Controlling waste from ship sources
Disposal of waste from ships was once merely a matter of throwing over the side everything that wasn’t wanted on board. MARPOL effectively ended that with different categories of waste being categorised into one of the six annexes. MARPOL Annex V Prevention of Pollution by Garbage from Ships (entered into force 31 December 1988) deals with different types of garbage and specifies the distances from land and the manner in which they may be disposed of.
As what is effectively a mobile community, every ship produces quantities of garbage from daily routines. In addition there is also waste products associated with some of the cargoes carried and from the upkeep and maintenance of the ship. Among these will be food waste, packaging, dunnage, rags, containers for grease, paint, and other chemicals, rust scale, cargo sweepings and more.
Just recently, the amount of plastics in the sea has become a globally recognised problem and although some plastic waste undoubtedly comes from ships, most of the current attention is focussed on plastic in general and for once shipping is not singled out as the most polluting source. In fact the types of waste plastic that are found in the gyres at sea are most likely to have originated on land. Ironically, under the latest IMO rules on garbage, ships are obliged to dispose of waste into shore facilities and it very likely it from these that the waste may find its way back to the oceans. Nevertheless, an important feature of Annex V that applies to ships above 400gt is the complete ban imposed on the disposal into the sea of all forms of plastics.
Despite the disposal of plastics being prohibited under Annex V, At MEPC 73, the IMO adopted a resolution MEPC.310(73) containing an Action Plan towards preventing marine plastic litter entering the oceans through ship-based activities. The actions in the Plan are projected to be completed by 2025.
Among the provisions of the plan are amending Annex V to apply to ships above 100gt instead of the current 400gt, mandatory reporting of loss of containers at sea, improved reception facilities in ports, provision for fishing vessels allowing better identification and control of fishing gear.
In July 2011, IMO adopted extensive amendments to Annex V which entered into force on 1 January 2013. The revised Annex V prohibits the discharge of all garbage into the sea, except as provided otherwise, under specific circumstances. Getting rid of such waste costs money and it is likely that those costs have increased over the period since the 2011 amendments to MARPOL ANNEX V came into force on 1 January 2013. As well as the MARPOL rules, most coastal states have regulations concerning waste disposal at sea. The policing of these laws is variable but some states are diligent in enforcing them.
To reduce the quantity of waste materials produced and so reduce the cost of disposing it ashore, a number of methods are employed. Incinerators or compactors were already installed on many ships allowing them to manage their waste but others have only simple facilities. Even for those ships fitted with incinerators, the 2013 regulations mean the ash residue is considered as garbage and should be disposed of ashore.
Where incinerators are considered they must be type-approved and are subject to IMO and flag state regulation. The IMO standard for incinerators is contained in MEPC.244(66) title 2014 STANDARD SPECIFICATION FOR SHIPBOARD INCINERATORS. It is not unknown for some ships to burn garbage in improvised systems but while this is something that has been done for generations, it is not permitted under MARPOL Annex VI (emissions to air) where it states:
Regulation 16 - Shipboard incineration
(1) Except as provided in paragraph (5), shipboard incineration shall be allowed only in a shipboard incinerator.
The paragraph 5 mentioned relates to burning sewage and oil sludge as a fuel in the main power plant or boilers
Putting waste in its place
The Annex V 2013 rules contained detailed descriptions of different waste types and where they may be discharged at sea. According to revised MARPOL Annex V shipboard generated garbage is to be grouped into the following categories:
- Plastics – Garbage that consists of or includes plastic in any form, including synthetic ropes, synthetic fishing nets, plastic garbage bags and incinerator ashes from plastic products. Garbage under this category is prohibited to be discharged at sea.
- Food wastes – Spoiled or unspoiled food substances. Food wastes may be discharged at sea under specific circumstances/requirements (refer to the simplified overview of the discharge provisions of the revised MARPOL Annex V developed by IMO).
- Domestic Wastes – Garbage generated mainly in the accommodation spaces on board the ship (e.g. drinking bottles, papers, cardboard etc). Garbage under this category is prohibited
- to be discharged at sea.
- Cooking Oil – Edible oil or animal fat used for the preparation or cooking of food. Garbage under this category is prohibited to be discharged at sea.
- Incinerator ashes – Ash and clinkers resulting from shipboard incinerators used for the incineration of garbage. Garbage under this category is prohibited to be discharged at sea.
- Operational wastes – Solid wastes (including slurries) that are collected on board during normal maintenance or operations of a ship, or used for cargo stowage and handling. Operational wastes also includes cleaning agents and additives contained in cargo hold and external wash water that may be harmful to the aquatic environment. Operational wastes does not include grey water, bilge water, or other similar discharges essential to the operation of a ship (boiler/economizer blowdown, gas turbine washwater, machinery wastewater etc). Garbage under this category is prohibited to be discharged at sea.
- Cargo residues – Remnants of any cargo which remain on the deck or in holds following loading or unloading. This category does not include cargo dust remaining on the deck after sweeping or dust on the external surfaces of the ship. Such garbage may be discharged at sea under specific circumstances/requirements (refer to the simplified overview of the discharge provisions of the revised MARPOL Annex V developed by IMO). It is essential to remember
- that besides other requirements (e.g. distance from shore) cargo residues in order to be discharged at sea they should not be harmful to the marine environment. Cargo residues which are considered harmful to the marine environment are classified according to the criteria of the United Nations Globally Harmonized System for Classification and Labelling of Chemicals (UN GHS) meeting parameters such as: acute aquatic toxicity category 1,
- chronic aquatic toxicity category, carcinogenicity, mutagenicity, reproductive toxicity etc
- Animal Carcasses – Bodies of any animals that are carried on board as cargo and that die or are euthanized during the voyage. Discharge of such wastes permitted at sea under specific circumstances/requirements (refer to the simplified overview of the discharge provisions of the revised MARPOL Annex V developed by IMO).
- Fishing Gear – Physical device that may be placed on or in the water or on the sea-bed with the intended purpose of capturing marine or fresh water organisms. Garbage under this category is prohibited to be discharged at sea.
Segregating the waste requires effective management on board and alongside the new discharge regulations is a requirement for every ship above 100gt to have in place a garbage management plan and to carry a record book detailing all aspects of waste handling and disposal.
A ship’s garbage management plan should contain a list of the particular ship’s equipment and arrangements for the handling of ship-generated garbage, and may contain extracts from and/or references to existing company instructions and manuals. In addition, a crew member has to be designated as the environmental control officer responsible for maintaining records and arranging disposal.
Any garbage that cannot be disposed of onboard will need to be sent to a shore waste facility any may need to be segregated. The most appropriate procedures for handling and storing garbage will vary depending on factors such as the type and size of the ship, the area of operation, shipboard garbage processing equipment and storage space, the number of crew or passengers, the duration of the voyage, and regulations and reception facilities at ports of call.
However, in view of the cost involved with the different garbage handling options, it is economically advantageous first to limit the amount of material that may become garbage from being brought on board the ship and, second, separate garbage eligible for discharge into the sea from other garbage that may not be discharged in this way. Limiting potential garbage can be done by requesting shipchandlers to remove unnecessary packaging from supplies taken in ports.
Several companies provide segregation and compacting plant suitable for any size of ship, although on small vessels it should be quite easy for the crew to fashion something suitable themselves. Compactors, baling presses, shredders, and crushers, can reduce the volume of ship generated waste by up to 90%. That is significant if the cost of shore disposal is taken into account.
As an example of the technology employed in commercial systems, one (the EVAC system) waste that can be burned is separated and first macerated and then passed into a briquetting unit which operates at 150bar pressure. The resulting briquettes is claimed to reduce waste volume by a factor of 10. Each individual briquette is small and easily handled but together they have a density of about 550-600kg/m3. Both the macerator and the briquetting unit have a foot print of around 4m2 and between them can handle up to 5,500kg per day making them suitable for vessels with large waste streams. The briquettes can be burned in an incinerator onboard or disposed of ashore.