Over 90 percent of world trade is carried across the world’s oceans by some 90,000 marine vessels. Like all modes of transportation that use fossil fuels, ships produce carbon dioxide emissions that significantly contribute to global climate change and acidification. Besides carbon dioxide ships also release a handful of other pollutants that contribute to the problem.

The shipping industry is responsible for a significant proportion of the global climate change problem. More than three percent of global carbon dioxide emissions can be attributed to ocean-going ships. This is an amount comparable to major carbon-emitting countries — and the industry continues to grow rapidly.

In fact, if global shipping were a country, it would be the sixth largest producer of greenhouse gas emissions. Only the United States, China, Russia, India and Japan emit more carbon dioxide than the world’s shipping fleet. Nevertheless, carbon dioxide emissions from ocean-going vessels are currently unregulated.

Oceana is working to reduce greenhouse gas emissions from the shipping industry by petitioning the government to regulate shipping emissions.

What Oceana Does

Working with Earthjustice, Friends of the Earth and the Center for Biological Diversity, Oceana petitioned the EPA to regulate shipping emissions in October 2007.

Unfortunately, since the EPA did not respond accordingly, in July 2008 Oceana, along with the coalition of environmental groups and attorneys general from various states, filed a letter warning the EPA of impeding litigation if it does not respond to the petition.

Oceana has the following recommendations to reduce global ship emissions:

– Shipping fleets should implement technical and operational measures to reduce global warming pollution immediately. Such measures include speed reductions, weather routing, fuel switching and specialized hull coatings.

– Fleets should begin to implement longer-term measures to reduce global warming pollution, such as fuel-efficient design of new ships and engines created specifically for slow steaming.

– The IMO should set international emission standards to reduce global warming pollutants from the shipping industry.

Learn More: Shipping and Carbon Dioxide

Ships contribute a significant amount of carbon dioxide to the atmosphere. The International Maritime Organization (IMO) calculated that ocean-going vessels released 1.12 billion metric tons of carbon dioxide in 2007. This is equivalent to the annual greenhouse gas emissions from over 205 million cars, or more cars than were registered in the entire United States in 2006 (135 million).

Shipping is responsible for over three percent of global anthropogenic carbon dioxide emissions and is growing. Over the last three decades, the shipping industry has grown by an average of five percent per year. The IMO predicts that without introducing measures to reduce emissions from shipping, carbon dioxide emissions from the industry could rise to 1.48 billion metric tons by 2020, equivalent to putting 65 million new cars on the road.

Solutions: Reduced Speed

Overall, speed reductions are a quick, easy and effective way to achieve emissions reductions from ocean-going vessels. Given the recent increases in oil prices, speed reduction makes sense not only environmentally but also economically.

Emissions, especially those of carbon dioxide, are directly proportional to fuel consumption. Greater speeds require increased fuel consumption. Consequently, slowing down, even by a small amount, can result in significant fuel savings and emissions reductions.

The IMO calculated that a speed reduction of just 10 percent across the global fleet by 2010 would result in a 23.3 percent reduction in emissions. Hapag-Lloyd found that slowing some of their ships by just five knots, or 20 percent, resulted in savings of around 50 percent on fuel costs. Restrictions on vessel speed would reduce emissions of carbon dioxide, black carbon, nitrogen oxides, and nitrous oxide.

Recently, as the price of fuel has been increasing, shipping lines have been voluntarily reducing their speeds to realize financial gains through fuel savings. A senior official with the French line CMA CGM stated that in order to minimize fuel consumption, most lines will begin steaming at “economic speeds.”

Compared to other forms of transport, ships traveling at slow speeds have been found to be far more efficient and less polluting — roughly ten times more efficient than trucks and at least a hundred times more efficient than air transport. As ship speeds increase, much of this efficiency is lost. Ships traveling at very high speeds have been found to have similar energy demands to those of airplanes.

Learn More: Shipping and Black Carbon

Along with CO₂, ships emit various global warming  pollutants, including black carbon (BC), nitrogen oxides (NOx) and nitrous oxide (N₂O). These pollutants all contribute to global climate change either directly, by acting as agents that trap heat in the atmosphere, or indirectly by aiding in the creation of additional greenhouse gases.

Reducing black carbon from ships could slow warming, buying time for further steps to reduce carbon dioxide emissions. Black carbon, more commonly known as soot, is made up of fine particles created by the incomplete combustion of a carbon fuel source such as oil or coal. Aging engines and poor engine maintenance can also contribute to incomplete combustion.

Black carbon is known to be a potent warmer both in the atmosphere and when deposited on snow and ice. Black carbon contributes to warming in two ways – through direct absorption of heat in the top of the atmosphere and by lowering the Earth’s albedo, or reflectivity. Unlike greenhouse gases, black carbon is a solid and not a gas and it warms by absorbing sunlight, rather than absorbing infrared or terrestrial radiation.

Black carbon warms the atmosphere by absorbing light, which dries the surrounding air by evaporating the water in the air and on other nearby particles. This reduction of water content decreases the reflectivity of the other particles, thereby allowing them to absorb more sunlight and create an even larger warming effect in the atmosphere.