atmosphere

CH4

Methanotrophic oxidation: [aerobic] methane consumption in cover soils

CH4

CO2 O2

Methanogenesis: [anaerobic] methane production in waste

Uptake of atmospheric CH4

cover soil

Landfill Methane (CH4) Emissions & Oxidation

J. Bogner, Research Prof.

Dept. of Earth & Environmental Sciences (EAES) University of Illinois at Chicago (UIC)

K. Spokas, USDA/ARS, St. Paul, MN

ISTC Seminar

7 November 2011

Will address: •  Background on landfill gas (LFG) and

landfill CH4.

•  CH4 as a greenhouse gas (GHG)

•  Quantifying landfill CH4 emissions and CH4 oxidation at various spatial and temporal scales: global to site-specific.

Complex Polymers (cellulose, other polysaccharides, proteins)

Hydrolytic bacteria Monomers (sugars, amino acids)

Fermentative bacteria

H2 + CO2 Acetate Propionate, butyrate

H2 producing fatty acid oxidizing bacteria

Acetate Acetogenic H2 + CO2 Acetate bacteria

Methane Methanogens (Archaea)

Making methane in a landfill: pathways for anaerobic biodegradation of organic waste...

CH3COOH à CH4 + CO2 Acetate cleavage CO2 + 4H2 à CH4 + 2H2O Reduction of CO2 with hydrogen Pathways for CH4 oxidation: aerobic (net), methanotrophs CH4 + 2O2 à CO2 + 2H2O anaerobic, sulfate-reducers, archaea CH4 + SO4

-2 à HS- + HCO3- + H2O

Major Pathways for biogenic methane formation, anaerobic, methanogens:

What’s in landfill gas?? major components, minor components, and trace components...

Major components (CH4, CO2)—high % (v/v) anaerobic biodegradation of organic materials: cellulose, hemicelluloses, proteins, fats [Note-lignin not significantly degraded]

Minor components—up to a few % (v/v)

(O2, N2): air that is pulled into landfill gas extraction system; H2 : “young” landfill gas or hot landfills or specialized waste

Trace components--ppm (v/v) or less, >200 species, •  direct volatilization under landfill conditions (25-35 deg C):

hydrocarbons up to about C10, aromatics, reduced S gases, chlorinated species, volatile siloxanes, etc.

•  abiotic and biotic reaction products: anaerobic biodegradation

of higher chlorinated species; metalloids

Pathways for Landfill Methane:

CH4 recovered

methane oxidation in aerobic zone

emissions

Methane [CH4] produced = Σ (CH4 recovered + CH4 emitted + CH4 oxidized + CH4 migrated + Δ CH4 storage) units = mass/time [Bogner and Spokas, 1993]

CH4

migration

methanotrophs vertical gas well

CO2

methane production in anaerobic zone: methanogens

horizontal gas collector

Pathways for Landfill Methane(CH4) & Methane Mass Balance:

Atmospheric concentrations of CO2, CH4 and N2O over the last 10,000 years (large panels) and since 1750 (inset panels). Measurements are shown from ice cores (symbols with different colors for different studies) and atmospheric samples (red lines). The corresponding radiative forcings relative to 1750 are shown on the right hand axes of the large panels.

NOW (2005) CO2 380 CH4 1.8 N20 0.3 THEN (1750) “pre-industrial” CO2 280 CH4 0.7 N20 0.2 ppm v/v in the atmosphere (rounded))

“Hockey Stick” Curves

Source: IPCC 4th Assessment Report. 2007.Working Group I. www.ipcc.ch

1. Carbon Dioxide 2. Methane (Note: 30% from natural wetlands)

3. Nitrous Oxide

Landfills

Ruminants

Fertilized Soils

Rice Paddies

The greenhouse effect and the 3 major “anthropogenic” greenhouse gases...

Gas pipeline losses

IR

Fossil Fuel Combustion: stationary & mobile sources

Coalbed leakages

Biomass burning

Units, units, units... for GHG emissions, units often expressed as metric tons carbon dioxide equivalent... or Mt CO2 eq or Gt CO2 eq to convert to carbon dioxide equivalents.... multiply the mass of methane (metric) tons by the 100 year global warming potential (GWP) for methane relative to carbon dioxide (=1) 100 year GWP’s for methane: 21...IPCC Second Assessment Report (SAR) 24...IPCC Third Assessment Report (TAR) 25...IPCC Fourth Assessment Report (AR4)

Global GHG Emissions for 1990 and 2004 by sector in billion metric tons [Gigatons,Gt] CO2 eq:

Total for 2004 = approx. 49 Gt CO2 eq (+24% since 1990; +70% since 1970). [NOTE: All emissions normalized to CO2 eq based on 100-year Global Warming Potentials (GWPs) from IPCC 2nd Assessment Report, used for Kyoto Protocol compliance, shown at right.]

2004 Distribution: 77% CO2 14% CH4 8% N2O 1% F-gases

CO2 = 1 CH4 = 21 N2O = 310

Comparison of 1990 and 2004 Sectoral GHG emissions: From: IPCC 4th Assessment Report. 2007.Working Group III.Mitigation. www.ipcc.ch

Energy supply Transport Buildings Industry Agriculture Forestry Waste

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0 <20 <50 <100 <20 <50 <100 <20 <50 <100 <20 <50 <100 <20 <50 <100 <20 <50 <100 <20 <50 <100

Developing Countries Economies in Transition OECD Countries World total GtCO2-eq/yr

Economic mitigation potentials at various price levels ($ per metric ton carbon dioxide equivalent).

[Mt CO2 eq, rounded]

1990 2000 2005 2010 2020 2030 2050

Landfill CH4 average of (a) and (b)

550 (705)**

590 635 (767)**

700 910 (910)**

Wastewater CH4 (a)

450(354)**

520 590(425)**

630 670 (531)**

Wastewater N2O (a)

80 (67)**

90 100 (80)**

100 100 (97)**

Incinerator CO2 (b)

40 50 50 60 60 70 80

Total 1120 1250 1345 1460 1660

(a) Based on reported emissions from national inventories and national communications, and (for non-reporting countries) 1996 IPCC inventory guidelines, extrapolations,

and Business-As-Usual (BAU) projections (U.S. EPA, 2006)

(b) based on historic and future emissions using 2006 IPCC inventory guidelines and BAU projections (Monni et al., 2006)

Source: IPCC 4th Assessment Report Working Group III. Chapter 10, Bogner et al., 2007 www.ipcc.ch

The waste sector (including wastewater) accounted for <3% of global GHG emissions in 2005...

e.g., the lowest sectoral emissions at about 1.3 Gt CO2 eq. [**EPA, 2011, new draft report on global non-CO2 GHG emissions.]

Where do the numbers come from? Landfill CH4 Emissions at Various Spatial & Temporal Scales... Global estimates, by year= sum of national estimates, based on annual inventory reports to the UNFCCC by developed countries using latest IPCC National GHG Inventory Guidelines AND estimates for given year for developing countries (which do not report annually). Basis: estimated emissions from CH4 generation using a first order kinetic model based on national estimates of landfilled waste quantity and composition. Site-specific estimates for U.S. landfill regulatory purposes (NMOC emissions) = use of similar landfill gas generation model. Site-specific measurements = use of ground-level techniques (e.g., static closed chamber), above-ground techniques (e.g. dynamic plume tracer methods; micrometeorological methods), or below-ground techniques (e.g., diffusive flux calculations for cover soil).

Basic methodology for national GHG inventories...landfill CH4

2006 Intergovernmental Panel on Climate Change (IPCC)

National Inventory Guidelines for Methane Emissions from Solid Waste Disposal Sites http://www.ipcc-nggip.iges.or.jp/public/2006gl/ppd.html.

FOD (“First Order Decay”) Tier 1: FOD based on IPCC = multicomponent default spreadsheets for waste fractions. 1st order kinetic model

based on annual waste generation, fraction landfilled that is anaerobic, Tier 2: FOD based on country-specific Lo (methane generation potential), model. k (kinetic constant).

Tier 3: Use of more “complex,” “field-validated” methods

Tier 1 & 2 Emissions = Modeled Theoretical Generation - Measured Recovery - Estimated Oxidation, 10% or zero

also allowed is:

Some issues with the current FOD methodology.... 1.  Estimated uncertainty of FOD model (IPCC, 2006) “30% to more than 200%”. 2.  Waste data for many countries is uncertain or does not exist(?use of surrogate). 2. FOD models were never field-validated for emissions (only for recovery). 3. 10% is not representative of field measurements of CH4 oxidation. 4. No consideration of effect of cover materials to retard & reduce emissions. 5. Where site-specific emissions have been monitored, esp. sites with LFG recovery, FOD model basis can yield highly inaccurate results in 1:1 comparisons with field data.

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Marina

Scholl Canyon

Example for two California sites:

actual 2009 recovery was

2-3 times modeled recovery

using Tier I FOD model

(& assuming 75%

recovery as shown in figure)...

Tier I generation for 2 California landfills

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y = 0.9453x -

40.515

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Field-scale data have shown that modeled landfill methane generation is not a good predictor for emissions...

as it can be for recovery, where waste inputs are well-characterized...

French field scale study 2002-2005: Methane mass balance at 7 cells at 3 sites Methane [CH4] generated, kg/day = Σ (CH4 recovered + CH4 emitted + CH4 oxidized + CH4 migrated + Δ CH4 storage)

Replotted data from: Spokas et al., 2006. Methane mass balance at three landfill sites: What is the efficiency of capture by gas collection systems? Waste Management 26:516-525.

atmosphere

CH4

Methanotrophic oxidation: [aerobic] methane consumption in cover soils

CH4

CO2 O2

Methanogenesis: [anaerobic] methane production in waste

Uptake of atmospheric CH4

cover soil

What does the literature tell us about the major controls on emissions ? *LFG RECOVERY: reduces CH4 concentration in soil gas

at base of cover materials, thus reducing diffusive flux. FOD model: subtraction for gas recovery data only.

*Thickness and physical PROPERTIES OF daily, intermediate, and

final COVER MATERIALS to reduce emissions. FOD model: Not considered.

*Closely related is : SEASONAL rate of methanotrophic OXIDATION in

cover materials, which can reduce emissions depending on seasonal oxidation capacity vs. flux rate. FOD model: only allows 10% oxidation based on Czepiel et al., 1996, JGR.

Relating CH4 oxidation to soil temperature and moisture…

>2000 laboratory incubations using cover soils from two California sites…

Spokas & Bogner, 2011, Limits & dynamics of methane oxidation in landfill cover soils, Waste Management, 31:823-832

II. What is the effect of temperature on relative rates of CH4 oxidation?

(rate at specific temperature/

maximum rate for the corresponding soil moisture potential for each soil)

0.2 % v/v methane in headspace (average for 10 cm depth, field sites)

Temperature ( oC)

-10 0 10 20 30 40 50 60 70

Relative CH4 Oxidation Rate

0.0

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981.0

1.05rate relative2

59.96.27-temp

5.02

=

=!"

#$%

&'

R

e

Temperature range of -5 to 70 oC

What is the effect of temperature on relative rates of CH4 oxidation?

Soil Moisture Potential (kPa)

-2000 -1500 -1000 -500 00.0

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Soil Moisture Potential (kPa)

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994.0e1

0.852rate Relative

2

84.151754.1SMP

-

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+

=!"#

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R

Soil Moisture Potential (kPa)

-2000 -1500 -1000 -500 00.0

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Relative C

H4 Oxidation R

ate

Incubation Temperature < 5 oC Incubation Temperature 5-40 oC Incubation Temperature >40 oC

III. What is the effect of soil moisture on relative rates of CH4 oxidation? (rate at soil moisture potential divided by maximum rate for the corresponding temperature of the incubation) for:

(A)  temperatures less than 5oC (n=72) (B)   temperatures between 5 and 40oC (n=3192) (C)  for temperatures >40oC (n=192)

What is the effect of soil moisture on relative rates of CH4 oxidation?

Optimum approx. = -33 kPa (WHC). The soil moisture potential for 50% of the oxidation activity

for the two validation sites ≈ -600 kPa. Threshold approx. = -1200 kPa.

• Moisture range from -15 bar to zero (saturated) soil moisture potential

What is the effect of CH4 exposure time on oxidation rates with: No Pre-incubation/field-collected moisture VS 60-day pre-incubation at field moisture

VS 60-day pre-incubation at field-capacity moisture (-33 kPa)?

(averages of 6 replicates; SD in parentheses)

no pre-incub; field moist. oxid. range = 0.05 -211

pre-incub; field moist. oxid. range = 0.1 - 384

pre-incub; field capacity oxid. range = 112 -644

[micrograms CH4/g dry soil/day]

Marina Scholl Canyon Depth (cm) Daily Intermediate Final Daily Intermediate Final (ug CH4 gsoil

-1 day-1) A. Initial Rate – No Pre-incubation at field collected moisture contents 0-10 cm 0.05 (0.02) 0.4 (0.2) 0.3 (0.1) 0.1 (0.2) 0.2 (0.3) 0.2 (0.1)

10-20 cm 0.04 (0.08) 1.9 (0.4) 0.2 (0.1) 0.1 (0.1) 0.2 (0.1) 0.2 (0.3)

20-30 cm # 2.5 (0.6) 2.8 (0.5) # - 0.1 (0.1)

30-40 cm 171.3 (22) 2.6 (0.2) - -

40-50 cm 211.2 (36) 0.5 (0.3) - -

50-60 cm # 1.4 (0.2) - -

70-80 cm 0.4 (0.2) - -

B. Pre-incubation with 5% CH4 and 20% O2 (60 d) at field collected moisture contents 0-10 cm 0.4 (0.2) 0.1 (0.3) 3.6 (0.5) 1.7 (0.2) 0.2 (0.1) 0.9 (0.2)

10-20 cm 1.8 (0.1) 1.9( 0.1) 2.8 (0.4) 3.6 (1.4) 0.2 (0.1) 0.5 (0.1)

20-30 cm # 8.9 (0.4) 5.6 (10) # - 0.2 (0.5)

30-40 cm 384.2 (10.3) 111.3 (12) - -

40-50 cm 374.1 (7.1) 199.8 (14) - -

50-60 cm # 219.8 (28) - -

70-80 cm 212.7 (23) - -

C. Pre-incubation with 5% CH4 and 20% O2 (60 d) at field capacity moisture content (-33 kPa) 0-10 cm 142.2 (33.2) 416.8 (16) 593.8 (31) 112.4 (19) 211.4 (3.2) 212.9 (2.2)

10-20 cm 132.6 (20.2) 412.9 (13) 573.9 (14) 112.1 (13) 212.4 (3.9) 212.7 (1.8)

20-30 cm # 412.7 (15) 613.1 (14) # - 212.5 (0.72)

30-40 cm 412.4 (23) 594.2 (16) - -

40-50 cm 452.0 (12) 604.2 (15) - -

50-60 cm # NS - -

70-80 cm 644.2 (28) - -

California Field Sites

final cover: rectangle/square intermediate cover (largest area): circles daily cover: stars

Climate overview for California: Mediterranean climate, precipitation mostly during winter months (December through March). Scholl Canyon (Los Angeles): mean annual temperature (17.4°C) mean annual precipitation (334 mm) Marina (Monterey): mean annual temperature (10.4°C) mean annual precipitation (517 mm) (cdo.ncdc.noaa.gov/climatenormals/clim20/ca). March = wettest month August = hottest, driest month

field campaigns: March & August of 2007, 2008

Marina LF

Scholl Canyon LF

Field measurements of CH4 emissions at two California landfills using static chambers (>850 fluxes): •  fresh refuse (no cover) •  daily cover •  intermediate cover •  final cover Four field campaigns: March (optimum wet season) 2007, 2008 August (optimum dry season) 2007, 2008 Quantification of % CH4 oxidation using stable C isotopic method (Chanton) from chamber samples and soil gas probe samples Supporting data for each flux:

5 cm soil moisture (TDR), soil temperature 0-5 cm (RTD), air temperature, continuous chamber temperatures, and continuous water vapor (in chamber)

Marina cover soils: daily: 25-30 cm sand [soil gas CH4 at 25 cm=3000 ppm v/v] intermediate: 5 cm wood chips/45 cm sandy loam [CH4 at base=45% v/v] final: 5 cm wood chips/ 55 cm sandy loam/30 cm loam/

90 cm clay [CH4 at base=55% v/v]

Scholl Canyon cover soils: daily:25-30 cm sand [soil gas CH4 at 25 cm=10 ppm v/v] intermediate:50 – approx. 100 cm sandy loam [CH4 at 50 cm=2.4 ppm v/v] final:25 cm sandy loam/185 cm clay: [composite wellfield CH4 final cover area=35% v/v] NOTE: engineered gas recovery installed for 100% of area for all cover soils

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Scholl Canyon

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(+) Methane Emissions (-) Methane Emissions all values g CH4 m-2 d-1

Average Methane Emissions from 2 California Landfills

Fresh refuse (before daily cover) 0.053 = average SD ± 0.034 range = 0.0006-0.11

maximum CH4 uptake rate 3-yr study of California grasslands (-) 0.0006 g CH4 m−2 d−1 (Blankinship et al.,2010)

% Methane Oxidation using the difference* in δ13C CH4 between the anoxic zone (LFG collection system) and either: •  CH4 collected in chambers OR •  CH4 collected in soil gas probes

(depths)

*relies on temperature-dependent preference of methanotrophs for 12C over 13C in CH4

CALMIM Project 1: develop and field-validate an improved inventory methodology for California (2007-2010).

funded by California Energy Commission (CEC) Public Interest Energy Research (PIER) Program

in cooperation with Calrecycle (CA Department of Resources Recycling & Recovery) and the California Air Resources Board (ARB).

J. Bogner K. Spokas

J. Chanton (Florida State Univ., Tallahassee)

CALMIM Project 2: field-validate CALMIM internationally; improve & expand CALMIM user options (2011-2012). funded by Environmental Research and Education Foundation (EREF)

J.Bogner; K. Spokas, in collaboration with field research groups in the U.S., France, Austria,

Denmark, Germany, Australia, & South Africa.

Scholl Canyon LF Marina LF

CALMIM = a user-friendly, freely-available JAVA model for site-specific & cover-specific landfill CH4 emissions over a typical annual cycle, inclusive of seasonal microclimate & CH4 oxidation in each cover type...

CALMIM Model Overview

(2) Environmental Simulation/Meteorology air temperature, precipitation, solar radiation, evaporation

[Global TEMPSIM, Global RAINSIM, SOLARCALC]

(3) Soil Microclimate Model temperature and moisture (1-D)

[STM2]

(4) CH4 Emission/Oxidation Model (1-D diffusion based on CH4 concentration gradient)

(1) Site location; Daily, intermediate, & final cover(s) thickness & properties; % of each cover area with engineered gas recovery

(interactive template for each cover type)

Field

Validation and

Supporting Laboratory

Studies

Annual Methane Emission Estimate for Site : based on Integrated depth & time calculations (2.5 cm depth & 10 min time intervals) for 365 d. typical annual cycle for each cover type, summed for site.

(2),(3) referenced to lat. & long.

Driving force = CH4 concentration gradient through daily, intermediate, or final cover soil. CALMIM default values & boundary conditions based on literature and California field data. CALMIM “advanced” tab allows site-specific field values [recommended]. Oxidation scaled relative to maximum values for modeled soil temperature & moisture conditions [2.5 cm depths;10 min time steps]

CH4

CH4

Coupling CH4 oxidation to 1-D diffusional transport…

atmosphere

cover soil

refuse

O2

O2

Site Properties Cover Editor Weather

Simulator

CALMIM – COVER INPUT SCREEN for Marina Intermediate Cover

Emissions Model

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CALMIM Model: Marina - Intermediate Cover

CALMIM Model Results v.3

Modeled --- Field Results --- Results Mar. 2007 Aug. 2007 Mar. 2008 Aug. 2008Mean 77.983 0.032 53.2 34.2 238Std Dev 23.635 n/a n/a n/a n/aMin 32.984 n/a n/a n/a n/aMax 135.808 n/a n/a n/a n/aMedian 78.945 n/a n/a n/a n/a

Ave. Modeled

Rainfall (mm)

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nfal

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m)

Air Temperature and Rainfall

Notes: Cover type: Intermediate Cover: Sandy loam, 50cm Gas recovery: 100% Other parameters at default

Image creation: 8/23/2011

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Field Results:

comparative CALMIM modeling for Marina Intermediate Cover...

Some recent publications (relevant to this presentation): Journal articles: 1)Spokas, K., Bogner J., and Chanton, J., A Process-Based Inventory Model for Landfill CH4 Emissions Inclusive of Soil Microclimate and Seasonal Methane Oxidation, accepted J. Geophysical Research-Biogeosciences, Aug. 2011. 2) Bogner, J., Spokas, K., and Chanton, J., Seasonal Greenhouse Gas Emissions (methane, carbon dioxide, nitrous oxide) from Engineered Landfills: Daily, Intermediate, and Final California Landfill Cover Soils, J. Environ. Quality 40:1010-1020 (2011). 3) Spokas, K., and Bogner, J., Limits and dynamics of methane oxidation in landfill cover soils, Waste Management 31:823-832 (2011). CALMIM Model and User’s Manual (JAVA-based model for PC)... current version = CALMIM 4.3c http://www.ars.usda.gov/services/software/download.htm?softwareid=300 OR go to www.ars.usda.gov click on “Products & Services”, then on “Software”, then “CALMIM”.

We are grateful to the following organizations and individuals:

Project sponsors:

•  California Energy Commission PIER Program (G. Franco) 2007-2010 •  Environmental Research & Education Foundation (EREF) 2011-2012

Los Angeles County Sanitation Districts Monterey Bay Regional Waste Management Authority USDA field and laboratory personnel, including C. Rollofson, M. duSaire, D. Peterson UIC students, including P. Roots, T. Badger, M. Corcoran

Thanks for your attention! jbogner@uic.edu Jean Bogner kurt.spokas@ars.usda.gov Kurt Spokas