Comparative Study of Marine Biofuels: MGO, HVO, and FAME

Marine biofuels are increasingly being considered as viable alternatives to traditional fossil fuels in the maritime industry. The drive toward sustainability, coupled with stringent environmental regulations, has led to the exploration of various biofuel options. This article delves into three prominent types of marine biofuels: Marine Gas Oil (MGO), Hydrotreated Vegetable Oil (HVO), and Fatty Acid Methyl Ester (FAME). Each of these fuels has distinct properties, advantages, and challenges, making them suitable for different applications within the maritime sector.

Marine Gas Oil (MGO)

Marine Gas Oil (MGO) is a refined petroleum product that is lighter and cleaner than traditional marine diesel oils. It is the most commonly used fuel in the shipping industry, especially in coastal areas and emission control areas (ECAs) where stricter environmental regulations are in place.

Hydrotreated Vegetable Oil (HVO)

Hydrotreated Vegetable Oil (HVO) is a second-generation biofuel produced from renewable feedstocks such as vegetable oils, animal fats, and waste oils. It is chemically similar to traditional diesel but is synthesized through a hydrogenation process, which enhances its properties.

Fatty Acid Methyl Ester (FAME)

Fatty Acid Methyl Ester (FAME) is a first-generation biodiesel produced through the transesterification of vegetable oils or animal fats with methanol. It is one of the most common types of biodiesel and has been used in various transportation sectors, including maritime.

Chemical Composition Comparison

The chemical compositions of FAME and HVO differ significantly from conventional diesel. As shown in Table, FAME has a higher density and viscosity at 20°C compared to both HVO and diesel. HVO, with its lower viscosity and higher cetane number, offers superior combustion properties. Additionally, HVO contains no sulfur or aromatics, contributing to lower emissions, whereas FAME contains around 11% oxygen by volume, influencing its combustion characteristics and emissions profile.

PropertyFAMEHVODieselDensity at 20°C (kg/m3)885780825Lower Heating Value (LHV) (MJ/kg)37.144.143.1Viscosity at 20°C (mm2/s)7.53.0 (at 40°C)5.0Surface Tension (N/m)0.026–0.028Cetane Number (CN)5680-9940-50Stoichiometric Air/Fuel Ratio12.5–15Oxygen Content (% vol.)~1100Aromatics Content (% vol.)–0~30Sulfur Content (ppm)–0<3.5

Environmental Safety

Marine Gas Oil (MGO)

MGO, a type of conventional fossil fuel, is less biodegradable compared to biofuels like HVO and FAME. In the event of a spill, MGO poses significant environmental risks as it persists in the environment for longer periods. It can form oil slicks on the water surface, leading to severe marine pollution and affecting aquatic life. The spill response for MGO typically involves containment and mechanical recovery, as the oil does not degrade quickly.

Hydrotreated Vegetable Oil (HVO)

HVO, a second-generation biofuel, is more environmentally friendly than MGO. It is biodegradable and, in the case of a spill, HVO breaks down faster in the marine environment than MGO. While HVO may still cause some oil sheen and potential toxicity in the water column, its impact is generally less severe than that of MGO. The quicker degradation rate of HVO can reduce the duration and extent of environmental damage, making spill response easier and less damaging to marine ecosystems.

Fatty Acid Methyl Ester (FAME)

FAME, a first-generation biofuel, is the most biodegradable of the three fuels. In the event of a spill, FAME begins to degrade almost immediately upon contact with water, which minimizes long-term environmental impacts. However, like HVO, FAME can still cause temporary oil sheen and water column toxicity before it fully degrades. Its higher oxygen content aids in its biodegradation, making it a more environmentally sustainable option compared to MGO. Despite this, FAME’s tendency to oxidize and degrade means that spill response procedures are necessary, albeit potentially less intensive than those for MGO.

Fire Safety

Marine Gas Oil (MGO)

MGO has a relatively lower flashpoint, typically ranging between 52°C and 96°C (126°F to 204°F). This makes it more susceptible to ignition under certain conditions, particularly in confined spaces where vapor can accumulate. Standard fire safety protocols for handling MGO include maintaining proper ventilation, avoiding exposure to open flames, and using appropriate fire extinguishing methods like foam, dry chemical, or CO?. Due to its petroleum origin, MGO fires can be intense and require immediate and effective response to prevent escalation.

Hydrotreated Vegetable Oil (HVO)

HVO has a higher flashpoint compared to MGO, usually above 60°C (140°F), which reduces its flammability risk. This makes HVO safer to handle and store in terms of fire safety. However, it can still ignite under high-temperature conditions or when exposed to an ignition source. In case of a fire, HVO can be extinguished using similar methods as MGO—foam, dry chemical, or CO?—although the lower risk of spontaneous ignition makes fire incidents involving HVO less common.

Fatty Acid Methyl Ester (FAME)

FAME typically has the highest flashpoint among the three fuels, generally above 93°C (200°F). This significantly lowers its fire risk compared to MGO and HVO. FAME’s higher flashpoint means it is less likely to ignite in typical storage and operational conditions, providing a safety advantage. However, should a fire occur, standard extinguishing agents like dry chemical, foam, or CO? are effective. Given its lower flammability, FAME is considered safer to handle in environments where fire hazards are a concern.

1. Fuel Availability, Cost, and Storage

Marine Gas Oil (MGO)

• Availability: MGO is widely available globally and is the most commonly used marine fuel. Its supply chain is well-established, ensuring consistent availability in major ports worldwide.
• Cost: MGO is generally more expensive than Heavy Fuel Oil (HFO) but less costly than biofuels like HVO. Its price can fluctuate based on crude oil prices and regional market conditions.
• Storage: MGO is easier to store compared to biofuels. It has a relatively low cloud point and pour point, which makes it less prone to gelling in cold temperatures. Standard fuel tanks on vessels are typically suitable for storing MGO without significant modifications.

Hydrotreated Vegetable Oil (HVO)

• Availability: HVO is less widely available than MGO, but its presence is growing, especially in regions focused on reducing carbon emissions. Availability is higher in Europe and North America, where there is greater emphasis on sustainable fuel alternatives.
• Cost: HVO is more expensive than MGO due to its production process and the cost of raw materials. However, its price can be partially offset by subsidies or incentives for using renewable fuels.
• Storage: HVO has better storage stability than FAME and does not suffer from the same oxidation issues. However, it still requires dedicated storage solutions to prevent contamination with other fuels, especially due to its higher sensitivity to temperature variations.

Fatty Acid Methyl Ester (FAME)

• Availability: FAME is relatively available, particularly in regions with strong biodiesel industries. However, its availability can be inconsistent depending on the feedstock used and regional production capabilities.
• Cost: FAME is typically more expensive than MGO and can be more costly than HVO, especially if sourced from sustainable feedstocks. The cost is influenced by the availability of raw materials, such as vegetable oils and animal fats.
• Storage: FAME has more stringent storage requirements due to its higher susceptibility to oxidation and microbial growth. It has a higher cloud point and pour point than MGO, which can cause issues in colder climates, requiring heated storage tanks.

1. Bunkering and Maintenance

Marine Gas Oil (MGO)

• Bunkering: Bunkering MGO is straightforward and follows established procedures. It is compatible with existing fuel infrastructure, and there is a lower risk of contamination compared to biofuels. Bunkering time and handling are similar to that of traditional marine fuels.
• Maintenance: MGO generally requires standard maintenance practices. It is less corrosive than biofuels and does not significantly impact engine components or fuel systems, leading to lower maintenance costs over time.

Hydrotreated Vegetable Oil (HVO)

• Bunkering: HVO can be bunkered using similar procedures as MGO, but care must be taken to avoid contamination with other fuels. Some modifications to the bunkering process may be necessary to accommodate HVO’s properties, such as its lower density.
• Maintenance: HVO is less corrosive and cleaner-burning than MGO, leading to potentially lower maintenance needs and longer intervals between engine overhauls. However, its impact on engine wear over long-term use is still being studied, though it generally offers improved fuel lubricity.

Fatty Acid Methyl Ester (FAME)

• Bunkering: Bunkering FAME requires more attention to detail due to its hygroscopic nature (tendency to absorb water) and its higher risk of microbial contamination. Special care must be taken to ensure that storage tanks and fuel lines are clean and free of water.
• Maintenance: FAME can increase maintenance requirements due to its higher acid value, which can cause corrosion in fuel systems. Additionally, FAME’s propensity to oxidize and form deposits means that fuel filters may need to be changed more frequently, and tanks might require regular cleaning.

1. Vessel Design Considerations

Marine Gas Oil (MGO)

• Design Impact: Vessels designed for MGO require no special modifications to fuel tanks, engines, or fuel lines. MGO is compatible with existing marine engines and systems, making it a convenient choice for a wide range of vessels.
• Retrofitting: No significant retrofitting is needed when using MGO, which makes it a cost-effective option for existing vessels.

Hydrotreated Vegetable Oil (HVO)

• Design Impact: Vessels using HVO may not require significant modifications, as HVO is designed to be a drop-in replacement for conventional diesel fuels. However, minor adjustments may be necessary to optimize engine performance and fuel efficiency.
• Retrofitting: Retrofitting is minimal when switching from MGO to HVO, though some vessels may opt to adjust fuel injectors or other components to maximize the benefits of using HVO.

Fatty Acid Methyl Ester (FAME)

• Design Impact: FAME requires more careful consideration in vessel design, particularly concerning fuel storage and handling systems. Tanks may need to be heated or insulated to prevent gelling in cold climates, and materials used in fuel systems must be compatible with FAME’s higher acid content.
• Retrofitting: Vessels may require more extensive retrofitting to handle FAME, including modifications to storage tanks, fuel lines, and filtration systems to address its higher viscosity and oxidative stability issues.

1. Quality Regulations

Marine Gas Oil (MGO)

• Regulations: MGO is subject to stringent international standards, including those set by the International Maritime Organization (IMO) and ISO 8217, which ensure consistency in quality and performance. Compliance with sulfur content limits (e.g., 0.5% sulfur cap under IMO 2020) is critical for MGO.
• Standardization: MGO quality is well-regulated globally, making it a reliable choice for marine operators. Its production and distribution are closely monitored to meet specific marine fuel standards.

Hydrotreated Vegetable Oil (HVO)

• Regulations: HVO is also regulated under various international standards, including those by ASTM and EN, which ensure that it meets specific quality criteria. HVO’s compliance with these standards makes it a viable alternative to fossil fuels in terms of performance and emissions.
• Standardization: While HVO is produced according to stringent specifications, the variability in feedstock can lead to slight differences in quality. However, it generally meets the required standards for marine use, with regulatory bodies increasingly recognizing its benefits.

Fatty Acid Methyl Ester (FAME)

• Regulations: FAME is subject to strict quality regulations, particularly under ASTM D6751 and EN 14214 standards. These regulations cover aspects such as ester content, water content, and oxidation stability to ensure that FAME performs reliably in marine applications.
• Standardization: FAME quality can vary more than HVO due to the diversity of feedstocks and production processes. It is essential that FAME used in marine applications meets the necessary standards to prevent issues related to engine performance and fuel system degradation.

Conclusion

The comparative study of MGO, HVO, and FAME reveals that each marine biofuel has its unique strengths and limitations. MGO remains the most widely used due to its availability and compliance with current regulations, but it is still a fossil fuel. HVO emerges as a strong contender for reducing greenhouse gas emissions, though its cost and availability pose challenges. FAME offers a renewable and cost-effective alternative but requires careful management of fuel stability and engine compatibility.

As the maritime industry continues to navigate the path toward decarbonization, the choice of biofuel will depend on a range of factors, including environmental impact, cost, availability, and engine compatibility. The development and adoption of these biofuels will play a crucial role in achieving a more sustainable future for global shipping.

– Riya Yadav