For the first time since the late 1970s, U.S. CO2 emissions from the transportation sector exceeded electric power sector CO2 emissions on a 12-month rolling total basis, measured from October 2015 through September 2016. Electric power sector emissions are now regularly below those of the transportation sector despite making up a larger share of total U.S. energy consumption.
The reason for this is a significant decline in carbon intensity for the power sector as natural gas replaces coal as the preferred fuel of electricity generators. On average, emissions associated with combusting coal (~206 to 229 lbs CO2/MMBtu) are higher than those associated with combusting natural gas (~117 lbs CO2/MMBtu). Natural gas electric generators also tend to be more efficient than coal generators, because they require less fuel to generate the same output.
In the 12 months from October 2015 through September 2016, coal and gas accounted for 31% and 34% of electric power generation, respectively. However, their shares of electric power sector emissions were 61% and 31%, respectively, as coal is much more carbon-intensive. Overall power sector carbon intensity has also decreased as generation share of fuels such as wind and solar has grown.
Emissions from the transportation sector are primarily from fuels which have carbon intensities lower than coal but higher than natural gas. For example, gasoline emits an average of 157 lbs of CO2/MMBtu. In the months observed, motor gasoline represented 60% of the total emissions from the transportation sector, while 23% was from distillate fuel oil and 12% was from jet fuel.
Falling prices for natural gas have helped fuel the shift from coal to natural gas in the power sector.
Natural gas spot prices in 2016 averaged $2.49 per million British thermal units (MMBtu) at the national benchmark Henry Hub, the lowest annual average price since 1999. Warmer-than-normal temperatures for most of the year and changing natural gas demand were the main drivers of natural gas prices in 2016.
In the first quarter of the year, much warmer-than-normal winter temperatures and large amounts of natural gas in storage caused prices to decrease. Prices began to gradually increase in late spring, with increasing demand and decreasing production, before sharply increasing at the end of the year with the onset of cold temperatures in mid-December.
Because of warm weather, natural gas consumption in the residential and commercial sectors in 2016 declined 7% and 4%, respectively, from the previous year. As a result, natural gas storage inventories were at or near record levels throughout most of the year.
In November 2016, the United States became a net exporter of natural gas on a monthly basis for the first time since 1957, based on data from PointLogic.
U.S. pipeline exports to Mexico continued to grow throughout 2016, making up 87% of all U.S. natural gas exports and, in May 2016, the Sabine Pass terminal began commercial operations in the Gulf Coast to export liquefied natural gas.
Despite growing demand, low prices resulted in lower natural gas production in 2016. Based on preliminary data, the EIA estimates natural gas marketed production to face its first annual decline since 2005. The number of active natural gas drill rigs is down 19% from the year-ago count, however, production has not fallen as sharply as the number of active rigs, as producers have continued to make gains in drilling efficiency.