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Study Finds Large Cargo Ship Soot Emissions 2x Previous Estimates; Tugboats Are Top Emitters Per Unit of Fuel

Tugboats at work in Alameda Harbor, California. Click to enlarge. Source: NOAA

Large cargo ships emit more than twice as much soot as previously estimated, and tugboats emit nearly twice as much soot for the amount of fuel used than other commercial vessels, according to the first extensive study of commercial vessel soot emissions. Scientists from NOAA and the University of Colorado conducted the study and present their findings in the 11 July issue of the journal Geophysical Research Letters.

Daniel Lack, of NOAA’s Earth System Research Laboratory (ESRL) and the NOAA-CU Cooperative Institute for Research in Environmental Sciences (CIRES), and his colleagues observed emission plumes from 96 commercial vessels in open ocean waters, channels, and ports along the southeast United States and Texas during the summer of 2006.

From the NOAA research vessel, Ronald H. Brown, the team measured black carbon emitted by tankers, cargo and container ships, large fishing boats, tug boats, and ferries, many of them in the Houston Ship Channel.

Commercial shipping emissions have been one of the least studied areas of all combustion emissions. The two previous studies of soot emissions examined a total of three ships.  We reviewed plumes from 96 different vessels.

—Daniel Lack

Commercial shipping releases roughly 130,000 metric tons of soot per year—1.7% of the global total—much of it near highly populated coastlines, the authors estimate. In the coming years global shipping is expected to grow two to six percent annually.

Tugs emit nearly a gram of soot per kilogram of fuel burned—nearly twice as much as any other vessel type, the authors found. The high levels point to their low-quality fuel. Engine age and maintenance also play a role. Tugboats have a disproportionate impact on air quality because they travel within ports, emitting potentially harmful particles near populous urban areas, according to the authors.

Tugboats are a huge source of black carbon that may be under-reported or not reported at all in emissions inventories compiled by ports.

—Daniel Lack

Oceangoing tankers and container ships emit half a gram per kilogram of fuel burned when at dock and slightly less when traveling, according to the study. That’s more than twice as much as previously estimated.

A 2007 study by American and German scientists linked particle pollution from shipping to tens of thousands of premature deaths each year, most of them along coastlines in Europe, East Asia, and South Asia. Soot makes up a quarter of that pollution, said Lack.

On a global scale, soot currently traps about 30% as much heat as does carbon dioxide, the most important greenhouse gas, according to the latest assessment of the Intergovernmental Panel on Climate Change. The small dark particles absorb sunlight, create haze, and affect how clouds form and make rain, further altering a region’s heat balance, according to the new NOAA study. If commercial shipping extends new routes through Arctic waters as they become navigable, soot emissions there could increase.


  • Lack, D., B. M. Lerner, C. Granier, T. Baynard, E. Lovejoy, P. Massoli, A.R. Ravishankara, and E. J. Williams  (2008),  Light absorbing carbon emissions from commercial shipping,  Geophys. Res. Lett.,  doi: 10.1029/2008GL033906, in press. 


Henry Gibson

Penny wise and pound foolish? What is the percentage of soot emitted by trucks and cars in the areas concerned compared to that by boats. Every substance on the face of the earth, including water, is poisonous or dangerous. How many lives would be saved if federal laws had DUIs automatically causing a permanent revocation of a driving rights. The actual number of people killed at Chernobyl was 31 (readers digest) the possible estimated deaths by cancer 4000, but this can never be proven because all life forms have always had some radioactivity built into them and this has not been increased much on the average by Chernoble or any activity of man. There is an advantage for having any kind of power plant as it has been determined the people in areas with power live twice as long. We use cars eventhough 40,000 or more are killed with them each year, but how much more work gets done if they are used?? There has to be a balance that is mathematically justified. Not emotionally. ..HG...

Nate H.

So, what about when we used coal in this country for practically everything? Folks in their 80's and 90's today breathed air that was "unthinkable" today.

They are still alive and kickin'. This soot nonsense is rediculous. Most of it falls directly to the water anyways, deteriorating. The "fine" particles wouldnt be caught with soot-strainers either.

There are bigger fish to fry in this world than soot. How about lets focus that fervor on the Economy?

Nate H.
Dover, Ohio

stas peterson

Is this a report meant to encourage the adoption of improved Annex IV regulation?

Or is this meant to merely scare us. Is it meant to confirm the leftist propaganda that every source of American greatness, must be discredited and derided; the world stinks, and going to hell in a handbasket. Yada, yada, yada...

Now Maritiem is acused of creating 1.7% of the world's soot, it is surely a GIGANTIC and ENORMOUS, INSOLUBLE problem.

The fact that the world's Maritime nations have already negotiated, already reached agreement, and prepared approval for Tier IV cleanup, that will be adopted internatioanally, likely in 2009.

That planned international regulation solves this tiny problem, and very soon.

Bill W

I think the information is to highlight that while we restrict emissions from road going vehicles to a tiny amount, a boat 100 feet away is spewing like crazy.

Boats should have emissions control, and because they are emitting levels of particulates at a rate much higher than estimated, we should get controls to them as quick as possible.

Casual Observer

I really like the fact that Reader's Digest is used as a reference for facts concerning Chernobyl. When I need info on Hiroshima I always look for back issues of Good Housekeeping (great recipes to boot).


Stan: according to you everything is a leftist plot.


China and India just rejected the G8




...are 40 000 (USA) equivalent to 1 100 000+ (worldwide) ICE vehicles related deaths a year mathematically justified?

If so, one can wonder why many countries (including Canada) have banned the death penalty based or less than one unjustified death a year per 10 000 000 people?

Is this a case of, different country, different values or different person different values?

Do you know how much soot and GHG one beloved wood burning stove or fire place can emit every winter?

Do you know that one 2-cycle beloved lawn mower can create, in one year, as much GHG and fine particles as 43 new well designed cars used for 20 000 Km each?

Are they mathematically justified?


"Tugboats Are Top Emitters Per Unit of Fuel"...no surprise here - they have gargantuan engines that they are constantly revving to high rpms as they move ships around ports.


it seems that everyone wants to present A problem in our home called Earth that involves a lot of humans. Although I'm certain there's just not enough resources to solve all those problems, but chosing which problem to solve in priority seems to be a everyday struggle within us...


I used to live on a boat in Seattle just downwind from the main cargo terminals. My personal, anecdotal evidence supports what this study is saying. I washed my fiberglass boat about monthly and there would be this nasty, gooey, black stuff on it. I then moved further from the port, but closer to a freeway, and the amount of black goo decreased drastically. The thought that I was breathing that stuff wasn't too comforting.

I would hope that there is a global move to adopt lower sulfur fuels for large marine diesel engines. The bunker fuel they use is nasty, nasty stuff. By going to better fuel it would be a relatively low cost and easy way to dramatically improve the air quality of our coastal cities.


No suprise at all. One can imagine the variable duty cycle short haul engine must be running at anything but peak efficiency.
As they would spend more time operating in the port areas, they should be likely candidates for post emissions reductions as well.


@ Casual:

Thanks for the laugh - it made my morning!


JustinVP...Ditto. Ships, tugboats & dock machinery are obviously dirty & all the talk here saying otherwise is unwise. Are we, Northwesterners, the only ones that know how bad particles are?

Also, those comparing ships vs. 'cleaner' vehicles with their 3-way catalytic converters & DPFs & saying particles aren't a problem with land-based vehicles, aren't reading the latest delayed & neglected reports on fine & nano particles. Large, fine & nano particles are a major problem, even if we don't pay attention to the increasing evidence that these particles are tragically in our human systems. The ostriches on this website who are sticking their heads in the ground, must think dirt over their heads is filtering particles.


Coastal areas are some of the most densely populated in the world. As far a ships are concerned, it really doesn't matter how many diesel trucks and buses are active in these coastal areas since these mobile sources are regulated by both state and federal rules, and are in the process of being cleaned up through the use of ULSD, and tighter emission standards that will require retrofits of emissions control systems or conversion to alternative fuels. The point is that shipping is starting at a couple percent of all soot emissions worldwide, pollutes twice as much per unit of fuel as other mobile sources, and total emissions are growing faster than almost any other mobile source in the world.

We have learned in the South Coast AQMD, the most polluted in the country, that you have to control practically all emission sources, large and small, to have any hope of meeting federal clean air standards that are designed to protect the most vulnerable segments of the population.

I would support a study that would provide a voluntary opportunity for all the folks on this site that favor uncontrolled tug boat and ship emissions to live on houseboats downwind from these highly polluting sources. I guarantee, if their elderly, they won't live long.

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