The jokes about bovine belches melting the polar ice caps can be shelved for the moment, according to a new EPA annual report on U.S. greenhouse-gas production. “Data on oil and gas show that methane emissions from the sector are higher than previously estimated. The oil and gas sector is the largest emitting sector for methane and accounts for a third of total U.S. methane emissions,” said the EPA. Agriculture accounted for 32 percent of methane emissions and 9 percent of all U.S. greenhouse gases.
Until now, agriculture was tagged as the largest U.S. source of methane, a more potent greenhouse gas than carbon dioxide but one that dissipates more quickly. The Environmental Defense Fund, a green group, said methane is responsible for a quarter of global warning and “the report confirms that the oil and gas sector is the largest source of our nation’s methane pollution, beating out livestock and agricultural production for the first time.”
The EPA said its new report “incorporates significant new emissions data” that drove up the methane total for the oil and gas industry. Argus said the new calculations show that methane for oil and gas rose 8 percent from 2004-14, compared to previous estimates of a 9-percent decline from 2005-13.
“The new data could undercut a key argument U.S. oil and gas companies have made in their push to avoid federal methane regulations,” that the industry has ethane under control, said Argus. “The methane-emissions increase coincides with the U.S. shale drilling boom.”
Livestock, especially cattle, produce methane as part of digesting feed. “This process is called enteric fermentation, and it represents almost one third of the emissions from the agriculture sector,” says EPA. “Greenhouse gas emissions from agriculture have increased by approximately 11 percent since 1990. One driver for this increase has been the 54 percent growth in combined methane and nitrous oxide emissions from livestock manure management systems, reflecting the increased use of emission-intensive liquid systems over this time period.”
The EPA report said greenhouse-gas emissions declined 9 percent from 2005-14, although it was up 1 percent from 2013. Year-to-year fluctuations are typical so it is better to look at longer-term changes, the agency says. Electricity accounted for 30 percent of greenhouse gases, followed by transportation at 26 percent and industry at 21 percent.