The Energy Department's Energy Information Administration, in its outlook for 2013, said energy-related carbon dioxide emissions are expected to stay more than 5 percent less than 2005 levels through 2040.
"Emissions from motor gasoline demand in (the 2013 outlook) are lower than (this year's) as a result of the adoption of fuel economy standards, biofuel mandates and shifts in consumer behavior," the EIA said in a statement.
The White House this year called for better fuel economies for passenger vehicles while increasing the level of biofuel usage. The EIA said it expected gasoline consumption in the transportation sector to continue to decline as efficiency standards come into force.
For cleaner fuels like natural gas, the EIA said the outlook "is somewhat more complex." Emissions from natural gas are expected to increase in the industrial and electricity sector but those are offset by the residential and commercial sectors.
The EIA said the share of renewable energy in the electricity sector should increase from 13 percent in 2011 to 16 percent in 2040.
"Renewable fuel use grows at a much faster rate than fossil fuel use," it predicted.