Coal is a mineralized fossil fuel, mined extensively throughout the world and widely utilized as a source of domestic and industrial power. As a seaborne commodity, it is nearly always carried in bulk and is of considerable importance, being shipped in large quantities from the United States East and Gulf Coasts, Canada’s West Coast, Australia, South Africa, Poland and Russia, other areas despite having prolific coal-mining industries, exporting somewhat smaller amounts. Types of coal vary widely, ranging from soft (bituminous) types to hard (anthracite), through to manufactured coal products, such as coal briquettes, peas or beans, and patent fuels – perhaps mixtures of coal dust and cement. Product used directly to generate heat – eg: for use in power stations – is termed thermal coal; whereas metallurgical or coking coal is processed to become coke prior to being utilized in certain industries – eg: in steelworks. Much of the seaborne trade in coals is confined to large bulk carriers – eg: Panamax size and above – for this is an industry truly relying on economies of scale on certain well-established trade routes. Few of these vessels have their own cargo-handling gear, relying instead on loading and discharging at modern, deepwater facilities fitted with sophisticated equipment.
Coke is half-burnt coal so deprived of its gases, and used for industrial purposes and as a domestic fuel. It tends to absorb moisture, perhaps up to 20% of its weight and, in the dry condition is very light stowing – between 70 and 100 cubic feet per tonne depending on type (foundry coke stows around 80/90 and furnace coke 70/80). Thus will the cargo compartments of most vessels be full before the permitted load-lines are reached. Consequently, in order to gain the maximum cargo intake, it may be possible to carry coke as a deck-cargo, although this, of course, depends on any necessity of avoiding contact with salt water, and on adequate stability of the deck stow to compensate for the possibility of water absorption by the coke. Carriage of coke on deck entails the laying of dunnage to facilitate drainage of water from the cargo, and the erection of frames made from wooden posts and chicken wire. As with coal, coke can be processed into manufactured derivatives – eg: beans – or shipped in small pieces such as coke breeze, the latter stowing somewhat heavier than larger coke, say around 50 cubic feet per tonne. The least coke is handled, the greater its value, as it is particularly prone to crushing by grabs.