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For entities that are focused on projects related to government facilities and operations

The exact process for developing a greenhouse gas (GHG) inventory for a local government will vary by entity. The guidance presented here outlines several key steps that are likely to be part of any inventory process. The steps are not necessarily intended to be pursued in linear order, and may require multiple iterations, as shown in the diagram. For example, data collection will occur over time and can influence decisions about other components of the inventory.

The industry standard for local government operations GHG inventories is the Local Government Operations Protocol (LGOP)Exit, developed in partnership by the California Air Resources Board, the California Climate Action Registry, ICLEI-Local Governments for Sustainability, and The Climate Registry. The LGOP provides guidance on calculation methodologies, emission factors, and other aspects of inventory development. The guidance here supplements the LGOP, summarizing key steps, lessons learned, and best practices for calculating local government operations GHG emissions.

• Step 1: Set Goals and Priorities

  Before you think about the specifics of your local government operations inventory, clearly articulate why you are creating a GHG inventory and how it will be used. Is it to comply with a regulation? Will it inform the development of a climate action plan? Will it provide a baseline from which to monitor progress? Will it enable you to join a GHG registry? Will it be used to inform residents or employees? Having a clear understanding of your goals will inform your decisions throughout the process.

  If your goal is...

  • To create a comprehensive, comparable inventory: Follow the LGOPExit and include emissions from all inventory sources. The protocol offers many ways to estimate emissions for many (though not all) sources even in the absence of all data.
  • To maximize limited resources, or make the most of a partial inventory: Consider doing a partial inventory based on the largest sources (likely building energy use and transportation), or the sources most relevant for your planned actions. You can always add other sources to your inventory over time if more resources become available.

  At this point in the process, think about the timeline and level of effort required to complete your GHG inventory. These will vary based on government size and what information is readily available. Consider whether it makes sense for you to do the inventory in-house, work with a local university, or hire a consultant. Also consider how the inventory will be updated, including who will update it and how often.

• Step 2: Define Scale of Inventory

  When deciding exactly which departments, activities, and operations to include in your local government operations GHG inventory, consider your goals for the inventory, as well as what falls under your jurisdiction, which sources you want to include, and how you want to organize your inventory. These considerations will help you to develop an estimate that includes all important emissions and avoids double counting.

  Set Organizational Boundaries: What Falls Under Your Jurisdiction?
  Setting organizational boundaries is an important first step in creating a GHG inventory. In other words, clearly define which facilities and operations fall within your entity’s jurisdiction. While this may seem like a straightforward step, there are multiple ways to define jurisdictional boundaries. The two primary options for defining a jurisdiction are:

  • Operational control: Under this approach, local governments account for the departments, activities, and operations over which they have “operational control,” or the authority to introduce and implement operating policies. This is the recommended approach in the LGOPExit and the most common way for local governments to set boundaries.
  • Financial control: Under this approach, local governments account for the operations over which they have “financial control,” or the operations that are fully consolidated in financial accounts. This approach is consistent with international financial accounting standards.

  Determine Which Sources to Include
  Next, decide exactly which emission sources to include in your inventory.

  The LGOP recommends including several “required” emissions sources in GHG inventories to ensure that they are comprehensive and comparable between communities. Consider which areas you may want to target for reductions in deciding whether to include each source, including the “optional” ones. Including “optional” emissions sources provides a more comprehensive image of your local government’s environmental impacts and areas to target with sustainability projects.

  LGOP “Required” Emissions Sources

  • Fuel combustion and electricity use in facilities (including public buildings, wastewater treatment plants, water pumping stations, and others)
  • Electricity use for streetlights, traffic signals, and other public lighting
  • Mobile fuel combustion in vehicle fleet and transit fleet
  • Solid waste facilities
  • Wastewater treatment facilities

  LGOP “Optional” Emissions Sources

  • Purchased goods and services
  • Waste generation
  • Electrical power distribution
  • Employee commutes
  • Employee business travel
  • Fugitive refrigerants
  • Other Scope 3 sources

  Thinking through how your inventory may be organized can be a helpful way to decide which sources to include. Options for organizing your inventory include categorization by scope (see Important Terminology), sector, department, or facility. Sectoral and scope categorization are recommended in the LGOP.

  Important Terminology

  Direct vs. Indirect Emissions

  Local government operations GHG emissions can be categorized as direct or indirect.

  • Direct emissions in government operations inventories are from sources that are located within the local government’s organizational boundaries and that the government owns or controls (e.g., emissions from a municipally owned landfill).
  • Indirect emissions occur because of the local government’s actions, but at sources outside the local government’s operational control (e.g., emissions from municipal waste sent to a privately owned landfill).

  Scopes
  The LGOP uses “scopes” to categorize emissions based on their source. Three scopes together provide a comprehensive account of GHG emissions:

  • Scope 1: All direct GHG emissions (e.g., emissions from heating oil use in city buildings, gasoline consumption in city vehicles, city-owned wastewater treatment plants).
  • Scope 2: Indirect GHG emissions resulting from electricity use. Scope 2 may also encompass emissions from purchased heating, cooling, or steam.
  • Scope 3: All other indirect emissions (e.g., emissions resulting from the extraction and production of purchased materials and fuels, contracted solid waste disposal or wastewater treatment, employee commuting and business travel, outsourced activities).

  Scopes historically have been used in community inventories as well, although with mixed results. The ICLEI U.S. Community ProtocolExit recommends a different way of categorizing emissions.

  Sectors
  The LGOP identifies the following local government sectors, which can also be used to categorize emissions: buildings and other facilities, streetlights and traffic signals, water delivery facilities, port facilities, airport facilities, vehicle fleet, transit fleet, power generation facilities, solid waste facilities, wastewater facilities, and other process and fugitive emissions.

  Activity Data
  Defined by the Intergovernmental Panel on Climate Change (IPCC) as “data on the magnitude of human activity resulting in emissions or removals taking place during a given period of time,” activity data are the primary pieces of information needed to calculate a GHG inventory. Examples of activity data include the amount of electricity used or vehicle miles traveled in a calendar year.

  Emission Factor
  An emission factor defines the quantity of emissions per unit of fuel or activity. Emissions are calculated by multiplying activity data by the emission factor. For example, emissions from fuel oil combustion are calculated by multiplying gallons of fuel oil used (the activity data) by emissions per gallon of oil (the emission factor). Default emission factors are readily available for many activities; some can be found in the LGOPExit. Keep in mind that emission factors differ for electricity in different parts of the country and for different kinds of fuel oil or natural gas.

  Carbon Dioxide Equivalents
  GHG emissions can be expressed either in physical units (such as grams, tonnes, etc.) of each individual greenhouse gas or in terms of carbon dioxide equivalents (CO₂e). A CO₂e measurement is derived by multiplying the physical units of the gas by the gas’s global warming potential (GWP). For example, grams of methane (CH₄) can be converted to grams of CO₂e by multiplying by 25, methane’s GWP.* Metric tons of CO₂e is a standard unit for reporting GHG emissions. Conversion factors and GWPs can be found in the LGOPExit.

  * Note that GWPs can change as science advances. The current GWP for methane used in the U.S. Greenhouse Gas Inventory is 25.

• Step 3: Collect and Compile Data

  Make a checklist of your data needs based on the sources you have decided to include, and begin collecting data on those sources. When you conduct your first, baseline inventory, collect data for all the potential base years that are readily available. In Step 4, you will set a base year, but it is often easier to collect data for multiple years at once than to go back to get data for additional years if your needs change (e.g., if certain data are not available for your desired base year).

  Keep in mind that data collection can be the most time-intensive step of the inventory process, and it may continue as you begin calculating your emissions.

  Start by reaching out to facility managers, utility representatives, and other individuals who may have data, and get a sense of what is and what is not available to you. Identify whether you need to make any institutional arrangements in advance to facilitate data collection. For example, utilities may have specific procedures for requesting data that may require advanced notice. Establishing a Memorandum of Understanding may be an appropriate mechanism to facilitate data-sharing between organizations, if needed.

  Tips for data collection:

  • Have a single person in charge of the inventory, an “inventory compiler,” who collects data from other entities, such as from a facilities energy lead or a wastewater treatment lead. This individual could not only keep track of the different components, but also help build capacity in the organization by becoming an inventory and emissions expert.
  • Minimize the burden of the data request and make it easier for someone to give you the information you need. It can be helpful to provide your data provider with a template to populate (such as a spreadsheet with labeled rows and columns) to help him or her understand exactly what you are looking for and how the data will be used. However, be prepared to take data in whatever form your provider has readily available, for whatever timeframe is available, and then adapt it to your needs.
  • Keep track of all units and follow up if the units are not clear in a dataset.
  • Keep all data received in an organized manner and carefully document all data sources (including points of contact for collecting the data). This will make it easier for you or others to collect updated data in the future to measure your progress.
  • Document the emission factors and GWPs used along with the data. Having these conversion factors readily available helps later when you are reviewing the data and making comparisons.
  • Consider what data may be helpful in the future. Try collecting related data if they are readily available, even if you are not sure yet how they may be used.

  The following table lists data that are commonly needed for inventories, along with corresponding possible sources of those data. This list is not comprehensive; it is intended to offer only a few common examples

  Data Commonly Needed	Possible Data Source
  Facilities
  Electricity use Fuel use, by fuel type (e.g., natural gas, heating oil, kerosene, propane, coal)	Accounts payable Facility managers Local government departmental records Public works department Utility representatives Fuel vendor EPA's ENERGY STAR Portfolio Manager
  Electricity emission factors	EPA’s eGRID (see individual power plant factors in “data files” and regional factors in the “subregion GHG output emission rates” file)
  Natural gas emission factors	Utility representatives (for utility-specific gas carbon content) LGOPExit (for national average)
  Fuel emission factors, by fuel type	LGOPExit
  Transportation
  Vehicle fuel use, by fuel type Vehicle miles traveled	Accounts payable Local government departmental records Fleet manager Fuel vendors Mileage reimbursement records
  Vehicle fuel emission factors, by fuel type	LGOPExit
  Solid Waste
  For emissions from city landfills (Scope 1): Amount of waste in city landfills Composition of waste in city landfills Landfill gas collected at city landfills Fraction of methane in collected landfill gas Landfill gas collection area	For emissions from city landfills (Scope 1): Landfill manager/department Default waste composition from the state or EPA’s annual report, Advancing Sustainable Materials Management: Facts and Figures EPA’s Landfill Methane Outreach Program
  For emissions from city-generated waste (Scope 3): Amount of waste generated Composition of waste generated	For emissions from city-generated waste (Scope 3): Waste audit Waste hauling company Default waste composition from the state or EPA’s annual report, Advancing Sustainable Materials Management: Facts and Figures
  Wastewater
  Wastewater treatment process details (e.g., aerobic, anaerobic, nitrification, denitrification, biogas collected, system Biological Oxygen Demand (BOD5) load) Population served by septic systems	Wastewater treatment manager/department

• Step 4: Set Base Year

  When choosing a base year, consider whether (1) data for that year are available; (2) the year represents a “typical” year for your locality (e.g., no unusual weather or economic conditions); and (3) the base year is coordinated to the extent possible with any goals or commitments your local government may have established (e.g., to reduce emissions by a certain percentage in a specific year, to align with other government programs, to comply with external requirements).

  Your inventory base year provides a benchmark against which you can compare future emissions. Of course, inventories can also be conducted (or simply updated) regularly, in order to track progress.

  GHG inventories typically describe emissions over the course of a calendar year for ease of data collection and comparison. Datasets that are available only for fiscal years or other periods can be converted to calendar years.

• Step 5: Calculate Emissions

  With data collected and a clear vision for which emissions to include, calculate emissions for each of the sources identified in Step 2 by plugging your data and emission factors into the appropriate equations. Several resources are available to help you do these calculations, including protocols that suggest methodologies or equations to use and tools that complete the calculations for you after you enter your data.

  For each source within your inventory, choose a methodology for calculating emissions. The primary protocol for local government operations inventories is the LGOPExit, which provides step-by-step instructions and equations for calculating GHG emissions. The LGOP also provides default emission factors and alternate methodologies to choose from based on data availability. The following tips can facilitate the calculation process:

  • Decide whether you want to calculate your emissions using a pre-built tool or using your own spreadsheet. Available tools include:
    • EPA’s Local GHG Inventory Tool: An EPA tool with two modules. The Government Operations Module implements the LGOP for local government operations GHG inventories.
    • ICLEI’s ClearPathExit: An ICLEI GHG inventory and emissions reduction calculator that replaces ICLEI’s Clean Air and Climate Protection software.
    • EPA’s ENERGY STAR Portfolio Manager: An EPA tool that estimates GHG emissions for individual buildings based on energy and water use, and allows users to compare their buildings’ performance to similar buildings.
    • EPA’s Center for Corporate Climate Leadership Simplified GHG Emissions Calculator: An EPA tool designed to help small businesses estimate and inventory their annual GHG emissions. 
    • Tools from your state environmental or energy agency.
       
  • Work through your inventory sector-by-sector. For each sector (buildings, streetlights, water delivery, vehicle fleet, power generation, wastewater, solid waste, etc.), try to find the most detailed activity data available and the most locally relevant emission factors. Possible sources of emission factors beyond the LGOP include:
    • EPA’s eGRID: Electricity use emission factors by region and power plant
    • EPA’s Power Profiler: Electricity use emission factors by ZIP code
    • EPA’s Waste Reduction Model (WARM): Solid waste emission factors for different material types
    • Carnegie Mellon University’s Economic Input-Output Life Cycle Assessment (EIO-LCA)Exit: Emission factors to estimate the GHG and energy impacts of purchased goods and services
  • If “ideal” data or emission factors are not available, think about alternate methods you can use to estimate emissions for each sector. For example, if local or state emission factors are not available, use national factors as proxies. If data are not available for the right year, use data from the closest year available and adjust by some factor (e.g., using population growth). The LGOPExit provides several methodologies. If the LGOP does not provide methodologies that meet your needs, other protocols can provide ideas, such as the following from the Greenhouse Gas Protocol:
    • Global Protocol for Community-Scale Greenhouse Gas Emission InventoriesExit
    • A Corporate Accounting and Reporting StandardExit
    • The GHG Protocol for Project AccountingExit
    • Corporate Value Chain (Scope 3) Accounting and Reporting StandardExit
  • Match methodology to goals and available resources. The best methodology to use will depend on the goals for the inventory, as well as the amount of time, resources, and data available. Detailed, bottom-up approaches may not be necessary in all cases, such as if your local government needs just a high-level, “order of magnitude” estimate of baseline conditions.
     
  • Review other GHG inventories. Review inventories from local governments, your state, and even the national GHG Inventory for inspiration about data sources and emission factors.
     
  • Document all assumptions and data sources.
     
  • Use other GHG inventories to help you check your results. Compare your estimated emissions to those of a similarly sized local government. Check whether your estimates are in the same order of magnitude. It may be most useful to compare estimates on a line-item basis (e.g., for only building energy use), as total emissions may be different due to a variety of factors, including community size, type of electric utility, and climate, as well as different sources included. Examples of local GHG inventories are available on the Local Examples page.
     
  • If you get stuck, contact us.

  Helpful Tip: How you choose to calculate your emissions can evolve throughout the inventory process, as more data become available or as your needs evolve. It is okay to revise your quantification approach throughout the process.

  Generally, approaches are either:

  • Bottom-up: Based on local data about activities in your government (e.g., emissions = natural gas use (derived from utility bills) × utility-specific natural gas emission factor). Bottom-up approaches are preferred for local government inventories, if data are available.
  • Top-down: Based on data compiled by a state, regional, or federal agency or office providing information for specific geographic areas (e.g., the Energy Information Administration (EIA) State Energy Data system). Local governments can use this information as part of a proxy methodology to estimate emissions if activity data are not available. For example, if a local government did not know the amount of natural gas used to heat buildings, it could use a national or state average for natural gas use per square foot (or similar) and the building’s size to estimate its natural gas use.

  Note: You cannot use a top-down approach to measure your progress toward reducing GHG emissions. To measure whether sustainability efforts are working, you must use actual measurements of energy use and other metrics in a bottom-up analysis.

• Step 6: Procure Certification (optional)

  Depending on your situation, you may want to consider enlisting a third-party review and certification of the methods and underlying data to ensure that the inventory is of high quality, transparent, accurate, complete, consistent, and comparable. Certification may also be required for participation in some greenhouse gas registries.

  Examples of GHG inventory certifications include:

  • California Climate Action Registry General Verification ProtocolExit
  • International Organization for Standardization (ISO) 14061-1 (inventory)Exit and 14064-3 (verification)Exit Standards
• Step 7: Analyze and Communicate Results

  Analyze Results
  Valuable lessons can be gained from your GHG inventory. Draw “big picture” lessons from the results to understand the driving forces behind emissions, answering questions like:

  • What are the largest sources of emissions in our local government’s operations?
  • Why are the emissions so high? Is it a result of high activity data, high emission factors, or both?
  • How do our operational emissions in a sector compare to those of other, similar governments? If they are noticeably higher or lower, why?
  • What are the drivers of our operational emissions?
  • What are our emissions per capita? Per employee? Per heating degree-day? Per cooling degree-day?  

  Degree-Days
  A degree-day is a unit of measurement that compares the outdoor temperature in a time period to a standard of 65°F. Degree-days are useful for comparing energy use across periods with different weather conditions. In GHG inventories, they can help determine how much of a year-to-year change in emissions was caused by weather instead of other factors. Hot days are measured in cooling degree-days and cold days are measured in heating degree-days. Additional information is available from the U.S. Energy Information AdministrationExit. Use the lessons learned from your inventory to inform emissions and energy use reduction efforts. See the Set Goals & Select Actions and Promote Green Government Operations phases for more information.

  Continue to monitor emissions over the course of your project (e.g., by regularly tracking key data such as energy use or by conducting an inventory every year or two) to evaluate the progress and success of your efforts. It is easier to update an inventory regularly than to collect data for several years at once to see trends. Visit the Track & Report phase for more information.

  Communicate Results
  Communicate the results of your inventory to community members and to others within the local government. Consider telling a story about the government’s energy use and emissions, rather than simply reporting the numbers. For example, you may explain that the local government has relatively low electricity use compared to other, similarly sized governments, but it gets electricity from a fuel source with higher carbon intensity. In subsequent years, you can tell the story about what is driving trends in your emissions (e.g., energy efficiency efforts, economic growth, population change, weather). Look at other inventory reports for inspiration on format and content.

  EPA’s GHG Equivalencies Calculator is a resource that can help translate GHG emission amounts into terms that are more easily understood. For example, the calculator translates emissions in metric tons of carbon dioxide equivalent (CO₂e) into more relatable terms, like “annual emissions from X number of cars.”

  You may also consider reporting your emissions through the Carbon Disclosure Project cities programExit.

  See the Reach Out & Communicate phase for more information on communicating inventory results to key stakeholders and the public.

Printable Checklist

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For entities that are focused on projects related to affecting change in the community

The exact process for developing a community-wide greenhouse gas (GHG) inventory will vary by entity. This guidance outlines several key steps that are likely to be part of any inventory process. The steps are not necessarily intended to be pursued in linear order, and they may require multiple iterations, as shown in the diagram.

The ICLEI U.S. Community Protocol for Accounting and Reporting of Greenhouse Gas Emissions (ICLEI U.S. Community Protocol)Exit provides guidance on calculation methodologies, emission factors, and other aspects of community-wide inventory development. The guidance presented here supplements the ICLEI U.S. Community Protocol, summarizing key steps, lessons learned, and best practices for estimating community-wide emissions.

• Step 1: Set Goals and Priorities

  Before you think about the specifics, clearly articulate your