Shipping is responsible for 4.5% of global CO2 emissions, double the amount produced by the aviation industry, making the development of reduced emission craft a priority. A study by University of California Riverside of the world's only hybrid electric tugboat confirms the effectiveness of the technology.

Built by Foss Maritime in Seattle, USA, the Carolyn Dorothy is no ordinary tug, she is the world's first hybrid, running on four diesel engines and 126 batteries. A side-by-side comparison of two Foss Maritime dolphin-class tugs—the Carolyn Dorothy and a conventional tug called the Alta June - showed significant emissions reductions - a 73 percent reduction for air polluting soot derived from burning diesel, 51 percent reduction for nitrogen oxide (responsible for smogs), and 27 percent for carbon dioxide.

All results exceeded initial expectations. The testing was performed by a team at the Center for Environmental Research and Technology at the University of California, Riverside (UCR). The testing program was conducted in the Ports of Los Angeles and Long Beach over a seven-month period from January to July, 2010.

The two port areas are largest contributors of air pollution in the Southern California area according to the California Air Resources Board (CARB). The two ports handle 40% of all containerised cargo entering or leaving the United States. So successful has the first trial hybrid been that CARB has commissioned the retrofit of a sister ship, the Campbell Foss, for an additional $1 million.

These are small steps though and the technology comes with an expensive price tag, but once fully proven the new hybrid shipping technology could go a long way to tackling rising emissions from the global shipping industry which has largely escaped scrutiny until now. Environmentalists were disappointed recently when China rejected the suggestion of minimum emissions standards for all new shipping.

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