1. LANDFILL ODOURS: ASSESSMENT AND MITIGATION MEASURES
7th European Biosolids Conference
Dr Peter McKendry
18 November 2002

2. Contents Background Monitoring Modelling & Sensitivity Analysis
Results
Prioritisation of Management Activities

3. Background

4. Introduction – Study Funding
Funded by Landfill Tax Credit Scheme
Viridis
SITA Trust
SITA
Millennium Science & Engineering Ltd

5. Introduction – Study Objectives
Assist site designers and managers to identify and assess management techniques for odour control
Guidance on odour management and control by identifying key parameters associated with odour production and its management
Prioritisation of odour control techniques and practices in terms of effectiveness

6. Introduction – Study Format
Study comprised four elements:
public questionnaire on odour
field measurement of methane emissions (as proxy for odorous emissions) from landfill sources
air dispersion modelling using field data
prioritising management options based on modelling results

7. Monitoring

8. Methodology - Questionnaire
Odour complaints should be seen in a positive light
EA inspections provide snap-shot
Local residents most likely to complain as potential exposure period up to 100% of the year
Use of historical data inhibited by accuracy, lack of completeness or total absence of data

9. Methodology - Questionnaire
Letter mailshot to residents
General response good (40%)
Lowest return rate for site with least current and historical complaints
Highest return rate for site with active site-liaison committee

10. Methodology - Questionnaire
Overview of findings:
Short term event (few hours duration)
Frequency once per week or greater
Usually a longstanding issue, commencing at site opening
Worst time of day mornings and/or evenings
Odours usually detected under still/foggy conditions
Odour strength typically ‘moderate/strong’
Generally rotten food/putrid/pungent
Most people do not complain about odours

11. Methodology – Monitoring Programme
FID used to monitor CH4
Site-boundary survey
Identification of off-site odours
Site survey
Identification of on-site odour sources
Flux-box (tent/bin/bag)
Monitoring on-site source emission rates
Meteorological assessment

12. Methodology – Flux-box monitoring device
Trench dug around perimeter of the flux-box
Flux box located with edge placed in trench, back filled and compressed
Monitoring point connected to FID
Monitoring concentration within flux-box until no change in concentration detected

13. Methodology – Site Descriptions
6 Sites included within study
Classified into 3 generic landfill types
Hill on a plain (P1-P3)
Hill on a hill (H1)
Hill in a valley (V1-V2)

14. Methodology – Site Design CharacteristicsP1 P2 P3 H1 V1 V2
Domestic 
Non-hazardous Commercial / Industrial
Special / Hazardous
Liquids / Sludges
Other
Annual Input (m3)
350,000
430,000
200,000
130,000
140,000
80,000
Total Site Area (ha) 50
140 26 27 21 9

15. Methodology – Monitored and Reported CH4 Surface Emission Rates
Odour Source
Methane Flux Rates (mg m-2 s-1 – areas, or mg s-1 – point sources)
Current Study Range (Average)
Range of Reported Values (Bond et al, 2000)
Active working area
n/a
4.2x10-2
Daily cover
3.1x10-1
Flank –temporary cover (Sandy)
1.2x10-2 –
2.4x10-1
Flank –temporary cover (Clayey Soil)
1.0x102*
5.0x10-3
Temporary Cap (Sandy)
6.0x10-2
Temporary Cap (Soil)
6.2x100
5.0x10-2
1.0x100
Restored (Capped)
0.0
4.0x10-3
5.0x10-5
4.1x10-2
Freely venting gas well
2.2x103
4.0x103
Man-hole cover over 1.2m diameter leachate chamber*
4.6x10-2
* Single observation: not to be regarded as typical

16. Methodology – Monitoring Comments 1
Monitored emission rates comparable to other literature reported values
Difference of emission rates between sandy and clayey soils attributable to differences in homogeneity
Sandy soils may be more coarse but are more homogeneous than insufficiently compacted clay soils

17. Methodology – Monitoring Comments 2
Odour with particular characteristics noted consistently at distinct thresholds at different sites
Leachate source 25ppm*
LFG Source ppm*
Note: ppm CH4 measured using FID

18. Modelling and Sensitivity Analysis

19. Modelling & Sensitivity Analysis
Data input:
Odorant emission rate: 5x10-5 gs-1
Point Source: Ø35.68m (1000m2)
Input values constant for all runs, excluding sensitivity analysis

20. Sensitivity Analysis Parameter Analysis Result Terrain
Inclusion vs Exclusion
Clear demonstration of the requirement
for including DTM
Grid Resolution (32x32
vs 64x64)
Greater resolution grid results in
improved definition of output
Fluctuations
Fluctuation Period (1s,
1min, 2min, 5min,
15 min)
Shorter fluctuation periods result in an
increased area potentially impacted.
Marginal difference for fluctuation
periods of <5min
Surface
Roughness
Surface Roughness
(0.2m, 0.3m, 0.5m,
1.0m)
Output decreases in aerial extent as
roughness increases

21. Sensitivity Analysis Parameter Analysis Result Wind Speed
Wind speed variation from 0.8ms-1 – 10ms-1
Complex output:
P3, Output decreases in area as wind speed increases
H1, ADMS 3.1 does not model accurately at wind speeds <1.5ms-1 given H1 parameters
At V2, output increases in extent as wind speed increases to ~2.5ms-1, then decreases as wind speed increases further
Emission Rates
5x10-5 gs-1
Output covers a greater area emission rate increases
Odour Detection Threshold
Variation in ODT
3x10-5, 3x10-6 & 3x10-7
Lower ODT results in a greater aerial extent covered by output

22. Results

23. Surface Roughness Output decreases in size as roughness increases.
More turbulence and mixing results in dilution
Animation

24. Fluctuations
.... 1sec
_ _ 5min
__ 15min

25. Wind Speed
Wind speed increase results in increased dispersion & dilution
Output aerial extent decreases
Animation

26. Wind Direction
Identical output
Rotation about central point
Animation

27. Complex Terrain Interactions 1H1 V2 6 5 4 3 2 1 1 2 3 4 5 6

28. Complex Terrain Interactions 2
Terrain is vital factor in determining dispersion of odours
The output not always as expected
Animation 1 (2D) H1
Animation 2 (3D) H1
Animation 3 (3D) V2 Wind Speed
Animation 4 (3D)V2 Wind Direction

29. Odour Rose 1
Probability analysis of meteorological conditions and terrain interactions

30. Odour Rose 2: % probability of odour event
Controlling Factor
Site P3 H1 V2
Wind Direction
8.5
7.5
5.3
58.3
37.7
26.7
55.9
50.6
35.8
Wind Speed
Receptor Availability

31. Prioritisation of Management Activities

32. Prioritisation of Management Activities
Initial Site Risk Assessment
Location of Potential Receptors
Terrain
Minimisation of:
Number of Sources
Types of Sources
Emission Area

33. Practical Examples Delivery vehicle routing
Prohibition of specific wastes
Waste Cover type / depth
Size of operational cells
Excavation of deposited wastes
Minimisation of cell flank areas
Minimisation of uncapped areas
Pollution control infrastructure
LFG system
Leachate collection disposal