Tankers, cruise liners and cargo ships are estimated to generate almost 30% of the world’s smog-forming nitrogen oxide emissions and nearly 10% of SO2 emissions from burning fossil fuels.
Posted by envirostats on Thursday, October 11, 2007
Nitrogen oxide, refers to any of these oxygen compounds of nitrogen, or to a mixture of them:
- Nitric oxide (NO), nitrogen(II) oxide
- Nitrogen dioxide (NO2), nitrogen(IV) oxide
- Nitrous oxide (N2O)
- Dinitrogen trioxide (N2O3), nitrogen(II, IV) oxide
- Dinitrogen tetroxide (N2O4), nitrogen(IV) oxide
- Dinitrogen pentoxide (N2O5), nitrogen(V) oxide
In the presence of sunlight, they form photochemical smog, a significant form of air pollution, especially in the summer, which could damage to lung tissue and reduction in lung function. Some nitrogen oxides are more active and more prevalent but all of these compounds have similar effects, only to different extents.
World nitrogen oxide (NOx only) emissions from ships had been academically noted in 2004 as being between 22-54 Gg[N]/year.
A Gg[N] is a gigagram (1 billion grams, million kilograms or kilotonne) of Nitrogen, and not NOx. The Nitrogen is but a percentage of the entire molecular weight pending the specific NOx dealt with. With NO2, as an example, Nitrogen has an atomic weight of 14.0, roughly, whereas each oxygen has a rough atomic weight of 16.0. Thus, an NO2 molecule has rough molecular weight of 46 so the Nitrogen portion is 14/46 or 30.4% of the same weight of NO2, so be careful when you see NO2 emissions to see whether they are talking about the NO2, or just the nitrogen like it is here. The same sort of calculations are sometimes done with carbon in carbon dioxide (CO2), as noted in Stat 0370, although the Gg unit is not used because CO2 emissions are on the order of megatonnes and gigatonnes, not kilotonnes that convert to gigagrams.
The world shipping NOx emissions range is quite wide, but it’s an just old estimate I came across in researching for this entry that allowed me to share the Gg[N] concept I saw quite often in my research and had to learn about myself. The value gives some context to the absolute total, but not the most accurate total.
I also came across some articles by the International Marine Organization (IMO) which stated the N2O output from shipping was about 7% of world totals. However, this was posted in 2002, which meant it was, at best, a 2001 statistic and so is way out of date, in the days when the Global Warming Potential (GWP) of N2O was thought to be between 170-290 times that of CO2 instead of 296 to 310 (Stats 0420 and 0017, respectively). The IMO estimate was also for just N2O and not all NOx so those are among other reasons why it would have been so low.
A related microcosm statistic found during research for this statistic stated that with more than 7,000 trips a year by cargo ships through the Santa Barbara Channel, cargo ships contribute about 50% of nitrogen oxide pollution in Santa Barbara, amounting to about 15,000 tons annually.
Italicized commentary and context provided by Envirostats author.
- Friends of the Earth via the European Federation for Transport & Environment, Nov 13 2006
- World N2O inventory quoted by Beirle et al in academic paper for method of ship N2O emissions estimation using miles long emission plumes seen in satelite photos, published in the American Geophysical Union, GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L18102, doi:10.1029/2004GL020312, Sep 17 2004
- Santa Barbara statistic via Medill Reports Washington, Oct 7 2007
Monday, October 29, 2007 at 12:44 pm
Not quite sure you have your facts straight.
a) where did you find the NO2 (not N2O) GWP?
b) the imo values are given in mass, not CO2 eq, so GWP is irrelevant.
c) MARPOL nox reduction guidelines are now in place which reduce NOx emissions by about 20% on new built engines.
d)looking through your other posts. GWP is in mass (kg) not volume (l)
Monday, October 29, 2007 at 9:31 pm
Thank you very much for your input, Niko. You are absolutely right. I do know the difference and I understood your comments immediately, seeing the errors in what I had blogged without having to check anything. It is N2O and not NO2, mass is the right unit to do the math I did, not Litres. Thanks for the update on MARPOL’s new NOx reduction guidelines as well. I have gone back to look through the GWP comments to edit changes where needed. Whatever caused them boils down to me and I’ll just own up for it. Critiques like yours are what makes this blog better. If you see anything else, please do feel free to point it out. Thank you for your comments again.