in the range of 0.8 to 2.5 km,. These distances are much lower than that from using same odor concentration under stable steady-state weather conditions. Different odor criteria should be used to determine setback distances under different weather conditions.

• The relationships between odor concentration and its occurrence frequency are

different between these two weather conditions.

• The odor criteria used to determine different setback distance were identified. Suitable odor criteria that should be used to achieve acceptable setback distance under either steady-state and variable conditions .

Acknowledgements

• Thanks to

– NSERC and CGSR (College of Graduate studies and research) of University of Saskatchewan

Thank you