Reducing ships' emissions

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 in Environmental Science & Technology.

The study examined a container ship operating under a 2009 California regulation requiring that ships switch to low-sulphur 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 sulphur dioxide and particulate matter, dropped by as much as 90 per cent.

Findings of this study could have national and global significance, as new international regulations by the International Maritime Organisation require vessels to switch to lower-sulphur fuel near US 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.

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-sulphur 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-sulphur regulated zone.

Sulphur dioxide levels, which were expected to drop, did do so, plummeting 91 per cent from 49 grams of emissions per kilogram of fuel to 4.3 grams. Sulphur 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 sulphur 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 per cent from 3.77 grams of emissions per kg of fuel to 0.39 grams.

Unexpectedly, black carbon levels also dropped, cut by 41 per cent, the team reported. Black carbon comprises dark-coloured 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-sulphur 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.

Source: http://www.tandlnews.com.au/