1. A Novel Approach to Control Atmospheric Methane Emissions from Diffused Area Sources and Low-Volume Point Sources
J. Patrick A. Hettiaratchi
Professor of Environmental Engineering
Department of Civil Engineering & CEERE
Schulich School of Engineering, University of Calgary
May 9, 2008
SWANA BC Chapter GHG from A to Z Workshop
Victoria, BC

2. Methane as a Greenhouse Gas
GWP over 100-year time-horizon = 23
GWP over 20-year time-horizon = 62
CH4 Atmospheric Lifetime = 12 years
(Source: IPCC, 2003)
Therefore, controlling methane could potentially
provide fairly high near-term global warming benefits than we realize.

3. Key Sources of Methane Emissions
Anthropogenic sources account for 60-80% of total emissions
Some Anthropogenic Sources:
Diffused Sources: Sanitary landfills (about 10% - 20% of global emissions)

4. High emissions during waste placement, before closure!
Methane Emissions at Landfills
High emissions during waste placement, before closure!

5. (Flames from the Abyss)
Hot Spots - Zambisa Landfill
(Flames from the Abyss)

6. Hot Spots – Effect of Clay Intermediate Covers
X-section along the transverse direction

7. Hot Spots
“Clear” evidence (at a BC landfill)

8. Key Sources of Methane Emissions
Additional Anthropogenic Sources:
Low-volume Point Sources: Oil and gas industry (about 15% of global emissions)
Flaring/Venting of solution gas and soil gas migration
Fugitive emissions and engineered emissions during gas transmission

9. CH4 Emissions at Oil Well Sites

10. Microbial Techniques to Control Methane Emisisons
Oxidize Methane to Carbon Dioxide Using a Naturally Available Microorganism

11. Methanotrophy
Oxidation of CH4 to CO2 by methanotrophic bacteria, or “methanotrophs”
(Methylomonas methanica)

12. Methanotrophy- background
Methanotrophs are aerobic, attached-growth organisms
They are naturally found:
in paddy fields
around gas leaks
in landfill cover soils
Three types of methanotrophs have been identified; I, II and X

13. Methanotrophy- background
Methanotrophs require:
Oxygen (could operate at low oxygen)
Moisture (optimum MC around 15%)
High temp (optimum around 25-35oC)
Nutrients (N, P. Carbon source is methane)
(Methylomonas methanica)

14. Methanotrophy Methanotrophs are naturally occurring bacteria capable
of using methane as a carbon/energy source. They are
found in forest soils, landfill cover soils, and around
“gas leaking” oil wells/pipes
Methanotrophs require: oxygen (can function in
micro-oxygen environments), moisture, nutrients,
moderate temperature, and a good solid medium
Challenge: How to maximize the methane oxidation
potential of methanotrophs under field conditions??

15. Methanotrophy- Current R & D
Identify optimum conditions for different types of methanotrophs
Determine the best granular medium and flux rates (determine oxygen availability)
Predict behavior under various conditions (mathematical modeling)
Study the effect of by-product formation on environment/methane oxidation (CO2, H2O, heat and EPS)
(Methylomonas methanica)

16. Moisture Needs of Methanotrophs (very important with compost based Biocaps)
Optimum Moisture Content for Max. Oxidation for Various Soil/Compost Mixtures (data from lab
incubation studies)

17. Passively-aerated Column Performance
% oxidation vs time in Sedge Peat
(average CH4 input = 160 and 320 g m-2 day-1)

18. Actively-aerated Column Performance
% oxidation vs time in Compost
(average CH4 input = 650 g m-2 day-1)

19. Engineering Applications - Current R & D
Provide optimum conditions for methanotroph growth on a continuous basis in field situations
Predict field behavior, using
Laboratory results
Mathematical models
Identify the best configurations of Biocaps and MBFs to suit each situation

20. Engineering Applications of Methanotrophy
Biocaps
at landfills to control diffused sources
(Methylomonas methanica)
MBF (Methano-Biofilter)
to control point emissions in oil/gas industry
to oxidize gas collected from landfills (instead of flaring!)

21. Type I Biocaps: To control regular emissions from a closed landfill
30-60 cm thick layer of soil with about 5% C content
Medium permeability
Support vegetation (to increase evapo-transpiration; ET cover)
With or without a 30 cm sub-soil layer
Oxidize g/m2/d (average flux from a typical landfill is about 100 g/ g/m2/d)

22. Biocap Modified Landfill Cover System
Commercial Recovery
CO2 emission
CH4 & CO2 emission
Oxidation in Landfill Cover
(Methanotrophs)
CH4 & CO2 Generation
CH4 & CO2 migration

23. CH4 Oxidation in Biocaps: field testing

24. East Calgary Landfill Test Cell
Field Measurements:
1. Surface flux
2. Depth Profile:
Gas Concentration
Temperature
Moisture Content
Pressure

25. Type II Biocaps To control higher emissions (with some “hot spots”)
30-60 cm thick layer of compost/soil (medium permeability)
Above a gas distribution layer (high permeability)
Support vegetation (to increase evapo-transpiration; ET cover)
Oxidize g/m2/d

26. Type III Biocaps To control “hot spots”
30-60 cm thick layer of compost/soil (medium permeability) above a thick gas distribution layer (high permeability)
Control lateral flow within the gas distribution layer
Support vegetation (to increase evapo-transpiration; ET cover)
Oxidize g/m2/d
(Methylomonas methanica)

27. Distribution layer (high k) “Hot Spot” flux (1,200 g/m2/day)
Soil/compost Bio-cap (medium k)
0.6m
400 g/m2/day
Distribution layer (high k)
“Hot Spot” flux (1,200 g/m2/day)

28. Why soil/compost and not compost alone?
Optimum Moisture Content for Max. Oxidation for Various Soil/Compost Mixtures (data from lab
incubation studies)

29. Type IV Biocaps: Intermediate Thin Biocovers (TBCs)
To control emissions during cell filling
30 cm thick layer of compost/coarse grain medium (high permeability) as intermediate covers
Use high permeable material, if the cell is operated as a Bioreactor
Open for a short time period
Oxidize about g/m2/d
(Methylomonas methanica)

30. Intermediate TBC at Calgary Biocell (unique “bioreactor landfill”)

31. TBCs in Calgary Biocell
CO2 emissions
CH4 & CO2 emissions
Commercial recovery
Oxidation in landfill bio-cover (Methanotrophs)
Solid waste-1st lift (5m)
Solid waste-2nd lift (5 m)
2nd Intermediate thin biocover (30 cm)
1st Intermediate thin biocover (30 cm)
Solid waste-3rd lift (8 m)
Final bio-cover GL
CH4 & CO2
generation

32. 1st Intermediate Bio-cover 2nd Intermediate Bio-cover
(80m*80m)
2nd Intermediate Bio-cover
(110m*110m)

33. Mathano-biofilters (MBFs)
To control “point sources” (could be “hot spots” at landfills)
Collect gas from a (small) landfill and oxidize in a MBF.
Point sources in oil/gas facilities
Typical medium: fully stable compost
(Methylomonas methanica)

34. Field Scale MBF @ a natural gas metering stationX
35cm
Compost
Gravel
Geotextile
Geomembrane
Cross section on XX

35. Type I MBFs Passively aerated compost or compost/soil MBFs
Bed thickness; 30 to 50 cm (depends on surface area)
Oxidize about g/m2/d

36. Type II MBFs Actively aerated compost or compost/soil MBFs
Bed thickness; 50 to 100 cm (higher thicknesses are possible because of active aeration)
Oxidize about g/m2/d or more

37. Field Application of MBFs – Our Experience
Passively aerated compost based MBFs:
Control vent gases from natural gas metering stations (volume: m3/day)
Operated during cold winters (heat generated by methanotrophic activity)
Maximum oxidation: about 400 g/m2/d

38. Field MBF Experimental Results
max 33
min 10
max 34
max 24
min 14
min 20
% Methane Oxidation vs Time
High
Moisture
Temperature profile (5, 20 & 35 cm)
Atmospheric temperature = 10 0C

39. Field Application of MBFs – Our Experience with Solution Gas Oxidation
Passively aerated compost based MBFs to control casing/solution gas at oil
well sites:
Divert gas normally vented
into the atmosphere through
a compost biofilter
Low efficient, low
maintenance unit at a
heavy oil well site

40. Field Application of MBFs – Our Experience with Landfill Gas
Actively or Passively aerated compost based MBFs to control landfill gas (from a passive extraction system):
To be installed at a landfill in Ecuador
Final design (size, active or passive aeration) depends on gas flow rates and lab experiments/mathematical modeling

41. Mathematical Modeling: Reactive-Transport Model
Model Input
Bulk density
Soil particle density
Soil moisture content
Biological kinetic parameters (Ko2, KCH4, Vmax)
Soil temperature
CH4 source strength
Model Output
Gas concentration profiles
CH4 oxidation rate

42. Design Curves from 1-D Reactive Transport Model Simulations
a. depth=0.3m; m.c.=7.5%
b. depth=0.3m; m.c.=15%
c. depth=0.9m; m.c.=7.5%
d. depth=0.9m; m.c.=15%

43. Advantages of Biocaps and Biofilters
Methane oxidation without undesirable by-product formation (compare with flaring of landfill gas)
Cost effective (compare with combustion with or without energy recovery, catalytic oxidation)
Cost of Biocaps; $1 to $5/tonne of CO2E
Cost of MBFs; $2-10/tonne of CO2E
Low operation/maintenance requirements

44. Barriers to Large-scale Application of Biocaps
Not well known to landfill operators, consultants and regulators
need more pilot projects, field demonstration projects (Nanaimo landfill project with SHA, Nanaimo municipality)
Too simple, too cheap and not established, yet. More expensive, well established technologies are available (gas extraction for energy recovery or flaring)
But no competition for low volume diffused gas escape via final covers
No benefits other than GHG credits
Regulatory requirements for landfill covers.
Biocaps are not compatible with dry-tomb covers, but compatible with ET covers)

45. Issue 1: Formation of Exo-polysacharides (EPS)
EPS is a by-product of methanotrophy
Observed in laboratory flow-through column studies
Decreases methane oxidation efficiency over time (at least in 15 cm diameter columns)
However, this may not be an issue in field biocaps or MBFs
Or develop biocap/MBF maintenance plan to eliminate EPS impacts

46. The growth of slime (extra-cellular polymeric substances) reduces CH4 oxidation efficiency.

47. Issue 2: Stability of granular medium (eg. compost))
Stability is an issue when the biocap granular medium contains high levels of organic material (eg. compost)
If compost is not fully stabilized, it will be difficult to establish methanotrophic bacteria

48. Issue 3: Determination of methane oxidation in the field
Needed to determine Carbon off-sets of a Biocap project
Measure methane oxidation directly (from field data)
Carbon isotope measurements (expensive; good for research projects)
mathematical modeling (not popular)
universal method not yet available
Could measure methane emissions before and after Biocap implementation
Need several field measurements (before and after)
easier, need less equipment/expertise but labor intensive
Need regulator “buy-in” (who are the regulators?)
Flux chamber method being used at Nanaimo landfill

49. Operational Problems with MBF: Gopher and
Badger damage results in short-circuiting of CH4

50. Operational Problems: Cold Climate
Heat generated by bacteria and compost’s self- insulation help keep the biofilter warm
Heating is required for the really cold days

51. Conclusions
High quantities of CH4 are emitted from landfills and oil and gas industry sources
Methanotrophy-based technologies can be applied to reduce these emissions in a cost effective manner
Biocaps with soil or soil-compost mixtures can be used effectively to eliminate low volume diffused CH4 emissions
MBFs, either passively or actively aerated, could be used to control low-volume point sources of CH4
Mathematical models could be used to optimize design of Biocaps and MBFs
Need more field pilot-scale demonstration projects to “educate” stake holders
Thank You!!!