The world's 90,000 commercial cargo ships carry about 90 percent of the global trade on its decks. As you might expect, these massive, coal-fired ships are also some heavy-duty polluters, emitting 800 million metric tons of carbon dioxide each year, or about 5 percent of the world's total. But with rising fuel prices, the shipping industry is getting wise about its energy usage, and coming up with some innovative solutions.

The 'MS Beluga SkySails' is a 10,000-ton freight tanker that “set sail” from Bremen to Venezuela last week with the help of a 160-square-meter (1,722-square-foot) computer-controlled kite that flies at a height of 600 – 1000 feet, where winds are stronger and more stable. With the kite power, the ship's engines can operate on reduced power, which means fewer carbon emissions, and lower fuel costs. SkySails, the German company that manufactures the sails, estimates that by using the towing-kite system, a ship’s average annual fuel costs can be reduced by 10 to 35 percent (the MS Beluga expects to save $1,600 per day on its journey.) SkySails expects to expand the size of its kites to 320 and 600 square meters by 2009, and outfit 1,500 ships by 2015. At $725,000, the sail is relatively inexpensive, and as fuel costs continue to rise, that type of investment should be a no-brainer for major shipping companies.

Wind power isn’t the only way cargo ships are using technology to cut costs and reduce pollution. Some of the other measures include using weather forecasts to select optimal routes, employing slower-speed engines with greater fuel efficiency, cleaning the ships regularly to remove sediments that cause resistance, and using fuel additives for better performance.