Green Bulk Carrier Low-poly 3D model

A bulk carrier or bulker is a merchant ship specially designed to transport unpackaged bulk cargo, such as grains, coal, ore, steel coils, and cement, in its cargo holds. Since the first specialized bulk carrier was built in 1852, economic forces have led to continued development of these ships, resulting in increased size and sophistication. Today's bulk carriers are specially designed to maximize capacity, safety, efficiency, and durability.

Today, bulk carriers make up 21% of the world's merchant fleets and range in size from single-hold mini-bulk carriers to mammoth ore ships able to carry 400,000 metric tons of deadweight (DWT). A number of specialized designs exist: some can unload their own cargo, some depend on port facilities for unloading, and some even package the cargo as it is loaded. Over half of all bulk carriers have Greek, Japanese, or Chinese owners and more than a quarter are registered in Panama. South Korea is the largest single builder of bulk carriers, and 82% of these ships were built in Asia.

On bulk carriers, crew are involved in operation, management, and maintenance of the vessel, taking care of safety, navigation, maintenance and cargo care, in accordance with international maritime legislation. Cargo loading operations vary in complexity, and loading and discharging of cargo can take several days. Bulk carriers can be gearless (dependent upon terminal equipment) or geared (having cranes integral to the vessel). Crews can range in size from three people, on the smallest ships, to over 30, on the largest.

Bulk cargo can be very dense, corrosive, or abrasive. This can present safety problems: cargo shifting, spontaneous combustion, and cargo saturation can threaten a ship. The use of ships that are old and have corrosion problems has been linked to a spate of bulk carrier sinkings in the 1990s, as have the bulk carriers' large hatchways. These hatchways are important for efficient cargo handling, but allow the entry of large volumes of water in storms or if the ship is endangered by sinking. New international regulations have since been introduced to improve ship design and inspection, and to streamline the process of a crew's abandoning ship. The term bulk carrier has been defined in varying ways. As of 1999, the International Convention for the Safety of Life at Sea defines a bulk carrier as a ship constructed with a single deck, top side tanks and hopper side tanks in cargo spaces and intended to primarily carry dry cargo in bulk; an ore carrier; or a combination carrier. Most classification societies use a broader definition, by which a bulk carrier is any ship that carries dry unpackaged goods. Multipurpose cargo ships can carry bulk cargo, but can also carry other cargoes and are not specifically designed for bulk carriage. The term dry bulk carrier is used to distinguish bulk carriers from bulk liquid carriers such as oil, chemical, or liquefied petroleum gas carriers. Very small bulk carriers are almost indistinguishable from general cargo ships, and they are often classified based more on the ship's use than its design.

A number of abbreviations are used to describe bulk carriers. OBO describes a bulk carrier that carries a combination of ore, bulk, and oil, and O/O is used for combination oil and ore carriers. The terms VLOC, VLBC, ULOC, and ULBC for very large and ultra-large ore and bulk carriers were adapted from the supertanker designations very large crude carrier and ultra-large crude carrier.