From Corn Fields to Cargo Ships: Shipping’s Fuel Transition Could Open an Ocean-Sized Market for U.S. Agriculture

The global fleet burns roughly 250 million tonnes of fuel a year, and the race to decarbonize it has already put corn ethanol and soybean oil on the water. But the rules — and the fuel supply chain — are controlled far from the Midwest, Brazil has grabbed the early lead, and Washington’s fight against the IMO’s “global carbon tax” cuts both ways for farmers. Here’s how the marine market stacks up against the year-round E15 push.

In early July, a container ship named the CMA CGM Iron eased out of the port of Santos, Brazil, bound for Asia. What made the voyage historic wasn’t the cargo — it was the fuel. The vessel, adapted to run on methanol, ethanol or conventional bunker fuel, sailed on ethanol, the same alcohol distilled from corn in Iowa and sugarcane in São Paulo state. Weeks earlier, Danish shipping giant Maersk had quietly completed its first two voyages on 100% ethanol. Brazilian mining giant Vale has ordered dual-fuel vessels that can burn it. Engine makers say the roughly 107 methanol-capable ships already on the water — a fleet projected to top 450 by 2030 — can switch to ethanol without major retrofits.

For U.S. agriculture, the significance is hard to overstate. Global shipping consumes on the order of 250 million tonnes of fuel a year and accounts for about 3% of world greenhouse gas emissions. Because ships can’t plug into a power cord mid-ocean, liquid fuels — including biofuels made from corn, soybean oil and other farm feedstocks — are essentially the only path to cutting those emissions. If ethanol captured just 10% of the marine fuel market, industry figures note, demand would reach some 8.4 billion gallons a year — nearly the size of Brazil’s entire ethanol industry and more than half of America’s.

The Renewable Fuels Association pegs a more modest 5% share at 4 to 5 billion gallons of new ethanol demand — roughly 1.5 billion bushels of corn. For comparison, the National Corn Growers Association says full nationwide adoption of year-round E15, the policy the industry has chased for more than a decade and which finally passed the House in May, would add up to 2.4 billion bushels of corn demand — a ceiling that even supporters concede is years away and that first must survive a skeptical Senate.

In other words: the ocean could eventually rival, and perhaps outgrow, the biggest domestic policy prize corn agriculture has on the table. But between the Corn Belt and that blue-water market stand three obstacles — a stalled global regulatory regime, European sustainability rules that currently shut crop-based fuels out, and a marine fuel supply chain controlled by trading houses and ports thousands of miles from the nearest ethanol plant.

A market measured in hundreds of millions of tonnes

Maritime shipping moves roughly 80–90% of world trade, and it runs almost entirely on the bottom of the oil barrel: heavy fuel oil and marine gasoil. The industry is the textbook “hard-to-abate” sector — vessels last 25 to 30 years, can’t electrify on deep-sea routes, and refuel wherever in the world fuel is cheapest. That makes shipping one of the last great untapped markets for renewable liquid fuels — and one of the most contested.

The scale of the opportunity, and of the challenge, shows up in one comparison. DNV, the marine classification society, estimates the world produced about 11 million tonnes of oil equivalent (Mtoe) of sustainable biofuels in 2023, a figure projected to roughly double to 23 Mtoe this year. Full decarbonization of shipping alone would require something like 250 Mtoe annually — more than ten times today’s entire global sustainable biofuel output. And shipping must compete for every gallon with aviation’s sustainable aviation fuel (SAF) push and with road-transport mandates.

Chart: DNV and IEA figures. Shipping alone would need roughly ten times today’s global sustainable biofuel supply to fully decarbonize — which is why every alternative fuel pathway, including farm-based ones, is in play.

Actual uptake so far is tiny — pure biofuels were roughly 0.1% of marine fuel consumption as recently as 2022 — but the growth curve has bent sharply upward. Singapore, the world’s largest bunkering (ship-refueling) port, sold a record 1.36 million tonnes of biofuel-blended bunkers in 2025, up 56% in a single year, and has overtaken Rotterdam as the world’s biggest biofuel bunkering hub. Most of those blends are B24-style mixes of conventional fuel oil with biodiesel — the fatty-acid methyl ester (FAME) fuel made from used cooking oil, animal fats and vegetable oils, including soybean oil.

The rules that will make — or break — the market

Nobody buys a more expensive fuel at sea out of altruism. The demand for renewable marine fuels is being created by regulation, and the regulatory story of the past fifteen months is one of historic breakthrough followed by a Washington-led stall.

In April 2025, the UN’s International Maritime Organization approved, in principle, its “Net-Zero Framework” — the first binding emissions regime ever imposed on an entire global industry. The framework would set a fuel greenhouse-gas-intensity standard that tightens each year through 2035, charge financial penalties to ships that miss it (in effect, a carbon price on marine fuel), let cleaner ships sell credits to dirtier ones, and recycle penalty revenue into rewards for zero- and near-zero-emission fuels. The IMO’s stated ambition: 5–10% of shipping’s energy from such fuels by 2030, and net-zero around 2050.

Then came October 2025. At the extraordinary session called to formally adopt the framework, the Trump administration mounted a full-court press against what the State Department branded “the UN’s first global carbon tax,” threatening visa restrictions, port fees and sanctions against countries that voted for it. The adoption vote was postponed a year. When talks resumed at the IMO’s Marine Environment Protection Committee in April 2026 (MEPC 84), delegations mostly restated known positions; two additional negotiating sessions have been scheduled ahead of MEPC 85 this November, with adoption — if it happens — pointing to entry into force around 2028.

Table: The regulatory timeline. Sources: IMO, European Commission, DNV, Global Maritime Forum.

For American farm groups, the U.S. position is a double-edged sword. Killing a global carbon price spares U.S. exporters (including grain shippers) new freight costs — the World Trade Organization of it all is genuine. But the same framework is what would create guaranteed, worldwide demand for the low-carbon fuels U.S. agriculture wants to sell, complete with reward payments for fuels like ethanol. Meanwhile Europe is regulating anyway — and Europe’s rules, as written, are hostile to crop-based fuels. FuelEU Maritime assigns fuels made from food and feed crops an emissions factor equal to the least favorable fossil fuel, making corn ethanol and soy biodiesel effectively useless for EU compliance regardless of their actual carbon scores. The fight over whether the IMO’s lifecycle-assessment rules will follow Europe’s crop exclusion or Brazil’s crop-friendly approach may matter more to U.S. agriculture than the carbon price itself.

Who controls the fuel?

Here is the structural reality American farm-state readers should understand: the marine fuel business is controlled at three levels, and U.S. agriculture currently sits at none of them.

The ports. Ships refuel where fuel is cheap, plentiful and on the way. Singapore alone sold a record 56.2 million tonnes of bunkers in 2025 — roughly a quarter of the world market — followed by the Rotterdam/Antwerp region and Fujairah in the United Arab Emirates. U.S. ports (Houston, New Orleans, New York, Los Angeles) are, combined, a modest player. Whatever renewable fuel conquers the seas will be blended, certified and sold mainly at those foreign hubs — which is why the first commercial ethanol bunkering operations are expected within 12–24 months at Santos, Brazil, and Singapore, not at a U.S. port.

Chart: Maritime & Port Authority of Singapore (2025); Port of Rotterdam (2024); Fujairah and U.S. figures are approximate industry estimates. “ARA” = Amsterdam–Rotterdam–Antwerp.

The suppliers. The physical fuel is sold by a concentrated club of specialist bunker companies, commodity trading houses and oil majors. Denmark’s Bunker Holding leads with about 24 million tonnes supplied in 2025, followed by Gibraltar-based Peninsula, Minerva Bunkering (the marine arm of Geneva trader Mercuria), Miami-based World Fuel Services and Vitol, the world’s largest independent oil trader. Behind them stand the majors — BP, Shell, ExxonMobil, TotalEnergies — and state oil companies such as Saudi Aramco and Brazil’s Petrobras. These are the gatekeepers who decide which renewable fuels get blended, certified and offered at scale.

Table: Ship & Bunker “Top 10 Bunker Companies,” 2026 edition (2025 volumes).

The buyers. Unlike gasoline’s millions of motorists, marine fuel demand is concentrated in a few dozen shipping lines and cargo giants — Maersk, CMA CGM, MSC, Hapag-Lloyd, COSCO, and commodity charterers like Vale and Cargill. When one of them commits, demand moves in million-tonne increments: CMA CGM alone plans roughly 200 renewable-fuel-capable ships by 2031 out of a 700-vessel fleet. That concentration is an opportunity for U.S. ethanol — a handful of supply contracts could move more product than years of retail E15 expansion — but it also means the buyers, not the growers, set the specifications.

Notice who is integrating fastest: Brazil. Raízen — the world’s largest sugarcane ethanol producer, and a joint venture with Shell — is testing marine ethanol with engine maker Wärtsilä. Petrobras is in the bunker business. Vale is ordering the ships. Santos is set to become the first ethanol bunkering port. Brazilian sugarcane ethanol also carries a lower official carbon-intensity score than U.S. corn ethanol under most international accounting — a decisive edge if IMO rewards are paid per tonne of carbon saved. The U.S. industry’s counterweights are scale and infrastructure: roughly 200 biorefineries producing 15–16 billion gallons a year, about 2 billion gallons of idle nameplate capacity, and established rail, storage and export channels, as the U.S. Grains Council argues in its recent white paper making the maritime case for ethanol.

The ag-sector stakes: soybean oil first, corn ethanol next

The biodiesel bridge (soybeans). The renewable fuel flowing into ships’ tanks today is overwhelmingly biodiesel blended into conventional fuel oil — the drop-in route that requires no engine modifications. That’s a soybean-adjacent story, but only partly a soybean story: the blends sold in Singapore and Rotterdam lean heavily on used cooking oil and animal fats, because Europe’s sustainability rules penalize virgin vegetable oils and reward wastes. Soybean oil’s biggest fuel market remains onshore and domestic: EPA’s final Renewable Fuel Standard volumes for 2026–27 set record biomass-based diesel obligations of roughly 8.9 billion gallons (over 9 billion after reallocating small-refinery exemptions), with rules that favor domestic feedstocks — a policy structure worth watching as a template for what U.S. negotiators might eventually seek at the IMO.

The ethanol breakout (corn). Ethanol’s marine moment arrived through a side door: the methanol fleet. Shipping lines ordered hundreds of methanol-capable vessels expecting green methanol to scale — and it hasn’t. Green methanol runs $1,000 or more per tonne, when it can be found at all. Ethanol, at roughly $700 per tonne on a U.S.-loading basis (a bit over $800 delivered in Asia), is suddenly the affordable alcohol — comparable to conventional low-sulfur fuel oil, which has traded above $750 per tonne in Asia. Because ethanol runs in methanol engines with minor adjustments, every methanol-capable ship is a potential ethanol customer. Hence Maersk’s 100% ethanol voyages, X-Press Feeders’ ethanol-methanol blend trial in Rotterdam, and the CMA CGM Iron’s run from Santos.

Chart: Hydrocarbon Processing/industry projections (fleet); Maritime & Port Authority of Singapore (biofuel-blend sales, includes 25,500 mt of pure B100 in 2025).

The catch is physics and paperwork. Ethanol carries about 35% more energy per kilogram than methanol but still far less than fuel oil — a ship needs roughly 50% more fuel by weight to sail the same distance, which costs cargo space and complicates long-haul economics. And the certification question looms over everything: if the IMO’s lifecycle rules follow FuelEU’s food-and-feed-crop exclusion, corn ethanol would be scored as if it were the dirtiest fossil fuel — locked out of the very market that’s opening. If instead the IMO adopts genuine well-to-wake carbon accounting, U.S. corn ethanol — with a carbon-intensity score that keeps falling as plants add carbon capture, and lower still under climate-smart farming practices — competes on its merits. That single methodological fight, being waged in London committee rooms, is arguably the highest-stakes biofuel policy battle American agriculture isn’t watching.

Table: How the alternative marine fuels stack up for U.S. agriculture. Sources: DNV, IMO, U.S. Grains Council, trade press.

A better bet than year-round E15?

Which brings us to the question corn country readers are already asking: is chasing the marine market a smarter play than the industry’s long slog toward year-round, nationwide E15?

The E15 campaign finally cleared a historic hurdle in May, when the House passed the Nationwide Consumer and Fuel Retailer Choice Act, 218–203. NCGA president Jed Bower called it “essential to the success of corn farmers and rural communities, particularly as our growers face their fourth year of net losses.” But the bill’s Senate prospects are dim — one Republican Senate staffer flatly predicted “it won’t pass” — and even if it did, the NCGA’s 2.4-billion-bushel figure describes full national adoption: every station, every pump, every driver choosing the blend. The realistic near-term gain is a fraction of that, constrained by retail tank-and-pump infrastructure, automaker warranty language and consumer habit. And it all pours into a gasoline pool that is structurally shrinking as vehicle efficiency and electrification advance. E15 raises ethanol’s share of a declining market.

The marine market inverts nearly every one of those constraints. There is no blend wall at sea — a ship can burn 100% ethanol, so one vessel conversion does the work of tens of thousands of retail pumps. The customers number in the dozens, not the millions, and they are actively shopping: methanol-fleet owners need an affordable alcohol now, and ethanol is currently the only one at scale. Demand is growing, not shrinking — global freight volumes keep rising. Ethanol is already price-competitive against green methanol without a dime of U.S. subsidy. And the volumes are enormous: the RFA’s 5% scenario (4–5 billion gallons, ~1.5 billion bushels) approaches the practical upside of E15, while a 10% share (~8.4 billion gallons, ~3 billion bushels) would exceed E15’s theoretical ceiling.

Chart: NCGA estimate for full nationwide E15 adoption; RFA estimate for marine share scenarios (1 billion gallons of ethanol ≈ 350–360 million bushels of corn); USDA for current grind. The marine scenarios assume ethanol wins certification under IMO/EU fuel rules — the big “if.” Another big issue: how long it will take for E15 implementation in states outside the Corn Belt. 

But the honest answer is that marine ethanol is the higher-ceiling, higher-risk, longer-dated play. E15’s obstacles are political and domestic — a Senate vote and pump infrastructure. Marine ethanol’s obstacles are structural and foreign: an IMO framework that may not be adopted until late 2026 and not bite until 2028–29; European rules that currently score crop-based fuels as worse than fossil fuel; carbon-intensity accounting that today favors Brazilian sugarcane over U.S. corn; a fuel-density penalty that narrows the addressable routes; and a supply chain — ports, blenders, traders, certifiers — in which no U.S. farm organization currently holds a seat. It is also worth noting the intra-agriculture tension: the American Soybean Association declined to support the E15 bill, citing research that corn-favoring fuel policy could pressure soybean prices — a reminder that “agriculture’s” interest in fuel policy is really several interests.

The strategic conclusion isn’t either/or. E15 is the near-term, home-field fight worth finishing. The marine market is the diversification play — the hedge against a shrinking gasoline pool — and it is the only ethanol market on Earth with a plausible path to billions of gallons of new demand that doesn’t depend on American drivers. The industry groups seem to grasp this: the U.S. Grains Council is already promoting ethanol bunkering from Panama to Singapore, and the RFA is publishing marine-demand math. The question is whether U.S. policy — which is currently fighting the very IMO framework that would pay premiums for low-carbon fuel — will help or hobble them.

Bottom line — and what to watch

Shipping is where aviation was five years ago: a giant, captive, hard-to-abate fuel market on the verge of writing the rules that decide which feedstocks win. The difference is that the alcohol-capable ships are already on the water, the fuel-price math already works, and the first mover — Brazil — is already bunkering. For U.S. agriculture the marine market is not a substitute for E15; it is the bigger, slower prize behind it, and one that will be won or lost in venues most of American agriculture has never lobbied.

Analysts say to watch these markers over the next 18 months: whether the Senate takes up the E15 bill; whether the IMO’s MEPC 85 in November — or a resumed session in 2027 — finally adopts the Net-Zero Framework, and crucially, how its fuel-certification rules treat crop-based biofuels; whether commercial ethanol bunkering starts on schedule at Santos and Singapore; whether Maersk, CMA CGM or MSC signs the first term contract for U.S.-origin ethanol; and how EPA’s record 2026–27 biomass-based diesel mandates reshape the soybean oil balance that marine biodiesel blenders draw on. Any one of them could move a billion bushels.