A speed limit of 12 knots, down from the current cruising speeds of 20 to 25 knots, would cut nitrogen oxides by 55 per cent and soot by almost 70 per cent, according to the University of California, Riverside study. It also would reduce emissions of the main greenhouse gas carbon dioxide by 60 per cent.
All ocean-going vessels, when they are within 10 nautical miles of a US port, must slow down, to typically 12 knots. The voluntary programmes in Los Angeles/Long Beach and New York-New Jersey slow them farther out, up to 40 miles offshore.
The study measured the emissions of two container vessels travelling between the Ports of Los Angeles/Long Beach and the Port of Oakland on the US West Coast. Emissions were measured near the ports and in international waters.
Source: Environmental Health News, 19 November 2012