The timber provided by our suppliers travels approximately 14 500 km with various modes of transport before reaching its final destination in the form of woodchips at a customer’s pulp and paper mill in Japan or China.
Woodchips are mostly shipped in woodchip ships that are specifically designed to maximise the volume of woodchips, as woodchips have a very low bulk density when compared to other bulk cargoes like coal. Depending on its size, such a ship can carry between 36 000 and 47 000 tons of woodchips.
The ship is normally owned by one of the large Japanese shipping companies like NYK and MOL. The pulp and paper companies then conclude a 15-year time charter contract with the shipping company. These ships have a life span of 20 to 25 years before they are scrapped. The ships sail empty from Japan to Richards Bay, with the voyage taking around 26 days, depending on the weather conditions at sea. The average sailing speed is 14 knots, or 26 km per hour, and the vessel consumes on average 30 tons of fuel and oil per day, equating to 1 560 tons of fuel and oil for a round trip. The ships normally stop over in Singapore to take on fuel for their voyage. It takes on average three days to load a ship and three days to unload it, equating to a round trip of 58 days, inclusive of loading and unloading. A ship can therefore do six round trip voyages from Japan to Richards Bay every year.
The ship normally has a crew complement of 23, mostly of Filipino origin, and they do a six- to nine-month stint of consecutive voyages before resting for three months.
Depending on the price of the fuel and oil consumed during the voyage, the total cost of a round-trip voyage from Japan to Richards Bay and back is around R25 million. It is therefore very important to maximise the volume of woodchips loaded onto a ship so as to reduce the cost per ton for shipping the woodchips.
During the loading process, the woodchips on the stockpile are pushed by three large, wheeled dozers into a reclaim pit, where the chips are then fed onto a set of conveyors approximately 4 km long, providing a direct link to a dedicated pneumatic woodchip ship loader in the port at the berth where the vessel is being loaded. The loading takes place at a rate of 850 tons an hour. The pneumatic loader has a large blower that forces air into a pipe together with the chips to effectively blow the chips into the hold under pressure. Due to the high speed of loading, friction is created in the loading pipe of the loader and approximately 2 000 tons of water per shipment is induced in the loader together with the chips to reduce the friction.
A woodchip ship has six separate holds into which the woodchips are loaded. In order to maximise the volume of woodchips loaded onto the ship, the holds are all loaded in a specific sequence to 80% of capacity at first, which allows the chips to settle before the holds are topped up in the same sequence.
The loading takes place 24 hours per day until the vessel is full. Loading can, however, be interrupted due to high wind speeds, when the port closes for all loading and ship movements in and out of the port. Woodchips are one of the very few bulk cargo commodities that can be loaded while it is raining.
If there are any non-weather-related delays that interrupt ship loading, for example equipment breakdowns, or if the vessel has arrived for loading but there is another vessel at the berth, TWK as the supplier is charged a demurrage fee of $12 500 per day by the customer if it takes longer to load than the contractually agreed loading time. It is therefore very important to ensure that the ship is berthed and loaded with minimum delays.
In order to ensure that no contaminants enter together with the woodchips while the chips are being loaded, the conveyor route of 4 km is patrolled by four persons at all times and we have persons on the ship also dedicated to watching for any possible contaminants that may enter the hold during the loading process. We use a total staff and contractor complement of 17 persons per shift for all the vessel-loading activities.
In order to determine the final quantity of woodchips that are loaded into a ship, draught surveys are conducted by a marine surveyor before loading commences, and when loading has been completed. The draught survey determines the displacement of the vessel in the water, and the difference between the draught survey before loading and that after loading determines the quantity of woodchips loaded. In order to determine how well a ship has been loaded, we calculate two measurement parameters:
Stowage, which is expressed as cubic foot hold space utilised per metric ton of chips loaded.
Compaction, which is expressed as cubic foot hold space utilised per bone-dry ton of woodchips. This is the important measurement parameter for our customers, as they effectively purchase the woodchips from us measured in bone-dry tons.
A woodchip ship normally has a conveyor running on the deck along the length of the ship and three cranes with large grabs that are used to discharge the woodchips at the customer’s unloading port. The cranes and their grabs are used to lift the chips out of the holds into hoppers that feed the conveyor, which is connected to a shore conveyor to discharge the chips to a storage area. Small dozers are placed in the holds during the unloading process to accumulate the chips into piles for the grabs to effectively maximise the volume per grab load. In many cases when the pulp and paper mill is not situated adjacent to the unloading port, the woodchips are then loaded from the storage area in trucks with a 20 ton capacity, which equates to 2 000 loads to transport a shipment of 40 000 tons of chips to the mill where the journey ends before the chips are converted into pulp and paper products.