Marine Food Waste Solutions
With the implementation of the revised Marpol 73/78 Annex V regulations vessels are obliged to comminute food waste before discharge into the sea is allowed. Depending on vessels distance to shore, location and special area discharge of food waste, grounded or not, is allowed, restricted or prohibited.
Food waste disposers, grinders or macerators
Leftovers are a tough nut to crack. The composition of substances such as: bones, fish-skin, rice, pasta, vegetables and fibrious materials poses a challenge and is high in fat content and acidic nature. Food waste also decays rapidly by bacteria under higher ambient temperature causing odor and smells. Processing at the source such as: galley, scullery or mess is the most hygienic solution.
Food waste disposers, grinders or macerators are used to physically reduce food scrap to particle sizes below 25 millimetres for proper dispersion with seawater at discharge. Fresh water is used to convey the grounded food waste or slurry through vessel’s drain system for further processing, temporary storage or directly to overboard.
Most common installed are gravitational drain system, although ships with high waste volumes prefer vacuum operated systems, due to significantly lower freshwater consumption thereby reducing the volume generated and increasing the hold time of food waste tank.
Checklist
…to select/ install fit-for-purpose machinery:
- Size based on daily gen & isolation duration
- Sloped drain connection & pipe to tank/overboard
- By-pass or tie-in downstream grease separator
- Cast alloy rotor-stator grinder unit, +/- 2.0 kW
- Expected freshwater consumption: gravity vs vacuum based
- Steel quality AISI316 or higher is preferred
- Holding tanks: hot water flush & open flow path
- Tanks easy cleaning access port, inspection hole
- Extra aux flanges for up set conditions & dewatering
Requirements regarding food waste management according to Marpol Annex V
The regulations for the prevention of pollution by garbage from ships, clarified in the MARPOL Annex V, was revised and entered into force on January 1st, 2013. This Annex applies to all ships. The main changes in the revised MARPOL Annex V regarding discharge of food waste are as follows:
- Discharge for comminuted or ground food waste is allowed for distances
- Greater than three (3) nautical miles from nearest land outside special areas.
- Discharge for food waste (not comminuted) is allowed for distances greater than twelve (12) nautical miles from nearest land outside special areas.
- Discharge for comminuted or ground food waste is allowed for distances greater than twelve (12) nautical miles from nearest land inside special areas.
- Those “special areas” are – according to MARPOL rules – most European waters such as Baltic Sea, North Sea or Mediterranean Sea. The comminuted or ground food waste has to be able to pass through a screen with openings not larger than 25 mm.
- To fulfill this requirement, the installation of a food waste grinder will be necessary.
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