Towards Safe Maritime Decarbonization: Safety Barriers of Methanol Fuel

Abstract

In response to global concerns about climate change and decarbonization across every sector, pressure has mounted on the maritime industry to reduce its environmental impacts, specifically its greenhouse gas (GHG) emissions, representing around 2.8% of the global total. As such, it prompts new alternative fuels that align with the International Maritime Organization (IMO)’s 2050 net-zero target. In recent years, several alternative fuels, such as hydrogen, ammonia, and methanol, have been proposed. However, alternative fuels face many challenges regarding cost, safety, and efficiency compared to traditional fossil fuels. Currently, methanol is considered one of the most promising alternatives since it is available, easy to store, and can take full advantage of existing infrastructure in situ. Moreover, methanol has a lower carbon intensity than conventional fossil fuels. However, its usage poses related risks of toxicity and flammability; thus, this area still needs in-depth research regarding hazard control. This study implements a systematic five-step methodology. Through a comprehensive literature review, the predominant hazards are delineated. To systematically analyze these risks, this study introduces a novel hazard-based coding system developed to categorize hazards into three classifications: toxicity, flammability, and explosivity. This system is specifically designed to analyze qualitative reports from thirty methanol accident investigations utilizing MAXQDA software. Subsequently, safety barriers related to methanol are identified, followed by a gap analysis to evaluate the effectiveness of existing safety measures. The findings indicate that physical hazards, including flammability and explosivity, represented the majority of identified risks. Furthermore, tank explosions emerged as a prominent sub-hazard, frequently linked to the highest number of reported fatalities. A gap analysis delineates the identified barriers related to Equipment and Personal Protective Equipment (PPE), Human Error Reduction, the Legal Framework, and First Aid, comparing them against the current measures outlined in IMO Circular 1621 and other legislative frameworks. Consequently, the analysis highlights critical gaps in technical guidelines and operational procedures related to methanol use. The study recommends the development of fuel-specific safety protocols, mandatory training for seafarers, and regulatory updates to address the unique hazards of methanol. These measures are necessary to create higher safety standards and make methanol a viable alternative fuel by ensuring its safe integration into the industry.

1. Introduction

1.1. Historical Context and Regulatory Motivation

Since the early 20th century, fossil fuels have served as the primary source of propulsion for ships, enabling significant growth in vessel size and global trade. However, the widespread reliance on fossil fuels has led to considerable emissions of harmful pollutants, including nitrogen oxides (NOx), sulfur oxides (SOx), carbon monoxide (CO), carbon dioxide (CO₂), and particulate matter (PM) [1]. According to the International Maritime Organization’s (IMO) Fourth GHG Study, the shipping sector’s greenhouse gas (GHG) emissions accounted for approximately 2.89% of global anthropogenic GHG emissions in 2018. Furthermore, these emissions are projected to increase, potentially reaching between 90% and 130% of 2008 levels by 2050 [2]. Therefore, the sector needs to take action to decarbonize in line with efforts in other sectors. Maritime decarbonization has been defined as “the process of eliminating ships” CO2 and other GHG emissions through mitigation measures or balance of surplus emissions by removal, leading eventually to net-zero CO2 emission by 2050, while energy transition [3,4], which has the same target, is defined as “the process of changing shipping status from being high energy consumers, dependent on fossil fuels to being efficient consumers that depend on green fuels and renewable energy” [5].

The IMO [6] has taken significant steps to reduce GHG emissions from ships, aiming to achieve net-zero emissions by or around 2050. The IMO has established two key interim targets to track progress towards this goal. The first checkpoint aims to reduce GHG emissions by at least 20%, with a target of 30%, by 2030, compared to 2008. The second milestone seeks to decrease total annual GHG emissions from shipping by at least 70%, with an aspirational target of 80%, by 2040, also using 2008 as a baseline. In addition to the GHG strategy, the IMO has established specific limits for SOx and NOx under MARPOL Annex VI, with SOx controls outlined in Regulation 14 and NOx limits defined in Regulation 13.

1.2. Alternative Fuel and Methanol’s Role

As a result of IMO regulations and the global drive to reduce emissions from ships, several alternative fuels have appeared as potential replacements for traditional fossil fuels. These alternatives, which are considered more environmentally friendly, include ammonia, biofuels, dimethyl ether (DME), ethanol, hydrogen, liquefied natural gas (LNG), and methanol (methyl alcohol). Studies and organizations have highlighted the advantages and disadvantages of each of these fuels in terms of their potential to reduce emissions and their suitability for maritime use [1,7,8,9].

Methanol has gained increasing attention in the maritime industry due to its potential to reduce GHG emissions and its compatibility with existing ship engines when appropriately modified. Bio-methanol, green methanol, and e-methanol can achieve 60–90% reductions in well-to-wake emissions compared to conventional marine fuels [10]. In addition, the current fuel-handling infrastructure requires only minor modifications to accommodate methanol, making it a relatively cost-effective option compared to other alternative fuel sources [11].

The first methanol-fueled vessel was operated in 2015. These vessels can operate on carbon-neutral or fossil-based methanol and conventional fuels [12]. Moreover, the LR [13] reports highlighted the demand for methanol-capable and methanol-ready ships, which is projected to rise sharply in the coming years. In 2022, methanol-fueled ships accounted for 3% of the global order book (7% based on GT), and this share is expected to increase to approximately 20% by 2030, representing around 1200 ships.

1.3. Technical Risks and Study Motivation

However, as methanol is toxic and highly flammable, it presents distinct safety challenges compared to traditional fossil fuels such as heavy fuel oil (HFO) and marine diesel oil (MDO). This research emphasizes the risks associated with methanol’s lower flashpoint and toxicity and the necessary safety precautions for storage and transfer onboard vessels.

The selection of methanol as the focus of this study is driven by its rising adoption in various vessel types as the industry seeks to comply with stricter environmental regulations. Several ships have already integrated methanol-fueled engines, and their crews are actively managing the unique requirements of this alternative fuel [14] by examining the operational experience of these vessels.

This study’s overarching objective is to provide insights into current safety measures required for methanol use and contribute to a broader understanding of the potential hazards associated with its continued implementation in the maritime sector. The research questions—RQ1: Are the current IMO safety measures effective in mitigating ship methanol-related hazards? RQ2: Can evidence from industrial methanol accidents be translated into improved maritime safety protocols? RQ3: What additional safety measures could enhance methanol operations, and how can their effectiveness be verified? —are set to be commensurate with the study aims.

2. Literature Review

Chemically, methanol is an alcohol and is known as methyl alcohol, having the formula CH₃OH. It is a simple alcohol usually known as wood alcohol [15]. There are several concerns with the safety of the crew and the ship during handling and use. Significant safety problems arise because methanol is toxic and flammable, with specific ship-handling requirements.

Although the use of methanol as a marine fuel is currently growing in popularity, its application is not a recent development. Methanol has been used as a fuel in motor vehicles since as early as 1954, highlighting its long-standing potential in various industries [16].

2.1. Properties and Risks

Methanol poses significant risks due to its flammability. Its low flashpoint is 12 °C, and its auto-ignition temperature is 470 °C [17], making it highly susceptible to ignition. Additionally, water is ineffective in cooling methanol below its flashpoint [18], limiting its use in controlling fires involving methanol.

The methanol explosive range (volume percentage) falls between 6.7% and 36% [17]. This means that it can ignite at a wide range of concentrations. It becomes highly hazardous in confined or unventilated areas, especially when vaporized and in the presence of an ignition source. Even relatively low concentrations, about 6.7%, can ignite and burn, while concentrations above 36% remain flammable until the oxygen available becomes limited.

When burned, pure methanol produces a clean, blue flame with limited luminosity, which makes the flames hard to detect [19]. Water is often ineffective in combating methanol fires, which can release poisonous gases. To prevent accidental combustion, it is essential to keep methanol and its containers away from heat and ignition sources [18].

Additionally, methanol vapors are heavier than air, allowing them to travel long distances and potentially causing fires far from the initial source [20]. Runoff from fire suppression efforts or water dilution may contribute to environmental pollution. Furthermore, methanol containers are susceptible to explosion when exposed to heat, and runoff into sewers can create an explosion hazard [21].

Moreover, methanol belongs to class 3 flammable liquids (UN dangerous products classification), alongside many other liquid fuels, including petrol and petroleum distillates [22]. However, the corrosive characteristics present significant challenges for handling and storing methanol. Ships cannot use standard fuel tanks used for HFO and MDO. Therefore, ships using methanol as a fuel require special stainless steel or carbon steel tanks [13]. Furthermore, the experiment shows that pure methanol is particularly aggressive toward essential engine components, such as pistons, rings, and valves, leading to increased corrosion risks [23].

2.2. Human Health Hazards

Methanol poses significant risks due to its toxicity. Methanol exposure can adversely affect the human body through four primary routes: inhalation of vapors, dermal contact, ocular exposure, and ingestion.

Inhaling methanol vapors causes irritation within the respiratory system [24]. After minor exposure, symptoms may include cough, headache, dizziness, and nausea. Higher or lengthier exposure to methanol can then lead to more severe symptoms: disturbances of vision, muscular weakness, somnolence, dyspnea, and severe poisoning, which may cause convulsions or even loss of consciousness. Methanol is of particular concern because it can affect the central nervous system, so chronic exposure to it could be interpreted as the development of more severe effects [25].

The odor threshold for methanol, which lies within the range of 100 to 1500 ppm, reflects the concentration where the mildly sweet, alcoholic smell turns perceptible to the nose of a human being. The variation in sensitivity means that some can detect it when as low as 100 ppm, while others may only become aware of it at much higher concentrations of around 1500 ppm [20]. On account of this high Threshold Limit Value (TLV), exposure due to the inability of a person to detect most cases of methanol due to its odor at sufficiently lower concentrations is a significant concern.

For safety purposes, the Occupational Safety and Health Administration (OSHA) provided a legally permissible airborne exposure limit of 200 ppm [26]. Similarly, the National Institute for Occupational Safety and Health (NIOSH) established an exposure limit of 200 ppm averaged over a 10 h workday, with a short-term exposure cap of 250 ppm for any 15 min [21]. This TLV for 8 hr average exposure and short-term exposure limit (STEL) also agree with the suggested actions forwarded by the American Conference of Governmental Industrial Hygienists (ACGIH), at 200 and 250 ppm, respectively [24], because these recommendations provide stringent monitoring of methanol traces in the environment where avoidances are not fully inconspicuous by pre-emption due to health issues posed during inhalation.

Dermal exposure to methanol presents some health hazards [24]. Brief exposure leads to slight irritation, dryness, and skin reddening. During more extensive or extended periods of exposure, methanol could be absorbed through the skin, and systemic toxicity could thus be possible. Because methanol is absorbed through skin exposure, it could be introduced into the bloodstream, thereby giving symptoms that involve inhalation or ingestion exposure, including visual disturbances, lethargy, and acidosis in severe situations [27].

In one case reported by Mojica et al. [28], a man developed high toxicity after his feet and clothes were exposed to methanol during the cleaning of an industrial tank. He showed symptoms such as lethargy, blurred vision, and severe acidosis. This indicates that toxic dermal exposure could be possible if the area is extensive; hence, protective wear is essential even in industrial handling.

Ingested methanol poses serious health risks, with as little as 30 mL potentially leading to severe outcomes, including serious complications such as blindness and life-threatening conditions [24]. Once metabolized in the body, methanol is oxidized to formic acid and formaldehyde; these are highly toxic to the optic nerve and central nervous system. This may cause symptoms such as loss of vision, respiratory failure, or even, if not treated, death [29].

Methanol poisoning can occur when methanol is ingested accidentally or used as a substitute for ethanol, especially among individuals with alcohol dependence. Cases have also been reported in instances of bootlegged or adulterated alcoholic beverages [30]. A lack of awareness may lead to crew members inadvertently ingesting methanol on ships, thinking that it is safe to drink as an alcoholic beverage, especially on dry ships without alcohol onboard.

In addition, methanol has the potential to act as a teratogen in humans, as evidenced by its similar effects observed in animal studies. This implies that methanol exposure may lead to birth defects by adversely affecting the developing fetus [20]. Further research is essential to validate these scientific findings. This underscores the necessity for female seafarers to be cognizant of contact hazards, especially considering the ongoing calls for gender equality within the maritime industry and the anticipated rise in the number of female seafarers.

The most critical toxic effect of methanol is its ocular toxicity, which can, in most cases, cause severe visual impairment. Symptoms of ocular exposure to methanol include irritation. Ocular exposure is a perilous route of exposure to methanol, and it takes only one drop of this substance to penetrate through the eye and cause violent irritation that may be irreversible. This toxicity is one of the most serious results of methanol poisoning and has some possible long-term effects on vision [31].

2.3. Regulatory Framework

Methanol must be adopted as fuel in the shipping industry under a strong regulatory compliance regime for safety and environmental concerns. IMO plays a vital role in establishing global standards concerning ships using methanol as fuel. The International Code of Safety for Ships Using Gases or Other Low Flashpoint Fuels (IGF Code) prescribes the mandatory requirements necessary for the safe design, construction, and operation of methanol-fueled ships, covering fuel storage safety, handling systems, and fire protection [32].

Complementing this, Annex VI of MARPOL by the IMO demands that limits related to sulfur oxides, nitrogen oxides, and particulate matter be followed; hence, methanol fits into international efforts toward reducing air pollution. Examples at the regional level include the European Union’s directive 2014/94/EU and the FuelEU maritime regulation, both of which are supportive of alternative fuel infrastructure and thus incentivizing the adoption of low-emission fuels such as methanol [33,34]. The Energy Efficiency Design Index (EEDI) and Ship Energy Efficiency Management Plan (SEEMP) frameworks also provide a platform for adopting alternative fuels, such as methanol, to reach energy efficiency with minimal emissions [35].

While addressing methanol’s safety challenges concerning its low flashpoint and toxicity, the IMO’s Maritime Safety Committee (MSC) issued interim guidelines on technical and operational safeguards, especially MSC.1/Circ.1621 [36]. Methanol systems also need to comply with requirements under the SOLAS convention, Chapter II-2, on fire safety, detection, and suppression. Similarly, the United States Coast Guard enforces safety standards for alternative fuels in concert with the Clean Air Act to ensure environmental compliance [37].

More specific technical guidance on methanol-fueled ships is given by classification societies such as [38,39,40,41]; all provide risk assessments, system approvals, and design specifications to mitigate the added risks due to the more corrosive and flammable nature of methanol. Apart from this, methanol bunker operations are dealt with by ISO 20519:2017, which details requirements on safety and environmental matters related to the transportation and storage of liquid fuels [42]. Industry bodies like the Methanol Institute also contribute to recommendations for harmony.

Moreover, the IMO [43,44] emphasized that seafarers responsible for the handling or utilization of fuels on ships subject to the IGF Code must be appropriately qualified and certified. In addition, ITF [45] highlighted that safely using methanol as a marine fuel requires crew training consistent with the IMO’s STCW Convention. Crews should be suitably trained regarding specific properties, safety aspects, and emergency handling of methanol. Complementing the training programs, voluntary certifications such as ISO 14001 on environmental management and green marine certification push operators beyond regulatory compliance to minimize their environmental footprint.

3. Methodology

This study follows five systematic consecutive steps: a literature review to identify the main hazards, developing a hazard-based coding system, collecting 30 methanol accident investigation reports from various industrial sources, analyzing methanol accident reports qualitatively, and conducting gap analysis for the related IMO instrument. The findings illuminate safety challenges and suggest proposals to improve the safety framework of methanol for maritime applications.

3.1. Review of Existing Knowledge

The first step includes reviewing all methanol literature through a wide range of academic sources, including peer-reviewed scientific articles, industry reports, and various technical documents as cited in the literature review. Methanol data, such as the flashpoint and vapor pressure, slightly vary depending on the product specification and use. The methanol characteristics used in this research were obtained from the International Chemical Safety Cards (ICSC) digital platform [25]. Based on the review, the dominant hazards (HAZIDs) that the ship’s operator could encounter during the three operations involving methanol bunkering, handling, and stowage were identified.

3.2. Development of a Sub-Hazard-Based Coding System

An outcome of the methanol literature reviews is a novel hazards-based coding system, created based on the three hazards identified through literature and industry: toxicity (T), flammability (F), and explosivity (E), as shown in

Table 1. Hazards-based coding system. Source: Author.

GHS Classification	Main Hazards	Coding	Sub. HAZID/Exposure Method	Notes
Health Hazards	Toxicity (T)	T1	Dermal	Contact
		T2	Ocular	Splash/contact
		T3	Inhalation	Vapor inhalation
		T4	Ingestion	Accidently as alcohol
Physical Hazards	Flammability (F)	F1	Highly flammable liquid	Low flashpoint (9–12 °C)
		F2	Invisible flames	Colorless during Daylight
		F3	No smoke/no soot	Methanol burns efficiently
		F4	Flammable Methanol Solution	Methanol + Water
	Explosivity (E)	E1	Tank explosion/explosion	Confinement led to an explosion (explosive range between 6.7% and 36%)

. Those hazards are the primary consequences of methanol accidents for drivers. The sub-hazards were identified by linking methanol’s physicochemical properties to the exposure path and the initial event in the incident report. Alphanumerical coding was created to ease traceability (e.g., T1, F1). For instance, methanol’s very low flash point—between 9 °C and 12 °C, well below ordinary ambient temperatures—means its vapors can ignite readily whenever a spark, hot surface, or other ignition source is present. This intrinsic property–scenario pairing justifies coding it as sub-hazard F1: Highly flammable liquid. The coding system was then used to conduct a qualitative analysis of 30 methanol accident investigation reports using MAXQDA software. The sub-hazards-based coding system was instrumental in identifying trends in these reports and accident patterns, providing a fresh perspective on the data.

The three groups of hazards shown in Table 1 have been classified as physical or health hazards, following the UN Global Harmonized System (GHS) for chemical classification [46]. Toxicity hazards fall under the health hazards category in the GHS, while flammability and explosivity are categorized as physical hazards. This aligns the current research, results, and outcomes with a global system for classifying hazards associated with substances. However, environmental hazards are excluded due to the scope and limitations of this study and the data used in the analysis.

3.3. Accident Reports Collection

A broad collection of accident investigation reports is undertaken to comprehensively understand the safety challenges and risks associated with methanol use in industrial settings. These accident reports provide valuable data on incidents involving methanol across different industries, helping to offer a well-rounded view of the hazards associated with the substance. Since methanol is relatively new as a marine fuel, gathering accident data from various sectors enables a complete understanding of the potential risks and safety barriers. The collected data include various incidents, such as fires, explosions, and toxic exposures, contributing to a holistic perspective on methanol-related hazards.

The accident investigation reports were obtained from various databases. The inclusion criteria were methanol accidents investigated through a governmental entity or an international safety body and involved methanol, either pure methanol or blended with other types of fuel, but its characteristics shaped the negative outcomes of the accident. The search examines accidents across all domains associated with different tasks, including storage, transfer, and industrial or operational use. The inclusion criteria encompass all severity levels. The search excludes non-investigated accidents. An accident with non-reliable sources, such as newspapers or the media. The search resulted in twenty-four reports being obtained from the Occupational Safety and Health Administration (OSHA) of the U.S. Department of Labor. The search criteria for those reports focused on industrial incidents involving methanol between 1985 and 2021. The IMO Global Integrated Shipping Information System (GISIS) provides three additional reports for methanol by applying search criteria for methanol accidents including contact, spill, fires, and explosions. In addition, three reports were collected from different European entities, including the International Marine Contractors Association (IMCA) and the Bureau for Analysis of Industrial Risks and Pollutions (BARPI), by applying the inclusion criteria of methanol accidents in any domain.

The fact that most of the accident investigations reports have been obtained from non-maritime sources limits the generalizability of the outcomes to the maritime domain. This limitation is acknowledged and addressed in the recommendation.

3.4. Hazard Severity and Trends Classification

Each incident’s hazard severity has been recorded and classified into three categories: mild injury, severe injury, and fatality. The three-level severity system was investigated and recorded for each hazard type. A simple severity criterion, shown in

Table 2. Three-level severity system. Source: Author.

Severity	Criteria
Fatality	Death, either immediately or within months after the exposure
Severe	Burns (degree I, II, and III) require from 3 to 30 days to heal Injuries in head area Injuries cause permanent disabilities Injuries that required hospitalization for more than one day
Mild	Injuries that require only first aid measures Injuries that require hospitalization for less than one day

, was created to assist in measuring injury severity.

3.5. Gap Analysis and Safety Barriers

Finally, a gap analysis will be conducted to determine which barriers should be implemented instead of what was already implemented [47]. Examining what barriers should be in place to prevent trendy occurrences and patterns resulting from the qualitative analysis of accident report text. With particular focus on bunkering, storage, and handling, without covering the propulsion system, which might require additional technical information.

The outcome barriers are listed against the current measures provided through the IMO’s applicable tools to identify gaps in the current legal framework covering methanol safety in general, focusing on fire safety. The guidelines provided by the IMO safety committee in circular 1621 [36] and the IGF’s stipulated requirements represent the applicable safety framework. The barrier should be in place to prevent further occurrences, detailed using a risk-based approach.

The study developed a safety framework outlining potential hazards and corresponding mitigation strategies. This framework is designed to assist stakeholders in determining the necessary precautions and best practices for ensuring safety during various methanol operations.

4. Results and Discussion

4.1. Results

This section presents the findings from the analysis of methanol-related accident investigation reports, focusing on the identified hazards and their frequency of occurrence. By employing a hazard-based coding system, the study categorizes the hazards associated with methanol use into key domains, enabling a systematic examination of their prevalence and impact.

Table 3. Analysis of methanol accident reports by hazard type and frequencies 1985–2021 (n = 30). Source: Author.

Color Code	GHS Classification	Main Hazards	Sub-Hazard Coding System	Code Segments for Accident Reports	Frequency
●	Physical hazards	Flammability (F)	F1 Highly Flammable Liquid	18	3.40 × 10−1
●			F2 Invisible Flames	1	1.89 × 10−2
●			F3 No smoke/No soot	1	1.89 × 10−2
●			F4 Flammable Methanol Solution (methanol–water)	3	5.66 × 10−2
●		Explosivity (E)	E1 Tank explosion/explosion	20	3.77 × 10−1
●	Health hazards	Toxicity (T)	T1 Dermal	1	1.89 × 10−2
●			T2 Ocular	2	3.77 × 10−2
●			T3 Inhalation	4	7.55 × 10−2
●			T4 Ingestion	3	5.66 × 10−2
Total occurrences				53	-

synthesizes 53 hazard exposure events. Showing that GHS physical hazards dominate the risk profile (81%), while health-hazard pathways—dermal, ocular, inhalation, and ingestion toxicity—make up the remaining 19%. Within the physical category, tank-explosion scenarios are the most frequent and severe: explosivity accounts for 38% of all coded events, with debris-propelled blast patterns typically modeled as fireballs or BLEVEs, which coincides with Methanol Institute [48] data, and is consistently linked to high fatality rates. Fire follows as the second-most common occurrence (34%), reflecting methanol’s low flashpoint and the added complexity of invisible flames (2% of all occurrences), which demand well-equipped and specially trained responders. Extinguishment relies largely on dilution, and even mixed-fuel fires—methanol–water solution fires represent 5% of sub-hazards—require substantial water volumes to remove the heat component of the fire tetrahedron. Collectively, these findings underscore the imperative for proactive explosion-prevention measures and advanced firefighting capability whenever methanol is stored, transferred, or used.

It is vital to note that methanol solutions diluted with up to 74% water remain flammable, highlighting the need for foam to smother the fire. However, since methanol is miscible with water, regular foam becomes ineffective as it breaks down the foam structure. Alcohol-resistant (AR) foam contains a polymer agent that forms a barrier between the methanol and the foam structure [49], enabling it to smother the vapor and suppress the fire more effectively. The IMO mandates the use of AR-AFFF. However, the foam solution mixing ratio with water, application rate, and coverage time need verification through lab and empirical tests before standardization through IMO-applicable tools.

This fundamental knowledge is essential for preventing catastrophic events during emergency responses involving methanol [48] and improving maritime safety emergency protocols. Furthermore, Figure 1 illustrates the percentage of methanol hazard trends based on a comprehensive review of accident investigation reports.

A crucial aspect of methanol operations is the associated fatality rate. Out of 30 incidents, 19 fatalities were primarily linked to four types of sub-hazards, as detailed in

Table 4. Analysis of methanol accident reports by severity and frequencies 1985–2021 (n = 30). Source: Author.

Sub-Hazard Coding System	Severity	Recorded Severity	Frequencies in the Same Severity Level	Frequencies in all Severity Level
E1 Tank explosion/explosion	Fatality	15	7.89 × 10−1	3.41 × 10−1
F4 Flammable methanol solution	Fatality	1	5.26 × 10−2	2.27 × 10−2
T3 Inhalation	Fatality	2	1.05 × 10−1	4.55 × 10−2
T4 Ingestion	Fatality	1	5.26 × 10−2	2.27 × 10−2
E1 Tank explosion/explosion	Severe Injury	13	6.50 × 10−1	4.55 × 10−2
F1 Highly flammable liquid	Severe Injury	6	3.00 × 10−1	2.27 × 10−2
T3 Inhalation	Severe Injury	1	5.00 × 10−2	2.27 × 10−2
E1 Tank explosion/explosion	Mild Injury	2	4.00 × 10−1	2.27 × 10−2
F1 Highly flammable liquid	Mild Injury	1	2.00 × 10−1	2.95 × 10−1
T1 Dermal	Mild Injury	1	2.00 × 10−1	1.36 × 10−1
T3 Inhalation	Mild Injury	1	2.00 × 10−1	2.27 × 10−2
TOTAL		44

. Notably, tank explosions accounted for 15 of these 19 fatalities (79%). In addition to fatalities, operators sustained severe injuries, predominantly third- and second-degree burns, with some requiring hospitalization for up to two months. Again, tank explosions were the leading cause of these severe injuries. Although inhalation toxicity represented only 7% of the sub-hazards, it had a high fatality rate of 50% during incidents correlated to this sub-hazard, underscoring the severity of inhalation risks. Finally, five mild injuries, constituting 11% of the total recorded severities, are associated with four types of sub-hazards, as expressed in Table 3. Occurrence frequencies are presented either at the same severity level or across all severity levels to be comparable and indicative.

4.2. Discussion

This section evaluates the study’s findings in the context of existing regulatory frameworks and industry practices, highlighting the implications for methanol safety in the maritime industry. It also underscores the gaps and limitations in the existing safety measures by comparing the identified hazards and barriers with the current regulatory provisions.

The IMO Circular 1621 is crucial as it introduces comprehensive safety measures for ships using methanol as fuel, enhances safety protocols, and establishes a regulatory framework. However, the circular is considered an interim set of guidelines for the industry, and the requirements are generic and do not include specific technical details and Standard Operating Procedure guidelines [36]. Compared to current measures, the barriers identified highlight gaps in the existing safety framework for methanol safety, particularly regarding fire safety. A comparative analysis of these barriers, aligned with those provided by IMO’s existing tools, highlights the need for additional measures to address and prevent recurring incidents. The results of this comparison are summarized in

Table 5. Gap analysis for current safety barrier. Source: Author.

	Barrier Provided Through IMO Tools	The Barrier Should Be in Place (From Incident Review, Severity Level)
Code	IGF Code, MSC.1/Circ.1621 and SOLAS	System, Equipment and PPE	Human Error Elimination	Legal Framework	First Aid
F1	-Inerting the methanol tank using nitrogen or other inert gases. -Usage of Foam (AR-AFFF). -Material safety data sheet MSDS Ch.VI/5.1.	-MOC value validation for Inert gas system provides more durability. -The amount of AR-AFFF application rate needs to be standardized.	Methanol risk perception needs to be elevated.	Stipulated requirements and validation for enhancing the durability of the Inert gas system.	Amendments to the IMO Medical Guide 3rd edition address the trended hazards with reactive measures to contain the medical consequences and support the measures detailed in the methanol product material safety data sheet (MSDS).
F2	No mandatory requirements for colorless flame detection during firefighting, only fixed gas detectors are stipulated.	Thermal imaging camera (TIC); as part of firefighting teams’ standard equipment.	Methanol Safety awareness—emphasize the TIC usage.	Stipulated requirements for thermal imaging camera (TIC) application. Emergency Standard Operating Procedure (SOP).
F3	-No mandatory requirements for vapor detections except for gas release during a spill.	Thermal imaging camera (TIC); as part of firefighting teams’ standard equipment.	Methanol Safety Awareness.	Stipulated requirements for TIC application.
F4	-Usage of alcohol resistance AFFF (AR-AFFF). -Checklist for bunker safety. -Electrical bonding.	-Formal Safety Assessment (FSA) for the usage of Compressed Air foam system (CAFS). -Calculation for coverage time needs to be standardized.	Elevate the risk perception of using water only for fighting methanol fires.	Stipulated requirements for crew training to elevate methanol risk perception. -Adopt criteria for AR-AFFF concentrate quantity calculation, application rate and coverage time.
E1	-Hazards zone classification to zero, one, and two. -Use explosion-proof electrical apparatus. -eliminate any sources of ignition.	-	Methanol Safety Awareness.	Stipulated requirements for visualization of hazardous zones at safety plans in conspicuous places.
T1	-Tank monitoring for overflow risk. -Generic requirements for PPE without specific technical details.	PPE: Acid gloves Chemical suits to contain the spill without exposure.	Methanol Safety Awareness.	Stipulated requirements for specific technical details.
T2	Generic requirements for PPE without specific technical details.	PPE: face mask or Hood suitable for methanol exposure.	Methanol Safety Awareness.	Stipulated requirements for specific technical details.
T3	-Portable gas detectors are available during bunkering. -Electrical bonding.	Single gas detector (methanol) for 100% of operators with toxicity indicator not only flammability. PPE: Hood suitable for methanol exposure.	Training in methanol TLV and STEL awareness.	Stipulated requirements for personal single gas detectors for each crew member involved in methanol operation.
T4	-Checklist for bunker safety.	PPE: Hood suitable for methanol exposure	Methanol Safety Awareness Course.	-

.

The proposed barriers are categorized into four approaches: First, equipment and personal protective equipment could mitigate methanol occurrences. Second, human error actions should be eliminated to enhance safety during methanol operations. Third, the proposed regulatory framework should be in place to provide a legal safeguard to foster the operator’s safety during methanol operations. Finally, first aid management should be considered.

The risk of flammability (F1) is mitigated through the use of Inerting, as specified by the IMO. Inerting is one of the primary proactive measures for fire prevention. The inert gas system typically employs nitrogen or carbon dioxide to reduce the oxygen concentration below the Minimum Oxygen Concentration (MOC) required to sustain a fire. Each flammable gas vapor has its own MOC, making it essential to standardize these values for system manufacturers and designers. For instance, the known MOC for methanol is 8.5% O₂ when using nitrogen as the inert agent and 10% O₂ when using carbon dioxide [49]. According to the IMO’s specifications detailed in Chapter 15 of the Fire Safety Systems (FSSs) Code, any inert gas injected should have an oxygen percentage not exceeding 5% [50]. This aligns well with the MOC for methanol. However, these percentages require validation to ensure their suitability for methanol, considering applicable safety margins.

Current IMO fire-safety provisions specify fixed gas-detection systems but impose no requirement for equipment to detect the colorless flame characteristic of methanol fires. This leaves a critical visibility gap during emergency response, sub-hazard (F2). Integrating thermal imaging cameras (TICs) into the standard kit of shipboard firefighting teams would close this gap by allowing responders to visualize otherwise invisible combustion zones, thereby improving hose-line placement and reducing re-ignition risk. To make such integration effective, TIC use should be embedded in methanol-specific safety-awareness training, codified through explicit performance criteria and maintenance intervals, and anchored in an emergency Standard Operating Procedure (SOP).

Tank explosions designated (E1) are the single-most frequent and damaging event in the incident database, appearing 20 times and accounting for ≈38% of all coded methanol hazards; when they occur, the probability of severe injury is high (13 recorded cases, p ≈ 0.65) while the residual fatal-injury risk remains non-negligible (p ≈ 0.05). To confront this threat, hazardous areas around cargo tanks must be formally zoned—Zone 0, 1, and 2—fitted with explosion-proof electrical apparatus, and kept scrupulously free of ignition sources. Equally important is the human-factor layer: methanol-specific safety awareness and prominently posted safety-plan graphics that visualize the zoned boundaries ensure that every person on board recognizes the elevated explosion risk and applies the prescribed precautions without hesitation.

Although IMO guidelines recognize the need for personal protective equipment (PPE) during methanol operations, they describe it only in general terms, lacking the technical details necessary for real protection. This can lead crews to choose gear that does not effectively block methanol vapors or splashes, sub-hazard (T2). To address this, regulations should specify requirements such as full-face respirators or positive-pressure hoods certified for methanol resistance. These equipment standards must be supported by methanol-specific safety training, so seafarers know when specialized PPE is required and how to check its condition before use. By clearly defining PPE performance criteria and pairing them with practical training, regulations can bridge the gap between intent and actual safety on board.

The risk of inhaling toxic methanol vapors coded with (T3) is mitigated using portable gas detectors, as outlined in IMO Circular 1621. However, the stipulated requirements do not specify toxicity alarms or the TLV that operators should not exceed. According to the American Conference of Governmental Industrial Hygienists (ACGIH), the TLV for methanol is 200 PPM for a time-weighted average (TWA) of 8 h [20,26,51]. It is important to note that 1% methanol by volume equals 10,000 PPM. Consequently, lethal doses of methanol vapors can accumulate well before reaching flammable limits.

Unlike the detailed provisions for flammability hazards, toxicity measurements are notably absent from the IMO tools, except as generic requirements and fixed systems without specific toxicity levels or alarms [36]. For example, the circular specifies that visual and audible alarms are activated when the fuel vapor concentration reaches 20% of the lower explosive limit (LEL). However, findings suggest that each crew member should have a personal methanol gas detector with standardized TLV and specific alarm values. Different stakeholders may interpret this issue variably, highlighting the need for clarity in the circular to ensure uniform understanding and compliance. These omissions confirm that the present IMO toolkit partially mitigates the principal hazards, satisfying RQ1 by identifying concrete areas where the current measures’ effectiveness is limited.

Equally important is the need to address the medical emergency response in case of exposure to methanol either via dermal, ocular, or inhalation, which will depend on information extracted from the product’s material safety data sheet (SDS), which can be oversimplified. Notably, neither the Medical Guide, third edition, nor the Ship Captain’s Medical Guide addresses the toxicity hazard associated with methanol, which is accepted by the ingestion method [52,53]. Furthermore, the potential medical risks associated with ocular exposure and inhaling airborne particulates, which can easily enter the bloodstream, are often neglected [52]. Hence, new medical hazards associated with the utilization of methanol as a marine fuel should be reflected in the relevant medical instruments to ensure comprehensive preparedness and response.

Finally, the articulated safety measures in Table 5 could enhance methanol operations and address RQ3. However, it will be essential to undertake further research into the full cost-effectiveness of these proposed barriers in the maritime context, as only generic examples have previously proven their cost-effectiveness within different industries. Furthermore, it must be emphasized that economic parameters and operation modes differ significantly between industries, and they can change rapidly in certain instances. The unique challenges associated with maritime operations, such as international regulations, logistical constraints, and the need for specialized equipment and training, could influence the overall cost–benefit balance of implementing these barriers.

Besides, the scale of operations, potential environmental impacts, and long-term sustainability of the barriers preclude judgments about financial viability. In that respect, a tailored cost-effectiveness analysis, including the peculiarities of the maritime industry, will be highly instrumental in deciding whether these barriers can be implemented without placing undue financial burdens. Its results will prove helpful in identifying the most economically viable solutions and in elaborating more operational and practical risk management strategies in the maritime industry.

5. Validation of Proposed Measures and Impact

The identified safety gaps could be addressed by reviewing and amending the IMO Circular 1621 and IGF Code accordingly.

The cost-effectiveness of personal detectors and enhanced PPE sets needs to be assessed according to the cost-effectiveness criteria of the IMO formal safety assessment.

The Medical Guide is generic medical guidance and does not address the hazards related to specific types of cargo or fuel. Hazardous cargo medical hazards are addressed via the IMDG medical first aid guide MFAG, while the hazards related to fuel, especially alternative fuels, are not addressed in other material safety data sheets (MSDSs) of those fuels. The specific medical measures must be well-known to engineers and officers and well-studied. The proposal here is an alternative kind of fuel, not only methanol, but also a medical first aid guide.

The proposed measures can serve as good safety practices for recognized organizations (ROs), considering that they have not yet qualified as mandatory provisions.

6. Conclusions

This study provides a comprehensive review of the safety challenges posed by methanol as an alternative marine fuel. It identifies the main hazards and sub-hazards involved with methanol as a ship fuel and evaluates the effectiveness of potential safety measures through a structured approach based on a literature review and qualitative analysis of 30 accident investigation reports. The findings underscore the dominant risks of methanol’s explosivity, which account for most identified hazards. In addition, a few hazards regard toxicity, although less frequent, because of harm to human beings through dermal, ocular, and inhalation contacts and ingestion.

6.1. Regulatory Implications

Results show critical gaps in the present safety framework for methanol use in shipping. The IMO Circular 1621 provides interim guidelines for ships using methanol as fuel; however, it does not provide anything beyond interim guidelines on methanol as fuel on ships. In this regard, the document lacks the technical specificity and operational details necessary for addressing the far-reaching risks of methanol. For instance, the circular identifies general safety measures without giving enough details on operational guidelines and standard operating procedures to efficiently avert fire and explosion accidents.

The study also contributes to the broader implications for the energy transition in the maritime industry, meaning that there is a need for regulating authorities, industry stakeholders, and researchers to cooperate in safety measures, particularly to alternative fuels.

6.2. Operational Implications

The barriers identified have highlighted areas where enhancements are necessary compared to current regulatory measures. These range from enhanced fire safety systems to advanced detection mechanisms and detailed operational training for personnel involved in methanol handling and bunkering. Moreover, this study emphasizes the need to adopt a proactive approach to safety, where lessons learned from accidents in other industries should be integrated into maritime practices.

Addressing these challenges, the research contributes to further developing the safety standards for methanol-fueled maritime operations and supports the industry’s transition toward low-carbon fuels. Methanol is a promising alternative fuel. However, whether it will see widespread adoption depends on the industry’s ability to mitigate associated risks with robust safety protocols and a wide-ranging regulatory framework.

Second, integrating innovative technology such as advanced hazard detection systems and data-driven risk analysis is indispensable for enhancing operational safety. While this study provides foundational insights, future research should focus on longitudinal monitoring of safety barrier implementation in shipboard environments. Such studies are essential to assess these measures’ long-term effectiveness, adaptability, and practicality in real-world maritime operations.

6.3. Medical Implications

Although less frequent, toxicity-related accidents from dermal, eye, and inhalation exposure to methanol continue to be serious and under-reported. New clinical recommendations should be designed for shipboard settings, such as shipboard first-response procedures and seafarer medical training, particularly for ocular and inhalation exposure.

6.4. Limitations

Despite its contributions, this work also has some limitations. For example, one key limitation is reporting accidents that occurred in industries other than maritime accidents. This limitation is due to the relatively limited number of cases involving methanol on board ships, which indicates the relative novelty of methanol as a marine fuel. Evidently, such inter-industry observations are extremely valuable; however, they may be inadequate to accurately reflect the specific conditions in which each maritime use of methanol fuels occurs.

Moreover, the study is confined to the bunkering, storage, and handling operations of methanol onboard and does not extend to the propulsion systems. Propulsion systems may have different safety challenges that need to be identified