2011 News & Events

Air pollution caused by ships plummets when vessels shift to cleaner, low-sulfur fuels

12 September 2011

container ship taken from research aircraft
The container ship Margrethe Maersk, operated by the Maersk Line, steams toward California in May 2010. NOAA researchers and collaborators studied the ship's emissions in detail from a research aircraft (from which this photo was taken) and a research ship. The team found that as the container ship shifted to low-sulfur fuels and slowed down near the coast, air pollution emissions plummeted, with some pollutants dropping by as much as 90 percent. Photo: Dan Lack, NOAA / CIRES

New clean fuel regulations in California and voluntary slowdowns by shipping companies substantially reduce air pollution caused by near-shore ships, according to a new NOAA-led study published online today in Environmental Science & Technology.

The study examined a container ship operating under a 2009 California regulation requiring that ships switch to low-sulfur fuels as they approach the California coast, and also adhering to a voluntary state slowdown policy, intended to reduce pollution. The research team found that emissions of several health-damaging pollutants, including sulfur dioxide and particulate matter, dropped by as much as 90 percent.

Findings of this study could have national and global significance, as new international regulations by the International Maritime Organization require vessels to switch to lower-sulfur fuel near U.S. and international coasts beginning in 2012. The research team found reductions in emissions even where none were expected, meaning even greater reductions in air pollution, and associated respiratory health effects in humans, than regulators originally estimated.

"This study gives us a sense of what to expect in the future, for the people of California, the nation, and even the globe," said Daniel Lack, chemist at CSD and the Cooperative Institute for Research in Environmental Sciences (CIRES). "This really is where science gets fun – a study with first-rate institutions, equipment and people, probing the effects of policy. It's important to know that the imposed regulations have the expected impacts. The regulators want to know, the shipping companies want to know, and so do the people."

In May 2010, a NOAA research aircraft flew over a commercial container ship, Maersk Line's Margrethe Maersk, about 40 miles off the coast of California. Researchers on the aircraft used sophisticated custom instruments to 'sniff' the ship's emissions before the ship switched to lower-sulfur fuels (by law, within 24 miles of the California coast) and slowed down voluntarily.

A few days later, scientists aboard the NOAA-sponsored Woods Hole Oceanographic Institute's research vessel Atlantis sampled emissions of the same ship as it cruised slowly within the low-sulfur regulated zone.

Sulfur dioxide levels, which were expected to drop, did do so, plummeting 91 percent from 49 grams of emissions per kilogram of fuel to 4.3 grams. Sulfur dioxide is best known as a precursor to acid rain, but can degrade air quality in other ways, directly and indirectly through chemical reactions in the atmosphere. In particular, emissions of sulfur dioxide lead to formation of particulate matter in the atmosphere which poses serious public health concerns.

Particulate matter pollution, regulated because it can damage people's lungs and hearts, dropped 90 percent from 3.77 grams of emissions per kg of fuel to 0.39 grams.

Unexpectedly, black carbon levels also dropped, cut by 41 percent, the team reported. Black carbon comprises dark-colored particles that can warm the atmosphere and also degrade air quality.

In 2009, the U.S. Environmental Protection Agency and its Canadian equivalent, Environment Canada, estimated that shifting to low-sulfur fuels near coasts could save as many as 8,300 lives per year in those two countries, and ease the acute respiratory symptoms faced by another 3 million. But that 2009 assessment did not include the observed drops in several pollutant categories that Lack and his colleagues found, so the authors suggest the impacts could be greater.

Finally, the new paper discusses the net radiative (warming vs. cooling) effect of the ship's fuel switch. Changes in the emissions of various air pollutants – some which have a warming effect, others which have cooling effects – likely mean net warming.

The project was funded by NOAA and the California Air Resources Board and conducted in close collaboration with the Maersk Line.

"These scientific findings clearly demonstrate that ships off our coast now emit significantly less sulfur pollution than in the past," said California Air Resources Board Chairman Mary D. Nichols. "This is good news for California and for the nation. When the federal regulations kick in for ships to use low-sulfur fuel, communities throughout America that live near shipping lanes and next to ports will see clean air benefits."

The new paper "Impact of Fuel Quality Regulation and Speed Reductions on Shipping Emissions: Implications for Climate and Air Quality" is available from Environmental Science & Technology. Lack's 28 co-authors are from 10 research institutions from both the U.S. and Canada.

Daniel A. Lack1,2, Christopher D. Cappa3, Justin Langridge1,2, Roya Bahreini1,2, Gina Buffaloe3, Charles Brock1, Kate Cerully4, Derek Coffman5, Katherine Hayden6, John Holloway1, Brian Lerner1,2, Paola Massoli7, Shao-Meng Li6, Robert McLaren8, Ann M. Middlebrook1, Richard Moore4, Athanasios Nenes4,9, Ibraheem Nuaanan6,8, Timothy B. Onasch7, Jeff Peischl1,2, Anne Perring1,2, Patricia K. Quinn5, Tom Ryerson1, Joshua P. Schwartz1,2, Ryan Spackman1,2, Steven C. Wofsy0, Doug Worsnop7, Bin Xiang0, and Eric Williams1,2, Impact of fuel quality regulation and speed reductions on shipping emissions: Implications for climate and air quality, Environmental Science and Technology, doi:10.1021/es2013424, 2011.

  • NOAA Earth System Research Laboratory, Boulder, Colorado, United States
  • University of Colorado, CIRES, Boulder, Colorado, United States
  • Department of Civil and Environmental Engineering, University of California, Davis, California, United States
  • School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
  • NOAA Pacific Marine Environment Laboratory, Seattle, Washington, United States
  • Air Quality Research Division, Environment Canada, 4905 Dufferin St., Toronto, Canada
  • Aerodyne Research Inc., Billerica, Massachusetts, United States
  • Centre for Atmospheric Chemistry, York University, 4700 Keele St., Toronto, Canada
  • Earth & Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, United States
  • Department of Earth and Planetary Science, Harvard University, Cambridge, Massachusetts, United States

Atmospheric emissions of gas and particulate matter from a large ocean-going container vessel were sampled as it slowed and switched from high-sulfur to low-sulfur fuel as it transited into regulated coastal waters of California. Reduction in emission factors (EFs) of sulfur dioxide (SO2), particulate matter, particulate sulfate and cloud condensation nuclei were substantial (≥90%). EFs for particulate organic matter decreased by 70%. Black carbon (BC) EFs were reduced by 41%. When the measured emission reductions, brought about by compliance with the California fuel quality regulation and participation in the vessel speed reduction (VSR) program, are placed in a broader context, warming from reductions in the indirect effect of SO4 would dominate any radiative changes due to the emissions changes. Within regulated waters absolute emission reductions exceed 88% for almost all measured gas and particle phase species. The analysis presented provides direct estimations of the emissions reductions that can be realized by California fuel quality regulation and VSR program, in addition to providing new information relevant to potential health and climate impact of reduced fuel sulfur content, fuel