Measuring & Quantifying CH4 from MSW Landfills

Prepared for the National Academy of Sciences

June 1, 2017

Bryan Staley, PhD, PE President & CEO

bstaley@erefdn.org www.erefdn.org

EREF History & Mission

• Mission: To fund and direct scientific research &

educational initiatives for sustainable waste

management practices to benefit the solid waste

field and the communities it serves.

• 501(c)3 charity began in 1992

• Non-lobbying, non-advocacy organization

• Not a membership organization

MSW Management in the U.S.

MSW Managed in the U.S.

Tonnages

• Methodology used a facility-based, bottom up

approach

• 347 million tons MSW managed (2013)

– 6.8 lbs/person-day

• Majority is landfilled

EREF & US EPA

Difference by End Point

• Difference for landfill tonnage also observed by: – Biocycle State of Garbage reports: state-provided statistics

– Powell et. al. (2015): facility data from GHG reporting tool

• This is not all the tonnage that goes to MSW landfills – More tonnage (non-MSW) also goes to MSW landfills (~1/3 more)

Type of Facility EREF Estimate

(million tons)1

EPA Estimate

(million tons)

Percent

Difference

Landfills 222.0 134.3 65 %

Recycling 73.0 64.7 13 %

Waste-to-

Energy

30.7 32.6 5 %

Composting 21.3 22.4 5 %

TOTAL 347.0 254.1 37 %

MSW Organics

Tonnage

Facility Type Million Tons MSW Organics Managed

%

Landfills 133.6 79.0

Composting 21.3 12.6

Waste-to-Energy 11.0 6.5

Mulching 2.5 1.5

Anaerobic Digestion 0.8 0.5

Tons MSW Organics Managed 169.2 100

• Mulching tonnage based EPA estimates

• Re-use/On-site management tonnage is unknown

• Total MSW Managed = 347 million tons

• Organic fraction = 48.8%

Organics in Landfilled MSW

Organics Composition

• MSW organics managed (2013): 169.2 million tons

Food Waste in Landfilled MSW

Landfill Gas Emissions

Research Focus Areas

• Emissions quantification done via: • Modeling • Direct measurement on the landfill

• Modeling • Use of guideline values

• Estimating Degradable Organic Carbon • Decay rates (k value) [research not described here]

• Methane Oxidation through Soil Covers

• Direct Measurement • Best measurement technique • Accurate data under varying field conditions

Modeling Landfill Gas Emissions

GHG Inventory Models

• Based on Simplified Mass Balance:

Source: University of Illinois-Chicago

Recovered Methane

Recovered CH4

(based on tonnage)

~84% of

tonnage

goes to LFs

that flare or

beneficially

use

generated

methane

Roughly 80

million more

tons goes to

private vs

public LFs

77%

89%

Methane Generation

• Landfill Gas (LFG) generation is estimated, in part, using the Degradable Organic Carbon (DOC) content of the waste materials entering LF.

– Input to the First-Order Decay (FOD) model

• Intergovernmental Panel on Climate Change (IPCC) provides recommended values and methodologies

• USEPA uses FOD calculations for 2 key efforts: 1) Facility GHG Reporting Program (Subpart HH) 2) U.S. Inventory of Sources and Sinks (to IPCC)

Importance of Degradable Organic

Carbon in Estimating Emissions

Remaining Carbon

Municipal Solid Waste

(MSW)

Non-MSW in 45 states

DOCf

A fixed amount enters the landfill but it is based on waste composition

Biogas from DOC, beneficially used or as emissions

Only a fraction of DOC degrades, the remainder is sequestered

Degradable Organics Carbon and

the Impact on Emissions Estimates

Estimating DOC:

EPA Guidelines and Project Goals

1. EPA default value DOC = 0.31 for MSW-only waste • Is this representative of MSWLFs accepting only MSW (DOCMSW)?

• Assess using waste composition data from 16 studies, conducted in 13 states (2001 – 2015)

2. EPA default value DOC = 0.2 for MSW LFs (bulk method) • Is this representative of MSWLFs accepting other Subtitle D wastes

(DOCSubD)?

• Assess using 2013 reporting data from MSWLFs in 14 states

Estimating LFG:

EPA vs. State Studies

Calculated DOC values are lower than respective EPA guidelines for both waste streams; especially MSW-only waste streams.

In 2014, 919 MSWLFs used 0.31 or 0.20 when completing the mandatory GHG reporting (Subpart HH)

EPA – 𝑥 = 0.13

EPA – 𝑥 = 0.05

Methane Oxidation

CH4 Oxidation Across Multiple Sites

% Oxidation with diffusion correction surface CH4

0 10 20 30 40 50 60 70 80

Arid

Mediterranean

Humid cont cool

Humid cont warm

Humid Sub trop

EPA Oxidation Guideline

28-43% (mean)

21-40% (median)

Suggested value = 30%

CH4 Oxidation:

Validation from UIC Project

California monthly landfill CH4 oxidation (372 sites)

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10 11 12

% o

xid

atio

n

Month

30 cm IC

45 cm IC

50 cm IC

EPA Guideline

Direct Measurement of Emissions

Direct Emissions Measurement:

Methods Evaluation

• Study re-defined EPAs perspective on measuring fugitive emissions

• Help industry improve gas collection efficiency, reduce emissions, refine carbon footprint estimates

Emissions Measurement Method

EPA’s OTM-10

Method

Tracer Correlation Technique most accurate

Quantifiable Results for Whole Landfill

Emissions Using Tracer Correlation Technique

Measured CH4 Emissions from New Waste Cell

Southeastern US Landfill

Comparison of Direct Measure vs. GHG Reporting Southeastern US Landfill

• 1st order decay model

HH-1

= 1,954 metric tons CH4/yr

HH-5

= 1,759 metric tons CH4/yr or 3,346 g CH4/min

Measured values for 2012 ranged from 460 – 941 g CH4/min

Comparison to Mandatory GHG Reporting Calculations (2012)

• Organics diversion trends will likely significantly impact emissions from landfills over the next 1-2 decades

• Data Inventories (developed/in progress) – Landfilled Tonnage – Waste Composition – Landfill gas collected/beneficial use

• Research Funded (completed/underway) – Methane oxidation – Improving models – Direct measurements of emissions

Summary

EREF Funded Landfill Emissions Research

• Development and Application of a Tracer Gas Correlation (FSU)

• Assessing Accuracy of Tracer Dilution Measurements of Methane Emissions from Landfills with Wind Modeling (U. Delaware)

• Assessing Accuracy of Tracer Dilution Measurements of Methane Emissions from Landfills with Wind Modeling (U. Delaware)

• Constraining the Effects of Secondary Porosity on CH4 Oxidation (FSU)

• Joint Air Emissions Testing Development (SCS Engineers)

• International Field Validation of a New IPCC Tier IV Inventory Model for Landfill Methane (CH4) Emissions (U. Illinois-Chicago)

• Modernizing Models and Data on Methane Production from Landfills (NC State)

• Quantifying Capture Efficiency of Gas Collection Systems with Gas Tracers (U. Delaware)

• Greenhouse Gas Emissions from Municipal Solid Waste Management (URS)

• Landfill Gas Management: A Roadmap for EREF Directed Research (NC Stae/U. Central Florida)

EREF Funded Landfill Emissions Research

• Updating EPA's Landfill Gas Emission Factors (EPA)

• Field Test Measurements at Five MSW Landfills with Landfill Gas (EPA)

• Moisture Consumption During Gas Production in Landfills: Implications to Permitting ET Caps (Mich. State/NC State)

• Evaluation of a Biologically Active Cover for Mitigation of Landfill Gas Emissions (SCS)

• Field-Scale Assessment of Evapotranspirative Methane Oxidation (ETMO) Caps for Sustainable Management of MSW Landfills in Sub-Humid Climates (Mich. State)

• Methane Oxidation: Field-Scale Test Sections Experiment (FSU)

EREF Funded Landfill Emissions Research

• Impact of organics diversion

• Minimizing estimates via ‘guideline’ values and instead using site specific values

• Use of tech to advance inventories/measurements – Drones to measure emissions

Future Considerations

Questions?

Contact Info

Bryan Staley, PhD, PE

bstaley@erefdn.org

www.erefdn.org