The usual mix of vessel types in recent contracts list includes orders for the largest classes of vessel: VLCCs (Very Large Crude Carriers), a capesize bulk carrier and post panamax container ships. One class of vessel that does not feature in the orders list, and has not done so for several years, is the combined carrier - a ship which can carry both wet and dry bulk cargoes. These ships are also referred to as OBOs (oil, bulk and ore carriers).
It is said that about 20 years ago the fleet of combined vessels comprised about 400 units, equaling about 45 million tonnes deadweight. During the last decade, most of the larger oil companies imposed an age limit of a maximum 15 years on combined vessels, which in effect stopped the contracting of such tonnage and thus the renewal of the fleet. As a result, the fleet of combined vessels today comprises 150 units only, or about 15 million tonnes deadweight. And of this total, probably only a portion are actually trading in both wet and dry trades.
It is claimed that the "5th generation" combined vessel design fully satisfies the oil companies' demands for stability and tightness of hatches. OBOs are considered to have the same life span as a tanker or a gas carrier, that is 20 years plus 10 years CAP, provided that the vessels can comply with all applicable technical and operational requirements which include a centreline bulkhead.
It is further claimed that the differential in newbuilding price that put owners off building OBOs has reduced dramatically, from over 20 per cent to about 6 per cent. As for the environmental benefits of using OBOs, there is a potential to reduce the greenhouse gas emissions (CO2 and NOx) in order to stop the global warming. By using combined carriers, 25 per cent of tankers and drybulk carriers between 60,000 dwt and 200,000 dwt would be surplus to requirements. This would, in return, save the world annually a CO2 emission equivalent to about seven million cars, or NOx emission equivalent to about 185 million cars.