On a medium-sized cruise ship carrying roughly 1,500–2,500 passengers, guests and crew together create more than 715,000 gallons of waste per week. That includes sewage, oily waste and solids. Multiply that by the 310 ships in the Cruise Lines International Association (plus all non- member cruise lines), plus the heat and exhaust produced, and that’s a lot of waste.

Luckily, it’s not all pumping into the ocean. Cruise lines big and small have implemented waste management systems allowing them to turn onboard waste into onboard energy. On Holland America Line, for example, engine waste heat goes through a power evaporation system that helps turn seawater into fresh water for use throughout the ships, producing heated water for the galley, laundry, pools and hot tubs. With Aurora Expeditions, food waste — including scraps, peels and organic material — goes through onboard biodigesters to break it down into safe-to-release gray water. This process helps reduce the ships’ environmental impact by completely eliminating the need to store or incinerate food waste.

Additionally, an onboard reverse osmosis water system desalinates seawater to provide guests with fresh water in water bottle refill stations.

Royal Caribbean Group, the line sailing Icon of the Seas, the world’s largest cruise ship, aims for 100 percent landfill-free operations. Taking a cue from land-based waste-to-energy processes, both Icon and Silversea Cruises’ Silver Nova are now outfitted with microwave-assisted pyrolysis and micro auto gasification systems.

These collect food and organic waste matter from the ships, turn it into a product called synthesis gas, or syngas, and then use that to power the hotel facilities on the vessels. Royal Caribbean was the first line to adopt this syngas technology, though others are expected to follow — like Norwegian Cruise Line, which began investigating the waste-to-energy technology in early 2025.

Smaller ships aim to turn waste into energy, as well, just not yet on the ships themselves. EYOS Expeditions, for example, works with superyachts to reduce greenhouse gas emissions and instead directs the extra energy toward renewable power in developing countries.

And Ecuadorian line Ecoventura compresses all its waste into small recyclable packages so nothing goes to a landfill.