By Amos Santiago (@hasantiago7)
Cruise Ships are the staple luxury vacation experience: all-you-can-eat buffets, island paradises, on-board commodities, all-day entertainment… However, beneath it all, lies an overwhelming amount of energy consumption and waste management to operate smoothly. These large cruise ships are practically floating cities navigating through the ocean, often in immaculate coastal waters and delicate marine ecosystems. Hence, they require the same management as a city (maybe even more just because they are literally floating over the largest ecosystem in the world). Furthermore, this global industry has been growing substantially from 17.8M passengers in 2009 to around 30M passengers in 2019.[1] Therefore, there is a need to shift this industry into a more sustainable enterprise if it were to avoid serious environmental impacts. This issue is broad and complex, although cruise ships generate around 0.2% of global CO2 emissions (this includes fossil fuel combustion and cement production)[2] and produce other gas pollutants, we shall be focusing on the impact generated by two of its liquid waste stream: oily bilge water and gray water.
This global industry has been growing substantially from 17.8M passengers in 2009 to around 30M passengers in 2019.
Oily Bilge Water
Bilge water is a mixture of water, oily fluids, fuel, lubricant, cleaning agents, engine fluids, and other components that end up at the bottom of the vessel from different onboard sources such as machinery leakage, cleaning, and spilling.[3] This waste mixture can either be contained in storage tanks and disposed in an onshore facility, or processed on board with an Oily Water Separator (OWS) and discharged into the ocean if the stream reaches a maximum legal oil discharge concentration of 15mg/L (U.S. EPA, 2008). This regulation applies to all marine vessels and it seems reasonable when the discharged volume is small; however, large cruise ships produce around 5 to 20 cubic meters (for those who don’t understand the metric system, this is about 1320.86 to 5283.44 gallons) of bilge water daily which translates to 75 to 300 grams (0.165 to 0.661 lb) of oil discharged daily assuming such cruise ship releases the maximum legal oil concentration of 15mg/L.[3] Of the oil released by the shipping industry (not just cruise ships), 25% is reported to come from spills and 75% from operational bilge water discharges.[4] Considering this issue, some experts believe that the legal maximum discharge concentration should be lowered and strictly enforced.
Large cruise ships produce around 5 to 20 cubic meters of bilge water daily which translates to 75 to 300 grams of oil discharged daily assuming such cruise ship releases the maximum legal oil concentration of 15mg/L.
Cruise ship companies are particularly notorious in violating oil discharge regulations. In 1999, Royal Caribbean Cruises Ltd. plead guilty in illegally dumping oily bilge water to 21 criminal counts by 9 of its ships across U.S. waters.[5] Engineers used a bypass pipe to discharge oily waste and falsify its discharge records in a company-wide conspiracy. Royal Caribbean paid a total of $27M in fines (a record for its time). In an attempt to redeem their reputation, today the company claims that they invested in technology to discharge oily bilge water at less than 5mg/L, which is 3 times less than the EPA’s maximum legal concentration.[6]
Carnival Cruise Lines has a long history of oil discharge violations. In 2002, the company pleaded guilty to discharging illegal amounts of oil by tricking the OWS sensor.[7] Engineers fooled the sensor by flushing clean water while the oily bilge was being discharged hence the sensor incorrectly read the actual concentration thus bypassing the separation unit. There was evidence that at one instance, they discharged a flow containing 104 ppm of oil. Moreover, the engineers falsified their logbooks. In this instance, they agreed to pay $18M in fines, which was less than 1% of their earnings from the six year period covering the plea. Despite this occasion, Carnival continued to dump oil illegally and plead guilty in 2016 with its Caribbean Princess Cruise Line. Oily water was discharged through a bypass pipe so-called the “magic pipe”.[8] The company was fined $40M, the highest of its kind! And if that wasn’t enough, in 2019, Carnival and its Princess line acknowledged violating its probation terms from 2016 by polluting the water around the Bahamas with plastic, falsifying discharge records, and interfering in court supervisions of ships environmental violation![9] They were fined an additional $20M with three more years of probation.
Engineers fooled the sensor by flushing clean water while the oily bilge was being discharged hence the sensor incorrectly read the actual concentration thus bypassing the separation unit.
Clearly, this behavior is not isolated incidences, but underlying criminal patterns. The reason for these violations was always constant: save money. The separation process of oil from water is an energy-intensive process and, in some cases, highly stable dispersed oil droplets in water make separation harder or even impossible using conventional techniques. But these companies can and should invest in better technologies (it’s not like they lack in the resources). Some companies, like Celebrity Cruises, changed their engines from diesel to gas powered to avoid diesel leakage into the bilge.[6] Other petrochemical fluids can be replaced by bio-based oils with better environmental profiles. Companies can even invest in research to understand how bilge water-oil mixtures form in the first place with the goal to minimize or prevent oil leakage and dispersion.
Graywater
Generally, graywater is the waste generated from sinks, baths, showers, laundry, and galleys.[3] So basically anything that does not have poop, toilet waste is considered sewage. A large cruise ship can generate from 36 to 119 gallons of graywater per day per person, on average 67 gallons per day per person. (U.S. EPA, 2008b) Curiously enough, cruise ships are not required to treat this discharged waste stream if they are traveling at least 6 knots at a distance between 1 to 3 nautical miles from shore or if they are in Alaskan waters. (U.S. EPA, 2008a)
A large cruise ship can generate from 36 to 119 gallons of graywater per day per person, on average 67 gallons per day per person.
Graywater can increase the nutrient content of the water which potentially leads to toxic algae blooms and disrupt the marine ecosystem. Graywater also contains detergents, which although some companies are required to be biodegradable, could bioaccumulate in marine biota and emulsify oil droplets. Alaska has fought to demand stricter regulations in their water because their coastal communities depend on marine life and water quality for their consumption and industry.
Another issue with greywater hasn’t been discussed in much detail in EPA regulations because it is not well understood but has been an emerging environmental issue: microplastics. Microplastics are those synthetic polymer materials that are between 5 micrometers to 100 nanometers in size. In general, these particles can either be primary or secondary microplastics, depending on its source.[10] Primary microplastics are commercially designed to that size, normally to be used as exfoliants for cleaning and cosmetic products, for example, microbeads. Secondary microplastics are those that degrade or shed from a larger source of plastic like the breakdown of macroplastic components to smaller bits or the shedding of polymer textile fibers like polyester. Microplastics can bio-accumulate in marine tissue and climb the food chain into human bodies. If plastics are untreated in the environment, they can further degrade with UV light to reach nanoscale sizes, called nanoplastics.[11] At the nanoscale, they could readily interfere in DNA. The effects of micro- and nano-plastics are still not well understood, much less their long-term effects.
Microplastics can bio-accumulate in marine tissue and climb the food chain into human bodies.
Graywater from cruise ships could be a significant source of microplastics in the ocean. Primary microplastics, like products containing microbeads, are banned from North America; however, microbead products are still used in other countries.[11] Although a cruise ship is from North America, international tourists can travel and use their products. These products might end up in the graywater stream and discharge into the ocean. Secondary microplastics can have a wider impact. Research suggests that large amounts of synthetic polymer fibers and filaments can shed from clothing and enter the wastewater stream through laundry cleaning washing machines.[12][13] Because cruise ship untreated gray water is often discharged, these companies are likely dumping significant amounts of microplastic textiles into the ocean!
Conclusion
This has come into the attention of experts and they are demanding regulation updates to address this issue. [14] Some are pushing for gray water treatment, however, conventional water treatments used in land are not effective in separating microplastics from the waste stream. [15] However, initiatives, such as one in Canada, are investing in designing new water treatment technologies for cruise ships to efficiently separate these microplastics from graywater.[11] But as we’ve seen from the past, technologies have to work hand in hand with policy to efficiently address the current environmental problems and shift the industry into one that is in harmony and respects the marine resource it aims to exploit.
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Email: hosea.santiago@upr.edu
Instagram: @hasantiago7
References:
[4] Alper, H., & Corp, P. T. (2004). Evaluation of IMO and Naval Type Bilge Cocktails. 1–9.
[6] Clancy, M.; Klein, R. A.; Terry, W.; Font, X.; Navarrete, M. G.; Bonilla Maria Jesús; Dowling, R.; Weeden, C. Cruise Ship Tourism; CABI: Oxford, 2017.
[10] https://sustainabledevelopment.un.org/content/documents/5854Marine%20Litter%20-%20Microplastics.pdf
[12] Kelly, M. R.; Lant, N. J.; Kurr, M.; Burgess, J. G. Importance of Water-Volume on the Release of Microplastic Fibers from Laundry. Environmental Science & Technology 2019, 53 (20), 11735–11744.
[13] Hernandez, E.; Nowack, B.; Mitrano, D. M. Polyester Textiles as a Source of Microplastics from Households: A Mechanistic Study to Understand Microfiber Release During Washing. Environmental Science & Technology 2017, 51 (12), 7036–7046.