A Novel Approach to Control Atmospheric Methane Emissions from Diffused Area Sources and LowVolume P

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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
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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.
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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)

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Methane Emissions at Landfills
High emissions during waste placement, before
closure!
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Hot Spots - Zambisa Landfill
(Flames from the Abyss)
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Hot Spots Effect of Clay Intermediate Covers
X-section along the transverse direction
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Hot Spots

• Clear evidence (at a BC landfill)

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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

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CH4 Emissions at Oil Well Sites
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Microbial Techniques to Control Methane Emisisons
Oxidize Methane to Carbon Dioxide Using a
Naturally Available Microorganism
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Methanotrophy

• Oxidation of CH4 to CO2 by methanotrophic
  bacteria, or methanotrophs

(Methylomonas methanica)
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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

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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)
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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??

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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)
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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)
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Passively-aerated Column Performance
oxidation vs time in Sedge Peat (average CH4
input 160 and 320 g m-2 day-1)
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Actively-aerated Column Performance
oxidation vs time in Compost (average CH4
input 650 g m-2 day-1)
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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

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Engineering Applications of Methanotrophy

• MBF (Methano-Biofilter)
• to control point emissions in oil/gas industry
• to oxidize gas collected from landfills (instead
  of flaring!)

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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 100-200 g/m2/d (average flux from a
  typical landfill is about 100 g/ g/m2/d)

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Biocap Modified Landfill Cover System
Commercial Recovery
CO2 emission
CH4 CO2 Generation
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CH4 Oxidation in Biocaps field testing
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East Calgary Landfill Test Cell
Field Measurements
1. Surface flux
2. Depth Profile

• Gas Concentration
• Temperature
• Moisture Content
• Pressure

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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 200-400 g/m2/d

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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 200-400 g/m2/d

(Methylomonas methanica)
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Soil/compost Bio-cap (medium k)
0.6m
400 g/m2/day
Distribution layer (high k)
Hot Spot flux (1,200 g/m2/day)
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Why soil/compost and not compost alone?
Optimum Moisture Content for Max. Oxidation for
Various Soil/Compost Mixtures (data from
lab incubation studies)
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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 50-100 g/m2/d

(Methylomonas methanica)
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Intermediate TBC at Calgary Biocell (unique
bioreactor landfill)
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TBCs in Calgary Biocell
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1st Intermediate Bio-cover (80m80m)
2nd Intermediate Bio-cover (110m110m)
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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)
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Field Scale MBF _at_ a natural gas metering station
Cross section on XX
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Type I MBFs

• Passively aerated compost or compost/soil MBFs
• Bed thickness 30 to 50 cm (depends on surface
  area)
• Oxidize about 200-400 g/m2/d

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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 600-750 g/m2/d or more

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Field Application of MBFs Our Experience

• Passively aerated compost based MBFs
• Control vent gases from natural gas metering
  stations (volume 5 -10 m3/day)
• Operated during cold winters (heat generated by
  methanotrophic activity)
• Maximum oxidation about 400 g/m2/d

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Field MBF Experimental Results
Methane Oxidation vs Time
High Moisture
Temperature profile (5, 20 35 cm) Atmospheric
temperature 10 0C
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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

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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

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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

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Design Curves from 1-D Reactive Transport Model
Simulations
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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

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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)

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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

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

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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

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Operational Problems with MBF Gopher and Badger
damage results in short-circuiting of CH4
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Operational Problems Cold Climate

• Heat generated by bacteria and composts
  self- insulation help keep the biofilter warm
• Heating is required for the really cold days

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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!!!