Maritime cargo maybe classified into three (3) categories:
- Bulk Cargo
- General Cargo
- Specialized Cargo
Bulk cargo maybe classified further into liquid bulk cargo (such as crude oil, molasses, chemicals, vegetable oil, etc.), which is transferred in tanker vessels, and dry bulk cargo (such as iron ore, grain, scrap metal, coal/coke, cement, sugar, and fertilizers), which are transferred in dry bulk vessels.
Crude oil is carried in large consignments over long hauls in a relatively small number of routes. Specialized ports and terminals (such as jetties, single buoy, or single point moorings) are used to service the very large tankers. Oil products are carried in smaller shipments to numerous consignees and over many ports.
Grain is carried in dry bulk carriers and occurs in small to medium-size consignments. Handling rates vary and there are several major export and import ports. Vessel range from small to medium size. Ores and coal are carried in large consignments and hence in bigger vessels and over long hauls. The cargo is handled at moderately fast handling rates. There are specialized terminals for handling such types of cargo.
General cargo is subdivided into break bulk cargo (such as sacks, cartons, crates, drums, pallets, and bags) and is transferred in general cargo ships, neo-bulk cargoes (such as lumber, paper, steel, and autos), and containerized cargoes (such as containers, Lo/Lo, and Ro/ Ro), which are transferred in containerships. General cargo is carried in small consignments to numerous consignees. It originates from numerous ports and production areas and is carried across a multitude of routes to arrive at varied destinations. The nature of the cargo means that handling rates are very slow. General cargo has been unitized with the advent of containerization. Cargo handling has improved markedly, and the cost of handling and transportation has decreased significantly. Progressively bigger containerships are being developed to carry unitized general cargo.
The quantity of cargo that is transported by ship is measured in metric tons (the term tons may be used interchangeably in this book) whereas the maximum that can be placed in a ship is measured by the ship’s deadweight which is a measure of how much cargo can be placed in a ship’s holds for safe carriage.