Carbon dioxide (CO2) emissions in the United States rose last year due to higher demand at power plants as well as greater energy use within the transportation sector, from industrial activity and in buildings—demand that energy-efficient systems could not fully offset.
Power plant CO2 emissions in 2018 rose 0.6 percent from a year earlier to 1.93 billion tons, according to preliminary data from the U.S. Environmental Protection Agency (EPA), which deemed the increase modest as electric generation increased by 5 percent. The agency collected data from plants in the lower 48 states.
The agency also noted that 2018 power plant emissions of nitrogen oxides declined 3.8 percent to 1.02 million tons, and sulfur dioxide emissions declined 5.9 percent to 1.26 million tons.
“Through state and federal fulfillment of the Clean Air Act, and advances by the power sector, we’ve seen significant reductions in key pollutants while electricity generation has increased,” said Bill Wehrum, EPA’s assistant administrator for air and radiation.
However, a report by Rhodium Group LLC based in New York City states U.S. power sector CO2 emissions increased by 1.9 percent in 2018 as power consumption “increased meaningfully” in 2018. U.S. power sector emissions rose by 34 million metric tons in 2018, compared to a decline of 78 million metric tons in 2017 and a 61-million-metric-ton average annual decline between 2005 and 2016.
“While a record number of coal-fired power plants were retired last year, natural gas not only beat out renewables to replace most of this lost generation but also fed most of the growth in electricity demand,” Rhodium Group’s energy and climate staff writes in the report.
Between January and October, U.S. power companies added a greater share of gas capacity than the share of retired coal capacity, and twice as much gas went online as combined wind and solar capacity additions during that period, according to the report. Natural gas-fired generation increased by 166 billion kilowatts during the first 10 months of 2018—three times the decline in coal generation and four times the combined growth of wind and solar.
Rhodium also considered CO2 emissions from other sources, including energy use statistics in certain industries and buildings based on emissions data from the Energy Information Administration (EIA) for the first three quarters of the year, weekly EIA petroleum supply data, daily power generation data from Genscape and natural gas data from Bloomberg.
Overall, energy-related CO2 emissions increased by 3.4 percent in 2018, Rhodium estimates—the second largest annual gain since 1996. Last year’s rise was surpassed only by the 3.6 percent increase that occurred in 2010 when emissions rebounded from a recession-driven 7.2 percent decline the year before.
The largest source of CO2 emissions in the country continues to be the result of energy use by the transportation sector, with demand for diesel and jet fuel rising by 3.1 percent and 3 percent, respectively, during the first nine months of the year. For the full year, Rhodium estimates transportation emissions grew by 1 percent, roughly the same as the 2017 growth rate.
“This highlights the challenges in decarbonizing the transportation sector beyond light-duty vehicles,” the report states. “Here we see efficiency improvements and electrification beginning to make a dent, albeit not nearly a big enough one to meet medium- and long-term U.S. emissions targets.”
The biggest year-over-year growth in emissions came from energy use in buildings and industrial activity, according to the report. In 2018, direct emissions from the combustion of fuel oil, diesel and natural gas within residential and commercial buildings rose by 10 percent to their highest level since 2004. Last winter was colder than the prior winter, but 2017 overall was also warmer than normal, making the year-over-year increase even more marked.
“While there have been modest improvements in the efficiency of oil and natural gas furnaces, it is not enough to offset the emissions impact of population growth and increased demand for heating and other non-electric building energy services,” the authors write. “Building electrification has recently gained traction as a concept within the energy and climate wonkosphere, but much less headway is being made on the ground among actual building owners and operators.”
The industrial sector posted the largest emissions gains in 2018 at 55 million metric tons, due mostly to growth in industrial activity, according to the report.
“Absent a significant change in policy or a major technological breakthrough we expect the industrial sector to become an increasingly large share of U.S. greenhouse gas (GHG) emission in the years ahead (including non-CO2 gases),” the authors write. “We expect it to overtake power as the second leading source of emissions in California by 2020 and to become the leading source of emissions in Texas by 2022.”
The United States will need to reduce energy-related CO2 emissions by 2.6 percent on average over the next seven years—and more if emissions from other gases don’t continue to decline at the same pace—if the country is to meet the Paris Agreement target of a 26–28 percent reduction from 2005 levels by 2025, Rhodium’s staff assert.
“That’s more than twice the pace the U.S. achieved between 2005 and 2017 and significantly faster than any seven-year average in U.S. history,” the report states. “It is certainly feasible, but will likely require a fairly significant change in policy in the very near future and/or extremely favorable market and technological conditions.”