A practical, data-backed guide to marine fuels—VLSFO, MGO, LNG, biofuels, and methanol—covering real-world performance, risks, and decarbonisation trade-offs for shipowners.
The conversation around marine fuels has shifted dramatically in just a few years. What used to be a straightforward choice between HSFO and MGO has evolved into a much more nuanced landscape, largely because the IMO keeps tightening the screws on emissions. Many owners now find themselves comparing fuels they barely considered a decade ago — and trying to make long-term decisions in a market that still feels like wet cement.
What follows isn’t meant to be an academic white paper. It’s a grounded overview of the fuels most shipowners are looking at right now, supported by current data and the latest scientific findings — including this in-depth IMO-aligned LCA review — but written with the realities of commercial operations in mind.
For context, many of these choices filter down to the same question:
What can we use today without painting ourselves into a corner tomorrow?
Let’s take a closer look.
1. Very Low Sulfur Fuel Oil (VLSFO)
VLSFO quickly became the industry’s default after the 2020 sulfur cap, but anyone who’s dealt with it on the ground knows that it’s not a uniform product. One batch behaves beautifully; the next looks identical on paper but sludges the separators by breakfast.
According to a 2024 global quality review, more than 5% of VLSFO samples were off-spec. That number sounds small until you consider the operational fallout of just one contaminated stem. A separate peer-reviewed analysis of fuel variability confirms what engineers on board already know: the blending process behind VLSFO introduces a lot of variability.
Why people use it: It’s cheap (relatively), available everywhere, and doesn’t require new tanks or engine modifications.
Where it bites back: Instability issues, incompatible blends between ports and sometimes even within the same port, and emissions that look increasingly out of place in a decarbonising industry.
2. Marine Gas Oil (MGO)
MGO has a reputation for being the “clean” and “safe” choice — and it is, in many ways. It burns well, rarely causes combustion surprises, and it’s essential for ECA compliance. But the idea that it is virtually risk-free isn’t entirely accurate.
The 2024 VPS testing report found 7.9% of tested MGO samples were off-spec, which tends to surprise people. Most of the issues relate to contamination picked up during handling and storage rather than the refining process itself.
Why people use it: Straightforward to manage, reliable ignition, lower local pollutants, ideal for smaller vessels and coastal trades.
Where it falls short: High price, fossil-based emissions profile, and not really a long-term solution if your company has a decarbonisation roadmap.
3. Liquefied Natural Gas (LNG)
LNG is the most established alternative fuel, and depending on who you ask, it’s either a smart transitional move or an expensive detour. What makes the debate tricky is methane slip — something that significantly impacts LNG’s real-world climate footprint.
A comparative scientific study suggests LNG can achieve 10–25% GHG reduction versus conventional fuels when methane slip is tightly controlled. But when engines operate under varied loads — as ships do — methane slip can creep up.
Why people use it: It drastically cuts SOx and PM, reduces NOx (depending on the engine), and the infrastructure is expanding quickly.
Where it gets complicated: Higher CAPEX, inconsistent methane slip performance and the fact that the fuel is still fossil-derived unless you switch to bio-LNG later.
4. Biofuels (FAME, HVO & Advanced Bio-Oils)
Biofuels have become the industry’s “no-regrets” option because they let shipowners cut emissions without modifying their vessels. But the term “biofuels” covers a wide spectrum. Some blends behave beautifully; others can oxidise, absorb water or create microbial growth if stored too long.
A 2023 marine biofuel LCA found that sustainable waste- and residue-based biofuels can reduce well-to-wake GHG emissions by 50–80% — numbers that are hard to ignore.
Why people use them: Minimal modifications required, immediate emissions improvement, and growing regulatory acceptance (especially under ISO 8217:2024).
Where the friction lies: Limited global scaling, variability in cold-flow performance, and above all, differences in feedstock sustainability — a polite way of saying that not all “green” biofuels are genuinely green.
5. Methanol (Grey, Bio- and E-Methanol)
Methanol went from fringe concept to mainstream contender astonishingly fast. Part of the appeal is practicality: it’s liquid at ambient temperature, far easier to handle than LNG, and dual-fuel methanol engines are now rolling out in significant numbers.
Yet the environmental performance varies dramatically depending on the production pathway. As explained in a scientific comparison of methanol vs. other alternative fuels, fossil methanol offers fairly modest improvements, while bio- and e-methanol can cut emissions by over 70%, making them among the strongest “near-zero” candidates.
Why people use it: Straightforward storage, cleaner local emissions, and a clear path to deep decarbonisation once green methanol becomes widely available.
What limits it: Lower energy density (bigger tanks), safety considerations and the current scarcity — and cost — of green methanol.
So What Should Shipowners Actually Do?
If there were a neat answer, the industry wouldn’t be debating this every week. According to a major multi-fuel decarbonisation analysis, the most realistic outcome is a patchwork future: different fuels for different trades, and maybe even different fuels on the same vessel over its lifetime.
A practical way to think about it:
2025–2030
- VLSFO and MGO remain the backbone
- Biofuels scale up fastest
- LNG grows on established long-haul trades
2030–2040
- Green methanol becomes more widely available
- Regulatory pressure sharpens
- Carbon pricing reshapes fuel economics
2040 and beyond
- e-methanol, e-ammonia, advanced biofuels and synthetic hydrocarbons begin to dominate newbuild designs
None of this is static. Technology shifts, regulations change, and supply chains mature — often faster than expected.
Marine Fuels – A Sensible Starting Point
For most operators, the next step isn’t choosing “the” fuel of the future — it’s understanding what fits their fleet, routes and commercial reality. That usually means:
- Running small biofuel or methanol pilots
- Comparing total cost of ownership, not just fuel price
- Mapping out where alternative fuel bunkering is feasible
- Keeping an eye on carbon intensity rules and regional taxes
- Avoiding investments that limit future flexibility
