|US GHG emissions by sector, 1990-2013. Source: EPA. Click to enlarge.|
Total US greenhouse emissions were 6,673 million metric tons of carbon dioxide equivalent in 2013, an increase of 2% (127.9 MMT CO2 Eq.) over the prior year, according to the EPA’s newly published Inventory of US Greenhouse Gas Emissions and Sinks: 1990–2013. Total US emissions have increased by 5.9% from 1990 to 2013.
The increase from 2012 to 2013 was due to an increase in the carbon intensity of fuels consumed to generate electricity due to an increase in coal consumption, with decreased natural gas consumption, according to the report. Additionally, relatively cool winter conditions led to an increase in fuels for the residential and commercial sectors for heating. The transportation sector was the second largest sector source, at 27%. Transportation emissions increased as a result of a small increase in vehicle miles traveled (VMT) and fuel use across on-road transportation modes.
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.