Warning on risks of olive waste cargoes

The cargo, essentially a waste product from the production of olive oil, is shipped from typical olive-producing countries, such as Tunisia or Greece.

When producing olive oil, the by-product ‘olive mill waste water’, can be treated to extract the majority of the liquid. The remaining solid substance is known by a number of names, such as ‘olive mill solid waste’, ‘olive millcake’ or ‘olive margine’ and can be used for soil stabilisation or biomass fuel.

Following the IMSBC Code

Currently, there is no specific schedule in the IMSBC Code for this cargo. Therefore, Section 1.3 of the IMSBC Code (‘Cargoes not listed in the IMSBC Code’) must be followed.

It is, of course, vitally important that the identifiable hazards inherent to the cargo are known and understood through appropriate testing methods.

What are the Hazards?

Material experts Roxburgh advise that in the first instance initial guidance on the potential hazards can be found in the Seed Cake schedules of the IMSBC code, which now also cover “other residues of processed oily vegetables”.

The cargo does, however, usually contain moisture, but testing using normal TML (transportable moisture limit) assessment methods is not appropriate.

Roxburgh states:

“An approach solely focusing on the application of a TML test methodology is inappropriate for this material and will not adequately assess the risk to vessel and crew.

TML assesses the likelihood of liquefaction, which is a phenomenon primarily based upon void ratio, saturation and pore water pressure increase. Due to the inherent moisture content of this material i.e. a wet vegetable solid waste, the water is not freely available in the void spaces to affect stability because it is integral to the plant matter.

Excluding the risks of self-heating, the problems will occur as a result of limited interparticle friction, therefore a different type of assessment method will be required outwith the limitations of normal TML testing focusing on the effect of oil and moisture content on the material.”

In other words, the inherent remaining moisture can present a hazard, however the usual TML test methods will not work on their own for this material.

Seek guidance

The cargo should be carried as per Section 1.3 of the IMSBC Code. However, the importance of following Section 1.3 lies within recognising the hazards of the cargo, not simply issuing paperwork. Consider, for example, a seed cake cargo: have the shippers determined if the material will self-heat? Will the moisture and oil content be an issue for carriage at sea?

These variables need to be fully assessed and this is the purpose behind Section 1.3.

Roxburgh state:

“Chemical characterization of the source material pre-loading to determine the hazards during its life cycle when extracted, stored and transported will be necessary, with moisture content being a key parameter for assessment as it is fundamental to the thermochemical process that is likely to occur, with degradation and emissions a subsequent output from this process. The volatile matter can represent up to 75% of the dry mass of the material.

Typically, knowledge on the pre-loading composition – i.e., raw or processed (dried, milled or pressed) material – will give a good indication of the likely moisture content. It is not unusual for moisture content to be in the range of 25 – 70%, which can present problems for storage, transportation, and its end use.

As always, particle size distribution will impact upon the behaviour of the cargo, especially from a thermal decomposition perspective.”

If considering carrying this cargo, Members should approach their usual contact at North and seek expert assistance. Safe carriage relies on ensuring testing that is appropriate for the material has been carried out prior to loading.

With thanks to Roxburgh for their assistance with this article.