Understanding Updates to the EPA Inventory of Greenhouse Gases (May 2017)
Understanding Updates to the EPA Inventory of Greenhouse Gases
The Environmental Protection Agency (EPA) made substantial updates to its estimates of methane emissions in its Inventory of U.S. Greenhouse Gases and Sinks: 1990–2015 that it released in April 2017. The Inventory now incorporates new data available from studies on emissions as well as its 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. Less than 0.1 percent of produced natural gas is emitted from distribution systems owned and operated by local natural gas utilities. Annual emissions from these systems declined 75 percent from 1990 to 2015 even as natural gas utility companies added nearly 600,000 miles of pipeline to serve 19 million more customers.
This exceptional record can be traced to safety as the top priority for gas utilities who continue to be vigilant and 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 natural gas resource.
- Annual methane emissions from natural gas distribution systems declined 75 percent from 1990 to 2015.
- The natural gas emissions rate of production from distribution systems is now less than 0.1 percent.
- Industry-wide the natural gas emissions as a rate of production (the "leakage rate") increased to 1.2 percent—a level still 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 two and a half decades, dropping 46 percent since 1990.
- Total methane emissions from all natural gas systems have declined 16 percent from 1990 to 2015.
- Methane emissions economy-wide represent 10 percent of all greenhouse gas emissions in the United States. Along with natural gas systems, methane emission sources include enteric fermentation and manure management (livestock), landfills, coal mining petroleum systems, wastewater treatment, and others.