3.1.1. Trends in the Management of Waste from Passenger and Cruise Ships
The frequencies of the different synonyms applied to food waste and greywater found in cruise and ferry ship operators’ webpages by using search engines (Google, Yandex, etc.) are shown in Figure 3
. Companies apply these synonyms in informative sections for any interested website visitors in order to exhibit the approach used for treating their ships’ generated sewage.
The results of information analysis for the data found on the websites of 27 ferry line companies revealed that most ferry operators (more than 70%) did not specify waste management in terms of efforts to reduce eutrophication through, e.g., food waste, sewage, or greywater. We discovered “food waste” or its synonyms in 11% of visited websites. Shipping companies applied the terms “solid waste” or “waste” in 26% of all cases. This type of waste could theoretically contain food waste. Shipping companies mentioned “greywater” in 19% of the websites reviewed. Shipping companies used “wastewater” slightly more frequently (26%) than the synonyms “food waste” (11%) and “greywater” (19%), as demonstrated in Figure 3
Ferry operators provide more detailed analyses on their websites in the case of “food waste” discharge to PRFs. Operators using the terms “waste” or “solid waste” emphasized the delivery of these wastes to the landfill.
A study of 36 cruise ship companies’ websites revealed that the term “food waste” was mentioned more often than by ferry operators. “Food waste” was found on 33% of cruise ship websites, while in 22% of cases “waste”/“solid waste” was mentioned, which may also have included food waste. Furthermore, about 47% of cruise companies used “sewage” on their websites, while 39% of cruise ship operators selected the synonym “greywater”. Only five cruise companies applied the term “wastewater”.
The further analysis found that 12 cruise ship operators used “food waste”. Of these, more than half had indicated disposal of food waste at sea, either as the only applied food waste management scenario or in combination with discharge to the PRFs at port or incineration. Four operators also mentioned combined incineration and discharge to PRFs. One of the assessed cruise ship operators described food waste dehydration into a compact form and delivery to the port for further processing.
Cruise ship operators using the terms “waste”, or “solid waste” were analysed separately. Six of the eight operators reported waste discharge to PRFs and two of them performed waste incineration. In addition, one of the cruise ship operators compressed the waste before releasing it to PRFs. Finally, one of the reviewed cruise ship operators mentioned waste treatment but did not provide a detailed characterization of the process.
3.1.2. Trends in Ships’ Waste Management
The food waste management survey involved 42 respondents whose work on board was basically or partially related to food waste handling for the galley. We recorded respondents’ answers in accordance with the confidentiality agreement. Of the respondents, 8 worked as cooks and 22 as cook assistants. Furthermore, 12 cook assistants identified themselves as cadets in the period from 2019 to 2020.
The respondents of the survey worked or had worked on different types of ships during the survey period. In total, 20 respondents were active sailors on tankers and 7 worked on tankers before the period of the survey. In addition, three respondents worked on general cargo ships and five respondents worked as cadets on general cargo ships. Seven respondents worked on passenger and cruise ships, i.e., five respondents worked on passenger ships and two on cruise ships.
We divided the questionnaires into three groups before statistical data processing and analysis. The first group consisted of the answers from 23 respondents who worked on transport ships and the second group consisted of the responses from 12 respondents (cadet cook assistants) from transport ships as well. The third group consisted of seven respondents who worked on passenger and cruise ships.
Responses to the question “When is the food waste treatment on board?” were as follows:
The obtained responses revealed the different food waste management strategies on board ships, as demonstrated in Figure 4
a–g. In addition, the management strategies were affected by the specific situations in which the vessels may have been during voyages.
The 17 respondents of the first group and 5 respondents from the second group indicated the answer “food waste discharged into the sea” for the case in which ships were sailing in the open waters of the Baltic Sea area (further than 12 NM from the shore), as demonstrated in Figure 4
a. Furthermore, six respondents from the first group and four respondents from the second group indicated the response “food waste was shredded through a disperser, mixed with greywater and discharged into the sea”. Three respondents from the second and seven respondents from the third groups marked the answer “food waste collected and delivered to the PRFs”. As the respondents from the third group noted that “food waste was collected and discharged to the PRFs”, they were excluded from the rest of the survey.
Seventeen responses from the first group and seven responses from the second group indicated “food waste collected and stored” with regard to a described situation of a vessel being located close to the shore, as demonstrated in Figure 4
b. Finally, six respondents from the first group and four respondents from the second group indicated that “food waste was stored in containers” but one respondent selected “other” without any additional explanation.
Seven respondents from the first group and four respondents from the second group indicated “food waste collected and stored”. One of these respondents also indicated that “food waste is stored in a container” when the vessel is anchored in the port, as demonstrated in Figure 4
Sixteen respondents from the first group and seven respondents from the second group chose “other”. In total, 14 respondents from the first group and 7 respondents from the second group added an explanation:
Thirteen responses—“food waste was stored, sorted, and incinerated”;
Six responses—“food waste was sorted, compacted, and incinerated”.
Two respondents indicated that “food waste was sorted and treated” but did not provide a detailed explanation, as shown in Figure 4
We concluded that all the interviewed respondents who had worked in the transport fleet during or before the survey applied discharge into the Baltic Sea in terms of the food waste management practice described in MARPOL 73/78. In addition, seven respondents working on passenger and cruise ships indicated that food waste was collected and discharged to PRFs.
Food waste can also be collected and incinerated outside territorial waters in order to meet the MARPOL 73/78 requirements for the Baltic Sea area. Ships visiting a port in the Baltic Sea region pay a sanitary fee at a specific rate. The cost depends on the type of ship and the gross tonnage and includes payment for specified waste reception services [20
]. For example, the Freeport of Riga determines the sanitation fee for 15 m3
of waste as defined in MARPOL Annex V [21
]. The shipping company must pay the presented cost independently of the fact of discharge. The payment for waste increases in accordance with the tariff defined by the service provider for cases that exceed the default limit. In addition, transport vessels have a higher sanitary fee compared to passenger and cruise ships.
The results of further analysis of the questionnaire indicated that respondents worked on transport vessels with crews of over 20 crewmembers. Seventeen responses from the first group and five responses from the second group stated that “food waste was discharged to sea”; therefore, the question, “How often is shredded or ground food waste discharged into the sea?” was additionally asked, as demonstrated in Figure 4
Sixteen respondents from the first group and four respondents from the second group indicated that the discharge of mostly shredded or ground food waste into the sea occurred once a day. One respondent reported that such an activity occurred twice a day. The first group of respondents acknowledged that the frequency of food waste discharge differed due to visits to ports in which operators discharged all waste (including food waste) to PRFs.
The following question, “Approximate amount of food waste discharged into the sea each time,” allowed us to clarify the approximate amount of food waste discharged into the Baltic Sea. The answers offered varied within the range of a few kilograms, as shown in Figure 4
The obtained data indicated that 10–15 kg of food waste is generally disposed of at sea each time.
Both the group of respondents who had previously indicated that “food waste was discharged at sea” and those who indicated that “food waste was stored in a tank, mixed with greywater and discharged into the sea” answered the question, “How often was the food waste shredder used (if installed)?” with the answer that the “food waste shredder is operated once a day”, as shown in Figure 4
g. Two respondents indicated that the food chopper was operated every two days. However, nine respondents chose a different answer, explaining that the shredder was used when necessary.
Generally, the responses obtained revealed that the food shredder was frequently used on board transport vessels for daily purposes.
The ten respondents who had previously stated that “food waste was stored in a tank, mixed with greywater and discharged into the sea” received the following question: “How much food waste is ground during the day?” The answers from these respondents varied within a range of a few kilograms. We would like to emphasize that none of the respondents marked the weight range of ground food waste from 1 up to 3 kg per day. The principal amount of ground food waste reported by the seven respondents ranged from 3 to 5 kg. Three respondents from both groups indicated that the amount of food waste ranged from 5 up to 10 kg. Also, none of the respondents chose the option “other” as the answer. Thus, the data show that the predominant amount of ground food waste stored in the tank and mixed with greywater before discharge into the sea was significantly lower than the amount of food waste discharged into the sea itself. Finally, we asked the concluding question: “Are there other methods used in the management of food waste on board that are not mentioned in this survey?” Five respondents from the first group indicated that “due to disposal restrictions or due to sanitary difficulties, food waste is placed in a room where it is cooled or frozen”. However, the other 30 respondents indicated that operators did not apply other food waste treatment or disposal methods on board vessels.