It’s nice to get away and head to the Caribbean, especially when its freezing cold here in NYC. But as I was enjoying my frosty beer and endless buffet, I started to wonder about the environmental impact of my trip. So, because I can’t help myself, I did a little research on the environmental sustainability of the cruise ship industry – with a particular focus on carbon intensity. Deep down I had a nagging concern that cruise ships might be awful for the environment. Bottom line: cruising is indeed very carbon intensive!
I just got back from a 7-day trip aboard the Norwegian Escape. Built in 2015 for €815 million, this is Norwegian’s newest and largest ship. It is 3.5 football fields long and ranks as the fifth largest ship in the world. The ship carries 6,000 passengers and crew. My week cruise included a 2,028-mile loop through the Caribbean.
The Escape is powered by five diesel engines with a total generating capacity of 76.8 megawatts (MW). These generators power the ship’s propulsion and provide electricity for all on board systems. It is basically a floating power plant. The 76.8 MW provides enough power to serve over 60,000 homes. As far as fuel choices, the ship burns heavy fuel oil (HFO) with a total capacity of 3,372 cubic meters. That works out to approx. 445,000 gallons per week of fuel consumed. HFO has a carbon intensity that is 78% of a coal-fired power plant. The fuel has a carbon content of 85% vs. about 65% for bituminous coal. For now, HFO is the predominant fuel used by the shipping industry (in the future, a switch to liquefied natural gas may be possible).
To figure out the carbon intensity of the trip, I calculated the carbon footprint per person per day and compared that to the national average. Per capita greenhouse gas emissions per day works out to 124 pounds (based on 2015 data). This includes emissions from all sources—electricity, transportation, industrial, and agriculture. HFO generates 26 pounds of CO2 emissions per gallon burned. That works out to over 5,200 metric tons of CO2 per week on the Escape. If we divide this by 6,000 people and divide by seven days, that comes to a daily average of 275 pounds. I estimate the 275 pounds daily average may be 15-20% below the cruise industry average to reflect the fact that the Escape is a newer and more efficient ship.
Lastly, we want to add the carbon footprint of the round trip air from NYC to Miami. It’s an 1,800-mile trip each way. Using the ICAO Carbon Emissions calculator, we estimate the round trip air at 700 pounds of CO2 per person. So, my weekly carbon footprint is 1.25 metric tons or 400 pounds per day (including food). That’s over 300% of the US per capita average! I feel a little bad about that but at least it’s only 1 week, not all the time.
Source: US EPA, Norwegian Cruise Line, www.engineeringtoolbox.com
As a final point, I was worried about how the ship handles sewage and other wastewater. In the past, ships have dumped raw sewage in international waters. While this practice may still exist in some instances, Norwegian has a state-of-the-art water treatment plant on board to process its sewage and grey water. The water is treated to “near drinking water standards.” According to the company's sustainability report, its newest ships have water treatment that exceeds international sewage regulations. Releasing this treated water at sea may seem somewhat dodgy but the ship’s water systems probably perform better compared to the 500 billion annual gallons of water treated by NYC’s sewage system and systems in other large cities.