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State and Local Climate and Energy Program

Developing a Greenhouse Gas Inventory

What is a Greenhouse Gas Inventory?

A greenhouse gas inventory is an accounting of greenhouse gases (GHGs) emitted to or removed from the atmosphere over a period of time. Policy makers use inventories to track emission trends, develop mitigation strategies and policies, and assess progress. An inventory is usually the first step taken by entities that want to reduce their GHG emissions. An inventory can help state governments:

  • Identify the sectors, sources, and activities within their state that are responsible for greenhouse gas emissions
  • Understand emission trends
  • Quantify the benefits of activities that reduce emissions
  • Establish a basis for developing an action plan
  • Track progress in reducing emissions
  • Set goals and targets for future reductions
  • Engage residents and businesses in GHG reduction opportunities

Steps to Conducting a GHG Inventory

Set boundaries Define an inventory's physical, organizational, and operational boundaries.
Define scope Decide which emissions source and/or activity categories and subcategories should be included in the inventory as well as which specific greenhouse gases. The scope and detail of will drive the level of effort required.
Choose quantification approach Depending on the data available and the purposes of the inventory, choose to take a top-down, bottom-up, or hybrid approach to data collection.
Set a baseline When choosing a baseline year to provide a benchmark to compare progress going forward, consider whether (1) data for that year are available, (2) the chosen year is representative, and (3) the baseline is coordinated to the extent possible with baseline years used in other inventories.
Engage stakeholders Bring stakeholders into the inventory development process early on to provide valuable input on establishing a baseline; help build public acceptance of policies to address climate change; and provide data, information on data resources, and personnel resources or outreach assistance.
Consider certification Consider a third-party review and certification of the methods and underlying data in an inventory to assure that the inventory is high quality and that it is complete, consistent, and transparent. Certification may be required for participation in some greenhouse gas registries.

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Training

EPA's Webcast Training Series: Greenhouse Gas Inventory 101 for Local, Regional, and State Governments is available in three installments. Recordings and transcripts can be downloaded below.

Creating an Inventory
Topics include understanding the purpose and scope of a GHG inventory, inventories vs. registries, setting a boundary, setting a baseline, quantification approaches, certification and reporting protocols, comparability, and level of effort.

Translating Inventory Results into Action
Topics include describing the various uses of GHG inventories, including benchmarking, tracking emissions and progress over time, setting emission reduction goals, policy options for meeting goals, evaluating policy options, and processes for setting goals and policies.

State Inventory Tool (SIT) Training Session
Topics include background information on the development of the SIT modules and a live demonstration of the CO2 from Fossil Fuel Combustion Module, Natural Gas and Oil Module, Synthesis Module, and Projection Tool.

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Tools

EPA's Greenhouse Gas Reporting Program

Through EPA's Greenhouse Gas Reporting Program facilities that emit 25,000 metric tons or more per year of GHGs are required to annually report their GHG emissions to EPA. Well over half of total U.S. greenhouse gas emissions are accounted for in this facility level data set, including nearly complete coverage of major emitting sectors such as power plants and refineries. This "bottom up" data can be used to supplement or complement a top-down inventory developed using the State Inventory and Projection Tool. For more information about accessing the data and how it may be used in state inventories, please see the materials from our March 2012 webcast.

Emissions & Generation Resource Integrated Database (eGRID)

eGRID contains a comprehensive inventory of environmental attributes of electric power systems including air emissions data for nitrogen oxides, sulfur dioxide, carbon dioxide, and mercury. The data are organized in a series of Microsoft Excel files that state governments can use to find data on emissions from electricity generation within their state and/or emissions associated with electricity within their state.

Energy CO2 Emissions by State

These tables present state carbon dioxide (CO2) emission inventories from fossil fuel combustion from 1990 through 2012, organized by end-use sector (commercial, industrial, residential, transportation, and electric power), in million metric tons of carbon dioxide (MMTCO2). EPA developed these state-level CO2 estimates using (1) fuel consumption data from the DOE/EIA State Energy Data 2012 Consumption tables and (2) emission factors from the Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2012.

ENERGY STAR Portfolio Manager

Portfolio Manager is a Web-based resource that benchmarks the performance of commercial buildings on a scale of 1-100 relative to similar buildings nationwide using EPA's national energy performance rating system. Buildings rating 75 or greater may qualify for ENERGY STAR. The tool's data on short- and long-term trends in energy performance can be used to make budget and management decisions regarding investments in energy-related projects. A Statement of Energy Performance is provided for each building, summarizing important energy information and building characteristics. State governments can use the tool to create an inventory of greenhouse gas emissions from government buildings, set efficiency investment priorities, identify under-performing buildings, verify efficiency improvements, and receive EPA recognition for superior energy performance.

State Inventory and Projection Tool

EPA’s State Inventory and Projection Tool is an interactive spreadsheet model designed to help states develop GHG emissions inventories, and provides a streamlined way to update an existing inventory or complete a new inventory. The tool gives users the option of applying their own state-specific data or using pre-loaded default data for each state. The default data is gathered by federal agencies and other sources covering fossil fuels, electricity consumption, agriculture, forestry, waste management, and industry. The State Inventory Tool consists of 11 estimation modules, and one module to synthesize estimates across all modules. The State Projection Tool allows users to create a basic "business as usual" forecast of emissions through 2030.

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