Data Story — Key Signals in Sustainable Aviation & Shipping

Aviation and maritime shipping together account for 5% of global emissions—a share projected to triple by 2050 as other sectors decarbonize and transport demand grows. Unlike road transport where electrification provides a clear pathway, these sectors face fundamental physics constraints that make decarbonization uniquely challenging. Understanding the trade-offs between sustainable aviation fuel, green ammonia, hydrogen, and efficiency measures is essential for corporate travel and logistics sustainability strategies.

Why It Matters

Aviation emissions have recovered to pre-pandemic levels, reaching 1.05 billion tonnes CO2 in 2024. Shipping adds another 1 billion tonnes. While representing "only" 5% of global emissions, these sectors are among the hardest to abate—energy density requirements for long-haul flight and trans-oceanic shipping preclude battery electric solutions for the foreseeable future.

Corporate exposure is significant. For companies with global supply chains or significant business travel, aviation and shipping often represent 30-50% of Scope 3 emissions. As carbon pricing expands—EU ETS now includes maritime shipping—these emissions carry direct cost implications. Customer pressure adds urgency: CDP reports that 40% of supplier engagement letters now explicitly address transportation emissions.

Key Concepts

Aviation Decarbonization Options

• Sustainable Aviation Fuel (SAF): Drop-in fuels from feedstocks including used cooking oil, agricultural residues, municipal waste, and synthetic production (e-fuels)
• Hydrogen propulsion: Direct combustion or fuel cells for regional aircraft; requires aircraft redesign
• Electric/hybrid: Battery or hybrid systems for short-haul routes under 500 miles
• Operational efficiency: Continuous descent approaches, optimal routing, weight reduction, fleet renewal

Maritime Decarbonization Options

• Green ammonia: Zero-carbon fuel from renewable hydrogen and nitrogen; leading candidate for deep-sea shipping
• Green methanol: Lower toxicity than ammonia; Maersk's preferred pathway with vessels already ordered
• LNG (transitional): 20-25% emissions reduction versus heavy fuel oil; bridge fuel with methane slip concerns
• Wind-assisted propulsion: Rigid sails and rotor sails providing 10-30% fuel savings
• Shore power: Eliminating port emissions through grid connection

Sector Benchmark KPIs

• Aviation: grams CO2 per revenue passenger kilometer (g CO2/RPK); industry average 88g, best-in-class 70g
• Maritime containers: grams CO2 per tonne-kilometer (g CO2/tkm); industry average 8g, best-in-class 5g
• SAF blend rate: percentage of sustainable fuel in total consumption; current average 0.3%, 2030 target 10%
• Energy Efficiency Existing Ship Index (EEXI): IMO metric for vessel efficiency

What's Working and What Isn't

What's Working

SAF production scaling: Global SAF production reached 600 million liters in 2024—still only 0.3% of jet fuel demand but doubling annually. Neste, World Energy, and new entrants are adding capacity. Announced projects would bring production to 35 billion liters by 2030, potentially meeting 10% of demand.

Methanol-ready vessels: Maersk has ordered 25 methanol-capable container ships, with the first entering service in 2024. The dual-fuel design allows operation on conventional fuel while green methanol supply develops. Other carriers including CMA CGM and Evergreen are following with methanol or ammonia-ready orders.

Corporate SAF agreements: Over 30 major corporations have signed multi-year SAF offtake agreements, creating demand certainty for production investment. Microsoft, Meta, and JP Morgan collectively committed to over 100 million gallons annually, helping derisk new production capacity.

Wind-assisted propulsion: Cargill, Vale, and other commodity shippers are deploying rotor sails and rigid wing sails, achieving 10-30% fuel savings on bulk carrier routes. Bound4Blue and Anemoi Marine Technologies report 50+ vessel installations with proven performance data.

What Isn't Working

SAF feedstock constraints: Used cooking oil and waste fats—current primary SAF feedstocks—have limited supply. Meeting 10% SAF targets would require all available UCO globally plus agricultural residues. Synthetic e-fuels (from green hydrogen and captured CO2) solve feedstock limits but remain 3-5x more expensive than bio-based SAF.

Ammonia infrastructure gaps: Green ammonia production capacity is minimal—under 100,000 tonnes globally versus the millions of tonnes shipping would require. Bunkering infrastructure doesn't exist at major ports. Ammonia toxicity raises safety concerns for crew and port communities.

Hydrogen aircraft timelines: Airbus's ZeroE hydrogen aircraft targets 2035 entry to service—too late for 2030 emissions targets. Hydrogen's low volumetric energy density requires aircraft redesign, limiting range to regional routes. Long-haul flight will depend on SAF for decades.

Carbon offset quality: Airlines using carbon offsets to claim "carbon neutral" flights face growing scrutiny. Academic studies show 85%+ of aviation offset projects deliver less benefit than claimed. Regulators are restricting offset claims in advertising.

Examples

1. United Airlines Eco-Skies Alliance: United's SAF program pools corporate demand, with over 60 companies including Nike, Deloitte, and Siemens purchasing SAF credits attributable to their business travel. The program purchased 100 million gallons of SAF in 2024, reducing participant Scope 3 emissions by 400,000 tonnes CO2e. United's approach demonstrates that demand aggregation can accelerate SAF scaling despite individual corporate volumes being too small for direct offtakes.

2. Maersk Laura Maersk, Denmark: The world's first container vessel powered by green methanol entered service in 2024 on the Baltic-Mediterranean route. The 2,100 TEU vessel demonstrates that zero-carbon shipping is technically feasible today. Maersk sources green methanol from European production using renewable hydrogen and biogenic CO2, though supply constraints limit scaling. The vessel carries cargo for H&M, LEGO, and other shippers paying green premiums for verifiable decarbonized logistics.

3. Singapore Maritime Decarbonization Hub: Singapore, handling 20% of global container transshipment, is investing S$250 million in maritime decarbonization infrastructure. The hub includes ammonia and methanol bunkering trials, shore power deployment across major terminals, and a green corridor to Rotterdam with standardized fuel specifications. Singapore's strategy recognizes that its port competitiveness depends on enabling shipping's energy transition.

Action Checklist

• Calculate transport Scope 3—disaggregate emissions by mode (air, sea, road) and trade lane to identify highest-impact intervention points
• Join SAF purchasing coalitions—participate in aggregated SAF offtake programs like United Eco-Skies or KLM Corporate SAF Program to access sustainable aviation fuel
• Specify low-carbon shipping in RFPs—require carriers to disclose Carbon Intensity Indicator (CII) ratings and offer low-carbon shipping options in logistics tenders
• Set modal shift targets—identify air freight that can shift to sea or rail with acceptable service levels, typically 20-40% of volumes
• Engage freight forwarders on visibility—require emissions reporting at shipment level using standardized methodologies (GLEC Framework)
• Avoid offset-based neutrality claims—regulators and stakeholders increasingly reject offset-based "carbon neutral" transport claims

FAQ

Q: What's the real-world emissions reduction from SAF? A: Lifecycle emissions reductions vary by feedstock: used cooking oil SAF achieves 80-90% reduction versus jet fuel; agricultural residue SAF delivers 70-80%; synthetic e-fuels can approach 100% reduction if produced with renewable electricity and captured CO2. Book-and-claim accounting allows emissions benefits even when SAF isn't physically in your aircraft's tanks.

Q: How should we account for maritime emissions? A: Use the Global Logistics Emissions Council (GLEC) Framework methodology, which provides standardized calculation approaches for sea freight. Request Well-to-Wake emissions data from carriers including vessel efficiency and fuel type. The IMO's Carbon Intensity Indicator (CII) ratings provide vessel-level efficiency benchmarks.

Q: Is green ammonia safe for shipping? A: Ammonia is toxic but has decades of safe handling history in chemical shipping. New marine engines are being designed with appropriate safety systems. The IMO's interim guidelines establish safety standards. Crew training and port facility requirements are being developed. While not zero-risk, ammonia appears manageable with proper protocols.

Q: What's the cost premium for sustainable transport? A: SAF currently costs 2-3x conventional jet fuel, translating to 3-8% flight cost increase at 10% blend rates. Green methanol shipping adds approximately 20-30% to container rates. Premiums are declining as production scales—SAF costs have fallen 40% since 2020.

Sources

• International Air Transport Association, "Net Zero 2050: SAF Production Trajectory," IATA, 2025
• International Maritime Organization, "Fourth IMO GHG Study: 2024 Update," IMO, 2025
• Maersk, "Green Methanol Transition Progress Report," Maersk Sustainability, 2025
• Rocky Mountain Institute, "The Sustainable Aviation Buyers Alliance: Market Report 2025," RMI, 2025
• Global Logistics Emissions Council, "GLEC Framework 3.0," Smart Freight Centre, 2025
• Getting to Zero Coalition, "Mapping the Zero-Emission Fuel Landscape," Global Maritime Forum, 2025