Understanding Updates to the EPA Inventory of Greenhouse Gases

Report May 23, 2019


Understanding Updates to the EPA Inventory of Greenhouse Gases

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summary graphic ea 2019-02

The Environmental Protection Agency (EPA) made further updates to its estimates of methane emissions in its Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2017. The Inventory incorporates new data available from studies on emissions as well as the EPA’s own Greenhouse Gas Reporting Program (GHGRP).

The Inventory reveals once again that natural gas distribution systems have a small emissions footprint shaped by a declining trend. Distribution systems owned and operated by local natural gas utilities emit less than 0.1 percent of produced natural gas. These annual emissions declined 73 percent from 1990 to 2017, even as natural gas utility companies added more than 760,000 miles of pipeline to serve 20 million more customers.

This exceptional record can be traced to gas utilities continuing to make safety their top priority and remaining deeply committed to systematically upgrading infrastructure through risk-based integrity management programs. As companies and the country continue to modernize the natural gas infrastructure base and connect homes and businesses, there will be new opportunities to achieve low-cost carbon emissions reductions by leveraging this existing infrastructure and the nation’s abundant natural gas resource.

Key Findings:

  • Annual methane emissions from natural gas distribution systems declined 73 percent from 1990 to 2017.
  • The natural gas emissions rate of production from distribution systems is less than 0.1 percent.
  • Industry-wide natural gas emissions as a rate of production (the “leakage rate”) is 1.3 percent – a level well below even the most stringent thresholds for immediate climate benefits achieved through coal to natural gas switching.
  • The ratio of methane emissions per unit of natural gas produced has declined continuously during the past 2 and a half decades, dropping 48 percent since 1990. Total methane emissions from natural gas systems have declined 15 percent from 1990 to 2017. 
  • Along with natural gas systems, methane emission sources include enteric fermentation and manure management (livestock), landfills, coal mining, petroleum systems, wastewater treatment, and others. Methane emissions from all economic sectors represent 10 percent of all greenhouse gas emissions in the United States; methane released from natural gas systems accounts for 2.6 percent of all U.S. greenhouse gas emissions.

For more information, contact:
Gina DeFrancesco, Clean Energy Analyst, Energy Analysis
gdefrancesco@aga.org  (202) 824-7127