Hawkins has investigated many cases of damage to bulk agricultural cargoes such as maize (corn), wheat, soybeans, soybean meal, palm kernel expeller and copra. Damage to agricultural cargoes can occur as a result of self-heating, mould growth, ineffective fumigation or simply as a result of the natural degradation of the product due to prolonged storage time in a ship’s hold. Early intervention by an expert can help minimize damage and subsequent losses. Hawkins use the latest technology when investigating incidents of this nature, for example, the use of thermal imaging cameras can help detect parcels of hot cargo and is invaluable in locating the source of a fire in a smoke-filled hold.
Whilst Hawkins have dealt with fires and fire damaged agricultural cargoes, the majority of agricultural incidents that we investigate are the result of cargo degradation. The causes of this degradation include human error, such as hold lights left energised after loading but, more commonly, are the result of natural deterioration of the product due to storage related issues.
The subject of storage of agricultural cargoes is a complex one with many variables to consider. However, it is widely accepted that the three most important factors affecting the transportation of agricultural products are moisture content, temperature and cargo age. Agricultural products are hygroscopic, which means that they will absorb or desorb moisture depending on the local humidity. High moisture content promotes microbiological activity and increases the risk of self-heating during transit. Similarly, high temperatures increase microbial growth and pest activity. Agricultural products are best stored at low temperatures and low moisture levels.
Agricultural products are not homogenous, consequently, there may be variability within a cargo in terms of disease load, moisture content or stages of self-heating. Pockets of damage may occur within a hold when poorer quality parcels of produce are loaded with an otherwise sound cargo. In order to avoid costly damage, good quality produce, low moisture, low temperature and short storage times on board ships are recommended.
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The common causes of damage in agricultural cargoes that lead to deterioration during transportation include pest infestation, mould growth and self-heating and these are discussed briefly below.
Pests are a common problem in agricultural cargoes, and one that is controlled using fumigation. If fumigation is carried out effectively, then it would be expected to control pest infestations for the duration of a typical voyage. However, if the voyage time was significantly extended, and holds ventilated, then it is possible that the cargo would require a further dose of fumigant.
Agricultural cargoes are susceptible to moulds growing during transportation, which can be exacerbated by condensation. In order for moulds to grow, they require the ‘right’ combination of temperature and moisture content. If the moisture content is sufficiently low, then moulds will not be an issue. If the moisture content is high but the temperature is low then again mould will not be an issue.
Principal factors involved in the self-heating process include moisture content, mould growth, supply of air to the cargo, external heating and the biological age of the cargo.
‘Safe’ storage time
Table 1 below provides approximated maximum storage time in days. Sourced and adapted from USDA research at IOWA State University (ISU).
The table shows that increases in temperature and moisture content reduces the safe storage time of soybeans. For example, at 11% moisture content and 21°C, it should be possible to store the cargo for just over two years, but at a moisture content of 14% and a temperature of 26°C, the maximum time before one grade of degradation occurs will be approximately 48 days.
Cargo quality at loading is the principal determinant of cargo quality at discharge. The list below, although not exhaustive, provides an outline of actions that can be taken to help minimize any damage occurring during sea transportation of agricultural cargoes:
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