Containers overboard

Shipping containers lost from ships are a cause of pollution in the marine environment.

Container shipping is big business. During 2019, more than 6000 ships carrying 226 million containers moved more than US$4 trillion (around 80%) of world trade, including Australia’s. Contents include raw materials, manufactured products, food, household effects and frozen products, together with their packaging. Every year the volume grows, as trade grows, freight costs fall and ship sizes rise. The largest ships can now carry more than 20,000 containers. 

Losses from container ships are caused by many failures. As there is no internationally agreed way to measure or record losses, accurate data is difficult to find. Most often the cause is either solely or a combination of poor seamanship, severe weather, rough seas, structural failures, ship collisions or groundings, and handling errors during loading. 

Container losses generate complex marine pollution problems that don’t fit neatly into any national or international regulatory framework. No country, nor the IMO, seems to have satisfactorily solved this problem. AMSA considers shipping containers lost from ships to be a cause of pollution in the marine environment, and takes the view that neither containers nor their contents should be permitted to remain in the marine environment where removal is practical.  

Being steel, most general purpose containers sink quickly due to damage and cargo weight. Some take longer to sink due to cargo buoyancy or foam wall construction. Floating containers can drift many hundreds of kilometres before breaking up, sinking or stranding on coastlines. If buoyant, discharged contents can travel even further, affecting locations long distances from the original incident. Many Australian currents would bring any floating pollution into contact with our coast before long. 

Containers and their cargoes do not belong in the sea. Pollution by containers and from container contents has a serious impact on the ocean and coastal environment, its uses and users, and its values. In the past, the main concerns have focussed on containers creating navigation threats, or the safety or ecological threats as contents wash up on coasts. Other now recognised threats include those to open ocean animal species, ecosystems, wider human health and safety, amenity values, community uses, and commercial users of the ocean such as aquaculture and fishing.

Containers alone create pollution. If steel, they will rust over many years, and iron oxide is poisonous to many species. Insulation foam is one of many synthetic polymers (plastic) that will degrade over time and add to the ocean plastics load. Paints often contain additives (heavy metals) to prevent rust during transport at sea, and these are harmful to marine life. 

Cargo contents are the most diverse source of harmful pollution. Most common are synthetic plastics found in cargo items and packaging. Plastics are persistent (long-lived over hundreds of years), break down to mimic food, float where they can be fed on by marine species and birds, and chemically attract and concentrate other poisons. Microplastics are now recognised as one of the most serious international ocean pollution problems, irrespective of their source.   Plastic also has the propensity to float free and entangle and smother anything it encounters. It provides a place for undesirable species to colonise and drift beyond their natural ranges, creating biosecurity threats. 

Cargoes also contain other chemicals. Substances that are inert outside the ocean environment can become dangerous in the water. Food and organic materials can break down in their packaging or the container and generate poisonous gases (hydrogen sulphide), or remove oxygen from the water through bacterial growth and death. Nitrogen-rich chemicals used for fertilizer or fire extinguishers are benign on land, but are super fertilisers in the ocean. Any number of chemicals, from flea collars to refrigerants carried in the container cooling systems can become poisonous, either immediately or building up over time.

This is why AMSA takes a strong stance on container losses, and in recent times has acted immediately in response to incidents of container losses in its waters. 

Last updated: 

Friday 5 March 2021