Environmental Protection: A Contribution of Maritime Autonomous Surface Ships

Introduction

Maritime Autonomous Surface Ships (MASS) are vessels that can operate with varying degrees of automation, either with no crew, reduced crew, or remote control, using advanced digital technologies such as artificial intelligence, sensors, and autonomous navigation systems. The International Maritime Organization (IMO) defined MASS as “Ships that can operate independently of human interaction to varying degrees” (IMO, 2018). In addition, Denmark defines MASS as “a term for a vessel that is capable of automatically assessing the situation, analyzing the situation, evaluating the situation, and making decisions to control the vessel. This control can be performed automatically, either in part or in full, with the participation of the crew in some situations. This participation can take place from anywhere, without necessarily requiring the crew to be present on the vessel” (IMO, 2018). The study by (Dremliuga and Mohd-Rusli 2020) argues that MASS is a type of autonomous vessel capable of performing certain autonomous operations at sea, whether the crew is present on board. In a report by Wariishi (2019), it is argued that autonomous ships are vessels that are fully or partially controlled to perform activities such as maneuvering, observing the surrounding environment, docking, and controlling the engine.

The IMO divides MASS into four levels, while individual countries have different ways of classifying levels of automation based on various criteria. For example, in the United States, when considering the involvement of machinery and equipment, automation is divided into three levels: intelligent, semi-automatic, and automatic. Additionally, based on the interaction between the crew and the system, it is divided into four levels: common, intelligent, semi-automatic, and fully automatic (IMO, 2018). Meanwhile, the UK defines six levels of automation, ranging from the conventional operation level (Level 1) to the fully automatic level (Level 6) (Maritime UK, 2022). The European Commission classifies automation into three levels: operational, automatic, and fully automatic (UKP&I, 2019). In terms of navigational functions, automation can be divided into five levels: Conventional Operation Function (M), Decision Support System Function (DS), Decision Support System Function with Conditional System Performance (DSE), Self-Control Function (SC), and Autonomy Function (A). The international certification agency Bureau Veritas has also published a guide on automated shipping. In this guide, Bureau Veritas identifies five levels of automation, ranging from the crew operation level (A0) to the fully automatic level (A4) (Bureau Veritas, 2019).

Currently, countries and organizations have varying views and assessments regarding MASS. However, in general, autonomous surface ships can be understood as vessels that apply different levels of automation to analyze, evaluate, and make decisions based on programmed data. The goal is to develop fully autonomous ships that operate without any crew intervention throughout the entire voyage—from the port of departure to the port of destination.

In addition, it is important to recognize the distinction between unmanned vessels and MASS as they represent two fundamentally different concepts. “Unmanned Vessels” are understood as vessels that have no crew on board but are controlled remotely from a shore-based station. In contrast, MASS are preprogrammed to operate using algorithms. The goal of MASS is to eliminate human intervention entirely in the operation of the vessel.

In order to enable the practical implementation of MASS, the IMO has undertaken several important activities focused on assessing the regulatory compatibility of MASS with existing maritime conventions. The Regulatory Scoping Exercise (RSE) is considered an important action taken by the IMO on issues related to MASS, and it was completed in 2021. The RSE examined how existing IMO instruments (e.g., SOLAS 74, MARPOL 73/78, COLREGs 72) apply to MASS. It also identified gaps, challenges, and potential amendments needed to accommodate different levels of autonomy. These activities are essential to ensure that MASS can operate safely, legally, and consistently within the current international maritime framework. In addition, the Maritime Safety Committee (MSC) is developing a nonmandatory, goal-based MASS Code, expected to be completed by 2025, with the aim of adopting a mandatory version by 2028. The focus areas include functional requirements, safety and risk management, and the integration of the human element (particularly remote operators), as well as communication and control systems.

Impact of Pollution from Ship Sources

Initially, among the various forms of pollution caused by ship-source pollution, oil spills remain one of the most significant and detrimental. They are considered one of the most serious sources of marine pollution resulting from maritime activities. The history of the shipping industry has witnessed several catastrophic oil spills that have severely impacted the marine environment, including the following notable examples: The Exxon Valdez oil spill remains one of the most infamous maritime environmental disasters in history. Occurring in Prince William Sound, Alaska, in 1989, the incident resulted in the release of approximately 11 million gallons of crude oil into the marine environment after the vessel struck a reef. The environmental consequences were catastrophic, including the mass mortality of marine birds, sea otters, and fish, as well as the long-term contamination of over 1,300 miles of coastline (NOAA, 2020). Another major incident, the Amoco Cadiz oil spill, occurred in 1978 when the vessel ran aground off the coast of Brittany, France, releasing approximately 1.6 million barrels of oil. This event is considered one of the largest oil spills by volume and caused widespread ecological damage to marine and coastal ecosystems (ITOPF, 1978). Similarly, the Hebei Spirit oil spill occurred in 2007 after a collision with a crane barge off the coast of Taean, South Korea. Approximately 2.7 million gallons of crude oil were discharged, contaminating extensive stretches of coastline. The spill affected over 300 fishing communities and required a large-scale cleanup operation involving government agencies, military personnel, and civilian volunteers (Kim et al., 2009; ITOPF, 2007). These incidents, among numerous others across the globe, have resulted in significant and lasting environmental degradation and economic disruption, underscoring the urgent need for stringent preventive measures and effective response mechanisms in maritime oil spill management.

Such oil spills have led to devastating consequences, including the destruction of marine ecosystems and the mass mortality of marine fauna and flora. In addition, they cause significant economic disruptions—coastal areas lose their tourism appeal, and fishing, aquaculture, and resource exploitation zones are severely affected (Peterson et al., 2003; Whitehead et al., 2011). Furthermore, governments are often forced to spend enormous amounts of money to manage and remediate these environmental disasters (Sumaila et al., 2011). Most critically, oil spills pose serious risks to human health through direct exposure and long-term contamination (Goldstein et al., 2011).

Moreover, ship-generated sewage is also recognized as a significant source of pollution to the marine environment. Sewage discharged from ships, including both blackwater and greywater, is regulated under Annex IV MARPOL 73/78. The main sources of sewage on ships include toilets and urinals, medical facilities, showers, sinks, and washbasins, laundry facilities, galley (kitchen) sinks, vacuum toilet systems, and other sources generated on board ships.

Ship-generated wastewater can have significant adverse impacts on marine ecosystems. It can lead to oxygen depletion (hypoxia) and the formation of dead zones where aquatic life cannot survive. Elevated concentrations of nutrients and pathogens in wastewater can damage sensitive marine habitats, including coral reefs. Moreover, toxic substances present in wastewater—such as mercury and polychlorinated biphenyls—tend to bioaccumulate in marine organisms (Booth and Zeller, 2005). Predatory species, including tuna and dolphins, often exhibit high levels of such pollutants, posing ecological risks and potential health hazards to humans through the consumption of contaminated seafood (Booth and Zeller, 2005). When the marine ecosystem is disrupted, marine organisms are adversely affected in various ways, including genetic mutations, stunted growth, reduced fertility, and increased mortality. These effects are primarily caused by exposure to toxins, hypoxic conditions, and the accumulation of pathogens and pollutants. As a result, many marine species may become unsafe for human consumption.

In addition, research on marine waste has historically received less attention compared to studies on oil-contaminated wastewater and ship emissions. One of the earliest investigations by Paul V. Horsman revealed alarming statistics regarding the volume of marine waste generated and directly discharged into the ocean (Horman, 1982). Subsequent research by Chen and Liu focused on fishing vessels and identified the most common types of waste as plastic bottles, plastic bags, metal cans (tin or aluminum), fishing gear (primarily nets, lines, buoys, and ropes), and batteries (Chen and Liu, 2013).

In the case of cruise ships, Nickie Butt estimated that an average vessel generates at least 1 kg of solid waste, along with two plastic bottles and two metal cans per passenger per day (Nikie Butt, 2007). The findings from these studies indicate that a substantial portion of ship-generated waste continues to be released directly into the marine environment, despite the implementation of Annex V of the MARPOL 73/78 Convention.

Annex V explicitly highlights plastic waste and plastic products as particularly harmful pollutants due to their persistence in the marine environment and their potential to cause long-term ecological damage. These materials are known to directly cause injury and death to marine animals through ingestion or entanglement (Kühn et al., 2015). Furthermore, recent scientific evidence has demonstrated that plastic particles can negatively impact human health, with observed effects including DNA damage, alterations in gene and protein expression, cell aggregation, reduced cell viability, bone inflammation, and lesions in various organs (Gallo et al., 2018).

Furthermore, recent studies have demonstrated a clear link between plastic waste and climate change. For instance, according to the Center for International Environmental Law (2019), the life cycle of plastic—from production to final disposal through incineration—can result in the emission of over 850 million metric tons of greenhouse gases annually. Similarly, research by Zheng and Suh (Zheng and Suh, 2019) highlights that the incineration of plastic waste not only emits significant quantities of carbon dioxide (CO₂) and greenhouse gases but also releases a range of toxic substances that contribute to air pollution. Moreover, microplastics in the ocean have been found to harm plankton populations, which play a crucial role in carbon sequestration within marine ecosystems (Long et al., 2015). The disruption of these populations can therefore diminish the ocean’s capacity to absorb CO₂, thereby accelerating the progression of climate change.

In addition to environmental concerns, marine debris poses serious navigational and safety hazards. Debris can entangle or obstruct vital parts of a vessel, such as rudders, propellers, and intake pipes, increasing the risk of maritime accidents (Newman et al., 2015). Beyond these physical threats, marine debris also has profound socioeconomic impacts. It negatively affects aquaculture operations, fisheries, and the aesthetic value of coastal areas, leading to declines in tourism and related services. Furthermore, the economic burden of removing waste from polluted beaches falls heavily on coastal nations, resulting in substantial cleanup costs (Newman et al., 2015).

Finally, ship emissions contain a range of components that are harmful to both the environment and human health, as identified under the MARPOL 73/78 Convention. These emissions include greenhouse gases such as carbon dioxide (CO₂), as well as air pollutants such as fine particulate matter (PM₂.₅—particles with a diameter of less than 2.5 µm), sulfur oxides (SO_x), nitrogen oxides (NO_x), and, to a lesser extent, carbon monoxide (CO) and volatile organic compounds.

Coastal regions and port areas are considered particularly vulnerable to pollution from ship emissions due to the high density of commercial vessels, fishing boats, and service ships operating in these zones. Ports are especially critical points, where loading and unloading activities are concentrated, contributing further to the degradation of air quality.

Ship-derived primary air pollutants are known to participate in atmospheric chemical reactions, resulting in the formation of secondary pollutants, including ozone and secondary particulate matter. According to studies, shipping emissions contribute approximately 9.4 percent to ambient concentrations of primary PM₂.₅ and 12.3 percent to concentrations of secondary inorganic particles (Andersson and Cuijpers, 2009).

Extensive research has confirmed that emissions from ships have both direct and indirect negative effects on the environment (Ayesu, 2023; Shi et al., 2023) as well as on human health (Tang et al., 2020; Ramacher et al., 2020). These health impacts include respiratory and cardiovascular diseases, particularly among populations living near busy ports and coastal areas.

MARPOL and Its Role in Environmental Protection

In order to prevent pollution from ship sources, IMO issued MARPOL. MARPOL was initially adopted in 1973 but was amended in 1978 due to the growing concern over oil tanker accidents. The resulting protocol, known as MARPOL 73/78, entered into force in 1983 and has since been regularly updated to respond to emerging environmental challenges.

The convention comprises a main treaty and six technical annexes, each addressing a specific type of pollution: oil (Annex I), noxious liquid substances (Annex II), harmful substances in packaged form (Annex III), sewage (Annex IV), garbage (Annex V), and air pollution (Annex VI). Annexes I and II are mandatory for all parties, while the others are optional but widely ratified.

MARPOL has been instrumental in reducing ship-based pollution globally. For instance, Annex I has led to significant reductions in oil pollution incidents through the mandatory use of oil discharge monitoring systems and double-hulled tanker designs. Annex I of MARPOL prohibits the discharge of oil into the marine environment unless stringent criteria are met, as stipulated in Regulation 15.1. Specifically, the discharge of oily wastewater in special sea areas is strictly prohibited unless certain rigorous conditions are fulfilled, in accordance with Regulation 15.2. To be permitted to discharge oily wastewater, ships must comply with the equipment requirements outlined in Regulation 14. These include the installation and proper maintenance of oily water separators, oil content meters, and oil discharge monitoring and control systems.

Furthermore, Annex I mandates that all ships maintain an Oil Record Book in compliance with the requirements of Regulation 17.2 to ensure accurate documentation of all oil-related operations. In anticipation of environmental emergencies, such as oil spills, ships are also required to carry a Shipboard Oil Pollution Emergency Plan, which provides standardized procedures for reporting oil pollution incidents and implementing immediate response measures to minimize environmental damage. In addition to shipboard measures, ports are also obligated under Regulation 38 to maintain adequate facilities and equipment for the reception, management, and response to oil spills, ensuring a coordinated and effective approach to marine environmental protection.

Annex IV of MARPOL addresses the prevention of pollution by sewage discharged from ships into the sea. This annex plays a vital role in safeguarding the marine environment, particularly in sensitive coastal and port waters. Regulation 11 establishes strict controls governing the discharge of sewage, prohibiting such discharges unless the conditions outlined in the regulation are fully met. In special areas, such as the Baltic Sea, even more stringent discharge standards are enforced. To ensure compliance, ships are required to possess a valid International Sewage Pollution Prevention Certificate. In many cases, vessels operating in special areas must utilize port reception facilities for sewage disposal, rather than discharging it into the marine environment. Furthermore, in accordance with Regulation 9, ships must be equipped with one or more of the following systems to prevent environmental pollution: a sewage treatment plant, a sewage comminuting and disinfecting system, or a sewage holding tank.

Annex V, which prohibits the discharge of plastics and other harmful garbage into the sea, has been a critical step in addressing marine debris. The annex stipulates that waste generated during the operation of ships may only be discharged into the marine environment if it meets the conditions outlined in Regulation 3. Discharge within special areas is subject to more stringent requirements. Notably, the discharge of plastics and plastic products is strictly prohibited in all sea areas, regardless of the ship’s location. Additionally, the annex mandates that ships must implement a Garbage Management Plan, maintain a Garbage Record Book (GRB), and follow appropriate discharge procedures in accordance with Regulations 8, 9, and 10. Furthermore, port facilities are required to provide adequate systems for the reception and treatment of ship-generated waste, ensuring environmentally sound management practices and compliance with international standards. Recent amendments to MEPC.295 (71), effective 2018 (IMO, 2017), introduced fishing gear reporting requirements. If fishing gear is lost or discharged, the event must be reported to the flag state and coastal state authorities, with entries made in the GRB. Especially (1) Mandatory GRB for smaller ships adopted via MEPC.360 (79) (IMO, 2022), entering into force May 1, 2024. The current regulations now apply to all ships of 100 gross tonnage (GT) and above, as well as to all passenger ships certified to carry 15 or more persons on international voyages—an expansion from the previous threshold, which applied only to ships of 400 GT and above. Under the revised requirements, smaller vessels between 100 and 400 GT are now obligated to maintain records in the GRB or an equivalent logbook. These records must document all discharges to reception facilities, onboard garbage incineration activities, permitted discharges at sea, and any accidental or exceptional losses of garbage; (2) under MEPC.382 (80) (IMO, 2023), Red Sea and Gulf of Aden designated a MARPOL V Special Area enforced from January 1, 2025; (3) Arctic regional port reception facility arrangements; and (4) incorporates the IMO Instruments Implementation Code (III Code) through Resolution MEPC.246 (66) (IMO, 2014), adding new audit definitions (Regulation 11–12) into Annex V.

Furthermore, Annex VI, introduced in 1997 and significantly revised in subsequent years, represents a progressive shift in addressing air pollution and climate change. It limits emissions of sulfur oxides (SOx) and nitrogen oxides (NO_x) and introduces emission control areas (ECAs) where stricter standards apply. This has had a tangible impact on air quality in coastal regions and contributed to global efforts to mitigate climate change.

Ship emissions have been regulated under MARPOL Annex VI since its entry into force in 2005. The primary objective of this annex is to establish regulatory limits on emissions of air pollutants from ships, including nitrogen oxides (NO_x) and sulfur oxides (SO_x), which have harmful effects on atmospheric and human health. Sulfur emissions are regulated by limiting the maximum allowable sulfur content in marine fuel, while NO_x emissions are controlled through specific emission limits applied to ship engines. These NO_x limits vary according to engine speed and are categorized into different tiers based on the construction or major conversion dates of the ship: Tier I (for ships constructed between 2000 and 2011) and Tier II (for ships constructed after 2011).

In addition, MARPOL Annex VI designates ECAs, within which more stringent emission standards apply. Since 1 January 2020, the global limit on fuel sulfur content has been reduced from 3.5 to 0.5 percent. In sulfur emission control areas (SECAs), the limit has been further reduced to 0.1 percent, down from the previous 1.0 percent. Recent amendments to MARPOL Annex VI, adopted between 2016 and 2022, reflect the IMO’s ongoing efforts to enhance environmental protection. These amendments include the promotion of cleaner alternative fuels, standardized procedures for sampling and verifying the sulfur content of fuel oil, and the implementation of the Energy Efficiency Design Index (EEDI). Additional measures include the designation of the Mediterranean Sea as a SECA for SO_x and particulate matter, the mandatory application of SECA and EEDI requirements to ro-ro cargo and passenger vessels, significant revisions to the Tier III NO_x ECAs in the Arctic, Canadian Arctic, and Norwegian Sea regions, and the mandatory recording of operational compliance with Tier III requirements in designated ECAs.

Analysis of the Contribution of MASS to Environmental Protection

Conclusion

As previously discussed, the volume of wastewater, garbage, and air emissions generated and discharged by ships into the environment depends on numerous objective environmental factors. Additionally, the extent and quantity of these pollutants vary across different types of vessels. However, the case study of the MV GOLD DUST clearly demonstrates that the application of MASS can significantly reduce these pollution sources, potentially eliminating their environmental impact altogether.

Nevertheless, practical implementation and other legal bases reveal that gaps still exist regarding data on shipborne sewage, garbage, and emissions, as analyzed above. For instance, monitoring compliance with Annex V regulations remains relatively challenging. In this regard, the Vietnamese merchant fleet can be cited as a representative example (VR, 2011–2024). Although in recent years the Vietnamese fleet has consistently appeared on the Tokyo-MOU white list (Tokyo-MOU, 2011–2024), deficiencies related to Annex V persist—such as failure to segregate waste, irregular or incomplete GRB entries, and missing signatures from the officer of the watch and the master. According to surveys conducted among seafarers currently working on board, compliance with garbage management regulations and GRB entries is often performed primarily to satisfy port authority inspections, rather than out of genuine concern for environmental protection. The verification of whether the data recorded in the GRB is truthful—and to what extent it is accurate—as well as the actual quantity of waste generated and discharged directly into the environment, remains uncertain. At present, only the crew members onboard possess the precise answers to these questions.

Therefore, if crew members remain onboard, issues such as human error or deliberate manipulation cannot be eliminated. To achieve more stringent control over all ship-generated pollution sources, in addition to legal measures, standards, and rigorous inspection protocols, minimizing or eliminating human-related errors and fraud should be considered. As previously analyzed, the deployment of MASS at various levels of autonomy could make a significant contribution in this regard.