Here are some other fascinating angles on HFO and maritime shipping fuel:
The Sulfur Revolution
For decades, HFO could contain up to 3.5% sulfur. The IMO 2020 regulation dropped the global cap to 0.5%, forcing a massive industry shift. Ships now either use “very low sulfur fuel oil” (VLSFO), install exhaust scrubbers to clean emissions mid-flow, or switch to LNG. It was one of the biggest regulatory shake-ups in shipping history.
Scrubbers and the “Loophole” Controversy
Ships that installed scrubbers can still burn high-sulfur HFO — they just wash the exhaust with seawater. The catch: that wash water, now laden with sulfur compounds and heavy metals, often gets discharged directly into the ocean. Critics call it moving pollution from air to sea. Several ports and countries have banned open-loop scrubber discharge entirely.
Bunker Fuel Pricing and Global Economics
The fuel used in ships is called “bunker fuel,” and its price is tracked globally as a key economic indicator. When bunker prices spike, everything from your Amazon package to your grocery bill eventually feels it. It’s one of the hidden transmission belts between oil markets and consumer prices.
The Cold Problem at Scale
That peanut butter consistency isn’t just an engine problem — it’s a port infrastructure problem. Ports need heated storage tanks, insulated pipelines, and heated delivery barges. If a ship gets stranded somewhere without heated bunkering infrastructure, it’s essentially stuck.
What’s Replacing It
The long-term pressure is real. LNG is growing, methanol-powered ships are emerging (Maersk has been leading this), and ammonia is the longer-horizon bet for zero-carbon shipping. But HFO still dominates simply because the infrastructure and price advantage are enormous and the transition costs are staggering.
The underlying tension in all of this is that shipping is both the backbone of global trade and one of the dirtier industries on earth — and the solutions are genuinely hard because the scale is so massive.
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Ken Kuang
All About Heavy Fuel Oil (HFO)
Think ships use normal fuel? Nope, they run on thick black oil that has to stay hot to flow, called heavy fuel oil 🚢
It’s a bit of a shock to most people that the massive vessels moving 90% of the world’s goods aren’t running on anything like the “normal” gas or diesel we put in our cars.
Heavy Fuel Oil (HFO) is essentially the “bottom of the barrel”—the thick, viscous residue left over after the cleaner, more valuable fuels (like gasoline and jet fuel) have been distilled from crude oil.
The “Peanut Butter” Problem
At room temperature, HFO is so thick and sludgy that it’s often compared to cold peanut butter or tar. You couldn’t pump it into an engine if you tried; it would just sit there. To make it usable, ships have to use a complex system of heaters and insulated tanks.
The Heating Process: Before it reaches the engine, HFO is typically heated to between 120°C and 150°C to lower its viscosity so it can be atomized (sprayed) into the combustion chamber.
The Purification: Because it’s “residual” fuel, it’s full of impurities like sulfur, ash, and heavy metals. Ships have to use centrifugal separators to spin out the grit and water before it’s safe for the engine.
Why use it if it’s so difficult?
It really comes down to two things: Cost and Power.
Economy of Scale: HFO is significantly cheaper than refined “distillate” fuels. When a container ship is burning hundreds of tons of fuel per day, a lower price point is the difference between a profit and a massive loss.
Energy Density: These massive low-speed two-stroke engines are some of the most efficient machines on Earth. They thrive on the slow-burning, high-energy punch that HFO provides.
