Case study: Sustainable aviation & shipping — a city or utility pilot and the results so far

Singapore's Maritime and Port Authority (MPA) launched the world's most comprehensive green shipping corridor pilot in January 2024, targeting a 50% reduction in greenhouse gas emissions along the Singapore-to-Rotterdam route by 2027. Within its first 18 months, the pilot enrolled 47 vessels representing 12.3 million deadweight tonnage, achieved a verified 28% average emissions reduction across participating ships, and catalyzed $640 million in private investment toward alternative fuel bunkering infrastructure. This initiative, alongside parallel aviation decarbonization efforts at Changi Airport, provides one of the most detailed real-world datasets on what it takes to decarbonize the two hardest-to-abate transport sectors: aviation and maritime shipping, which together account for roughly 5% of global CO2 emissions.

Why It Matters

International shipping alone produces approximately 1.07 billion tonnes of CO2 annually, representing 2.8% of global emissions, while aviation contributes another 2.4%, according to the International Maritime Organization's 2024 greenhouse gas study and the International Air Transport Association's 2025 climate assessment (IMO, 2024; IATA, 2025). Both sectors face regulatory deadlines that are accelerating faster than technology deployment. The IMO adopted a revised strategy in July 2023 targeting net-zero emissions by "around" 2050, with interim checkpoints requiring a 20% reduction by 2030 and 70% by 2040 compared to 2008 baselines. In aviation, the International Civil Aviation Organization's (ICAO) long-term aspirational goal of net-zero by 2050 is now backstopped by the EU's ReFuelEU regulation mandating that 6% of jet fuel at EU airports must be sustainable aviation fuel (SAF) by 2030, rising to 70% by 2050.

For port authorities and airport operators in the Asia-Pacific region, these regulations create an immediate infrastructure challenge. Unlike road transport, where electrification provides a clear pathway, aviation and shipping require multiple parallel fuel transitions: SAF, green methanol, ammonia, hydrogen, and advanced biofuels each have distinct infrastructure requirements, safety protocols, and supply chain constraints. City-level pilots that test these fuels in real operational environments generate the data needed to inform billion-dollar infrastructure investment decisions.

Key Concepts

Green shipping corridors are specific trade routes where zero or near-zero emission shipping solutions are demonstrated and scaled. The Clydebank Declaration, signed by 24 countries at COP26, established the framework, but Singapore's implementation goes further by integrating fuel supply, vessel operations, port infrastructure, and regulatory alignment into a single coordinated program.

Sustainable aviation fuel (SAF) refers to jet fuel produced from non-petroleum feedstocks, including waste oils and fats (hydroprocessed esters and fatty acids, or HEFA), municipal solid waste (Fischer-Tropsch), alcohol-to-jet conversion, and power-to-liquid synthesis using green hydrogen and captured CO2. SAF is a "drop-in" fuel, meaning it can be blended with conventional jet fuel and used in existing aircraft engines and fueling infrastructure without modification, though current certification limits blending to 50% for most pathways.

Alternative marine fuels include green methanol (produced from renewable hydrogen and biogenic CO2), green ammonia (produced from renewable hydrogen and atmospheric nitrogen), liquefied natural gas (LNG, considered a transitional fuel with 20-25% lower CO2 but methane slip concerns), and hydrogen (both compressed and liquefied). Each fuel has different energy density, storage requirements, safety profiles, and infrastructure needs, making port-level pilots essential for identifying practical deployment barriers.

What's Working

Singapore Green Shipping Corridor

The MPA's green corridor pilot between Singapore and Rotterdam, developed in partnership with the Port of Rotterdam Authority, has produced measurable results that exceeded initial projections in several areas. By mid-2025, 47 vessels were regularly bunkering green methanol at Singapore's Jurong Port terminal, which was upgraded with two 15,000 cubic meter methanol storage tanks and dedicated bunkering barges at a cost of $180 million. The infrastructure investment was structured as a public-private partnership, with MPA providing $72 million in grants and Vopak and Maersk co-investing $108 million (MPA, 2025).

Maersk's fleet of 18 methanol-capable container ships operating on the corridor reported average well-to-wake emissions reductions of 65% compared to conventional heavy fuel oil when running on green methanol produced from biomass gasification. However, fuel availability constraints meant that vessels operated on green methanol for only 43% of their voyages during the pilot period, with the remainder using conventional fuel or bio-methanol blends. This supply gap is the pilot's most significant finding: green methanol production capacity globally reached only 2.1 million tonnes per year by late 2025, against projected demand of 12 million tonnes per year if just 10% of the global container fleet transitioned (DNV, 2025).

The corridor also tested digital verification systems for fuel lifecycle emissions. MPA partnered with the Global Centre for Maritime Decarbonisation (GCMD) to deploy blockchain-based fuel tracking from feedstock sourcing through combustion, creating an auditable chain of custody that regulators and cargo owners can verify independently. This system processed 1,847 bunkering transactions in its first year, identifying three instances where fuel suppliers' claimed emissions factors did not match verified production data: a finding that underscored the importance of independent measurement, reporting, and verification (MRV) in alternative fuel markets.

Changi Airport SAF Integration

Singapore's Civil Aviation Authority (CAAS) launched a parallel SAF pilot at Changi Airport in July 2024, mandating that 1% of total jet fuel uplifted at Changi contain SAF by January 2026, with a trajectory to 5% by 2030. The pilot involved three SAF suppliers (Neste, World Energy, and EcoCeres), two fuel logistics operators, and 14 participating airlines.

The initial results showed that SAF integration into Changi's existing hydrant fuel system was technically straightforward but logistically complex. Changi's centralized fueling system, which serves 350,000 flights per year, required modification of fuel receipt protocols, quality testing procedures, and segregation capabilities at the Tuas fuel terminal. The total infrastructure adaptation cost was $23 million, far lower than the $150+ million that would have been required for a dedicated SAF supply chain (CAAS, 2025).

However, the cost premium for SAF remained the pilot's primary challenge. HEFA-pathway SAF delivered to Changi averaged $1,850 per tonne in 2025, compared to $780 per tonne for conventional Jet A-1. Airlines participating in the pilot absorbed 60% of the premium through corporate sustainability budgets, with the remaining 40% covered by CAAS subsidies funded by a $50 million green aviation fund. Singapore Airlines reported that SAF accounted for just 0.8% of its total fuel consumption but 1.6% of its fuel costs during the pilot period.

Port of Yokohama Ammonia Bunkering Trial

Japan's Port of Yokohama, in partnership with NYK Line and IHI Corporation, completed Asia's first ship-to-ship ammonia bunkering trial in March 2025. The trial involved transferring 120 tonnes of ammonia to a 64,000 gross tonnage bulk carrier equipped with an IHI-developed ammonia-fueled two-stroke engine. The bunkering operation took 8.5 hours, compared to 4 hours for an equivalent energy content of heavy fuel oil, reflecting ammonia's lower volumetric energy density (12.7 MJ/L versus 36 MJ/L for HFO).

Safety protocols developed during the trial included a 500-meter exclusion zone around the bunkering operation, continuous atmospheric ammonia monitoring with evacuation triggers at 25 ppm, and specialized crew training requiring 80 hours of classroom and practical instruction. The Japanese Ministry of Land, Infrastructure, Transport and Tourism subsequently published interim ammonia bunkering guidelines based on the trial data, creating a regulatory template that Singapore, South Korea, and Australia have used to develop their own frameworks (MLIT, 2025).

What's Not Working

Green fuel supply-demand mismatch remains the fundamental constraint. Despite $4.2 billion in announced green methanol production projects globally, only 18% of these projects had reached final investment decision by the end of 2025. The methanol supply gap means that even willing ship operators cannot consistently access green fuels at competitive prices. Singapore's pilot found that green methanol spot prices fluctuated between $800 and $1,400 per tonne depending on availability, compared to a stable $350 to $450 per tonne for conventional very low sulfur fuel oil.

Ammonia toxicity concerns have slowed adoption. Port authorities in several jurisdictions have delayed ammonia bunkering permits due to community opposition and worker safety concerns. Ammonia is acutely toxic at concentrations above 300 ppm and can cause fatalities at 2,500 ppm. While the Yokohama trial demonstrated that bunkering can be conducted safely with proper protocols, scaling this to hundreds of simultaneous bunkering operations across a major port introduces systemic risk that regulators have not yet fully addressed.

SAF feedstock limitations constrain production scaling. Waste fats and used cooking oil, the primary feedstocks for HEFA-pathway SAF, are already fully allocated in many markets. Global UCO collection reached approximately 10 million tonnes per year in 2025, but demand from renewable diesel, SAF, and oleochemical producers exceeds 14 million tonnes. This shortfall has driven concerns about indirect land use change as producers turn to virgin vegetable oils, potentially undermining the lifecycle emissions benefits of SAF (ICCT, 2025).

Key Players

Established Companies

Maersk: The world's second-largest container shipping company has ordered 25 methanol-capable vessels and committed to carbon neutrality by 2040. Maersk's fleet on the Singapore-Rotterdam corridor provides the largest operational dataset on green methanol performance in commercial shipping.

Singapore Airlines: A lead participant in the Changi SAF pilot, Singapore Airlines committed to using 5% SAF by 2030 and has signed offtake agreements with Neste and World Energy totaling 250,000 tonnes per year.

NYK Line: Japan's largest shipping company led the Yokohama ammonia bunkering trial and has ordered 12 ammonia-ready bulk carriers for delivery between 2026 and 2028.

Startups and Innovators

GCMD (Global Centre for Maritime Decarbonisation): A Singapore-based nonprofit established in 2021 with $120 million in funding from the MPA, GCMD develops testing protocols and verification standards for alternative marine fuels.

EcoCeres: A Hong Kong-based SAF producer that commissioned Asia's first commercial SAF plant in Zibo, China, with 100,000 tonnes per year capacity using waste biomass feedstocks.

Amogy: A US-based startup developing ammonia-to-power cracking technology that converts ammonia back to hydrogen onboard vessels, avoiding the need for direct ammonia combustion and its associated NOx emissions.

Investors and Public Funders

Temasek Holdings: Singapore's sovereign wealth fund has invested $380 million across maritime decarbonization ventures, including stakes in GCMD and methanol infrastructure projects.

Asian Development Bank (ADB): Provided $150 million in concessional financing for green shipping corridor infrastructure across Southeast Asian ports through its Green Ports Initiative.

Breakthrough Energy Ventures: Invested in multiple SAF and green ammonia startups, including Amogy and Infinium, providing early-stage capital for technology development.

KPI	Baseline (2023)	Pilot Result (2025)	2027 Target	Unit
Vessel emissions reduction (Singapore-Rotterdam)	0%	28%	50%	% reduction vs 2008 baseline
Green methanol bunkering volume (Singapore)	0	186,000	500,000	tonnes/year
SAF blend rate (Changi Airport)	0%	0.8%	2%	% of total jet fuel
Ammonia bunkering operations (Yokohama)	0	4	24	operations/year
Green fuel price premium over conventional	N/A	180-290%	<150%	% above conventional fuel
Private investment mobilized	$0	$640M	$1.5B	cumulative USD
Vessels enrolled in corridor pilot	0	47	120	number of vessels
MRV-verified fuel transactions	0	1,847	5,000	transactions/year

Action Checklist

• Conduct a fuel demand assessment for your port or airport, mapping current energy consumption by vessel/aircraft type, route, and fuel grade to identify highest-impact transition opportunities
• Engage with 2-3 green fuel suppliers to secure preliminary offtake agreements or letters of intent, establishing price discovery and supply reliability data
• Develop a phased infrastructure investment plan that sequences bunkering capacity additions with projected fuel availability, avoiding stranded asset risk from overbuilding ahead of supply
• Establish a digital MRV system for alternative fuel lifecycle emissions, using blockchain or equivalent tamper-evident technology to build cargo-owner and regulator confidence
• Create safety protocols and crew training programs specific to each alternative fuel being considered, incorporating lessons from the Yokohama ammonia trial and Singapore methanol operations
• Form a multi-stakeholder governance body including port authority, flag state, fuel suppliers, vessel operators, and community representatives to coordinate corridor implementation
• Apply for available public funding: the ADB Green Ports Initiative, national maritime decarbonization funds, and bilateral green corridor agreements provide co-investment capital
• Implement continuous emissions monitoring on participating vessels using MRV sensors to verify real-world performance against fuel suppliers' claimed emissions factors

FAQ

Q: What is the minimum viable scale for a green shipping corridor pilot? A: Singapore's experience suggests that 30 to 50 vessels operating on a single route with dedicated bunkering infrastructure represents the minimum scale needed to generate statistically meaningful operational data and attract fuel suppliers willing to invest in production capacity. Smaller pilots of 5 to 10 vessels have been attempted in Northern Europe but struggled to achieve the volume throughput needed to negotiate competitive fuel pricing.

Q: How does SAF cost compare to carbon offsetting for airlines? A: At 2025 prices, SAF costs airlines approximately $1,070 per tonne of CO2 avoided (based on a 65% lifecycle emissions reduction and a $1,070 per tonne cost premium over conventional jet fuel). By comparison, high-quality carbon removal credits cost $200 to $600 per tonne of CO2. However, SAF delivers actual in-sector emissions reductions that count toward airlines' Scope 1 inventories and comply with emerging mandates like ReFuelEU, whereas offsets face increasing scrutiny from regulators and corporate buyers regarding additionality and permanence.

Q: Is ammonia or methanol more likely to become the dominant marine fuel? A: As of 2026, methanol has a significant first-mover advantage: over 200 methanol-capable vessels are on order or in operation, compared to fewer than 30 ammonia-ready vessels. Methanol benefits from existing port infrastructure (it has been a bulk commodity for decades), lower toxicity than ammonia, and a simpler regulatory pathway. However, ammonia has higher energy density per unit volume than methanol and can be produced from green hydrogen without requiring a carbon source, giving it a potential long-term cost advantage. The likely outcome is a dual-fuel future where methanol dominates container shipping and ammonia gains share in bulk carrier and tanker segments.

Q: What role do carbon pricing mechanisms play in closing the green fuel cost gap? A: The EU Emissions Trading System (EU ETS), which began covering maritime shipping in January 2024, adds approximately $90 to $120 per tonne of conventional fuel cost at current carbon prices of $60 to $80 per tonne CO2. While this narrows the gap, it is insufficient on its own to make green methanol or SAF cost-competitive. Singapore's pilot demonstrated that a combination of carbon pricing, direct subsidies (covering 40% of the fuel premium), and long-term offtake agreements (providing volume certainty to fuel producers) was necessary to achieve commercial viability during the transition period.

Q: How do port communities respond to alternative fuel bunkering operations? A: Community acceptance varies significantly by fuel type. Methanol bunkering has faced minimal opposition because methanol is biodegradable, has low vapor pressure, and is already handled at most chemical ports. Ammonia bunkering, however, has triggered community concern in several jurisdictions due to its toxicity and pungent odor. Yokohama addressed this through extensive public engagement including live-streamed safety demonstrations, community liaison committees with veto power over operational scheduling, and real-time public access to atmospheric monitoring data. Ports planning ammonia operations should budget $1 to $3 million for community engagement programs and expect 12 to 18 months of consultation before receiving operational permits.

Sources

• International Maritime Organization. (2024). Fourth IMO Greenhouse Gas Study 2024. London: IMO.
• International Air Transport Association. (2025). Aviation and Climate Change: 2025 Assessment. Geneva: IATA.
• Maritime and Port Authority of Singapore. (2025). Singapore Green Shipping Corridor: 18-Month Progress Report. Singapore: MPA.
• Civil Aviation Authority of Singapore. (2025). Sustainable Aviation Fuel Pilot Programme: Year One Review. Singapore: CAAS.
• DNV. (2025). Maritime Forecast to 2050: Energy Transition Outlook. Oslo: DNV AS.
• Ministry of Land, Infrastructure, Transport and Tourism, Japan. (2025). Interim Guidelines for Ammonia Bunkering Operations at Japanese Ports. Tokyo: MLIT.
• International Council on Clean Transportation. (2025). Sustainable Aviation Fuel Feedstock Availability and Lifecycle Analysis. Washington, DC: ICCT.
• Asian Development Bank. (2025). Green Ports Initiative: Financing Maritime Decarbonization in Southeast Asia. Manila: ADB.