By sector, power plants were the largest source of emissions, accounting for 31% of total US greenhouse gas pollution. Industry and manufacturing were the third largest source, at 21%.

Transportation sector GHG emissions 1990-2013. Source: EPA. Click to enlarge.

Transportation End-Use Sector. The transportation end-use sector accounted for 1,743.0 MMT CO₂ Eq. in 2013, representing 33% of CO₂ emissions, 21% of CH₄ emissions, and 45% of N₂O emissions from fossil fuel combustion, respectively.

From 1990 to 2013, transportation emissions from fossil fuel combustion rose by 13% while the number of vehicle miles traveled (VMT) by light-duty motor vehicles (passenger cars and light-duty trucks) increased 35% from 1990 to 2013, as a result of a confluence of factors including population growth, economic growth, urban sprawl, and low fuel prices during the beginning of this period.

From 2012 to 2013, CO₂ emissions from the transportation end-use sector increased by 1.0 percent. EPA attributed the increase in emissions largely to small increases in VMT and fuel use across on-road transportation modes, as well as increases in other non-road sectors such as pipelines. Commercial aircraft emissions increased slightly between 2012 and 2013, but have decreased 18% since 2007.

Domestic transportation CO₂ emissions increased by 15% (225.6 MMT CO₂) between 1990 and 2013, an annualized increase of 0.6%. Light duty vehicles represented 60% of CO₂ emissions from fossil fuel combustion in domestic transportation sources, while medium- and heavy-duty trucks accounted for 23%, commercial aircraft 7%, and other sources 11%.

Almost all of the energy consumed by the transportation sector is petroleum-based. EPA capture the CO₂ emissions from the combustion of ethanol and biodiesel for transportation purposes, along with the emissions associated with the agricultural and industrial processes involved in the production of biofuel, are captured in other Inventory sectors.

Ethanol consumption from the transportation sector has increased from 0.7 billion gallons in 1990 to 12.6 billion gallons in 2013, while biodiesel consumption has increased from 0.01 billion gallons in 2001 to 1.4 billion gallons in 2013. EEEPA put CO₂ emissions from ethanol for 2014 at 73.4 MMT CO₂ Eq, up 2.7% from 71.5 MMT in 2012.

CO₂ emissions from LDVs totaled 1,028.0 MMT CO₂ in 2013, an increase of 8% (77.6 MMT CO₂) from 1990 due, in large part, to increased demand for travel as fleet-wide light-duty vehicle fuel economy was relatively stable (average new vehicle fuel economy declined slowly from 1990 through 2004 and then increased more rapidly from 2005 through 2013). CO₂ emissions from passenger cars and light-duty trucks peaked at 1,181.2 MMT CO₂ in 2004, and since then have declined about 13%.

The decline in new light-duty vehicle fuel economy between 1990 and 2004 reflected the increasing market share of light-duty trucks, which grew from about 30% of new vehicle sales in 1990 to 48% in 2004. Starting in 2005, the rate of VMT growth slowed considerably (and declined rapidly in 2008) while average new vehicle fuel economy began to increase. Average new vehicle fuel economy has improved almost every year since 2005, and the truck share decreased to about 37% of new vehicles in model year 2013.

Medium- and heavy-duty truck CO₂ emissions increased by 71% from 1990 to 2013. This increase was largely due to a substantial growth in medium- and heavy-duty truck VMT, which increased by 92% between 1990 and 2013.

Data Explorer. This year, EPA is publishing key data in a new, online Greenhouse Gas Inventory Data Explorer tool, which allows users to view, graph and download data by sector, year and greenhouse gas.