Marine cargo refers to the movement of goods by sea.
Shipping is often considered an efficient form of transporting goods on a per ton-kilometer basis. However, ships have been estimated to emit more particulate matter and black carbon per unit of fuel consumed due to the quality of fuel used. According to the Third International Maritime Organization (IMO) Greenhouse Gas Study in 2014, international shipping in 2012, which carried as much as 90 percent of the global world trade, accounted for 2.2 percent of the global CO2 emissions. Black carbon from the international commercial shipping industry is estimated to contribute around 2 percent of the total global black carbon emissions. The Annex VI of MARPOL aims to progressively reduce global emissions of SOx, NOx and particulate matter resulting from ships. In 2013, CO2 emissions prevention was added. An energy efficiency design index (EEDI) which relates to the CO2 emissions per transport work to ship size must be produced for all new ships. A ship energy management plan (SEEMP) is also now required.
There are a variety of vessels used for marine transportation. Dry-cargo ships, for instance, carry solid dry goods such as steel products and metal ores. The major types of dry goods transit are bulk carriers, which carry loose or unpackaged cargo, container ships, which carry containerized or non-bulk cargo, and reefer ships, which allow for refrigeration and are useful for transporting perishable goods like fruits. On the other hand, tankers are used to transport liquids like crude oil, liquefied natural gas and petroleum products, and chemicals, and these are classified as chemicals tankers, LNG carriers, oil tankers, hydrogen tankers. For wheeled cargo such as automobiles, tractors and construction vehicles, roll-on/roll-off ships (RoRo ship) are used.
The availability and the low cost of sea freight enabled the major shift towards industrial production in emerging economies. Shipping, however, generates a disproportionate share of air pollutants such as sulphur oxides, nitrogen oxides, and particulate matter. Moreover, shipping emissions in ports are also significant, although progress has been made over the years due to the implementation of clean shipping programs. According to IMO, the global shipping industry is firmly on track to reduce its greenhouse gas emissions per tonne-kilometre by more than 20 percent by 2020; however, shipping emissions are still expected to double by 2050, as are the related social and environmental effects. Several initiatives focus on tracking and benchmarking performance of global marine transport, such as the Clean Cargo Working Group which is a carrier-shipper initiative that focuses on creating and using the practical tools for measuring, evaluating, and reporting the environmental impacts of global goods transportation.
Opportunities for marine freight movement for a given area depend not only on the presence and size of regional port facilities, but also on the quality of the infrastructure itself. Some of the common barriers include the uncertainty over future fuel prices, over regulatory actions, concerns about technology and its payback, lack of access to low-cost financing, poor profit margins, lack of subsidies, split incentives (when a ship owner is making the investment, but the charterer is realising the benefit of the investment). Marine transportation is most sensitive to fuel cost, which is estimated to be between 60 to 80 percent of total expenditures. Given that marine bunker fuel costs have been on an upward trend, ensuring that fuel efficiency options are promoted for marine cargo transport is essential. Institutional barriers influence the implementation of fuel efficiency measures as, generally, these need to be taken within the context of specific contracts between relevant players such as charterers and ship operators. There have also been concerns about the transaction costs and the challenges associated with distributing costs and profits among the different companies involved in an investment that can improve fuel efficiency.
The options related to improving efficiencies and emissions from marine transport include the following: replacement of older engines with newer and more efficient ones (common rail fuel distribution, turbo chargers or turbo compounding, or diesel/electric engine configurations); use of improved propeller design, application of hull friction reduction technologies such as antifouling coatings and bubble lubrication, use of low sulfur fuels and alternative fuels such as biofuels and natural gas, encouraging solar cell and wind-powered options, route and engine optimization systems, operational changes such as cold ironing in port and slow-speed shipping while underway, and the application of add-on control devices.