Due to a couple of incidents in late 2015 and early 2016 shipments of palm kernel shells were were shown to emit very high levels of methane (flammable ) gas in the cargo spaces.
Why the highlight now of the carriage of palm kernel shells in bulk?
Palm kernel shells are not regulated by the International Maritime Solid Bulk Cargoes ( IMSBC) Code. Yet, it is being shipped in increasing volumes these days as natural biomass resource products. Due to a couple of incidents in late 2015 and early 2016 where the cargo was shown to emit very high levels of methane (flammable ) gas in the cargo spaces, a submission was made by various Member Government States and an industry organisation to the International Maritime Organization (IMO). Their proposal was for the cargo to be listed in the IMSBC Code so that a proper set of carriage requirements could be drawn up for palm kernel shells to be transported safely.
The proposal is still pending the receipt of more concrete information regarding the cargo’s properties and characteristics before it can be finalised.
What are Palm Kernel Shells?
Palm kernel shells are a natural by-product of palm oil processing. Due to its high calorific value and low ash content, it is now commonly shipped in bulk as natural biomass resource products.
Palm kernel shells are often confused with palm kernel expellers which are also a by-product of palm oil processing. Palm kernel expellers are obtained by crushing and expelling the oil from palm kernel and are properly classified in the IMSBC Code as “seed cakes”.
Based on information available, palm kernel shells are woody shell fragments. Whether they are shells obtained before the process of oil extraction from palm kernels begins or it is a residual product after completion of the oil extraction process remains to be confirmed at the IMO.
As the carriage requirements of palm kernel shells are not found in the IMSBC Code, shipment of such cargoes as a prudent measure, should never be perceived at any time to be a “non-hazardous” cargo.
What are the dangers associated with the carriage of palm kernel shells ?
The most obvious danger is that this is a cargo not regulated by the IMSBC Code so clearly there are no proper carriage requirements set out to enable this cargo to be shipped safely.
As for the hazards of the cargo, it is liable to self-heat and if wet, or if containing a certain proportion of unoxidized oil, it can ignite spontaneously.
When the cargo undergoes self-heating by oxidization via the unoxidized oil residues, resulting in depleting of oxygen and production of high carbon monoxide level in cargo spaces, this can pose a serious risk to the safety of the crew or anyone entering the cargo spaces as well as adjacent areas.
The cargo has also been known to emit high levels of methane as evidenced in at least two recent incidents. Emission of high levels of methane (a methane/air mixture containing between 5% and 16% by volume) can lead to explosion hazards that occur simply by ignition of sparks or any naked flame including a match or lit cigarette. It is thought that the production of methane could be attributed to the fermentation process caused by high moisture content. However, there is insufficient information presently to explain this methane production or how this could be avoided.
The proposed submission to the IMO stated that moisture content above 11% may result in the cargo's fermentation process that can lead to generation of toxic and flammable gases with methane gas going beyond flammable limits.
As for the loading of the cargo, it is normally loaded from open stockpiles and in tropical exporting countries, the usual element of the wet weather conditions will exacerbate the moisture uptake of the cargo.
According to Gard P&I Club, there is uncertainty though “cargo declarations and MSDS sheets provided by shippers state various moisture contents, usually in the range of 20% to 23%. However, actual moisture certificates or moisture declarations based on pre-loading sampling are usually not provided by shippers. Actual moisture contents may or may not be in excess of the above range. Once loaded, excess water may drain downwards within the stow during the voyage and accumulate on the tank-top and in the bilges. As a result, the moisture content of the cargo at the bottom of the stow is likely to be much higher than the average for the entire cargo. The oil content of the PKS is likely to be below 1%, although it is difficult to obtain firm evidence of this".
How can palm kernel shells be still transported under the IMSBC Code?
As it is a cargo that is not listed in the IMSBC Code, its transport will have to be governed by section 1.3 (cargoes not listed in the Code) of the IMSBC Code, ie, a tripartite agreement will be required before shipment can take place.
When such a tripartite agreement is obtained, the carriage requirement to ship the cargo in question will be set out clearly.
Below is an extract from Gard P&I Club’s recommendations ( kind courtesy of Brooke Bells, Hong Kong) for shipowners and operators:
When the carriage of PKS is proposed by the charterer, shipowners and operators are recommended to:
- Request cargo information in accordance with section 1.3 of the IMSBC Code. This should include a certificate issued by the competent authority of the port of loading, stating the characteristics of the cargo and the required condition for carriage and handling of this shipment. If the competent authority at the port of loading is of the view that the cargo poses a hazard, the flag state should be consulted to set the preliminary suitable conditions for the carriage of this cargo. For example, the flag state may require a vessel’s holds to be equipped with mechanical ventilation when cargoes emitting flammable gases are carried.
- Monitor the cargo surface temperature at the time of loading. The cargo shall be accepted for loading only if the temperature does not exceed 55°C and the moisture content does not exceed 11%.
Measure and record methane, oxygen and carbon monoxide levels during the voyage with a gas meter operating on either infrared or thermal conductivity. Catalytic sensors do not operate correctly below ~10% oxygen.
- Ventilate cargo spaces immediately if methane levels exceed 1% by volume of 20% LEL.
- Ban smoking and use of naked flames on deck while the cargo is on board.
- Do not permit personnel to enter the cargo holds and spaces adjacent to the cargo holds unless a proper risk assessment has been carried out and a permit for entry into an enclosed space has been issued.
- Apply water and/or CO2 in the event of a fire in the hold, as both are considered as suitable extinguishing media for the cargo. Bear in mind, however, that sealed holds may have an accumulation of methane gas which can ignite if the holds are opened during fire-fighting.
- The need to ensure sufficient ventilation to prevent a flammable atmosphere in the holds take precedence over considerations to keep the cargo dry or to maintain fumigation. If the methane level increases despite proper ventilation, Gard [or owner’s P&I Club] should be informed immediately and expert advice should be sought.
Shipper to provide a certificate as required under Section 1.3 of the IMSBC Code. Member’s P&I Club should always be consulted for assistance and guidance. Please also refer to our BIMCO FAQ - Solid Bulk Cargoes.