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Carbon Footprint Calculation Methodology

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WM’s carbon footprint comprises the anthropogenic Scope 1 (direct) and Scope 2 (indirect) GHG emissions from facilities and activities under our operational control in North America as well as Scope 3 (indirect) GHG emissions.

Scope 1 emissions include direct emissions from landfills, fleet vehicles, support vehicles, heating and refrigerants. Scope 2 emissions include indirect emissions from purchased electricity. Scope 3 emissions include purchased goods and services, capital goods, business travel, employee commuting, upstream and downstream leased assets, use of sold products and investments. Our carbon footprint calculation relies on company operating data collected from auditable corporate business, legal and accounting records, which have undergone internal quality assurance. Emissions factors and methodologies come from the following sources:

  • U.S. Environmental Protection Agency (EPA), Mandatory Greenhouse Gas Reporting Rule (MRR), 40 CFR Part 98
  • EPA, Emission Factors for Greenhouse Gas Inventories; Updated April 1, 2022
  • EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks
  • EPA, eGRID Technical Support document, Chapter 3
  • EPA, eGRID Summary Tables 2020 (February 2022)
  • The Climate Registry, 2018 Default Emissions Factor Document; Updated May 2018
  • Environment and Climate Change Canada, National Inventory Report 1990-2019: Greenhouse Gas Sources and Sinks in Canada (Part 3, Annex 13) (2021)
  • U.S. Department of Energy (DOE), 1605(b) Voluntary Reporting of Greenhouse Gases Program, Technical Guidelines
  • DOE Energy Information Agency (EIA), Emissions of Greenhouse Gases in the United States, documentation and Emission Factors
  • International Panel on Climate Change (IPCC), 2006 Guidelines for National Greenhouse Gas Inventories
  • IPCC, Climate Change 2013: The Physical Science Basis. Fifth Assessment Report
  • IPCC, Climate Change 2007: The Physical Science Basis. Fourth Assessment Report
  • Solid Waste Industry for Climate Solutions (SWICS) Protocol by SCS Engineers, version 2.2
  • EPA, Climate Leaders Program, Technical Guidance
  • World Resources Institute and World Business Council on Sustainable Development, The Greenhouse Gas Protocol
  • World Resources Institute and World Business Council on Sustainable Development, The Greenhouse Gas Protocol Scope 2 Guidance
  • U.S. Community Protocol for Accounting and Reporting of Greenhouse Gas Emissions, Method WW.14.
  • EPA, 2022 SmartWay Online Truck Tool: All Carriers Technical Documentation, U.S. Version 1.0 (Data Year 2021)
  • Gasoline: Final Rule on Light-Duty Vehicle Greenhouse Gas Emissions Standards and Corporate Average Fuel Economy Standards (75 FR 25324, May 7, 2010). The gasoline factor used in this rule was sourced from the California Air Resources Board and is based on measurement of carbon from a gasoline test fuel (indolene).
  • Diesel: Fuel economy calculations in 40 C.F.R 600.113.
  • Compressed Natural Gas (CNG): Calculations of Lifecycle Greenhouse Gas Emissions for the 2005 Gasoline and Diesel Baselines in the Notice of Availability of Expert Peer Review Record supporting the proposed revisions to the Renewable Fuel Standard Program (74 FR 41359) available in Docket EPA-HQ-OAR-2005-0161-0925.1 (Spreadsheet “Emission Factors”).
  • Liquefied Natural Gas (LNG): Calculations of Lifecycle Greenhouse Gas Emissions for the 2005 Gasoline and Diesel Baselines in the Notice of Availability of Expert Peer Review Record supporting the proposed revisions to the Renewable Fuel Standard Program (74 FR 41359) available in Docket EPA-HQ-OAR-2005-0161-0925.1 (Spreadsheet “Emission Factors”).
  • Carbon Footprint: Country Specific Electricity Grid Greenhouse Gas Emission Factors. 2019 Grid Electricity Emissions Factors v1.0 – June 2019.
  • GREET WTW Calculator.

Because a broadly accepted protocol for estimating the carbon mass balance of landfills does not yet exist, WM, along with other public and private owners and operators of landfills, funded the development of the Solid Waste Industry for Climate Solutions (SWICS) protocol by SCS Engineers. The protocol represents a first step in refining existing U.S. EPA models and protocols using peer-reviewed, published research to improve landfill GHG emission estimation. We employed the SWICS protocol in estimating the emissions associated with the landfill operations reported in our company-wide carbon footprint and the voluntary GHG reporting protocols in which we participate. The U.S. EPA’s Science Advisory Board views some sources of biogenic carbon dioxide emissions—including landfill gas and biogenic materials in waste—as carbon neutral, so these are not included in our footprint.

Carbon storage in landfills can significantly offset GHG emissions from landfills, as recognized by the United Nations Intergovernmental Panel on Climate Change, the EPA’s U.S. Inventory of GHG Emissions and Sinks, the Oregon Climate Trust and the California Air Resources Board—all of which recognize carbon storage in landfilled material as a “sink” in calculating carbon emissions inventories. We have used the SWICS protocol to calculate the amount of carbon permanently stored in landfills from the annual disposal of organic waste —i.e., carbon that will not decompose in the landfill to produce methane.

Beginning in 2013, we also aligned our emissions reporting with that of the U.S. EPA, which continues to refine its default assumptions and scope of reporting under its mandatory reporting program. For sites exempt from the U.S. EPA’s rule (too old, too small, non-MSW landfill), we use historical operating data to calculate the proportion of emissions exempt from regulatory reporting and increase the reported emissions included in our footprint to allow our emissions to be compared year over year. As part of this process of aligning our reporting with SWICS and the U.S. EPA, beginning with our 2013 emissions reporting, we are using the modified 100-year global warming potentials (GWPs) promulgated by the EPA in its November 29, 2013, revisions to 40 CFR Part 98 (78 Fed. Reg. 71904). Pertinent to WM’s carbon footprint, the EPA revised the GWP for methane from 21 to 25 and the GWP for nitrous oxide from 310 to 298.

Additionally, WM has developed a GHG Inventory Management Plan (IMP) for internal use. The IMP is a dynamic document to provide WM with a summary of emission sources associated with the company’s activities, and the associated emissions quantified using standardized methods. Included in the inventory are processes for:

  • Choosing a base year for the GHG emissions inventory against which future emissions will be tracked.
  • Identifying the sites to include in the inventory (“organizational boundaries”).
  • Identifying the sources within the sites to include in the inventory (“operational boundaries”).
  • Following a standardized and accepted methodology to calculate the GHG emissions from each identified source.

Our GHG inventory reflects the most accurate means available to calculate GHG emissions within our industry sector. We work with leaders in government, industry and academia, including staff of the multistate Climate Registry and the U.S. EPA, to develop our inventory processes and protocols.

Data Verification and Validation

We participate in multiple forms of data verification. First, in conformance with applicable state or provincial GHG emissions-reporting programs, an independent third party is hired to review original data and provide a verification certificate. Accordingly, the emissions from the landfill subject to the Alberta Provincial Specified Gas Emitters Regulatory Reporting Program were third-party verified by GHD for 2018 and 2019; 2020 is in progress and we anticipate a successful verification. Emissions from the landfill subject to State of California mandatory reporting program were third-party verified by Analytical Environmental Service (AES) for 2018, 2019 and 2020; 2021 is in progress and we anticipate a successful verification. Our facilities are subject to the federal Mandatory GHG Reporting Rule and they are subject to rigorous validation checks by U.S. EPA as part of its compliance assurance and enforcement program for the reporting rule.

In 2019 through 2022, WM hired Aster Global (AG) to conduct a third-party verification of the company’s 2018, 2019, 2020 and 2021 carbon footprint, respectively. These verifications were conducted in accordance with ISO 14064–3:2006 specification with guidance for validation and verification of GHG assertions to provide limited assurance that the Scope 1, Scope 2 and Scope 3 GHG data was prepared in conformance with World Resource Institute/World Business Council for Sustainable Development GHG Protocol: A Corporate Accounting and Reporting Standard and the internal WM Inventory Management Plan. As a result, 100% of our carbon footprint is verified by a third party.

In a second form of data validation, we report to a third party, such as a government-affiliated data tracking program, which provides quality assurance and quality control to the data but does not provide a verification certificate. Our transportation data is validated through the U.S. EPA SmartWay program; our GHG inventory from energy generation is validated by the U.S. EPA; and our GHG inventory from California, reported to the California Air Resources Board, is verified by SCS.

Further, WM has contracted with Enel X to collect and pay utility invoices, as well as to track usage data as part of an enterprise-wide utility bill management (UBM) program spearheaded by our supply chain procurement managers. Information from the UBM program is audited prior to bill redirection by WM to ensure correct processing of all future invoices. We review data through Enel’s online dashboard and have the capability to run reports on consumption, cost and GHG emissions on a facility, region, division, country and enterprise-wide basis. With this approach, our data collection and reporting program is robust and transparent.

Life Cycle Emissions Methodology

Our calculation of the potential GHG reductions or avoided emissions that our operations enable includes the following:

Electricity. Production of renewable waste-based energy that is used to replace electricity generated from fossil fuels.

Fuel. The use of renewable natural gas (RNG) to avoid the GHG emissions associated with annual use of fossil fuel.

Recycling. Recycling of postconsumer materials (e.g., paper, aluminum and plastics) using U.S. EPA’s Waste Reduction Model (WARM).

Carbon sequestration. Permanent carbon storage in landfills of biogenic materials that do not decompose in an anaerobic landfill environment.