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To understand their role in emitting GHGs, 38 states have conducted their own greenhouse gas inventories. EPA assists states in the inventory process by providing technical assistance, funding, and guidance on how to perform inventories. States use their inventories to develop action plans to reduce their GHG emissions. Based on these action plans (and other activities), states have implemented policies and programs to reduce GHG emissions.
The Intergovernmental Panel on Climate Change is the international organization responsible for developing coordinated methods for national greenhouse gas inventories. The most recent (1996) guidelines, IPCC Guidelines for National Greenhouse Gas Inventories,  provides methodologies and instructions for reporting. In many cases, these methods must be tailored to apply to specific national conditions. Like other nations’ inventories, the U.S. National Greenhouse Gas Inventory takes full advantage of the flexibility built into the IPCC guidelines, and adapts the guidelines to balance data availability constraints against the need for precision and accuracy in the estimates.
State inventories must perform the same balancing act. One of the first products of the EPA State and Local Climate Change Program was the State Workbook: Methodologies for Estimating Greenhouse Gas Emissions. This workbook, first published in 1995, provides methods to estimate GHG emissions and sinks from 14 sectors:
- Combustion of Fossil Fuels
- Industrial Processes
- Natural Gas and Oil Systems
- Coal Mining
- Municipal Waste Disposal
- Domesticated Animals
- Manure Management
- Flooded Rice Fields
- Agricultural Soils
- Forest Management
- Burning of Agricultural Crop Wastes
- Municipal Waste Water
- Methane and Nitrous Oxide Emissions from Mobile Combustion
- Methane and Nitrous Oxide Emissions from Stationary Combustion
For each sector, the methods describe sources of data, emission factors for GHGs, calculation methods, sources of uncertainty, and suggestions for reporting.
Since its initial publication, the State Workbook has been revised three times. Most recently, it was thoroughly reviewed, revised, and updated under the auspices of the Emission Inventory Improvement Program (EIIP). The EIIP is an effort to determine standard methodologies for performing air emission inventories, sponsored jointly by the State and Territorial Air Pollution Program Administrators/ Association of Local Air Pollution Control Officials (STAPPA/ALAPCO) and EPA. The program's goal is to provide cost-effective, reliable inventories by improving the quality of emissions information and developing system(s) for collecting, calculating, and reporting emissions data.
The Greenhouse Gas (GHG) Committee of the Emission Inventory Improvement Program (EIIP) was established to improve the quality, reliability, and verifiability of inventories of sources and sinks of GHGs. The committee has championed the development of high-quality GHG inventories primarily at the state and local level. Members represented state environmental and energy agencies, EPA, and consultants.
The EIIP Document Series, Volume VIII: Estimating Greenhouse Gas Emissions is available for downloading in Adobe Acrobat (PDF) format. Click here to view or download the documents.
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