Speed limit on ships urged for air quality

WASHINGTON, Oct. 24 (UPI) -- Setting a speed limit for cargo ships sailing near ports and coastlines could cut their emission of air pollutants by up to 70 percent, a U.S. study says.

David R. Crocker III of the University of California, Riverside, and colleagues say their evaluation of the impact of vessel speed reduction policies such as those proposed by the California Air Resources board suggests they would help reduce the impact of marine shipping on Earth's climate and human health.

While marine shipping is the most efficient form of transporting goods with more than 100,000 ships carrying 90 percent of the world's cargo, the researchers said engines on large cargo vessels burn low-grade oil that produce large amounts of air pollution.

Fuel consumption and smokestack emissions increase exponentially with speed, they said.

Slowing container ships to about 14 mph would reduce emissions of carbon dioxide by about 60 percent and nitrogen oxides by 55 percent compared with emissions at traditional cruising speeds of 25-29 mph, their evaluation found.

Soot emissions would fall by almost 70 percent with such speed reductions, the researchers said.

The study has been published in the American Chemical Society's journal Environmental Science & Technology.