June 15, 2021

Cruise Ships Set Sail with Power Knot Biodigesters on Board

Food is part of the cruise ship experience—both for passengers and the crew. Providing the ample food choices required to meet the dining expectations of the passengers means that the crew inevitably will be handling some food waste at the end of each meal. Disposing of this waste has, in the past, has been one more challenge in addressing the environmental impact of cruise ships

As more cruise lines seek to green their operations, balancing sustainability, operation costs, and MARPOL regulations, food waste has presented an opportunity to make a major difference. After all, a ship with 6,000 people onboard can generate as much as 24 tons of wet waste—including food waste and bio sludge from wastewater treatment plants—each day. As much as 30% of food loaded on a ship can be wasted, and that presents a significant opportunity for cruise ships to clean up their plates and the seas.

Cruise ship food waste disposal rules

Until recently, ocean-going ships would reach international waters (12 miles out from any coastline) and dump sewage and other waste into the ocean, introducing bacteria, heavy metals, pathogens, viruses, pharmaceuticals, and other substances potentially harmful to human and aquatic life. Environmental rules have been updated to limit the release of trash into the ocean.

The International Convention for the Prevention of Pollution From Ships (MARPOL) sets the rules around trash disposal. In many locations, ground food can be discharged beyond 3 nautical miles (nm) from shore, while food that is not ground can be discharged beyond 12 nm from shore.

Ships operating within 12 nm of the coast might store waste onboard for disposal once the ship returns to port. However, managing that process can be expensive. What’s more, countries lacking organic waste disposal might still discharge untreated food waste near shore, contributing to the negative environmental impact of cruise ships. Worse still, food waste is not always so easily sorted out from other types of garbage. It’s one reason that Carnival Corp. and its Princess Cruises subsidiary were fined $20 million in 2019 for environmental violations, including dumping organic waste mixed with plastic into the ocean.

Ships of all sizes have options in how they manage their waste, but many are finding that having onboard biodigesters present benefits in not only breaking down cruise ship food waste but minimizing the labor and costs associated with disposal.

Food waste disposal options

Today, cruise line operators have more healthy options for managing food and other waste than they have in the past. For example, Royal Caribbean designed its Symphony of the Seas, the largest cruise ship to date, as a zero-landfill ship. Waste—from recyclables to food—is fully managed onboard. Scraps from the ship’s 36 kitchens are segregated into different buckets, and then loaded into a pipe leading to the ship’s hydro-processor. From there the cruise ship food waste is incinerated along with other certain types of garbage. However, the ship’s incineration room must be manned 24 hours a day by crew members. What’s more, incinerators are increasingly becoming restricted in coastal waters due to their emissions. The Marine Executive calls the incineration of food waste onboard “the least green option under the waste hierarchy” and a contributor to cruise ships’ negative environmental impact.

Viking Line, on the other hand, has adopted processes for converting its cruise ships’ food waste into biogas. Food and other biowaste is stored onboard until a ship docks, at which point an environmental management company collects the waste and transports it for processing. In 2018, the biowaste collected from three Viking ships produced a total of 98,550 cubic meters of biogas, equivalent in terms of energy to more than 111,000 liters of gasoline. While beneficial, this process still requires significant space onboard and carries costs for the transport of waste.

However, more cruise lines are turning to onboard biodigesters. These machines can boost the efficiency of waste disposal by providing centralized onsite food waste management. Food scraps can be added to the biodigester throughout the day, where microorganisms then efficiently break down waste through an aerobic digestion process. The equipment releases as waste a translucent, environmentally safe liquid.

Because it requires only one step, located right in the kitchen, to get rid of food waste, crew members can reduce the amount of time spent managing waste. In addition, biodigesters catch any small plastic or other non-organic waste, ensuring compliance with environmental regulations. Add to this the reduction in material being incinerated, and biodigesters can make a major impact on ships’ carbon footprints.

Why cruise operators choose Power Knot

There are currently hundreds of biodigesters operating on the open seas, but not all biodigesters are created the same. While biodigesters offer a wide range of benefits, it’s important to invest in the right solution for your specific needs.

Power Knot’s LFC biodigesters are available in marine models specially designed to withstand the harsh conditions at sea. The company’s biodigesters are built stronger than shoreside counterparts and with additional features specifically required for installation on ships ranging from super yachts to cruise lines. Leading cruise lines including Disney Cruise have chosen to use Power Knot biodigesters as a result of its solid construction, simple operation, and advanced analytics.

To discover why more kitchens are installing biodigesters to manage food waste, contact Power Knot today.

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