Green Car Congress reports that the latest figures from the Energy Information Administration (EIA) show that total United States greenhous gas (GHG) emissions are up 2% in 2004, increasing to 7,122.1 million metric tons of carbon dioxide equivalent (MMTCO2e) from 2003’s 6,983.2 MMTCO2e.
Accoring to the EIA, the large growth in 2004 is the result of a surging U.S. economy, which in turn resulted in more energy use. GCC reports that the economy grew 4.4% in 2004 - the fastest since 1999 - and this in turn increased the carbon dioxide generated from energy use by 1.7%. However, greenhouse emissions grew slower than the economy which indicates that the U.S. greenhouse gas intensity - the amount of greenhouse gas emissions per unit of economic output - decreased by 2.1% in 2004.
Since 1990 (the benchmark year for the Kyoto Protocol), U.S. greenhouse gas emissions have increased by 15.8%, for an average annual increase of 1.1%, according to the EIA.
GCC reports that the 2004 increase in total greenhouse gas emissions is attributable primarily to a 1.7% increase in emissions of carbon dioxide to 5,973.0 million metric tons, along with increases in emissions of nitrous oxide (5.5%) and methane (0.9%). Emissions of engineered gases - hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) - also increased, by 9.6 percent.
[Graphic: GHG Emissions by Sector]
As in other countries seeing increasing GHG emissions, sometimes despite commitments to reduction targets [previous post], transportation is the biggest culprit here. Transportation emissions of CO2 climbed 3.1% from 2003 to 2004, and account for the largest percentage of carbon dioxide emissions (32.4%).
Almost all (98%) of transportation sector carbon dioxide emissions result from the consumption of petroleum products: motor gasoline, 1,162.6 MMT (60% of total); middle distillates (diesel fuel), 428.2 MMT(22%); jet fuel, 237.4 MMT(12%); and residual oil (heavy fuel oil, largely for maritime use), 54.6 MMT (2.8%).
The growth in transportation-related carbon dioxide emissions in 2004 included increases in emissions from the use of motor gasoline (21.2 MMT, up 1.9%), diesel fuel (17.9 MMT, up 5.1%), residual fuel oil (10.0 MMT, up 22.7%), and jet fuel (8.2 MMT, up 3.6%).
These figures indicate that if we truly want to reduce greenhouse gas emissions, we have to start doing one or both of the following:
(a) reduce the amount of transport fuel consumed, either through more efficient vehicles or through reducing vehicle miles traveled - i.e. simply driving less; or
(b) start using different transportaion fuels, fuels with reduced GHG emissions per vehicle mile traveled (VMT) - options include electric vehicles and plug-ins, cellulosic ethanol or FT fuels from biomass, zinc-air fuel cell vehicles and of course, hydrogen. The source of feedstocks for each of these fuels is crucial and effects the resulting GHG emissions per VMT. (Some, i.e. hydrogen from average U.S. electrical mix via electrolysis could even increase GHG/VMT).
Finally, while U.S. GHG intensity is decreasing, there is still much more we could do in terms of efficiency in the industrial, residential and commercial sectors as well as an accelerated transition towards clean, non-emitting, renewable sources of power including solar, wind, tidal, geothermal and low-impact hydro (and perhaps even nuclear although I'm still not sold there).