*Article* **The Analysis of Social and Situational Systems as Components of Human Errors Resulting in Navigational Accidents**

**Lech Kasyk 1, Anna Eliza Wolnowska 2, Krzysztof Pleskacz <sup>3</sup> and Tomasz Kapu´sci ´nski 1,\***


**Abstract:** As in any industry exposed to risk, human and organizational factors are the main stakes of maritime safety. Understanding the causes and risks of maritime accidents is integral to the sustainability of shipping. The investigation of marine accidents is a crucial tool for their identification in areas related to operations and ships, including social and situational systems, their design, and technical systems. The authors conducted a cause–effect analysis of marine incidents. For this purpose, case-by-case analysis and an Ishikawa diagram were used, which is a tool that helps identify actual or potential causes of accidents. The study showed that by far the most significant cross-section of causes of accidents were elements of social and situational systems that affect the safety of the ship, crew, and environment. The least significant contribution came from the machinery area. Through the detailed descriptions, a picture emerges not so much of a lack of knowledge of the regulations as of a failure to comply with existing procedures or best practices. In the authors' opinion, more emphasis is needed on preventive measures, including safety culture, training, competence assessment, and increased awareness of the need for sustainability.

**Keywords:** safety; social systems; situational systems; navigation; sustainability; marine accidents; Ishikawa diagram

#### **1. Introduction**

As in any risk-prone industry, human and organizational factors are a vital component of maritime safety. In most professional analyses carried out by authorized bodies, the human factor is important, if not the most important, out of the numerous factors leading to accidents. To reduce the number of adverse events, intensive research is carried out to identify their causes. Instructions, recommendations, regulations, and so-called checklists are developed. All these activities are intended to lead to the detailed development and strengthening of a safety culture [1,2], a term that first appeared in a preliminary report by the International Atomic Energy Agency (IAEA) after the Chernobyl disaster [3]. The early investigation into the accident initially focused on deficiencies in the power plant's design. However, more detailed analyses also pointed to problems with managerial and social and situational systems problems. Safety culture's primary objective is focused on creating and promoting certain habits among employees, following dedicated procedures in the work environment, paying special attention to any shortcomings, being cautious of any inconsistencies within equipment handling, and regarding other employees' labor. Similar aspects exist for shipping that are related to professions in general and, as per this article, its specific element, navigation. People working in the marine industry selected for interviews by Teperi [4] claim that safety culture has been shaped based on regulations and principles application.

**Citation:** Kasyk, L.; Wolnowska, A.E.; Pleskacz, K.; Kapu´sci ´nski, T. The Analysis of Social and Situational Systems as Components of Human Errors Resulting in Navigational Accidents. *Appl. Sci.* **2023**, *13*, 6780. https://doi.org/10.3390/ app13116780

Academic Editors: José A. Orosa and Atsushi Mase

Received: 17 March 2023 Revised: 28 April 2023 Accepted: 26 May 2023 Published: 2 June 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Beyond safety culture, there are several formal international organizations that regulate the organization of maritime labor, with safety as one of the main goals. In order to improve safety across marine areas, The International Safety Management Code has been established, with hopes that an introduction of this ISM code will directly lead to the significant upgrade of safety culture [5].

On top of formal organizations, multiple ship safety procedures are subject to detailed regulations. Their lack or omission usually results in death, pollution of sea and land areas, and damage to the cargo or ship.

Current literature and use cases, e.g., official incident reports, treat the human component in a holistic way as one of the reasons for sea incidents and accidents, next to, for example, hydrometeorological conditions, mechanical failures, or force majeure [6]. They analyze human element subcomponents in a very general way, investigating so-called social and situational systems. These approaches, while having several advantages and being described in multiple sources, due to their general nature do not allow for the detailed analysis of specific root causes of sea incidents and are not suitable for improvement programs, neither for current control procedures nor for screening procedures performed on the ship. They can neither be used directly in marine educational units nor in training programs within STCW centers.

The objective of this research is to build a multilayer taxonomy of isolated and defined elements as components of the human error category, which is one of the main factors behind marine incidents. An investigation was performed that included a review of subject matter literature, analyses of individual cases, and a weighted Ishikawa diagram. The authors also performed a qualitative analysis of selected cases of several various sea accidents, followed by qualitative and quantitative analyses of incidents causes performed using a modified hierarchical Ishikawa diagram, comparison matrix, and stratification analysis. The analysis led to an isolation of key causes of human error which, as already mentioned, is a main factor in marine incidents. This work represents an innovation of how one can investigate the human component as a cause of marine incidents. Examining individual factors such as air quality or perceived pain allows educational and training institutions to modify their programs and focus on top key incident contributors.

#### **2. Marine Safety in Relation to Human Errors and Their Root Causes: Background, Literature Review and the Concept of Social and Situational Systems**

#### *2.1. Marine Safety as a Goal of Formal Organizations*

Safety is one of the primary goals of multiple organizations around marine space. The most prominent one—The International Maritime Organization (IMO)—has adopted Resolution A.850(20), defining its vision, principles, and goals for the human element [7]. It was updated by Resolution A.947(23), which was adopted in 2003 [8] and assumes that human factors are a complex, multidimensional issue that impacts maritime safety, security, and marine environment protection. Additionally, effective remediation following maritime casualties requires a solid understanding of the human factor's contribution to causing accidents; that adequate safeguards be put in place; that rules and regulations are simple, clear, and comprehensive; and that communication is flawless. It also recognizes that crew endurance is a function of many complex variables, including personal knowledge, management principles, cultural factors, experience, training, professional skills, and work environment. The resolution has several objectives:


Thus, not only is the human factor being recognized as a key contributor to marine safety but there is also an understanding of how much culture can influence the practical application of formal rules. Another essential organization regulating maritime labor is the International Labour Organisation (ILO). Together with the IMO, they attempt to solve problems regarding the human factor in the marine sector. The result of this cooperation is the Seafarers' Employment Agreements from 2006, updated in 2016 [9,10].

Other organizations, such as the International Association of Ship Classification Societies (IASCS), are also contributing to improvements in safety on all ships by introducing their set of rules, regulations, and requirements. Also worth mentioning is the International Safety Management (ISM) Code, one of the most robust tools to prevent human errors in shipping, adopted by the IMO by Resolution A741(18), which became effective on 1 July 1998 as Chapter IX of the SOLAS Convention on the management of the safe operation of ships.

Every country has its own framework for ensuring that accidents are analyzed and learning applied. In Poland, for example, the body investigating the causes of incidents is the State Marine Investigation Commission (SMAIC), while in the UK, it is the Marine Accident Investigation Branch (MAIB). However, despite the ongoing detailed inspections of all ships sailing on the seas and oceans, and the detention of non-compliant ships, accidents happen almost every day due to the failure of safety mechanisms, and their number must be reduced. As systems improve, new and convenient technologies are introduced, resulting in excessive human reliance on them. [11]. Unfortunately, safety management systems are often over-regulated, too detailed, and too time-consuming [12]. Sometimes, such procedures are difficult to apply in real life, with multiple conflicting priorities around timeliness, cost, and efficiency [13]. While good practices exist to improve safety on every vessel, it is a common practice in the marine industry to purchase a standard, off-the-shelf safety management system designed and developed for a certain group of vessels or companies. This makes safety audits easier on the one hand, but these systems sometimes do not match the specific profile of a given ship [14,15]. For many seafarers, managing safety is an additional workload (documentation, procedures) requiring their concentration and distracting them from delivering their basic tasks [16,17]. Some researchers claim that managing safety takes time and may decrease seafarers' levels of concentration [18]. As displayed in multiple publications [19–21], safety procedures across many industries have been evaluated as too complex and requiring documentation that is too broad, which in itself could potentially lead to incidents. This leads to the conclusion that simply having formal organizations, regulations, and documented practices might not lead to an increase in safety. The marine industry must more actively adopt a safety culture by better analyzing past incidents and driving improvements to educational and training programs.

#### *2.2. Human Errors as Causes of Incidents*

Every marine accident may have one or more causes. More than one accident may be associated with one incident. The five categorized causes are human action, system or equipment failure, other agent or vessel, hazardous material, and unknown. Each accident can also have one or more contributing factors, which are divided into three main categories: external environment, shore management, and ship operation. Studies have shown [21] that human error contributes to the following:


Contemporary sources [25] show the following breakdown of accidents and contributing factors:

• Cargo ships—in more than 80% of cases, the human factor was the leading cause or at least a component.


As shown in Figure 1, considering the 67.1% of human action in the basic breakdown of accident factors and the corresponding human–related percentages in the groups of: system/equipment failure, other agent or vessel, and hazardous material, there is in total more than 81% impact of the human factor on causes of accidents. It is evident, that the human factor is a direct or indirect cause of almost all marine accidents; thus, a proper analysis of the components that influence such errors can positively influence safety at sea.

**Figure 1.** Tree of events of contributing factors to accidents. Source: own study based on [25]. H— Human behavior, E—Environment, R—Rules, procedures, and training, T—Tools and equipment.

#### *2.3. Review of the Literature*

A lot of documented research on the influence of the human factor on marine accidents is based on modelling techniques and focuses on the identification and quantification of the probability of human and organizational errors [26–29]. The HFACS method, being widely used, defines four cause categories: organizational influence, insufficient supervision, initial conditions for risky actions, and risky actions. In order to solve defined problems from a marine area, Chen et al. [30] proposed the HFACS—Maritime Accident (HFACS—MA) method. It uses a SHEL model, which stands for Software (S), Hardware (H), Environment (E), and Liveware (L), to describe initial conditions in a traditional HFACS environment. Another method based on a similar idea, HFACS for passenger vessels (HFACS—PV), has been proposed by Ugurlu et al. [31]. It treats operational conditions as a new HFACS category. The authors of this method believe that operational conditions are not a hidden fault but rather a result of a higher-level component that then leads to the accidental results of dangerous actions. Another modification of the original method is HFACS Fuzzy Cognitive Mapping (HFACS—FCM), proposed by Soner et al. [32], where a fuzzy cognitive map is used to identify and quantify definitions of causes that are initiated in HFACS. It is mainly used to strengthen organizational safety measures for fire accidents and collisions [33]. Other documented techniques that are a modification of HFACS include FAHP [34] and ANP [35], which use a process of fuzzy analytical hierarchy to identify causes contributing to HFACS; HFACS and Chi-square test [36]; HFACS and FTA [37]; and fuzzy FTA, ANN, and HFACS [38].

Another source [39] shows that human-related factors play a significant role in shipboard accidents. For example, in 2020, 63% of accidents were caused by human error and 37% of accidents had a technical cause. Therefore, this problem should still be presented and possible solutions proposed; all components of a ship's operation should be carefully analyzed, cataloged, and broken down into specific parts along with their source and a set of recommendations provided on how to counteract their negative effects on the safety of life at sea. An essential element is social and situational systems [40–42].

Looking further into significant causes of marine accidents, refraining from proper visual observation, over-reliance on GPS, fatigue, commercial pressures, and distraction are other significant causes of accidents. In an archive issue of The Navigator, David Patraiko, project director at The Nautical Institute, argued that new technologies and changing regulations can generate unknown direct causes of accidents [43]. A similar analysis can be found in another report from Acejo [44].

Nevertheless, shipping has maintained a long-term positive safety trend over the past year. Still, the recent COVID-19 pandemic and Russia's invasion of Ukraine are major impact factors on global supply chain routes and capacity that have placed enormous stress on the system, with potentially detrimental outcomes: loss of life, loss of ships, exacerbated crew crisis, trade disruption, sanctions burden, and increased cost and reduced availability of bunker fuel. The main places of incidents are Southern China, Indochina, Indonesia, and the Philippines. The increasing number of costly problems may be associated with manning larger ships, the challenges of port congestion due to the shipping boom, and managing ambitious decarbonization goals. Port congestion puts pressure on crews and facilities, meaning there is no room for complacency [43]. Additionally, the increased use of non-container ships to carry containers, despite bulk carriers not being designed to carry containers, can affect their maneuverability in bad weather, and crews may need assistance in responding appropriately to incidents.

All the mentioned components result in a situation where crew demand is high; however, many skilled and experienced seafarers are leaving the industry. A serious shortage of qualified staff is expected over the next five years. Among those who remain, morale is low as commercial pressures, cargo operations responsibilities, and workloads are high. This work situation is prone to error, with 75% of incidents involving human error, according to an AGCS analysis [45].

A Dutch study of 100 victims of navigation accidents [46] showed that the number of causes of accidents ranged from 7 to 58, with a median of 23. Therefore, half of the accidents had 7–23 causes and the other half had 23–58. Sometimes, small things go wrong or small mistakes may seem harmless. However, when these seemingly minor events come together, the result is a casualty. The study found that human error contributed to 96 of 100 accidents. In 93 accidents, there were multiple human errors, usually by two or more people, each making approximately two mistakes.

The key finding was that each human error was identified as a precondition for accidents. This means that if only one of these human errors had not occurred, the chain of events would have been broken, and the accident would not have happened.

There are many demanding aspects of shipping, such as the inability of employees to leave the workplace, extreme weather conditions, long periods away from home, and workplace traffic. Some of these are immutable and reflect the nature of the field. Sometimes, very ordinary situations, such as using the toilet, lead to a procedure breach (rest hours) when, for example, there is only a captain and an officer on duty on board the ship.

Nonetheless, it is possible to modify, supplement, and introduce new strategies or interventions to reduce the impact of these factors on the health and well-being of individual seafarers [47].

Maritime transport has a safety level that is comparable to rail transport and much higher than road transport. In the case of passenger transport in Europe, the risk of a fatal accident is estimated to be 1.1 for road transport and 0.33 for ferry transport [48]. In this context, accident risk and, more precisely, the place of the human factor in this risk, are central issues. Indeed, the human factor appears to be the leading cause of accidents at sea [49]. Among the factors that contribute to incidents are productivity loss (fatigue, stress, health problems), insufficient technical and cognitive skills, insufficient interpersonal competencies (communication difficulties, difficulty in mastering a common language), and organizational aspects (safety training, team management, safety culture) [34,49]. Following this, the article "On your watch automation on the bridge" took a closer look at issues of human–machine collaboration and the role of automation in marine accidents [50]. In the case of a collaborative crew or team, a shared mental representation is one of the key elements behind every safe action. Methods developed in cognitive psychology to analyze this mental structure can be used to assess its impact [51] on crew performance. A study of this type was conducted some years ago [51]. However, as presented in [52], this research remains marginal in maritime transport. Since human error (and usually multiple errors by multiple people) contributes to most marine accidents, preventing human error is essential to reduce the number and severity of maritime accidents. Many types of human error have been described, most of which are not the fault of the human operator. Instead, most of these errors occur due to technology, working environments, and organizational factors that do not account for the capabilities and limitations of the people interacting with them, thus setting up the operator for failure.

In general, there are ways to prevent some human errors or at least increase the chance that such errors will be noticed and corrected by improving the safety culture through better education and training for the better analysis of human factor causes of accidents. As such, we can achieve greater safety at sea and fewer casualties. Summarizing the available data, in the years 2014–2020 there were 6921 injuries, which corresponded to 6211 incidents, and crew members accounted for 81% of the victims [53]. These numbers are very high and should be a call to action for the marine industry.

#### *2.4. Social and Situational Systems*

To fully describe social and situational systems, it is first necessary to understand what the human factor is—the interaction of humans with the environment and such human behavior that results in an error [54]. Attention must be paid to the cause effect relationship that contributes to an accident, and that the behavior of the people involved need to change to improve the whole system in the future and reduce the number of accidents [55]. People management must be constantly being improved to prevent errors.

Social systems can be defined as complex entities, i.e., interrelated elements linked by a relationship and interacting with each other. They are separated from the external environment by a clear boundary. The most important factor of such a system is people, without which, it cannot function, let alone exist [56]. Elements of the social system, such as social pressure, role, or life stress, are prevalent in a seafarer's work. Their common denominator is stress, i.e., a reaction responsible for the equilibration of the organism as a result of disturbing external stimuli. This manifests during unusual events or situations not previously encountered. Stress harms the functioning of a person in various spheres of their life and can also cause a deterioration in health. It is essential to realize that anxiety will never disappear from a person's life; it cannot be eliminated in any way. The average individual only focuses on its adverse effects, but what is usually overlooked is that stress, when controlled, can be a factor in self-improvement.

Social pressure exists in every society. In the case of a ship's crew, a certain attitude, behavior, or mindset is expected from the employee [57,58]. How they cope with this type of pressure depends on their mental state. It will be more stressful for some and for others less so. An example of social anxiety on a ship could be the shipowner's expectations of the captain, e.g., punctuality, or the chief officer's expectations of other seafarers, e.g., to complete a task quickly [59]. As competence increases, so does one's responsibility for the ship and less competent staff. The consequences of poor decisions made under stress can result in an accident or disaster. The essential skill, in this case, is to focus on solving the problem that has arisen and treating it as a challenge rather than on minimizing the stress

caused by a problematic situation. In the case of life pressures, there are situations such as the death or illness of a family member, divorce, personal injury, loneliness, and risk of redundancy. These events usually cannot be influenced or changed; thus, adapting to a new situation is complex. With the intense emotional impact of such stress, a person can experience physical and psychological disorders [60] (Figure 2).

**Figure 2.** Mental factors that affect a person when working on a ship. Source: own study based on [61].

The situational system is the collection of individual factors that affect a person in a given environment and contribute to mistakes, such as employee fatigue during watch work, long physical work, perceived pain, and arduous hydrometeorological conditions. A tired worker is much more likely to make a mistake. These elements are interrelated to a greater or lesser extent [61].

Environmental stress occurs when the place where one works or lives is not organized correctly. Some external stimuli can cause this type of stress, such as air quality (dust, smells, allergic reactions); temperature (tropics or polar zone—high temperatures cause a decrease in employee efficiency and low temperatures increase drowsiness and decrease concentration, which affects one's ability to think quickly and logically and perform tasks flawlessly [62]); noise (operation of the main engine, navigation in ice); lighting (the polar night and tropical zones can cause eye pain and increase worker fatigue or feelings of drowsiness); and order in the room (personal space, the intrusion of others into one's living space when they are currently resting, constant intrusion, rocking of the ship, feeling physically threatened). The last example can be particularly stressful for people with seasickness. Even in the cabin, the rocking effect of the vessel can cause significant stress and discomfort. All this can lead to a deterioration in the quality of work and the possibility of mistakes [63].

There are also ergonomic aspects, such as repetitive tasks, hand strain, uncomfortable posture, vibration, and noise, which significantly affect the efficiency of the work performed and can cause adverse effects on human health. For example, repetition of the same activity can lead to monotony and fatigue. Continuous work with an uncomfortable posture can cause fatigue, discomfort, and pain. Vibrations from hand-held devices, such as electric and pneumatic hammers, grinders, and drills, can cause various types of diseases and damage to hand structures as well as fatigue, irritability, insomnia, and coordination problems [64,65]. These components that affect people at sea are pictured in Figure 3.

**Figure 3.** Physical factors that affect a person during work on a ship. Source: own study based on [61].

#### *2.5. Ship Safety: Training in Social and Situational Systems*

Training centers, universities, and schools related to maritime work teach the subject of Ship Safety, which is required by STCW and aims to provide knowledge of international and national regulations in which a ship's safety in various operating conditions has been addressed and to develop students' skills to apply them in hazardous conditions. The syllabus discusses the formal and process frameworks of the safety aspect, i.e., the regulations, organizations, processes, and procedures that are key to those in command of vessels and crews. However, a careful reading of post-accident reports shows that accidents are often caused not by a lack of knowledge of the regulations but by a lack of appropriate behavior. In one case, the commanding officer of the high-speed passenger ship, Express 1, undoubtedly knew the relevant rules, regulations, procedures, and laws. However, pressure from the shipowner—not explicitly stated, but hanging over the vessel in the form of a strict timetable—resulted in dealing with many issues simultaneously. This resulted in the commander being preoccupied with these activities instead of concentrating on navigation and steering in conditions of minimal visibility, leading to a collision with the Baltic Condor. The authors believe that both the captain and the second person at the helm of Express 1 would have been able to correctly apply radar noise reduction in calm conditions and consider the echo's potential position on the course dash. However, a flurry of tasks not directly related to steering in dense fog at very high speeds of more than 30 knots caused the echo of another craft on course to be overlooked, and a collision ensued [66].

When using any means of transport, accidents are inevitable and happen because of errors, with lasting consequences. Social and situational systems consider 12 types of effects of maritime accidents:

	- The collision resulted from a lack of watchkeeping on the vessel *m*/*v* Ulysse and an unreasonable anchoring position by CSL Virginia.
	- On the *m*/*v* Ulysse, the lack of proper observation was due to the lack of involvement of the officer on watch, who was occupied with his mobile phone. He was sitting in front of an unusable radar, depriving himself of the opportunity to make observations and correctly assess the situation. Using a second operational radar would have given him all the information he needed to evaluate the situation. Moreover, the place where he was sitting was lowered, which did not allow him to see the horizon line correctly.

• COLERG procedures and regulations were not carried out on both vessels.

The situational factor was the main component that caused the collision. There were other factors involved such as boredom, routine, and monotony associated with the length of periods at sea, which certainly affected the commitment of watch officers to their duties [67].


surrounding waters and a long stretch of beaches, and the ship sank. There were undisputed social and situational errors [72].

	- The control system was not fully commissioned before its use.
	- The company's internal project management systems were not fully utilized.
	- Communications and reporting lines within the project team and with offshore and onshore management were neither fully utilized nor understood.
	- Design intentions and pre-commissioning requirements for the safe operation of the new equipment had not been adequately communicated to the work team.
	- There were no secondary means of securing the active cursor.
	- A decision was taken to work under the cursor. The hazard of working under a suspended load was not recognized as it was not a typical load suspended from a crane [77].

This again describes an unfortunate set of errors triggered by situational and social systems.

	- Explosions, suffocation, and hypoxic-ischemic encephalopathy caused by hazardous and noxious fumes and gases.
	- Crushing while bunkering or mooring with a tug.
	- Trips and falls due to cluttered decks and workspaces [78].

It is evident from the above types of marine accidents that worker and operator errors play a significant role in causing accidents. Investigating a marine accident helps narrow down the actual cause of the accident, which helps those claiming damages assert their rights with absolute clarity. Some authors believe, however, that the complexity of causes of marine incidents and the lack of unified procedures for reporting such incidents makes it difficult to discover the real reasons and factors behind them [79].

#### **3. Materials and Methods**

The unique case method and a weighted Ishikawa diagram were used to address the complexity of the problem of the influence of social and situational systems on human error and, consequently, marine accidents considered in this paper.

The unique case method is dedicated to analyzing a specific single phenomenon, event, or person. For example, a special occasion or character can be studied in this way regarding the situation in which the object under study operates. This method is sometimes referred to as an individual case study. This method is often used to characterize an unusual case, often deviating from the norms commonly observed by society. It is widespread in the sciences, based on the analysis of specific issues, through which researchers can determine the causes of a situation. Thus, it has applications in medicine, law, environmental protection, and safety [80]. Using the unique case method, one can gain the necessary knowledge about a situation and obtain conclusions indicating whether a viable solution is possible. It is undoubtedly impossible to generalize based on research using the unique case method. Therefore, the results obtained in this way can only be applied to a select group. Given the above, the authors decided to use the following research methodology:


#### *3.1. Analysis of the Causes of Maritime Accidents*

The first use case worth highlighting in a discussion about marine incidents is the case of fishing. In just one region, commercial fishermen sail across the Gulf of Mexico in almost all weather conditions as commercial pressure grows. It is a physically demanding and dangerous job, and, unfortunately, some fishing boat owners disregard job safety. Every year, commercial fishing boat crew members die in preventable accidents. Over 10 years, 116 commercial fishermen died in the Gulf of Mexico alone, many due to falling overboard and injuries sustained onboard. Commercial shrimpers were involved in an alarming number of fatalities as well, with many more injured. This is an evident effect of negative social and situational pressures [81].

The Neva accident was the next to be examined regarding the social and situational system elements involved. The vessel departed from the Szczecin ship repair yard with a pilot on board and the assistance of a tugboat. It was heading to the Szczecin-Swinouj´ ´ scie waterway to head for Riga. The tug was slowed down as it passed Huta quay. While attempting to increase the vessel's speed, it was noticed that the main engine was not working correctly. After some time, the engine stopped working, and the vessel lost speed. The ship was forced to leave the fairway and drop anchor. The senior officer on the bow

supervised the anchoring maneuvers. The captain instructed him to throw one shackle of the chain. However, he executed this instruction incorrectly and threw more than two shackles. The additional 30 m of chain released contributed to the vessel partially running aground. At the same time, the ship's captain and pilot did not pay attention to the ship's position and the fact that it was not positioned with its bow to the wind. Their subsequent actions were based on poor judgment of the situation, related to the initial lack of communication between the navigation bridge and the bow position, leading to the ship running aground [68]. In analyzing the accident, it was found that the social system had an impact here. One of the two elements of this system that occurred in the described accident was social pressure; the master and the pilot did not obtain explicit information from the senior officer from the very beginning that he had made a mistake and the ship was not where it should be; thus, they made decisions chaotically and under pressure based on a misunderstanding of the situation. The second element was the role played by the senior officer on the bow. A person in such a position is expected to have the appropriate competencies, such as good situational awareness, quick responses, and proper communication skills to relay any relevant factors affecting maneuverability, including the immediate communication of an erroneous command.

The third accident investigated for the presence of social system elements was that of the ships Corvus J and Baltic Ace. Both ships had officers of Polish nationality on navigation watch. Corvus J was sailing from Scotland to Antwerp, Belgium, while Baltic Ace was leaving Belgium from the port of Zeebrugge to head to Finland. At some point during the voyage, the watch officer on the Baltic Ace vessel spotted the vessel Corvus J on the radar; it was about to pass within one nautical mile, and there were no vessels in the vicinity threatening safe passage. The ship Corvus J made a slight turn to the right, which prompted the officer of the watch on the vessel Baltic Ace to call the vessel on very high frequency (VHF) radio to understand its intentions and advised that it would alter course slightly to the left to increase the distance between the vessels. In the meantime, the vessel Corvus J again made a turn to the right and the Baltic Ace to the left. As the distance between the vessels decreased and the dangerous situation developed, it became increasingly difficult for the watch officers to communicate via VHF radio. The actions they agreed with each other during the conversation did not coincide with the actual steps, which resulted in the collision of the two vessels and the sinking of the vessel Baltic Ace [82]. Analyzing the accident studied, it was concluded that one element of the social system influenced the occurrence of the accident. Social pressure significantly impacted the course of events in this case. The watch officers of both ships attempted to communicate in English. However, their communication became increasingly incomprehensible to the other party under the influence of the developing dangerous situation. Actions that were agreed upon using VHF communication should have been followed. Under pressure and confusion, decisions to change course were taken chaotically and without analyzing the situation.

#### *3.2. Ishikawa Diagram*

One of the essential tools of quality management is the cause–effect diagram [83,84]. It was developed by Professor Kaoru Ishikawa and was first used by a Japanese company, Sumitomo Electric [85]. The diagram is known as the Ishikawa diagram after its creator [86]. Due to its structure and shape, this diagram is often called a herringbone or fishbone diagram. It visually represents causes and their interrelationships with a problem, error, or inconsistency in the area under investigation [87].

The Ishikawa diagram has a hierarchical structure in which the root causes are closest to the core, while the specific factors directly related to the root causes are their development. The principle of "from the general to the specific" applies in drawing the diagram. The leading causes are determined first, followed by the intermediate reasons: second-order causes and, if necessary, causes of subsequent orders [88]. Depending on the area under study, the diagram may use a layout appropriate to it:


The primary 5M method can be used to develop a cause-and-effect diagram or it can be extended or modified as appropriate, depending on the area under analysis: 5Ms + E, 6Ms, or 8Ms:


The Ishikawa diagram is also used outside its original production environment in the 8P design:


In services, causes can be grouped according to the 4Ss:


The classic Ishikawa diagram facilitates the analysis of a process in a cause–effect framework, but it does not contain quantitative information, only qualitative information. Gwiazda proposed supplementing the chart with the weights of individual causes. Once sets of primary and sub-causes for each leading cause have been determined, the next course of action is as follows:


The weights of the individual causal factors are determined using a matrix of pairwise comparisons using the following rule of thumb: if one of the comparable factors is considered more important, it is assigned a score of 1; the other element is given a score of 0. If both factors are considered equivalent, they are given a score of 0.5. A scale of 0.25 to 0.75

can be used to increase the precision of the assessment. These values denote being slightly less critical or slightly more critical, respectively [90].

#### **4. Results**

It is possible to analyze marine accidents using a weighted Ishikawa diagram when considering decision-making methods, including multi-criteria and multidimensional scaling techniques, which often support diagnosed issues and problems in various fields. The methodology above is divided into stages accordingly.

The determination of the problem category, i.e., causes of a marine casualty according to the selected 5Ms, 6Ms, 5Ms + E, or a combined idea is based on the previously conducted literature on the subject, with stages of the full process listed below:


Figure 4 shows the main categories of causes of marine accidents.

**Figure 4.** Ishikawa diagram leading causes.

The main cause weights were determined based on a comparison matrix, according to the 4Ms +A approach, i.e., Human, Machine, Management, and Other factor, see Table 1.

**Table 1.** Comparison matrix for leading causes.


Components under analysis have been placed in the last column (Validity of Factors) looking into their respective weights vs. the sum of other weights. Letter A stands for important components, while B is assigned to less important ones. This was the start of the stratification analysis.

The standardized weights for the main factors are placed in circles on the Ishikawa diagram. The upper part of the circle contains the relative weight related to the factor in question, while the lower part contains the absolute weight associated with the whole group. The two weights are equal for the main factors (Figure 5).

**Figure 5.** Weighted Ishikawa diagram with main cause weights.

Of the main reasons outlined, the group identified as "human" had the most significant weight, followed by "management", "machine", "environment", and "other". This preliminary assessment represents the beginning of inquiries in the area under investigation.

The next step is to identify the first- and subsequent-order sub-causes. A detailed set of causes with first-, second-, and third-order sub-causes is presented in Table 2.




#### **Table 2.** *Cont.*

As for the leading causes, i.e., based on the comparison matrix, relative weights were determined for the individual first-, second-, and third-order sub-causes. Subsequently, absolute weights were selected for the sub-causes based on the relative weights. The relative weights were multiplied by the value of the relative weight of the leading cause to which the sub-cause belonged. This can be written with a simple equation [91]:

$$\mathbf{W\_{a.sn} = W\_{\rm r.i.c} \ W\_{\rm r.c.sn}}$$

where

Wa.sn—Absolute weighting of sub-causes of n order,

Wr.i.c.—Relative importance of the main cause, Wr. sn—Relative weighting of sub-causes of n order.

Based on the results obtained, which were ranked in descending order of importance, cumulative weights were determined for the defined sub-causes. A reference field was calculated, as shown in Table 3. The value of the reference field was obtained by multiplying the value of the cumulative weight by the value of N = (55 − n), where 55 is the number of all reasons, and n is the number of the next sub-reason [92,93]. The grey color indicates the causes with the most significant impact on marine casualties.

The cumulative weights presented in Table 3 are the coordinates of the Lorentz Curve and the basis for a stratification analysis based on the Pareto Rule. Thus, a group of influential and less essential factors influencing marine casualties was identified. The data obtained were transferred to the graph shown in Figure 6.

**Figure 6.** Lorenz diagram and stratification analysis.

The so-called "reference area" was taken as the index of division. This is the rectangle's area defined by the Lorenz Curve's inflection point. This area reached its maximum for the 23 sub-causes and amounted to 9.520, thus constituting the limit of stratification and definitively determining the division into the group of essential sub-causes A (marked in grey in Table 3) and the group of less important causes B. The most important and frequent causes included those from the "Management" and "Human" groups.

The stratification analysis made it possible to develop the simplified weighted Ishikawa diagram shown in Figure 7. The final version of the diagram presented contains the most critical causes of marine accidents.



**Figure 7.** The final version of the Ishikawa diagram for marine accidents.

#### **5. Discussion**

The authors opened this article with a long review of the visions, objectives, and procedures in place of key industry organizations, aiming to improve safety across the maritime industry. With multiple checklists, procedures, audits, and inspections, one could think that shipping is as safe as aviation. Following this, there was a deeper dive into the literature on the subject of safety at sea, which contains a vast array of articles, publications, and reports, some from highly specialized agencies, many of which have found that incidents cause breaks down into various aspects and reasons [25]. Despite multiple safety measures and a large number of publications, the detailed descriptions of real-life sea incidents are striking regarding how trivial, simple, and obvious key root causes are. Hence, the objective of the authors was to go much deeper than an industry approach [6,25], whereby human errors are broken down into a few main categories, and, in reality, each category represents its own ecosystem of possible causes, triggers, and incident starters. This article goes as deep into the breakdown of components of human error as 'the death of a loved one or uncomfortable posture' components, analyzing how they potentially impact safety.

In this work, based on expert knowledge, 55 causes of incidents were included and, with the weighted Ishikawa diagram, 23 of causes were identified as playing the most significant role as contributors to accidents. Among them, as many as 16 were directly linked with social and situational systems, while an additional 5 were related to management, which is also a human factor element.

A causal analysis of the problem of the influence of social and situational systems on human error and, consequently, marine accidents based on the individual case method and weighted Ishikawa diagram provided positive evidence that this type of analysis can be applied to solve such complex issues.

A simplified version of the weighted Ishikawa diagram clearly showed the areas that require attention or even intervention by managers on ships and in ports. Decision makers have an impact on conditions. Among the most relevant issues are the following:


ability and efficiency in activities performed, exacerbating frustration and errors due to the desire to meet deadlines and speed up action. Illness or death of a loved one, lack of personal space, and social expectations are also examples of this.

• A lack of regular reviews.

The authors were able to demonstrate the influence of social and situational systems on marine incidents, which also corresponds to the known direction of growing situational awareness of seamen by a bottom-up management approach [94]. There is also an opinion shared across several publications that seamen want to have the option of participation in decision-making processes [95]. Experienced crew members can deal with extraordinary situations, are flexible, and are able to adapt [96,97] as, sometimes, safety can be secured by not applying procedures [98–100].

Working in a maritime education space, authors now have evidence based on the results of this work, and can discuss with the management teams of learning programs at all levels potential changes and improvements in how they organize, run, and certify students, officers, and practitioners. The aspect of safety culture, going way beyond pure knowledge and awareness of safety procedures and regulations, can be discussed with the current analysis results, thereby reinforcing the need to also adapt the culture at the class level to provide stricter ambiance and approaches, offering students the feeling of real-life stress in controlled situations.

#### **6. Conclusions**

Issues concerning the influence of individual components of the entire category of causes classified as human error as sources of marine accidents were discussed. The authors have shown that social and situational systems interact and influence shipboard safety through a case study method. In each case, a detailed analysis of specific subcategories of direct incident sources was necessary to identify potential improvements. Detailed descriptions of the causes of incidents revealed ignorance of regulations and non-compliance with applicable procedures, standards, and good practices. Pure knowledge of regulations should not be the only criteria to ensure safety. The authors cannot find any protocols to be implemented under high pressure nor amid numerous stimuli distracting attention nor requiring decision-making in training programs conducted in simulators. Today, official reports from marine incidents are indeed analyzing step by step the chain of causes behind an incident, but are often not investigating the sub-categories of human factor elements and are not unified across investigations. This is not helping to plan specific improvements to procedures, systems, and legislative solutions. In conclusion, this work provides an honest basis for potential detailed corrective actions and shows the need for constant changes and modifications to prevent people from making the same mistakes.

Human error can be significantly reduced. There is often a time lag between developing safety culture weaknesses and an event with significant safety consequences. These vulnerabilities can interact to create a potentially unstable state that exposes the organization to safety incidents. The organization (which may be a particular vessel) and its regulators must be alert to signs of potential weaknesses in social and situational systems.

A marine accident investigation is now an essential tool for identifying human factor issues which, when investigated with care, can be one of the pillars of preventing accidents and improving marine safety. The long-standing positive trend in ship safety, with yearon-year improvements, has now been reversed [101]. This is worrying. More emphasis is needed on safety culture, safety training, and competence assessment.

Statistics show that the frequency of accidents in the maritime industry, including those related to navigation, has skyrocketed. Still, authors believe that technology, regulations, and compliance can achieve expected safety levels by emphasizing the human element of accidents.

Historically, safety in shipping has focused on technical improvements. Most shipping company personnel involved in shipping operations have a technical background. Audits and inspections pay great attention to technical compliance. This focus on technical issues has led to significant improvements in ship safety. However, the time has come to focus more on other topics that the authors of the article have raised, namely, the very thoroughly analyzed causes of accidents, so far quite commonly classified as human error and more precisely as social and situational systems, which have not yet been sufficiently explored. To improve safety at sea, therefore, a threefold approach must be adopted:


This study's results indicate many areas for improvement in all parts of the traditional management system for the safe operation of ships, in which the human factor plays the most crucial role.

**Author Contributions:** Conceptualization, K.P., A.E.W. and T.K.; methodology, A.E.W. and L.K.; formal analysis, A.E.W. and L.K.; investigation, K.P. and T.K.; resources, K.P. and A.E.W.; data analysis, A.E.W. and L.K.; writing—original draft preparation, K.P. and T.K.; writing—review and editing, L.K. and A.E.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** The APC was funded by the Maritime University of Szczecin.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available upon request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **Abbreviations**


#### **References**


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**Vytautas Paulauskas 1,\*, Donatas Paulauskas <sup>2</sup> and Vytas Paulauskas <sup>3</sup>**


**Abstract:** The safety of shipping, energy consumption and environmental impact in ports and port channels is very critical. One of the most important elements in the provision of safe navigation, energy consumption and emissions generation is the depth of ports so that under all conditions the hull of a ship does not touch the bottom of the channels or the bottom of the basin, as well as optimizing energy consumption and minimizing the environmental impact. The very high depth reserves in ports make it possible to ensure the safety of shipping, but at the same time require huge investments in the dredging and maintenance of a port's channels and basins, which can have a negative impact on a port's economic results. Optimizing the depth of port channels and basins is very important from an economic, maritime safety, energy saving and environmental point of view, as vessels navigating port channels and basins must not only keep their hulls off the bottom of the channel or basin, but also have good controllability, use minimal energy consumption and minimize their environmental impact. With good maneuverability, the number of and need for auxiliary vehicles (tugs) can be minimized. This article analyses the relationship between ships' draught and port channels and basins depths, which influences the aspects of a ship's controllability, in order to optimize the depths of port channels and basins and, at the same time, minimize energy consumption and environmental impact while preserving the necessary navigational safety.

**Keywords:** ship draught; depth of port channels and basins; ship maneuverability at low depths; energy consumption; emissions generated by ships

#### **1. Introduction**

Depth in port channels and basins is one of the most critical elements in ensuring navigation safety in ports, which is why ports carry out maintenance and dredging operations to reach and maintain the necessary depths [1]. The depth of navigational channels is important to ensure not only that vessels navigating the channels do not touch the bottom of the channel with their hulls, but also that the vessel has good controllability [2]. The clearance (the distance between a ship's hull and the navigational channel bottom) in a port's channels and basins has an influence on energy consumption due to the ship's increased resistance while maintaining speed, as well as an environmental impact [3,4].

Today, the depth of channels and basins is calculated by mainly taking into account the potential maximum draught of the vessel; the accuracy of the depth measurement; the water level and its possible change (accuracy of the measurement); the variance in the ship's draft depending on the ship's speed and clearance [1,4,5]; the potential increase in the vessel's draft due to the vessel's corner angle; and the navigational margin, which takes into account the potential changes in the bottom of the channel (accumulations of soil sediments) [4,5].

**Citation:** Paulauskas, V.; Paulauskas, D.; Paulauskas, V. Impact of Port Clearance on Ships Safety, Energy Consumption and Emissions. *Appl. Sci.* **2023**, *13*, 5582. https://doi.org/ 10.3390/app13095582

Academic Editor: José A. Orosa

Received: 14 March 2023 Revised: 26 April 2023 Accepted: 27 April 2023 Published: 30 April 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

The depth of the channel must be sufficient enough to ensure the safe passage of vessels, including in and out of the ports under difficult conditions, i.e., when the speed of the biggest possible vessel entering the port may be increased by up to 1.3–1.5 times [1,5,6].

The maneuvering of vessels in port is subject to external forces such as wind, current, swell and the effects of tugboats, as well as internal influences such as the ship's own speed and the ship's inclination during maneuvering. Thus, all possible influences have to be taken into account when planning the depths of port channels and basins [2,4,5,7].

When planning the depths of port channels and basins, it is also necessary to take into account the processes of sediment accumulation, movement and the possibility of periodic dredging in order to guarantee optimum depths in port channels and basins at all times [4,8].

When ships are sailing in port approaches and port internal channels at shallow depths, the resistance of the ship's hull increases significantly [3,5]. To maintain the proper speed of the ship, it is necessary to increase the power of the main engine(s) of the ship [3,9,10]. Increasing the power of a ship's main engine(s) significantly increases fuel consumption [11,12] and, accordingly, generates more emissions [13].

Ports are trying to become "green ports"; therefore, the amount of emissions generated from shipping in ports is a very important goal, so it is necessary to follow international and national requirements to reduce emissions from shipping [14–16].

Air quality in regions and especially in large ports has a significant impact on human health; therefore, the issues of environmental protection and decarbonization of shipping are very important for the quality of life and the economy of countries [17–19].

People play a very important role in reducing emissions in ports, i.e., the human factor, without which significant results cannot be achieved in any field, including the development of "green port" ideas [16,20].

The main objective of this article is to develop a methodology to determine the required optimal or minimum possible ship clearance in port channels and basins (the space between the ship's hull and the bottom of the port channel) while maintaining the appropriate ship speed and guaranteeing the safety of shipping in port channels (shipping safety is a priority) and to assess the relationship between the ship's clearance and energy (fuel) consumption and emissions. In this way, the main aims of this article are as follows: to assess ships' safe navigation capabilities in port channels, i.e., the ability of a ship to navigate independently in the bends of a port channel with the existing relationship between the draft of the ship and the bottom of the navigation channel; to determine the change in the power of a ship's main engine(s) at shallow depths to maintain the specified speed of the ship in the navigation channel, i.e., at the existing draft of the ship and the depth of the navigation channel to maintain the prescribed safe cruising speed; to determine the change in energy (fuel) of a ship's main engine(s) and the emission levels generated based on the current ratio of the ship's draft to the depth of the port (navigation) channels.

In this way, the structure of the research and the article is oriented as follows: first of all, it must be assessed whether the ship can enter the port, which is related to the depths of the navigation channels (port entrance and internal navigation channels compared to the ship's berth). In the event that the ship has the opportunity to enter the port independently, then the following task is solved, i.e., the power of the ship's main engine(s), depending on the ratio of the ship's draft to the depth of the navigation channels, respectively, energy (fuel) consumption and the amount of generated emissions. If the depth of the port channels is satisfactory, the ship can enter the port independently or, if necessary, port tugs or additional special maneuvers can be used. In the event that it is possible for the ship to enter the port on its own, then the task is solved, i.e., the power of the ship's main engine(s), depending on the ratio of the ship's draft to the depth of the navigation channels, energy (fuel) consumption and generated emissions, respectively, is sufficient.

#### **2. Analysis and Literature Review of Clearance in Port Channels and Basins**

Many ports in the world have different requirements for minimum depths in port channels and basins and generally use guidelines such as PIANC [21] and EAU [22]. The distance between a ship's hull and the bottom of a navigation channel is very important in order to avoid the ship's hull coming into contact with the bottom of the navigation channel and to maintain sufficient controllability of the ship. Studies have been conducted on this topic [1,4,5,7,8]. At the same time, it should be noted that ship handling hearings require additional research, as ports try to attract larger and larger ships, and sometimes emergency situations occur due to too little clearance when ships touch the bottom of the navigation channel with their hulls due to ship heeling caused by external forces, or ships sink due to the ship's speed in the shipping channel or become uncontrollable and float outside the shipping channel [3,6,7].

At the same time, other very important aspects, such as the energy consumption of ships entering and maneuvering in ports and the environmental impact of low clearance under the ship's hull, have not yet been taken into account when assessing depths in port approaches and internal navigational channels and basins. The above aspects of energy consumption and environmental impacts from ships have been analyzed individually and without considering the potential impact of clearance on these aspects [16,23,24].

Vessel speeds are restricted in many ports and are linked to maritime safety and environmental impacts (the effect of waves generated by the vessel on moored vessels and the coastline) (Figure 1) [25–27].

**Figure 1.** LNG tanker sailing in port (Klaipeda port), permitted speed up to 8 knots.

Tugboats are widely used for assisting with maneuvering large ships in port because they are equipped with powerful engines and can use high engine power; however, they consume a lot of energy (fuel), generating large amounts of emissions, especially when turning ships and approaching or leaving the quay (Figure 2) [8].

**Figure 2.** LNG tanker turns in ships turning basin using port tugboats.

The assessment of sustainable transport systems in ports and their environmental impact is very important for the ports themselves and for individual regions, so research in this area is very essential [28,29].

Maritime transport plays an important role for many countries and creates a significant part of their gross domestic product (GDP). At the same time, maritime transport, especially in port regions, has a significant impact on the environment, so many countries are conducting research on that issue and are looking for optimal solutions to minimize the impact on the environment while improving the economic situation of the countries [29–33].

The emission control regions adopted by the International Maritime Organization (IMO) such as the SOx emission control areas—the Baltic and North Seas, the English Channel and the east and west coasts of North America—have allowed a significant reduction of SOx emissions from ships in these regions [13,34,35].

Ports, as the most important maritime transport points, also try to maximize their influence on the reduction of emissions from ships and other vehicles [15,16,36,37].

The navigational safety of ports and the necessary minimum depths of ports are studied in many countries, since dredging works are expensive and in the development of sustainable ports it is necessary to combine navigation safety, economic, environmental and other possible factors [16,17,24–26].

For the provision of navigation safety, when sailing ships in shallow depths, i.e., the minimum depth below the ship's hull, methods for its determination, such as Bernoulli's flow formulas ideas [4], estimates of the connected liquid mass and others [1,5,12,21,22], are used in many countries, but the results obtained are often similar.

As follows from the analysis of the situation and the literature, the necessary depths in ports and the minimum clearance under the ship's hull in ports and navigation channels, as well as emissions from ships, have been studied by many researchers. At the same time, the change in the ship's controllability at low depths (clearance under the ship's hull) and the clear connection between the clearance under the ship's hull and the ship's energy consumption and emissions are missed.

#### **3. Basis for the Theoretical Calculations of Possibilities for the Ships Sail in Port Channels and Basins, Energy Consumption and Emissions Generation**

*3.1. Steps of Research Methodology*

The following steps of research methodology were used to conduct the research (Figure 3). After conducting the literature review, the mathematical model was developed.

**Figure 3.** The steps of research methodology.

Based on the presented methodology, theoretical calculations of possibilities for ships sailing in port channels and basins, energy consumption and emissions created by ship were performed. The variation of hull resistance to longitudinal movement with clearance, i.e., the ratio *T/H* (draught to depth), was used to estimate the ship's sailing speed in ports [1,5]. For the assessment of the ship's controllability, the methods of calculation of the ship's circulation elements and trajectory at low depths were used [3,8,27]. The method of calculating the ship's circulation trajectory in shallow depth was applied as given in sources [4,5]. The method is based on the calculation of the basic ship movement parameters (ship speed, ship angular velocity and ship drift angle) and the ship's trajectory in the case of low clearance, which often occurs in port navigation channels and basins. Estimation of the ship's sailing trajectory in the presence of small clearances is necessary when navigating port approach and internal navigation channels so that the ship can safely pass through channel bends. Due to the variation of the ship's draft and the power of the main engine(s) when sailing in shallow waters (port navigation channels) and maintaining the set speed, at low depths (clearance), additional resistance forces of the ship hull are formed which are related to the change of the added water mass [4,5].

For the calculation of the ship's energy consumption, fuel consumption was calculated as a function of the engine power at a given speed, and for the assessment of emissions, the parameters of the ship's fuel consumption, engine power and operating time were used [15,38]. For this calculation, the maximal distribution method was used utilizing data achieved by conducting experiments on simulators and real ships [39]. The maximal distribution method could be applied in case at least 5 measurements were carried out.

In order to verify theoretical calculations and practical application of the presented methodology, experiments were performed with the assistance of a simulator and on real ships. Simulations were carried out using the full mission simulator "SimFlex Navigator" (Force Technology product) [40], which analyzed similar maneuvers as the real ships, considering the set forces acting on ships sailing in port channels and ships turning in

turning basins. Experiments performed on real ships covered two port areas with specific navigational conditions (port approach and internal navigational channels).

Then, the results were analyzed, discussions initiated, conclusions were drawn and suggestions for future research were outlined.

#### *3.2. Mathematical Model*

The results of the literature review, the results of simulators and the results of the real ship tests when different clearances were used between the ship's hull and the bottom of the channels were used to develop mathematical models of shipping navigational safety, energy (fuel) consumption and emission generation at shallow depths [1,9,15,37,41–44]. When conducting research and creating mathematical models, it was assumed that ships in navigational channels sail independently, and the controllability of the ship is ensured by the ship's own steering equipment. In channel bends and turning basins, ships turn with the help of their control equipment (propulsion complex), and if necessary, they can use the help of ship steering devices and tugboats [5,7]. It is also assumed that when ships move straight through channels due to the effect of low depth, only the longitudinal resistance of the ship changes, and when ships sail in bends of navigation channels and when turning in turning basins, the resistance of the ship's lateral movement additionally increases [43,45].

The safe depth of the port channels and port water areas, so that the largest ship in the port does not touch the bottom of the navigation channels and basins with its hull, can be calculated with the help of the following formula [1,4]:

$$H\_{\rm min} = T + \Delta T\_{\rm v} + \Delta T\_{\theta} + \Delta T\_{\Psi} + \Delta H\_{\rm m} + \Delta H\_{\rm V.L} + \Delta H\_{\rm AV.L} + \Delta H\_{\rm n.} \tag{1}$$

where *T*—the maximum draught of the calculated vessel; Δ*TV*—the increase in draught due to settlement (speed), sometimes named squat [4,5]; Δ*Tθ*—the increase in draught due to heeling [4,5]; Δ*Tψ*—the increase in draught due to the effect of swell (change in the difference) [5]; Δ*Hm*—the accuracy of the depth measurement, depending on the port depth measurement technique used; Δ*HV*.*L*.—the level of the water in the particular port; Δ*H*Δ.*V*.*L*.—the accuracy of the measurement of the water level, depending on the port water level measurement technique used; Δ*Hn*.—navigational margin, which can be decomposed into a direct navigational margin, which is assumed to be about 2–3% of the ship's draught, by means of accurate bottom depth measurements (using modern depth measurement techniques), and a layer of sediment, which has to be periodically removed (cleaning). The above elements of Formula (1) can be calculated using the methodology presented in [4,5].

The increase in draught (Δ*Tv*) due to low-depth effects and the ship's speed can be calculated using the following formula and graph (Figure 4) to estimate the added water mass coefficients [1,4,5]:

$$
\Delta T\_V = \frac{\rho LB}{\delta} \sqrt{\frac{1 + k\_{11}'}{1 + k\_{11}}} \tag{2}
$$

where *ρ*—water density; *L*—ship's length between perpendiculars; *B*—ship's width; *δ* overall hull fullness factor; *k*<sup>11</sup> and *k*- <sup>11</sup>—added water mass coefficients at high depth and in shallow water, depending on the ship's speed and *T*/*H* ratio (Figure 4) [5].

The added water mass depends on the speed of the ship and the draft of the ship, as well as the depths of the navigation channels and the port water area ratio (*T/H*). Added water mass coefficients, which are presented in Figure 4 when the ship is moving in the longitudinal direction, are usually used for calculation [4,5].

In the article, the water mass coefficients presented in Figure 4 are used to calculate the change in the ship's draft and the increase in the ship's draft, as well as the correspondence of the specified coefficients, verified by experiments by measuring clearance on real ships [4,5].

**Figure 4.** Dependence of the added water mass coefficients (*k*11—deep water, *T/H* ratio is zero); *k*- <sup>11</sup>—shallow water) on the *T/H* ratio and the vessel's sailing speed *v*.

Formulas can be used to calculate the trajectory of a ship at shallow depth and in the presence of wind and current, which is a characteristic of ports [4,40,43,45]:

$$X\_{0i(s)} = \int v\_{i(s)} \cdot \cos(\int \left(\omega\_{i(s)} dt - \beta\_{i(s)}\right)) dt + \int v\_{cr} dt \cdot \cos q\_{cr} + \int v\_d dt \cos q\_d;\tag{3}$$

$$Y\_{0i(s)} = \int v\_{i(s)} \cdot \sin(\int \left(\omega\_{i(s)} dt - \beta\_{i(s)}\right)) dt + \int v\_{l7} dt \cdot \sin q\_{l7} + \int v\_d dt \cdot \sin q\_{l7} \tag{4}$$

where *vi*(*s*)—ship's speed at low depths; *ωi*(*s*)—turning velocity at low depths; *βi*(*s*)—drift angle at low depths; *vcr*—current velocity; *qsr*—current course angle during the start of the maneuverer; *vd*—ship's drift speed; *qa*—wind course angle during the start of the maneuver. The above elements of Formulas (2) and (3) can be calculated using the methodology presented in [5].

When examining the passage of ships in ports, it is assumed that the movement of ships in the port approach and internal navigation channels lead to the fact that ships independently sail on a straight or almost straight trajectory (turning up to 30–40 degrees). The research also assumes that the change in the power used by the ship's main engine due to the effect of shallow water is basically related to the change in the resistance of the ship's longitudinal movement [3,10,11]. Experiments with real ships were carried out in the open sea and in ports (shallow waters) for the power factor, maintaining a set constant speed and accurately recording the main engine power, the speed of the ship with the help of electronic lag and DGPS and the depth with the help of echo sounder. On the basis of studies carried out on real ships, a dependence of the calculation of the power factor of the ship's main propulsion system (Δ*N*) on the *T/H* ratio (ship's draught/depth ratio) and the overall hull fullness factor is obtained as follows:

$$
\Delta N = (1 + 1.25 \left( \frac{T}{H} \right)^2) \sqrt{\frac{\delta}{0.65}} \tag{5}
$$

Calculation of the power factor of the ship's main engine due to the influence of shallow water according to Formula (5) and experimental tests with real ships showed that the difference between the calculations and the results of experimental tests is no more than 10%. Thus, Formula (5) can be successfully used in practice. The limitations of Formula (5) evaluated during the experiments are as follows: the speed of the ships should be between 6 knots and 10 knots, and the overall fullness factor of the ship's hull should be between 0.65 and 0.90. If the overall fullness ratio of the ship's hull is less than 0.65, Formula (5) can be used when the ratio of the ship's draft to the depth of the navigation channel (*T/H*) is greater than 0.3.

As hull resistance increases, the power of the ship's engine must be increased to maintain the ship's target or planned speed. The relative power of the ship's engine (*N'*) and the relative speed of the ship (*v*-) can be expressed in the following formula:

$$N' = \frac{N}{N\_0};\tag{6}$$

$$v' = \frac{v}{v\_0},\tag{7}$$

where *N*0—nominal power of the main engine(s) of the vessel; *v*—speed of the vessel at the power of the vessel's engine(s) *N*; *v*0—speed of the vessel at the nominal power of the vessel's engine(s) *N*0.

The relationship between the ship's relative speed and the relative power of the ship's main engine(s), presented in the literature [3,10,11], was verified by the authors through experiments on real ships of various types and sizes. Some of the results of the experiments carried out on real ships are presented in Table 1. Comparing the results of real ship experiments regarding the relative power of the ships' main engine(s) and the ships' relative speed using the maximum distribution method, the maximum changes, expressed as a percentage, were obtained (presented in Table 1). Experiments were carried out for many years on various ships, in which at least one of the authors of the article participated. The navigation equipment available on the ship was used for the experiments (ship speed was measured with an accuracy of at least 0.1 knots) as were the power measurement indicators of the main engine(s) on board the ships, the measurement accuracy of which was at least 2% of the instantaneous power.


**Table 1.** Experiments results of relative main engine power and relative speed of the real ships.

The power of the engine and the speed of the ship are related by a quadratic relationship [3,10,38]. In most cases, the relative power of the ship's engine(s) and the ship's speed can be used. For this purpose, a graph based on the experimental results from more than 1000 ship passages can be used [3,10,11] (Figure 5).

**Figure 5.** Relative vessel speed (*v*') versus relative engine power (*N*').

A limitation of the graph (Figure 5) with a very high overall hull fullness factor (δ) is that with the overall fullness factor of the ship's hull greater than 0.9, the form resistance parameters of the ship's hull shape change significantly and the accuracy of the graph is not good enough (error size can reach more than 10 percent).

Engine power can be calculated by taking into account the amount of fuel consumed over a given period of time, e.g., an hour, and the relative fuel consumption, i.e., [9,11,12]:

$$N = \frac{q\_k}{q\_k' \cdot t'} \tag{8}$$

where *N*—engine power, kW; *qk*—fuel consumption, kg; *q*- *<sup>k</sup>*—relative fuel consumption, kg/kWh; *t*—engine running time, h.

Due to their powerful engines, ships consume a lot of fuel while sailing, especially when performing additional, not always justified, maneuvers in ports. A ship's fuel consumption is often calculated over a voyage or other period. In a general case, the fuel consumption of a ship on a voyage (*qLP*) or other sailing places and times can be calculated according to the following formula [9,11,38,42]:

$$q\_{LP} = \int\_0^t q'\_k \cdot N\_{av} \cdot dt,\tag{9}$$

where *Nav*—ship main engine average power during time *t*.

The relative fuel consumption of the main and auxiliary engines of most ships ranges from 0.13 to 0.25 kg/kWh (for more precise data, please refer to the engine specification of the individual ship) [11]. Depending on the type of fuel, the amount of fuel used can be different, so when using LNG, its calorific value is on average about 15 percent higher than other petroleum products, which means that about 15 percent less fuel mass is consumed [15,46].

Emissions from ships and other transport vehicles directly depend on the quantity and quality of fuel used, engine power and engine running time [11,17,42]. The main emissions from ships constitute carbon dioxide (*CO*2), nitrogen oxides (*NOx*), carbon monoxide (*CO*), sulfur oxides (*SOx*) and particulate matter (*PM*) [11].

Emissions are calculated according to the formula that includes fuel consumption, actual engine power used and the relative magnitude of specific emissions. Thus, the carbon dioxide emissions are calculated according to the following formula [15,47]:

$$CO\_2 = q\_{LP} \cdot \Delta CO\_{2\prime} \tag{10}$$

where Δ*CO*2—carbon dioxide coefficient, which for petroleum products (diesel, fuel oil) is between 3.0 and 3.5 and for LNG between 2.5 and 2.9.

The Sulphur oxide content can be calculated using the following formula [14,15]:

$$
\Delta SO\_x = q\_{LP} \cdot \Delta SO\_{x\prime} \tag{11}
$$

where Δ*SOx*—Sulphur oxide coefficient, which depends on the type of fuel; for petroleum products, it ranges from 0.001 to 0.035 and for LNG it is around zero.

The carbon monoxide content can be calculated using the following formula [41]:

$$\text{CO} = \int\_{0}^{t} \text{N}\_{\text{av}} \cdot \Delta \text{CO} \cdot dt,\tag{12}$$

where Δ*CO*—carbon monoxide coefficient, which depends on the type of engine [42].

The amount of nitrogen oxides generated is calculated using the following formula [41]:

$$NO\_x = \int\limits\_{0}^{t} N\_{\text{dtr}} \cdot \Delta NO\_x \cdot dt\_\prime \tag{13}$$

where Δ*NOX*—nitrogen oxide coefficient, depending on the engine type.

The particulate matter generation is calculated using the following formula [48]:

$$PM = \int\_{0}^{t} \mathbf{N}\_{av} \cdot \Delta PM \cdot dt\_{\prime} \tag{14}$$

where Δ*PM*—the particulate matter coefficient, which depends on the type of engine and the type of fuel, and is up to 10 g/kWh for petroleum products and close to zero for LNG fuels [48].

The emission factors and sizes of marine engines depend on the type of engine and the type of fuel used. For marine engines, average emission factors and relative values are given in Table 2 (as an example) [11].

**Table 2.** Average emission factors for marine engines by fuel type.


Thus, the reduction of emissions from engines depends on the type and design of the engine, the type of fuel used and the engine's operating conditions (maneuvering mode). Fuel consumption depends on the operating mode of the engine, especially the modes of transitional mechanisms.

The qualifications and experience of ship crews and port pilots greatly influence the amount of emissions from ships [15,38,48,49].

The power of engines used in ships has a significant influence on the generation of individual emissions. Emission factors and relative magnitudes are shown in Table 3 (as an example) [11,49,50].


**Table 3.** The relative amount of emissions based on engine power.

Thus, shipping emissions depend on the type of fuel, the quality of the engine and its power. Knowing how much fuel is consumed in shipping, what type of emissions are emitted and what their quantities are, it is possible and necessary to look for opportunities and methods to reduce the impact on the environment.

#### **4. Case study and Results**

This case study has analyzed a few types of ships: PANAMAX type bulk ships (length about 206 m, width about 36.0 m, draft about 12.5 m, deadweight about 80,000 t), POST PANAMAX container vessels (length about 300 m, width about 46 m, draft about 13.0 m, container capacity about 8500 TEU, deadweight about 130,000 t), G class container vessels (length about 400 m, width about 61 m, draft about 13.5 m, container capacity about 19,500 TEU, deadweight about 220,000 t) and LNG standard tankers (length about 290 m, width about 49 m, draft about 12 m, capacity about 150,000 m3 LNG).

Real ships and the full mission simulator SimFlex Navigator were used for the experiments. The following methodology of conducting experiments was used: first, an experiment plan was drawn up to achieve specific goals, then possible real ships were selected and the possibility of using the simulator was checked. Experiments with real ships were carried out both at sea and while entering and leaving ports.

For the purposes of this article, previously mentioned conducted experiments and targeted experiments were used when sailing ships at sea at great depths and when sailing in ports or other navigational channels where there were limited depths, such as the Oresund, Belt and other straits where there are limited depths, in which one or all authors participated. During the experiment, the ship's speed was recorded using the ship's navigation equipment (DGPS or GPS and others on the ship's bridge), as well as a port pilot RTK (real-time kinematic) system, which was implemented in Klaipeda port, clearance (distance between ship's hull and navigational channels bottom) was measured by the ship's navigational equipment (ship's echo sounder on the ship's bridge), the load (power) of the ship's main engine(s) and the propeller rotation frequency (on the ship's bridge and in the ship's engine room) were measured and in separate cases, when there was a real possibility, fuel consumption during a particular voyage (in the ship's engine room) was measured.

Experiments were carried out to measure the advance of the ship during circulation (during the ship's waiting for entry into ports or special trials of ships after their construction or repair, in which at least one of the authors participated) as well as during navigation during large turns.

According to the obtained results of real ship experiments, a suitable ship was selected in the simulator and the relevant ship movement and other parameters obtained in real ships and in the simulator under identical conditions were compared. During the matching process between the real ship and the ship in the simulator, the calibration coefficients were calculated, and then the experiments were continued with the help of the simulator using the calibration coefficients.

For the checking ship's advance [5,51] (Figure 6), all tested ships sailed with an initial speed of 8 knots and a rudder turn angle of 25◦ to starboard. All tested ships had conventional propulsion, i.e., one propeller and one rudder [52]. The vessel's advance in circulation analysis is important to assess whether the vessel is able to turn on bends in the channel on its own, whether it needs the assistance of tugboats or whether additional maneuvers by the vessel are necessary [1,7,43].

**Figure 6.** Ship's circular trajectory details.

Ships advance testing was made in good navigational conditions, i.e., wind velocity less than 10 m/s, wave height less than 1 m and current less than 0.5 kn. The mentioned ship's advance testing results are presented in Figure 7. In all cases, a rudder angle of 25 degrees was adopted (to leave a margin of maneuverability). Tests of real ships for simulator calibration were performed as follows: bulk cargo ship—three ships; container ship (9000 TEU)—two ships; container ship (19,500 TEU)—one ship. The "Tables of maneuvering elements" available on the ship's bridge were also used. With the help of a calibrated simulator, at least 10 tests (for G class container vessel—10 tests; for 9000 TEU container vessel—12 tests; for 80,000 t bulk cargo ship—12 tests) of each mentioned ship were carried out. In the simulator, we selected ships from the simulator library which were analogous to real ships with which real experimental tests were performed in terms of type and parameters. The differences, although minor, were mostly due to differences in draft and displacement. For example, the simulator library contained a G-class container ship with an average draft of 14.0 m, while the real ship had a draft of 13.7 m. In order to unify the obtained results, it was necessary to calibrate the simulator, i.e., coefficients of the relationship of the received simulator data with the real ship. In practice, for such simulator calibration, one or two datapoints of a specific parameter of a real ship were sufficient. In the article, there were at least 2–3 real results for specific parameters of specified ships, and up to 7–12 such real ship test results were used for individual ships.

**Figure 7.** Ships advance on circular trajectory in deep and shallow waters (depending on *T/H*), received by calculation (lines), real ship experiments (G class container ship, container ship 9000 TEU, bulk ship 80,000 t) and calibrated simulator (G class container ship, container ship 9000 TEU, bulk ship 80,000 t).

The accuracy of the real ship test results obtained, necessary for research and simulator calibration using the RTK system, was: ship location—up to 0.1 m; ship speed—up to 0.1 knots; ship angular rotation speed—0.2 degrees per minute. When using the DGPS system, the accuracy of the received data consisted of: the location of the ship—up to 0.5–1.0 m (depending on the distance to the base station); the speed of the ship—up to 0.2 knots; the angular speed of the ship—up to 0.5 degrees per minute.

The study was conducted as presented in Section 3 using the full mission simulator SimFlex Navigator [40] and using real similar ships for experiments. All received data were filtrated by a Kalman filter [53] and the differences between calculated, simulated and real ships' experimental data were analyzed.

The results obtained from the advance calculation and experiments (Figure 7) show that the calculation results using the methodology presented in Section 3 are in high compliance with the results of the real ship experiments and the simulator results.

The results of calculation and experiments (obtained on real ships and with the help of a calibrated simulator) of ships' advance in circulation at a rudder angle of 25 degrees are shown in Figure 7, and the differences (accuracy) at different *T/H* ratios in meters and percentages from the experimental results are shown in Table 4.

The power changes in the main engines of the ships, due to hull longitudinal speed, and additional resistance in shallow waters were calculated according to the methodology presented in Section 3 and verified using a calibrated simulator and the results of real ship experiments under similar conditions (Figure 8).

At least eight types of ships were used to determine the power factor of the ship's main engine, depending on the ship's draft and the depth of the navigation channels, for conducting research and calibrating the simulator. During the experiments, equipment on the ship was used: ship echo sounders were used for depth measurement, the accuracy of which was up to 0.1 m, and the accuracy of the power of the ship's main engine(s) was up to 2% of the engine(s) power. During experiments, the fuel consumption of the real ships was measured by existing sensors in the ship's engine room, the accuracy of which was up to 2–3% of the amount of fuel consumed, and instantaneous fuel consumption sensors, the accuracy of which was about 4%. All data were recorded automatically.


**Table 4.** The difference (accuracy) between the results of calculation and experiments (obtained on real ships and with the help of a calibrated simulator) of ships' advance in circulation in meters and percentages from experimental results.

**Figure 8.** Ship's main engine power coefficient depending on ship's draft and depth ratio (*T/H)* and ship's overall hull fullness factor (DELTA) (calculation and experimental results).

The compliance between the results of the calculations and the experiments is quite high (the difference does not exceed 10 percent (Table 1)) (Figure 8), and therefore it can be concluded that the methodology presented in Section 3 for the calculation of the ship's engine power increasing during sailing at low depths can be used for practical purposes for the assessment of the performance of ships when sailing through channels and other similar locations with low depths.

The port of Klaipeda was chosen for the case analysis. The passage of a standard LNG tanker from the entrance channel to the southern turning basin of the port was analyzed (Figure 9).

**Figure 9.** LNG standard tanker sailing trajectory in Klaipeda port.

The main engine power, fuel consumption and emissions of the ships were calculated according to the methodology presented in Section 3. The SimFlex Navigator simulator was used to change the clearance under the hull. Experiments were carried out on real ships (LNG standard tankers, length approx. 290 m, beam approx. 49 m, draft approx. 12 m, overall fullness coefficient approx. 0.75). The speeds adopted and used in the calculations, simulator and actual LNG carriers for the majority of the passage (up to the turning basin) were between 7 and 8 knots.

The calibration of the simulator was carried out by comparing the results of a real ship and a ship in the simulator. The simulator calibration was produced by calibration coefficients for the ship's main engine power, fuel consumption and the ship's speed at high and low depths. Following the simulator calibration, experiments were carried out on the simulator at various depths and speeds in the range from 6 to 10 knots and at characteristic depths in harbor approaches and ports, i.e., a *T/H* between 0.6 and 0.92.

The main engine power, speed and fuel consumption of the LNG standard tanker in the approach and internal navigational channels of the port of Klaipeda, obtained in a calibrated simulator, are shown in Figure 10.

**Figure 10.** The LNG standard tanker engine power, ship's speed and fuel consumption obtained in a calibrated simulator.

The variation of the main engine power and fuel consumption factors for the LNG standard tanker sailing at a constant speed as a function of the ship's draught/depth ratio, which is characteristic of harbor approaches and internal navigation channels, using the methodology presented in Section 3, and the results obtained on the real ship, are presented in Figure 11.

**Figure 11.** Standard LNG tanker main engine power and fuel consumption factors depending on the ratio of the ship's draft and depth (*T/H*) received by the theoretical method (lines) presented in Section 3, and experiments' results of the real ship (fuel consumption factor, engine power factor) and calibrated simulator.

As can be seen from the results obtained, the methodology presented in this article for the estimation of the usable power of a ship's main engine for ships navigating in the port approach and the internal channels can be applied for practical purposes.

The comparative studies of the calculation and experimental results of the received engine power and fuel consumption factors of the ship showed (LNG standard tanker) that the maximum difference between the calculation and experimental results (real ship and calibrated simulator) was up to 0.23, or, as a percentage, up to 9.3 percent.

On the basis of the results obtained, it can be concluded that the methodology presented in Section 3 for the estimation of the fuel consumption of ships in port approach and internal navigation channels can be successfully used for practical purposes and further calculations, for example, for the estimation of generated emissions.

Fuel consumption of the standard LNG tankers while sailing (Figures 9 and 10) at the specified sailing distance using LNG and diesel fuel depending on the ratio of the ship's draft and depth while the ship is sailing at a speed of 7–8 knots obtained by calculation and experimentally are presented in Figure 12.

As can be seen from the obtained calculation results (ship's circulation advance at low depths and ship's main engine(s) factors using the methodology presented in Section 3) and the results of experiments on real ships in corresponding conditions, there is a good correlation between the calculation and experimental results, which allows the use of the methodology developed and presented in this paper for practical purposes. At the same time, it is necessary to appreciate the fact that fuel consumption for ships sailing and maneuvering in ports depends up to 10–12 percent on the qualifications of ship crews and port pilots [15].

**Figure 12.** The fuel consumption of a standard LNG tanker sailing at a speed of 7–8 knots at sea and when entering the port of Klaipeda, obtained by calculation and experiments (sailing distance 5 n. miles).

The methodology presented in Section 3 is used to calculate the emissions. Emission values were calculated using petroleum products (diesel) and LNG fuel. The values of *CO*<sup>2</sup> and *SOx* emissions, depending on the amount of fuel used, when sailing from the beginning of the port entrance channel to the turning basin (taking into account the differences in the energy capacity of LNG and diesel) were calculated. When the ship sails at a speed of 7–8 knots and different T/H ratios, the amount of *CO*, *NOx* and *PM* emissions of a standard LNG tanker, depending on the T/H ratio, was calculated according to the methodology presented in Section 3, based on engine power, engine operating time and the corresponding emission generation factors presented in Tables 1 and 2. The results of generated emissions are presented in Table 5.



The fuel consumption and emissions of the vessels to maintain the same speed in channels and other similar locations at low depths were calculated using the methodology presented in Section 3 and verified with simulators and real vessels under similar sailing conditions. As can be seen from the obtained results, the difference between the calculation and experimental results is not significant (maximum difference of 8 percent) and therefore the calculation methodology presented in Section 3 can be applied to the estimation of fuel consumption and emissions of ships sailing in harbors and other channels at low depths.

#### **5. Discussion**

For further studies related to fuel consumption and emissions, it is important to study the power of the ship's main engine when the ship moves at a constant speed, depending on the ratio of the ship's draft to the depth of the channel, which is typical for ships sailing in ports. Research on the variation of the power of the ship's main engine at shallow depths in the evaluation of the fullness factor of the ship's hull should cover a wider range of ship types and designs. In addition, additional aspects of further research such as ships turning in turning basins and ship towing to and from quays, including the performance of tugs at low clearances, are important for finding methods to reduce environmental impact. These could be further directions of research.

The research results presented in the paper are critical because they clearly showed the importance of finding optimal methods for ships to enter and leave ports safely, primarily to ensure the safety of shipping (safety first) and at the same time reduce energy (fuel) demand and emissions. In this way, further complex studies are very important for the safety of shipping in the approaches to ports while constituting as low a possible impact on the environment.

The results of the scientific literature review showed that a specific methodology for assessing the trajectory of a ship's movement in shallow depths is important for predetermining the ship's maneuverability and safe navigation in port entrances and internal port navigation channels. At the same time, in order to reduce non-standard situations as much as possible, especially when ships pass near port infrastructure and ships moored at the quays, further studies of the controllability of ships in difficult conditions, especially regarding the effect of tides on the trajectories of ships, are important.

The change in the power of the ship's engines at shallow depths is important; therefore, the developed methodology for estimating the power of a ship's engines when the ship is sailing at a shallow depth is extremely important in ensuring the safety of shipping in ports. At the same time, for ships with relatively low-power engines, such as some bulkers, a preliminary assessment of the capabilities of such ships and further research is very important. Vessels with relatively weak main engines often have to use maximum or nearmaximum main engine power when navigating port navigation channels in bad weather conditions where there is very little clearance, which requires high fuel consumption and generates high emissions. Therefore, according to the authors, similar studies are very important and may be another direction for future research.

The methodology developed to more accurately estimate the fuel consumption and emissions of vessels operating in shallow waters is very important, but further research is needed to determine the optimal safe speed of ships in ports while minimizing fuel consumption and emissions. This is especially important for ports that are within the boundaries of large cities.

#### **6. Conclusions**

This article examines the possibility of maneuvering ships sailing in port navigation channels and in the presence of small turns in the channels, and the obtained results allow for increasing the safety of navigation in port approaches and ports. Carrying out studies of the necessary energy (fuel) consumption while maintaining a planned speed is important from the point of view of shipping safety and environmental impact minimization. The results obtained in the article can be applied in the planning of port infrastructure (depths and turns of port navigation channels).

Developed and verified by experiments on real ships and with the help of a simulator, the methodology allows for estimating the power changes of a ship's main engine(s) at low clearances and can be successfully used in port planning and assessing possible emissions changes depending on the clearance. In this way, the methodology developed can help in planning the shipping channels of ports and the environmental impact of ships sailing in them (regarding the amount of pollutants emitted) depending on the depths of the existing or planned shipping channels.

The developed methodologies for evaluating the influence of shallow water on the required power of a ship's main engine, fuel consumption and emissions are important both for ensuring the safety of shipping in ports and for optimizing fuel consumption and reducing emissions in ports.

**Author Contributions:** Conceptualization, V.P. (Vytautas Paulauskas) and D.P.; methodology, V.P. (Vytautas Paulauskas); software, D.P. and V.P. (Vytas Paulauskas); validation, V.P. (Vytautas Paulauskas) and D.P.; formal analysis, V.P. (Vytautas Paulauskas); investigation, V.P. (Vytautas Paulauskas) and D.P.; resources, V.P. (Vytautas Paulauskas) and D.P.; data curation, V.P. (Vytautas Paulauskas), V.P. (Vytas Paulauskas) and D.P.; writing—original draft preparation, V.P. (Vytautas Paulauskas) and D.P.; writing review and editing, V.P. (Vytautas Paulauskas) and V.P. (Vytas Paulauskas); visualization, V.P. (Vytautas Paulauskas) and D.P.; supervision, V.P. (Vytautas Paulauskas); project administration, V.P. (Vytautas Paulauskas); funding acquisition, V.P. (Vytautas Paulauskas). All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** Information about authors reporting results could be find in Research-Gate platform

**Conflicts of Interest:** The authors declares no conflict of interest.

#### **References**


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**Riko Butarbutar, Raja Oloan Saut Gurning \* and Semin**

Department of Marine Engineering, Faculty of Marine Technology, Institut Teknologi Sepuluh Nopember, Surabaya 60111, Indonesia

**\*** Correspondence: sautg@its.ac.id; Tel.: +62-(0)82140060563

**Abstract:** The alternative use of environmentally friendly marine fuel by Indonesian vessel owners complies with IMO regulations. Marine fuels with low carbon and sulfur are alternative fuels to the current fossil fuels used by the shipping industry. Some alternative marine fuels are being used or developed such as LNG, hydrogen, and methanol. LNG is one alternative fuel that is used significantly as a marine fuel in the shipping industry. As one of the LNG producers, Indonesia is still behind in using LNG as an alternative marine fuel. One of the main reasons is the use of conventional marine fuels such as HFO, MDO, MGO and the understanding of LNG as an expensive and high-risk commodity. However, vessel owners face various challenges when selecting alternative fuel, which is associated with price and technology. This study aims to analyze a 600 TEU container vessel by calculating its net present value, the capital recovery factor and life cycle analysis (LCA) to determine whether owners carry out the investment. The result of the economic analysis for the 600 TEU vessel showed that the investment of retrofit for LNG as a marine fuel will be a good choice for owners due to the challenge of capital cost for financing a new vessel.

**Keywords:** fuel gas supply system; life cycle analysis; LNG

#### **1. Introduction**

The shipping sector is an important player in the Indonesian economy because sea transportation is cost-effective. Its growth is impacted by indigenous and international regulatory bodies such as IMO. However, the current regulatory standard adopted by IMO is emission control from the vessel's exhaust. Ref. [1] Arefin et al. stated that the increased demand for energy triggers the production of greenhouse gases (GHGs) in enormous quantities. GHGs are obtained from burning fossil fuels, which ultimately cause global warming. Since the implementation of emission control by IMO, several studies have been carried out on alternative fuels, and presently, various types are available in the market. Vessel operators have no choice but to select advanced alternative fuel technology as a management strategy. In terms of sulfur emission, traditional marine fuel is influenced by component and hydrocarbon composition and the structure of asphaltenes [2]. The characteristics, both physical and chemical, of asphaltenes will also impact the sulfur content [3]. The major alternative marine fuels in development are hydrogen, LNG, methanol and batteries [4]. Jack Sharples stated that transportation modes are significant sources of carbon emission (CO2) [5]. Air pollution containing SO, NOx and particulate emissions significantly impacts human health. In 2015, approximately 32.3 billion tons of CO2 emissions were recorded globally, of which 7.7 billion was obtained from the transportation sector with 5.8 billion tons on land. This is followed by sea transportation and aviation, with approximately 657 million tons and 530 million tons of emissions, respectively. While land transportation contributes a huge amount of CO2, NOx, and particulate emissions, the sea contributes approximately 90% of SOx emissions and impacts the local port [5]. One factor that causes high emissions from vessels is the cheap price and filtering technology of fuel.

**Citation:** Butarbutar, R.; Gurning, R.O.S.; Semin Prospect of LNG as Marine Fuel in Indonesia: An Economic Review for a Case Study of 600 TEU Container Vessel. *Appl. Sci.* **2023**, *13*, 2760. https://doi.org/ 10.3390/app13052760

Academic Editor: José A. Orosa

Received: 13 January 2023 Revised: 14 February 2023 Accepted: 16 February 2023 Published: 21 February 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

The use of LNG as alternative marine fuel for decarbonization is implemented in various types of vessels. In South Korea, there was a study on LNG fuel application to new bulk carriers [6]. LNG as a marine fuel is not only implemented in deep-sea shipping, but it has implemented for short-sea shipping or domestic shipping. Fishing vessels are another type of vessel that increase the impact on the environment due to vessel emission, and these types of vessels have started to use alternative marine fuels. The study shows that LNG fuel is a good option for fishing vessels to reduce environmental impact [7]. Another type of vessel that started to use LNG as a marine fuel is the Ro-ro ferry vessel. The conversion of Ro-ro vessels to LNG-fueled vessels will be technically feasible and a good option for local ship operators [8]. In Indonesia, vessel owners are usually more comfortable with conventional fuels such as HFO, MDO or MGO rather than engaging in environmentally friendly vessel operations. According to one study, heavy fossil hydrocarbons are transformed into natural gas, and their constituents can reduce emissions [9]. This flexibility is significant to the termination of dependency on conventional fuel; many countries are yet to develop renewable energy [10]. Yun et al. stated that energy derived from fossil fuels is expensive, impacts the economy, social life protection, welfare, and the educational sector and triggers air pollution [11]. The government needs to create awareness of the importance of environmentally friendly fuel, specifically in the shipping sector. Its realization is bound to impact the economy and social environment for decades significantly. Vessel owners can utilize several fuel alternatives to comply with the IMO regulation. Natural gas is the preferred fuel in this sector due to its innumerable advantages. These include GHGs reduction, better combustion efficiency, attractive cost, and renewability through biomass production [12]. Irrespective of the fact that natural gas is majorly used in the transportation sector due to its availability and environmental benignity, it is still limited to small engines, specifically spark-ignition (SI) and is rarely found in large diesel engines [12]. In the next decade, the number of LNG-fueled vessels is forecasted to increase immensely, even though certain segments are bound to experience massive expansion [13]. The possibility of vessels switching from using fossil fuel to LNG is because this has gained significant concern among the currently evaluated technologies [14]. In this present study, LNG is used as an alternative fuel due to its numerous advantages. These include advanced LNG vessel technology and the market price established across major ports globally. Another journal has studied the LNG fuel and diesel engine based on the Energy Storage System (ESS) using the NGSA-II algorithm and discovered the optimal scheme to reduce pollutants and cost [15].

Previous studies stated that LNG is the most advanced energy technology implemented on board vessels. Its source is readily available in terms of emission reduction compared to other alternative fuels. Natural gas is a promising alternative fuel source in transportation because of its remarkable advantages [1]. A survey was conducted in some shipping companies that render several services related to the container, offshore, general cargo vessels, and crew boats. The objective of the survey was to understand the emission control requirement mandated by IMO and vessel owners' plans for using environmentally friendly marine fuel. Eight companies were selected randomly as respondents, and due to confidentiality, the company name is classified. Their responses were used as sampling representatives with respect to marine fuel transition. These eight companies represented the types of vessels operating in Indonesia such as container vessels, general cargo vessels, oil tanker vessels, LCT and offshore support vessels.

In accordance with the distributed questionnaires, most respondents (70.6%) stated that they knew about IMO regulation to reduce sulfur content and even felt the impact on their businesses. The graphic representation in Figure 1 shows that the rest of the respondents do not understand the IMO regulation on emissions. The challenge is to ensure vessel owners in the country realize that IMO regulation should be implemented in target regions to obtain zero emissions by 2050.

**Figure 1.** Respondents' understanding of IMO emission control and impact.

The next questionnaire about the shipping company plan is on its use as an alternative fuel and interestingly only 35.3%, 17.6% and 29.4% plan to use, not use and consider using it, respectively. Figure 2 below illustrate the respond for ship owner plan on use of alternative marine fuel.

**Figure 2.** Plan for using alternative fuel.

Furthermore, approximately 45% of the respondents intend to use LNG, while 5% used other alternatives such as ethanol, methanol, and hydrogen. The remaining 14% and 9%, intend to use electricity and LPG, respectively. With respect to this question, respondents can use more than one energy alternative as planned. Figure 3 below illustrate the respond to alternate fuel for Indonesia shipping sector.

**Figure 3.** Alternative fuel for Indonesia shipping sector.

The majority of the shipping companies stated that the selection of alternative fuel was based on the considerations of low price investment (30%), government regulation or authorization (25%), advanced technology (25%), energy content (10%) and resource (10%). From this mapping, most of the companies tend to consider low fuel prices, which is the primary selection factor, followed by advanced technology. Figure 4 below illustrate the reason for select the alternative fuel.

Based on the earlier mentioned survey, several factors need to be taken into account by Indonesian vessel owners when investing in alternative energy. The most challenging factors to be considered are freight rate versus investment. Currently, some owners use conventional fossil fuels, such as MGO and HFO in their comfort zone. However, when IMO strengthened its position to reduce emissions from vessels, it was supported by environmental energy, which is the main objective, alongside domestic and international trade. The study of LNG-fueled vessel investment in recent years is increasing, although none analyzed the capability of Indonesian vessel owners to invest in this alternative energy. Therefore, this present study focuses on the challenges that vessel owners face in the country, specifically in understanding the investment strategy concerning the use of LNG as a marine fuel. It seeks to economically analyze this strategy by considering the potential retrofit for owners' existing fleets.

#### **2. Literature Review**

#### *2.1. LNG Technology*

The choice of alternative fuel by vessel owners is mainly driven by investment costs and advanced technology. Elkafas et al. stated that both natural gas and hydrogen are already used [16]. However, compared to natural gas, hydrogen has safety issues. The advanced technology depends on the availability of a bunker and related infrastructure. In 2019, DNV identified some alternative fuels used in shipping companies, such as LNG, LPG, methanol, biofuel and hydrogen. LNG is the most popular and promising alternative fuel because its technology is developed correctly [17]. It has been developed through significant innovation, hence, its ability to reduce the high content of fuel emissions. They also stated that the capability to reduce sulfur and nitrogen levels is due to the use of marine fuel, such as LNG, in a diesel engine [18]. Clean and renewable energies are ideal, although, in practice, LNG is usually selected by owners [19]. LNG is categorized as the leading alternative fuel, followed by methanol and biofuel [4].

LNG technology on board vessels depends on the fuel gas supply system (FGSS). Wang et al. stated that the fuel tank needs to be kept in the liquid phase at −163 ◦C. Furthermore, it is designed to supply gas to dual-fuel engines under the required temperature and pressure. It also needs to avoid being over-pressurized due to its ability to improve fuel efficiency [20]. Most vessel technology uses dual fuel systems, while the boil-off gas produced in the LNG tank is used for steam turbines [21]. In 2022, the Maritime Executive stated that the retrofit concept reduces the cost of LNG conversion operations [22].

#### *2.2. Investment Analysis Outlook*

Generally, vessel owners need a reference for their investment because they usually encounter difficulties, such as changing the current fuel to an alternative one that is environmentally friendly. Some previous studies stated that as a marine fuel, LNG would positively impact the future; its technologies are bound to pay off in a matter of years (DNV-GL, 2015). Some methods can help owners adopt an ideal investment strategy, for example, the cash flow. The uncertain price of LNG is also a huge drawback for transitioning to alternative fuel. Chen et al. stated that no international market is currently dealing with natural gas. Furthermore, the common economic analysis approach that considers time value, namely present, final, and annual worth methods, is employed in selecting these alternatives [14]. Some literature stated that most shipping investment evaluations use Real Options Analysis (ROA). ROA is used because it incorporates the uncertain prices of both LNG and conventional fossil fuels [14]. Previous studies stated that the shipping investment decision is based on the relation vessel between the current freight and trigger rates from ROA and Net Present Value (NPV). Kou et al. stated that it impacts the mean freight rate [23]. Figure 5 illustrates the challenges Indonesian vessel owners face regarding the regulation requiring them to comply with emission control. Another economic assessment method is using life cycle cost assessment (LCCA) which this method used to investigate the total cost including the sum of investment, maintenance and operations costs [24]. LCCA is a method for analyzing cost throughout the lifecycle of a product or service and it is a preferred method for the decision-making process. The LCCA method has been demonstrated to be effective when it is used for assessing the yacht cost model [25]. In the shipping industry, it is difficult to assess fuel prices for certain periods and the result from one study showed that the sensitivity of lifecycle cost for uncertain fuel prices can be observed [26]. In terms of LNG fuel options, a study from Alvestad which compares MGO, LNG and scrubbers has concluded that for new build vessels, LNG fuel might be the most economical marine fuel alternative [27].

**Figure 5.** Indonesian vessel owners challenging condition.

As mentioned earlier, vessel owners need to consider the capital cost of the initial investment whenever they want to use alternative fuels such as LNG. The owners were exposed to three options, namely building new LNG-fueled vessels, retrofitting and purchasing from the second-hand market. New build and second-hand purchase markets depend on sales, while their characteristics are centered on the vessel type [28]. According to Rivieramm News, DNV reported that 240 LNG-fueled vessels were ordered in 2021, consisting of the container ship, tanker and bulk carrier sectors. Snyder further stated that based on DNV data, 251 LNG-fueled vessels are presently in operation globally, and 403 fleets are under construction [29]. This implies that the development of LNG-fueled vessels has progressed significantly. Some studies were carried out to analyze the investment in fuel transition. [20] Wang et al. calculated the low-cost analysis (LCC) for boil-off gas management and discovered that the universal solution is not applicable in all situations. It was further stated that the fuel gas supply system depends on the vessel's scale, operation, and LNG fuel price [20]. Yoo conducted an economic assessment of LNG as marine fuel for CO2 carriers and compared it to MGO. It was found that LNG is more cost-effective compared to MGO. He also used the discount rate, and the project lifetime functions to calculate the annual cost index on LNG and MGO [30]. According to studies on Discount Cash Flow Method (DCFM) LNG fuel container vessels with low-speed diesel attract economic investment compared to the Tier III complied oil-fueled container vessels [26].

#### **3. Methodology**

#### *3.1. Selection for Vessel*

Vessel owners who invested in fuel transition are demanding to know when they can benefit from vessels in the market. The container vessel is extremely important in the Indonesian shipping industry and has an impact on emission control regulation. Other factors that need to be considered during selection are tankers, offshore supply vessels, tug boats, and fuels paid for or provided by the charterer. This restricts the vessel owners' flexibility to change to another alternative fuel. This study selected a container vessel with a capacity of 600 TEU because it was considered suitable and the capacity size is commonly available in the Indonesian shipping market compared to other container capacities. The container vessel with 600 TEU capacity is also the feeder size container that plays an important role in short sea shipping within Indonesia and the nearest regional countries such as Singapore and Malaysia. Furthermore, it has a company schedule and voyage, which simply means that assuming owners change to LNG, the maintenance program can be predicted and managed quickly. For this analysis, the vessel route is from the Port of Tanjung Priok, Indonesia, to the Port of Singapore, with a distance and economical speed of approximately 591 nm and 11 knots, respectively.

#### *3.2. Vessel Design*

In this study, the existing container vessel was used to carry out certain analyses. This is intended to provide an overview of the vessel owners' perspective on the fuel transition strategy. Assuming this is not a new build vessel, the ideal methodology that needs to be adopted is retrofit. The availability of technology reduces the cost of the vessel and improves efficiency. Furthermore, it was stated that zero-emission fuel impacts the alreadybuilt vessel [31]. It provides retrofit, which most vessel owners usually consider. The 600 TEU container vessel serves as a retrofit to dual fuel. According to the Retrofit Series (2020), the three vessels subjected to retrofit have significant potential savings, such as lube oil cleaning and other attributes that are often overlooked [32]. This includes potential savings from machine learning. Some other studies carried out on a mini-cape size bulk carrier stated that the payback period for LNG-fueled vessel retrofit is 4.5 years compared to a 0.5% compliant fuel vessel [33]. A retrofit vessel that uses LNG fuel is an attractive option to meet the new regulation. Another study stated that Hapag-Lloyd investigated a 15,000 TEU Sajir retrofitted for LNG fuel. This concept has LNG cylinders contained in open frames with 40-foot containers. The venting system and LNG piping, including the fire-fighting technique, are integrated into the container cell guide structures handling the gas adjacent to the storage. It feeds the low and high-pressure fuel gas system to the current four-stroke dual-fuel engines [22]. In this study, the 600 TEU container vessel has a similar concept with retrofit, as stated by previous studies on 15,000 TEU Sarji by Hapag-Lloyd. Wang et al. designed a three-configuration fuel gas supply system, and as mentioned earlier, FGSS is a critical factor in the LNG fuel system. The three configurations of FGSS are GCU, AE, and reliquefaction schemes with the combustion of boil-off gas-by-gas combustion unit (GCU), supply boil-off gas using auxiliary engine (AE) and reliquefaction boil-off gas by reverse Brayton cycle (RBC) system, respectively. In line with a previous study [20], this present study selected a suitable retrofit configuration for a 600 TEU container vessel dependent on a GCU scheme because the system is reliable, simple, and compact. Figure 6 illustrates the configured FGSS with boil-off gas handled by GCU. The configured FGSS is adapted from Wang et al.'s scheme [19], and the LNG Tank is fitted into a deck with a similar arrangement as a refrigerator container tank. It uses the plug-in system on the LNG tank and container cell, thereby reducing the cost of the conversion vessel [22].

**Figure 6.** Configuration of FGSS with BOG handled by GCU.

The retrofitted designed vessel has employed a promising strategy to avoid uncertainty. They defined the retrofit cost using a Pareto-optimal solution, and interestingly, it depends on different alternative fuel types. The retrofit cost was calculated by analyzing certain aspects, namely machinery, tank, piping, shipyard and lost income. Figure 6 shows an illustration formulated by Lagemann et al. [34] as a reference. Another study that proposed the use of the calibrated method for the fuel substitution ratio, economy and particulate matter emission proved brake-specific consumption for the dual fuel model is higher than the diesel [35]. The generated boil-off gas tends to have certain advantages, such as energy efficiency [36]. The calculated lost income and the time needed during retrofit at

the shipyard are perceived as a challenge to Indonesian vessel owners because it requires opportunity costs to compensate for the time lost.

#### *3.3. Maintenance and Crew Cost*

This study defined and considered three maintenance scenario assumptions. These consisted of high, medium, and low scenarios dependent on the Moore Maritime Index. For a high scenario, the assumption of all maintenance and crew costs is increased by 10%. Meanwhile, for the medium scenario, there is no difference between existing and retrofit vessels, and for the low medium, the lubricating oil and spare parts are reduced by 50%, as opposed to maintenance costs by 33% less than the initial. The maintenance and crew costs are the most significant operational expenditure, besides fuel oil prices.

Table 1 shows the information of these three scenarios with operational cost in accordance with Moore Maritime Index 2021 [37] on an average level.


**Table 1.** Maintenance and crew cost scenario.

#### *3.4. LNG Fuel Prices*

LNG fuel prices are the dominant factor in determining the economic analysis of its transition. The fuel cost depicts approximately 60 to 80% of the total operating cost, while the rising oil price poses a huge challenge [38]. From the beginning of the fuel transition plan, the vessel design is not altered since the vessel will be retrofitted, and the changing prices tend to impact the LNG fuel system [26]. The increasing LNG fuel cost affects the overall system as well. Further, Wang et al. stated that the preference for appropriate FGSS configuration depends on the LNG price [20]. Some other studies stated that the LNG investment option depends on three parameters. These include the price differentials between LNG and conventional fossil fuels, new build LNG fueled vessels compared to the conventional type that entails burning traditional maritime fuels, and the shared operations within ECAs. They also observed the cost change in different bunker locations, such as Japan [14]. The major source of LNG fuel prices referenced in the market is Henry Hub for the east coast US and TTG or NBP for North West Europe and Asian markets. Japanese prices are perceived as an option. Figure 7 shows the illustration of the marine fuel price differential [39], which is cheaper based on a negative differential.

Lagemann et al. also described the fuel prices for some alternative fuels within a certain period [34]. This group of fuel types was sorted based on prices and divided into fossil, bio, and e-fuel.

#### *3.5. Flow Analysis*

Another challenge encountered is that the Indonesian government has yet to implement green environmental fuel regulations to support vessel owners to change from conventional to alternative fuel. The government must provide some incentives to attract these individuals to use alternative fuels such as LNG. Figure 8 illustrates Indonesian vessel owners' challenging situation before changing their fuel management to an alternative type, such as LNG.

**Figure 7.** Marine fuel price differentials.

**Figure 8.** Flow Diagram for data analysis.

The data were analyzed using the lower scenario, assuming that the maintenance cost and spare parts were reduced due to LNG usage. This study employed some processes to obtain the cost recovery factor for investing in LNG fuel existing 600 TEU vessels. The first step for the analysis is gaining engine information from vessel owners. The expected data are engine power, specific fuel consumption, and type. The next step is to select the maintenance and crew cost scenarios. In addition, this study compared the high and low scenario investments. A particular study on Niigata's engine manufacturing proved customer satisfaction with gas engine series with low running cost and required maintenance at 4000 h running intervals [40]. Wartsila stated that switching to LNG as a marine fuel, whether new build or converting existing technology, will generate significant savings in fuel cost, thereby increasing profitability [41].

Operating Expenditure (OPEX) consists of the spares, lubricant, repair and maintenance. Retrofit investment for container vessel 600 TEU constitutes modifying the fuel and gas supply system. This is realized by installing the LNG tank, piping, changing the main engine and installing a gas combustion unit. As discussed earlier, vessel owners usually consider these, including vessel modification and additional equipment installation. The economic analysis requires a 10-year scheme because it is sufficient to review the potential payback from the vessel owners' view and offers future plans for vessel acquisition. Net Present Value (NPV), with respect to a 10-year investment scheme, shows differences between the present cash inflows and outflows.

Furthermore, the vessel owner requires an analyzed loan payment in a different scenario. It is calculated based on loan principal, interest, payment, and remaining amount. Some formulas used to calculate NPV and CRF [20] are as follows:

$$\text{NPV} = \sum\_{t=1}^{t} \frac{\mathbb{C}\_{t}}{\left(1 + r\right)^{t}} - \mathbb{C}\_{0} \tag{1}$$

where:

*Ct* = cash flow for time (t) *r* = interest rate *C*<sup>0</sup> = initial investment on year 0 *t* = time

$$\text{CRF} = \frac{i(1+i)^n}{\left(1+i\right)^n - 1} \tag{2}$$

An economic analysis of the investment in trans-ocean LNG-fueled container ships, 9300 TEU sailing between Asia and Europe, showed that the LNG low-speed diesel vessels compared to oil-fueled SCR is more attractive [27]. Furthermore, Adachi et al. discovered that the NPV with a lifetime of 20 years is larger, while the refund time to payback is shorter for LNG vessels. Wang et al. also economically analyzed the lowest CAPEX for retrofit fuel gas supply systems and discovered a lower LCC on the auxiliary scheme [18]. LCC analysis allows the assessment of some shipping costs. These include acquisition (capital cost), operation or running costs, fuel consumption, operational services, maintenance, and ship disposal costs [25]. Some of the important elements of this economic assessment can be defined as follows.

#### 3.5.1. CAPEX

Capital expenditure or cost is an essential element that owners consider when making investment decisions. Since the retrofit approach was employed, investing in conversion vessels has become a fundamental option. Wang et al. stated that there are three fuel gas supply systems, and the one with a gas combustion unit has a lower cost. However, this study used an FGSS with the GCU approach as the capital cost includes direct and indirect prices. Direct cost is related to purchase, installation and other related labor expenditures. The indirect costs are related to transportation, insurance, tax, construction overhead, and engineering expenditures [20]

#### 3.5.2. OPEX

Operating expenditure is all the costs related to operational activities, such as maintenance and crew costs. Wang et al. stated that, unlike onshore LNG plants, the FGSS has varying fuel consumption during the voyage [20].

The total expenditure in the lifetime system for LCC includes CAPEX and OPEX costs [18]. Furthermore, when the CRF has been determined, it is multiplied by the CAPEX using the formula:

$$\text{LCC} = \text{CAPEX} \times \text{CRF} \times \text{n} + \text{OPEX} \tag{3}$$

The use of LNG fuel after conversion is perceived as an annual saving despite the different fuel price increments per remaining vessel life cycle [42]. It includes emission reduction with respect to the alternative fuels used in the vessel.

#### **4. Case Study: Economic Analysis 600 TEU Fuel Transition from MFO to LNG**

Based on an economic perspective, this study analyzed the existing 600 TEU container vessel transition from MFO to LNG to determine the life cycle cost (LCC) of a 10-year investment retrofit scheme. The container vessel plies from Tanjung Priok, Indonesia, to Singapore, at a distance of 591 nautical miles. Therefore, the existing vessel will have to be retrofitted to the LNG system, and the major information extracted from the technical analysis of the owners' plans to change fuel, specifically the data concerning the Specific Fuel Oil Consumption from both main and auxiliary engines. The type of fuel used is MFO and Table 1 shows the estimated price of the new build 600 TEU container vessel in the market. PT Samudera Indonesia purchased this vessel for 8.5 million USD in 2018 from Jingjiang Nanyang Shipbuilding China [43]. This container vessel was an MFO-fueled vessel. Table 2 shows 2% inflation per year for new build vessels manufactured with FGSS installed on board culminating in two million USD. The estimated cost is based on 600 TEU newly build MFO fuel container vessel prices from 2018 from PT Samudera Indonesia and calculates 2% inflation each year.

**Table 2.** Estimated new build 600 TEU container vessel.


Furthermore, Figure 9 adapted from the Moore Index 2021 illustrates a container vessel OPEX with various sizes. There are no data for those below 1000 TEU as per the subject size vessel used in this study. For the new build, the analysis was carried out using vessel between 1000 TEU to 1999 TEU. The Moore Index was used to determine each sub-category independently. This study calculated the total OPEX expenditure, which includes maintenance and crew costs using the Moore Index as a reference.

**Figure 9.** OPEX cost for various container vessels.

#### *4.1. Cost Assessment for Retrofitting 600 TEU Container Vessel*

This analysis was centered on the assumption of retrofit cost in 2022, which encompasses main, and auxiliary engines, fuel gas supply system and installation. The conversion cost is USD 200 to USD 340 per HP, based on the upper bound assumption [39] Furthermore, this retrofit has an estimated cost of USD 3,600,000. Figure 10 is adapted from Lagemann et al. [26] and illustrates retrofit costs for various fuel types.

Banawan et al. stated that using gas as fuel reduces the deposit of organic material in the combustion chamber [43]. The reduction in hydrocarbons and other particles from the fuel affects its mass deposit. Some studies carried out on LNG as a marine fuel stated that the maintenance cost is reduced because a small amount of lubricating oils is applied on the spare part compared to the engine system using MFO or HFO. By reducing emissions, the annual expenditure determines the entire cost of natural gas applied on the main fuel onboard, including the capital expenses due to conversion [25].

Based on OPEX per year, the equivalent loading and offloading per year is 312 days. This is because the sailing duration from Jakarta to Singapore lasts for approximately three days. Based on an interview session held with one of the owners, the loading and offloading duration is usually two days for one trip, with the assumption that the in-container at the terminal is 60 containers/day.

Table 3 shows the engine information that it used for investment calculation which consist of data regarding power, number of unit, specific fuel oil consumption and type of fuel.


**Table 3.** Engine information.

Table 4 shows that the total OPEX/year after retrofit is usually within the range of minimum, average and maximum variables. All tend to be reduced according to the acquired data. This Table 4 ilustrate operation cost of spares, repair, maintenance, and lubricant based on the Moore Maritime Index [34]. The total OPEX per year was calculated using three variables, namely minimum, average and maximum.


**Table 4.** OPEX Calculation per year.

The fuel consumption of a 600 TEU container vessel that uses MFO is 6296.66 tons per year based on daily SFOC multiplied by 312 days of operation. For the calculation, the yearly consumption of LNG, based on the heating value of diesel oil, is 4958.2 tons per year or 228,871.27 MMBtu. Table 5 shows yearly fuel consumption LNG and MGO.

**Table 5.** Yearly fuel consumption LNG and MGO.


The annual pilot diesel fuel at the terminal is approximately 10% of the total MFO consumption per year or 629.67 tons [25]. The annual fuel price for LNG is 6.27 million USD compared to MFO, which is 8.13 million USD. Therefore, there is a difference of 1.86 million USD between LNG and MFO. It simply implies that the use of LNG is more economical compared to MFO. Supposing the annual OPEX is calculated yearly based on Moore Maritime Index, 2.228 million USD will be realized, meaning LNG is more economical.

Based on an interview with one of the vessel owners, the economic analysis for a 10-year scheme is shown in Table 6.



CAPEX was calculated using an approach based on a literature review, and USD 3,617,624 was realized. OPEX data were not given, and the interviewee only mentioned the profit per container, which is 10 USD. It simply implies that only 80% of the container vessel space is occupied by a total of 600 TEU. Assuming the vessel uses LNG as fuel, only 480 TEU container is conveyed on every single trip from Jakarta to Singapore. The total number of trips from Jakarta to Singapore is 48 trips per year. Target BEP (Break Even Point) for this analysis is 10 years with equity from the company of approximately 40% and 60% loan. Table 6 shows that the CAPEX obtained is USD 3,617,624, while the OPEX realized for 3 years is USD 183,900. Meanwhile, 60% of CAPEX and OPEX amounted to USD 2,280,933. This study used a bank interest of −8%, and in accordance with further calculations, the loan principal is USD 228,093. This loan repayment needs to be taken into consideration during LCC calculation under different vessel financing model scenarios created by each vessel owner.

Figure 11 illustrates a loan payment scheme for 10 years, as follows.

**Figure 11.** Loan payment illustration.

Cash flow is an important indicator of economic feasibility concerning the investment in the retrofit 600 TEU containership. Figure 12 shows an illustration of cash flow for 10 years. Vessel owners will encounter challenges in cash flow until the second year, and from the third, there is bound to be positive cash flow.

**Figure 12.** Cash flow for 10 years scheme.

For 10 years, the NPV with four Discount Factor (DF) variables tends to provide initial payback, which is used to calculate the Capital Recovery Factor on the investment scenario. Assuming the initial investment has a negative value, it is considered a capital expenditure. However, this scenario's initial cost (-) is USD 3,617,624.

Figure 13 shows the calculated NPV using various discount factors 25%, 30%, 35% and 40% and a positive NPV was realized during the 10 year scheme on the investment. The same interest rate for 10 years of investment was used for the calculation.

**Figure 13.** Net Present Value (NPV) for 10 Years Investment with various discount factor.

Furthermore, Figure 14 shows the Capital Recovery with three interest types such as 5%, 10%, and 15%. The CRF factor for an interest rate of 0.1 is 0.16, which was realized using the formula [2].

#### *4.2. Economic Analysis*

In accordance with the data acquired from the retrofit vessel, the new build 600 TEU that uses MFO and LNG fuels are shown in Figure 15. It is evident that the retrofit vessel tends to have a good competitive value compared to the MFO and LNG fuel used in the new build vessel. For the new build LNG fueled vessel, assume the OPEX is similar to the retrofit; the design will use an FGSS gas combustion unit system. The LCC of three 600 TEU container types is shown in Figure 15.

Figure 15 shows that the retrofit vessel with CAPEX on the FGSS only provides low cost with respect to the economic analysis. New build container vessels with LNG fuel consider the initial capital cost compared to the one that uses MFO. However, the OPEX cost on LNG fuel vessels continues to decrease while the vessel experiences low cost compared to the one that uses MFO. The future trend is cost-efficient for LNG fuel vessels.

**Figure 14.** Capital Recovery Factor for 600 TEU with various interest.

**Figure 15.** LCCA 600 TEU container.

#### *4.3. Sensitivity Analysis*

The sensitivity analysis shows the life cycle investment using the retrofit method for the transition process to LNG fuel, alongside some factors that influence the evaluation.

#### 4.3.1. Selection of Technology

The selection of technology has an important impact on retrofit. FGSS with GCU provides low-cost investment while the implemented advanced system depends on the sailing time of the 600 TEU container. Boil-off gas is one of the factors irrespective of whether or not a longer sailing time would have an impact on its loss.

#### 4.3.2. LNG Prices

LNG prices are also a critical analytical factor. The increasing LNG prices also have an impact on the overall LCC analysis. However, its uncertainty is one factor that needs to be considered in the present analysis.

#### **5. Conclusions and Recommendations**

The prospect of LNG as a marine fuel in Indonesia is growing because LNG is the most advanced technology for alternative marine fuel compared to other alternatives such as hydrogen, methanol and LPG. Furthermore, in terms of investment, LNG has shown good cost efficiency in long-run operations. In vessel design, the ship owner has the option to choose to retrofit technology for their current fleet instead of purchasing new vessels. The life cycle analysis of the retrofit 600 TEU container showed that the retrofit will bring low operational costs for vessel owners. This is aside from the investment, which is mostly for the FGSS on board the vessel. It helps owners to know when to use a retrofit to purchase a new build during the acquisition of a vessel. The FGSS with gas combustion unit is the first option to consider during the selection of technology. However, three comparisons made between retrofit and the other two new build shows that retrofit was the recommended option; the cost of retrofit of USD 6,156,058 is lower than the other two options for LNG fueled 600 TEUs container ship's new build (USD 11,547,860) and MFO fueled 600 TEUs container ship's new build (USD 10,702,872). Other savings that shipowners can obtain from retrofit is less time in dry dock for conversion from current MFO fueled to LNG fueled. The more time that the shipowner can save will provide an opportunity cost for the vessel to return to operation and generate income. LCCA is a tool used for life cycle and low-cost analysis with respect to retrofit investment. This analysis will be affected by LNG prices, especially when the uncertain price of LNG will bring a change in analysis.

LNG is one of the advanced technologies of alternative fuel and several studies proved that it is the most reliable energy source. From the economic analysis, it was discerned that LNG as a marine fuel reduces maintenance and spare part costs. With variable interest rates, the capital recovery factor shows a decrease in payment. The maintenance cost takes significant consideration due to the usage of LNG as fuel. The 600 TEU container vessel capital recovery result served as a reference or guide to vessel owners to be committed to using green fuels such as LNG.

This study already provided information about the challenges that Indonesian vessel owners face when they want to implement green alternative fuels. Some of these challenges are centered on technology, investment and potential profit. However, this is an opportunity for vessel owners to consider the use of LNG as marine fuel due to its long-term impact on cost efficiency and operating activities.

**Author Contributions:** Conceptualization, R.B. and R.O.S.G.; methodology, R.B.; software, R.B.; validation, R.B., R.O.S.G. and S.; formal analysis, R.B.; investigation, R.B.; resources, R.B. and R.O.S.G.; data curation, R.B.; writing—original draft preparation, R.B.; writing—review and editing, R.B. and R.O.S.G.; visualization, R.B.; supervision, R.O.S.G.; project administration, R.B.; funding acquisition, R.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


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