Lower fossil fuel releases are continuing to help drive US greenhouse gas (GHG) emissions lower, the US Environmental Protection Agency’s latest annual report showed. EPA said 2017’s GHG emissions totaled 6,456.7 million tonnes of carbon dioxide equivalent (tCO2e), or 5,742.6 million tCO2e after accounting for land sequestration.
This was 0.5% less than in 2016, after accounting for land sequestration, and 13% below the level in 2015, EPA said after releasing its Inventory of US Greenhouse Gas Emissions and Sinks: 1990-2017. The lower fossil fuel combustion rate that was largely responsible for the decline resulted from electric power plants continuing to move from coal to natural gas and renewable sources as well as milder weather, which reduced electricity demand, it said.
Carbon dioxide accounted for the largest single share, 81.6%, of US GHG emissions from human activities during 2017, EPA said. Combustion of fossil fuels—coal, gas, and oil—for energy and transportation was the main source, although certain industrial processes and land-use changes also emit CO2, the agency said.
Of the 2,898 million tCO2e from large facilities in the US during 2017, EPA said that power plants had the single biggest share—1,778 million tCO2e—followed by petroleum and gas systems, 285 million tCO2e; chemicals, 184 million tCO2e; refineries, 177 million tCO2e; minerals, 114 million tCO2e; waste, 106 million tCO2e; metals, 89 million tCO2e; pulp and paper, 36 million tCO2e; and other facilities, 130 million tCO2e.
Within the fossil fuels category, transportation was the single largest CO2 emissions source in 2017, accounting for about 34.2% of total US CO2 emissions and 27.7% of total US GHG emissions. This category includes sources such as highway vehicles, air travel, marine transportation, and rail, EPA said.
Type of fuel matters
Electricity was not far behind, accounting for about 32.9% of total US CO2 emissions and 26.7% of total GHG emissions. EPA noted that the type of fossil fuel used to generate electricity will emit different amounts of CO2. To produce a given amount of electricity, burning coal will produce more CO2 than oil or gas, it said.
US industry was the third-largest CO2 emissions source, representing 15.4% of the 2017 fossil fuels total and 12.5% of total GHG emissions. Several processes also produce CO2 emissions through chemical reactions that do not involve combustion, EPA noted.
These include the production and consumption of mineral products such as cement, the production of metals such as iron and steel, and the production of chemicals, it said. “Many industrial processes also use electricity and therefore indirectly cause the emissions from the electricity production,” EPA noted.
Methane releases were the second biggest 2017 US GHG emissions source, representing 10% of the total. They also rose 0.22% year-to-year to 656.32 million tCO2e in 2017 from 654.9 million tCO2e in 2016 but came in 15.8% below their 1990 total of 779.85 million tCO2e. Nitrous oxide, at 6%, and fluorinated gases, at 3%, accounted for the rest of EPA’s 2017 GHG inventory.
Numbers can fluctuate
Howard J. Feldman, the American Petroleum Institute’s regulatory and scientific affairs senior director, said that numbers within individual gas segments such as transportation, gathering, and processes can fluctuate as overall methane emissions continue to decrease as production grows.
“We are driving solutions to reduce our environmental footprint while meeting growing energy demand—actions evident in our innovation and technical work,” he told OGJ. “US oil production is at its highest level ever, oil imports are at their lowest level in more than 20 years, and CO2 and other emissions are at their lowest levels in a generation because of clean energy technologies.”
Climate change risks are real, Feldman said. “Because our industry is action oriented and results driven, during a period of significant production growth—with affordable energy driving the economy and generating billions of dollars in revenue for governments to spend on education, roads, and other public priorities—methane emissions went down,” he said.
“Abundant, affordable natural gas and oil have helped US households with their budgets. While spending for health care, education, and food rose significantly between 2007 and 2017, spending for household energy declined,” Feldman noted.
Contact Nick Snow at [email protected].
