According to Europa, in the EU ships are fast becoming the biggest source of air pollution. Unless more action is taken they are set to emit more than all land sources combined by 2020.
A 2003 study found that large ships generate 30 percent of global nitrogen emissions and 16 percent of sulfur emissions from all petroleum sources. Despite the fact that ships are more energy efficient than other forms of commercial transportation, marine engines operate on extremely dirty fuels. Most large ships use the dirtiest and least expensive diesel available, bunker oil.
Shipping is a small contributor to the world total CO2 emissions (1.8% of world total CO2 emissions in 1996)
According to a Reuters story, a group of north European companies plan to install a fuel-cell aboard a supply ship in 2008 and believe that a large share of the marine world will follow suit within 25 years. Norwegian shipping group Eidesvik Offshofre ASA plans to install a 330 kW fuel cell system on an oilfield supply vessel next year.
It is estimated that fuel cells now cost about six times more than diesel generators. But the technology can be up to 50 percent more efficient and much cleaner,
When powered by liquefied natural gas (LNG), as the first full-scale test model will be, carbon dioxide emissions are cut in half compared to diesel engines running on marine bunker fuel and sulphur and nitrogen oxide exhausts are nearly eliminated.
Iceland plans to convert its entire fishing fleet to hydrogen fuel cells as part of its environmental drive.
The shipping industry says it is more green than other modes of transport considering the huge amount of trade that ships carry, although the heavy fuel used in shipping emits 700 times more sulphur dioxide than diesel exhausts from road vehicles.
Sources and Emissions
Methane is emitted from a variety of both human-related (anthropogenic) and natural sources. Human-related activities include fossil fuel production, animal husbandry (enteric fermentation in livestock and manure management), rice cultivation, biomass burning, and waste management. These activities release significant quantities of methane to the atmosphere. It is estimated that 60% of global methane emissions are related to human-related activities (IPCC, 2001c). Natural sources of methane include wetlands, gas hydrates, permafrost, termites, oceans, freshwater bodies, non-wetland soils, and other sources such as wildfires.
Methane emission levels from a source can vary significantly from one country or region to another, depending on many factors such as climate, industrial and agricultural production characteristics, energy types and usage, and waste management practices. For example, temperature and moisture have a significant effect on the anaerobic digestion process, which is one of the key biological processes that cause methane emissions in both human-related and natural sources. Also, the implementation of technologies to capture and utilize methane from sources such as landfills, coal mines, and manure management systems affects the emission levels from these sources.
Emission inventories are prepared to determine the contribution from different sources. The following sections present information from inventories of U.S. man-made sources and natural sources of methane globally. For information on international methane emissions from man-made sources, visit the International Analyses Web site.
In the United States, the largest methane emissions come from the decomposition of wastes in landfills, ruminant digestion and manure management associated with domestic livestock, natural gas and oil systems, and coal mining. Table 1 shows the level of emissions from individual sources for the years 1990 and 1997 to 2003.