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Some cargoes have properties which can cause gradual heating during transportation.Unless the temperature is kept under control, the cargo is likely to ignite spontaneously and may give rise to situations which are potentiallythreatening to human life and property. The carriage of charcoal has sometimes given rise to such casualties

Most incidents reported to the Association concern charcoal destined for use in barbecues, shipped from South America and Indonesia. The commodity is usually packed in paper bags and carried in containers. Charcoal is a highly porous carbonaceous residue which is produced when organic material is heated to decomposition under conditions of restricted air supply – a process referred to as calcination. To avoid self-heating, the charcoal must be allowed to cool down sufficiently after manufacturing, before being packed and shipped out. However, investigation of the following reported cases gives us reason to suspect that in most instances the cargo may not have been given enough time to age prior to shipment, or that there may have been clusters of charcoal within the product which were not safe for shipment.
(1) In 1989 the crew of a container vessel on the way from Argentina to Europe detected smoke in two holds. Containers with charcoal were stowed in both holds. The vessel was instructed to call at Lisbon as port of refuge. In spite ofusing the ship’s entire stock of CO2, the fire was not contained until additional CO2 was provided by a shoreside supplier. The fire resulted in extensive cargo damage.
(2) A fire was also detected on board a container ship sailing from the Far East to Europe in 1990. This fire was among containers stowed on deck and developed into a near-catastrophe. The most likely source of the fire was a container with charcoal originating from Belawan-Deli in Sumatra. An "expedition" was sent to Sumatra to look at the relevant production sites. The resulting report is referred to later in this article.
(3) In 1993 a container with charcoal being carried from Sumatra to Taiwan caught fire in transit. Attempts to extinguish the fire by cutting holes in the container walls and injecting water had some effect; however, after discharge the fire started again.
(4) A similar case was reported in 1996 in which the vessel had to discharge the container in Singapore. The charcoal had been produced in Sumatra.
(5) In 1996 the crew of a container vessel in transit from Argentina to Europe detected fire in one of the vessel’s holds containing a cargo of charcoal. The fire was successfully fought by using CO2 but the incident resulted in serious cargo damage.

As mentioned above, the 1990 incident resulted in major cargo damage and in searching for a cause the Association decided to send a surveyor fromHong Kong to Belawan, Sumatra, which was the place of origin of the three containers with charcoal wherein the fire was suspected to have started. The report is quite informative and will probably be of general interest. The following
is a summary.

Investigation into the origin and production of charcoal in two sites at North Sumatra
The shipments in question came from two different sources: Fa. Sareena and C.V. Rimba Purnama. The charcoal from both producers originates from mangrove forests on the north-eastern coast of Sumatra. That of Fa. Sareena comes from a coastal area around Langsa whereas C.V. Purnama’s charcoal is produced further south. The coastal areas of these tidal bays are inundated with seawater where the mangrove grows and consist of alluvial formations intersected by numerous small rivers and creeks. Concessions for cutting the mangrove are controlled by the Indonesian government, from whom they are purchased.

Most of the charcoal is made from long straight poles from 1.5 to 4 inches in diameter and 10 to 15 feet in length. Some is also made from shorter but thicker trunks which are several inches in diameter. Small canoes take the woodcutters into the forest at high tide. They collect mangrove poles by cutting them off above the root complex and trimming off surplus twigs and branches, after which the poles are brought back to stockpiles near the kilns.

We visited kilns with a production capacity from 5 to 25 tons per firing. The kilns are usually beehive in shape and built of clay bricks. An arched tunnel provides access to the kiln so that it can be filled with mangrove poles and ultimately allows the removal of charcoal. Close to this arched tunnel is a small tunnel or port, by way of which the kiln is fired. Around the perimeter of the kiln at mid-height are three smoke vents.

After the kilns are packed with mangrove poles, stacked vertically, filling the kiln and the entrance tunnel, the entrance tunnel is bricked up and sealed with clay, leaving a single brick aperture at the floor of the entrance for ventilation. A fire is then started in the tunnel of the firing port which slowly spreads to the mangrove poles within. The fire is maintained continuously day and night slowly consuming the mangrove poles across the kiln within. The firing process lasts from 25 to 40 days, depending on the size of the kiln. The decision as to whether or not the fire has crossed the kiln completely is made by the head charcoal burner, based on the smell of the smoke coming from the smoke vents.

When the effects of the fire have spread the full width of the kiln, it is sealed off and left to cool. When the kiln is opened the charcoal is removed by hand. The charcoal is either graded and packed close to the kiln or transported to a godown where it is stockpiled in loose condition.

There is no government supervision of charcoal production and the producers advised that they had not experienced heating problems with the product offered for shipment until a recent case had changed the procedure. Shipowners were now asking for a "certificate of declaration" confirming that the charcoal offered for shipment had been cured for two or three weeks prior to loading.

Some comments
The calcination process which takes place at temperatures between 350 and 500°Cnormally produces a so-called non-activated charcoal. Additional treatment of the charcoal by enlarging the porous structure will give a product described as activated charcoal (activated charcoal is normally used as an absorbent).

Both activated and non-activated charcoal fall within Class 4.2 of the IMDG Code (spontaneously combustible). However, the Code does not apply to a consignment of charcoal if it passes the test for non-activated carbon described on page 4225 of the IMDG Code and is accompanied by a certificate from the shipper stating that the substance, as offered for shipment, has passed the test.

Charcoal which falls within Class 4.2 should not be carried in bulk. The cargo must be packed, stowed and segregated as indicated in the Code. Activated charcoal is subject to stricter packing requirements than non-activated charcoal, having to be carried in hermetically sealed packaging.