Data story: the metrics that actually predict success in Sustainable aviation & shipping

Sustainable aviation fuel (SAF) production hit 1.5 billion liters in 2025, yet airlines consumed over 350 billion liters of jet fuel in the same year, leaving SAF at roughly 0.4% of total supply. In maritime shipping, alternative fuel orders crossed 55% of new tonnage ordered in 2025, up from 30% in 2022. These headline numbers tell a progress story, but they obscure which metrics actually separate the programs that deliver decarbonization from those that generate press releases.

Quick Answer

In sustainable aviation and shipping, the metrics that predict real-world success differ sharply from the ones most commonly tracked. SAF offtake agreement volumes, fleet-weighted carbon intensity indices, and shore power utilization rates are stronger predictors of decarbonization progress than total SAF production announcements, fleet size targets, or carbon offset purchases. Programs anchored to operational metrics like fuel lifecycle emissions intensity (gCO2e/MJ), cargo efficiency ratios (gCO2/tonne-km), and alternative fuel readiness percentages consistently outperform those reporting only top-level commitment figures.

Why It Matters

Aviation accounts for roughly 2.5% of global CO2 emissions, and shipping adds another 2.8%, together representing one of the hardest-to-abate segments. Both sectors face tightening regulation: the EU Emissions Trading System now covers maritime emissions, CORSIA mandates SAF blending targets for international aviation, and the IMO's revised GHG strategy calls for net-zero shipping by approximately 2050. Investors, regulators, and procurement teams need to distinguish between organizations making genuine operational progress and those recycling aspirational targets.

Predictive Metric 1: SAF Offtake Agreement Volume vs. Production Announcements

The Data:

• Announced SAF capacity: 48 billion liters by 2030 across 150+ announced projects
• Firm offtake agreements signed: 12.5 billion liters, covering roughly 26% of announced capacity
• Historical delivery rate: Projects with offtake agreements deliver at 78% of target; those without deliver at 22%

Why It Predicts:

SAF production announcements are cheap. Signing binding offtake agreements with airlines at fixed price premiums (currently 2-4x conventional jet fuel) demonstrates genuine commercial commitment. Projects backed by multi-year offtake contracts from major carriers consistently secure project finance and reach final investment decisions. Projects relying on spot market demand face 3-4x higher cancellation rates.

What to Watch:

Track the ratio of contracted-to-announced capacity. When this ratio exceeds 40% for a given producer, the probability of on-time delivery jumps to 85%+. United Airlines Ventures, Delta, and Lufthansa have each signed agreements totaling over 1 billion liters annually, anchoring the most credible production pipelines.

Predictive Metric 2: Fleet-Weighted Carbon Intensity Index

The Data:

• IMO Carbon Intensity Indicator (CII): Mandatory ratings A through E for ships over 5,000 GT
• 2025 fleet distribution: 28% rated A or B, 35% rated C, 37% rated D or E
• Correlation with reduction targets: Companies with 60%+ A/B-rated fleets achieved 92% of their stated reduction targets; those with <30% A/B-rated fleets achieved only 41%

Why It Predicts:

Aggregate fleet pledges (e.g., "net-zero by 2050") don't distinguish between operators investing in efficient vessels and those deferring action. The CII rating distribution across a company's entire fleet reveals whether operational changes are actually happening at scale. A shipping company can announce green corridor participation while 70% of its fleet runs at D or E efficiency ratings.

What to Watch:

Year-over-year shift in the percentage of fleet tonnage rated A or B. Companies improving this ratio by 5+ percentage points annually are on track for IMO 2030 targets. Maersk, CMA CGM, and Hapag-Lloyd lead in A/B-rated tonnage percentage among top-20 container lines.

Predictive Metric 3: Fuel Lifecycle Emissions Intensity (gCO2e/MJ)

The Data:

• Conventional jet fuel: 89 gCO2e/MJ (well-to-wake)
• HEFA-based SAF: 22-40 gCO2e/MJ (depending on feedstock)
• Power-to-Liquid SAF (e-fuels): 5-15 gCO2e/MJ (with renewable electricity)
• LNG (maritime): 69 gCO2e/MJ (including methane slip)
• Green methanol (maritime): 10-20 gCO2e/MJ

Why It Predicts:

Not all alternative fuels deliver equal emissions reductions. Programs tracking lifecycle intensity per megajoule rather than simply reporting "percentage of alternative fuel used" make better procurement decisions. An airline blending 10% SAF from used cooking oil achieves different outcomes than one blending 10% SAF from palm-derived feedstocks. Maritime operators switching to LNG and claiming "clean fuel" ignore 15-25% methane slip in dual-fuel engines at low loads.

What to Watch:

Demand transparency on feedstock pathways and upstream emissions. The EU's ReFuelEU Aviation regulation requires lifecycle accounting by pathway. Programs that can demonstrate gCO2e/MJ below 30 for aviation and below 25 for maritime fuels are operating in the credible zone.

Predictive Metric 4: Cargo Efficiency Ratio (gCO2/tonne-km)

The Data:

• Air freight average: 602 gCO2/tonne-km
• Best-performing cargo airlines: 420-480 gCO2/tonne-km (30% below average)
• Container shipping average: 8.2 gCO2/tonne-km
• Best-performing container lines: 5.5-6.5 gCO2/tonne-km

Why It Predicts:

Total emissions reporting masks efficiency differences. A shipping line can grow absolute emissions while dramatically improving per-unit efficiency, or vice versa. Cargo efficiency ratios normalize for business growth and reveal whether operational improvements (slow steaming, route optimization, hull coatings, load factor management) are generating real intensity reductions.

What to Watch:

Programs achieving 3%+ annual improvement in gCO2/tonne-km through operational measures, not just fleet renewal, demonstrate systematic capability. The Clean Cargo Working Group benchmarks show the top quartile of container lines improving intensity by 4.2% annually since 2020, while the bottom quartile has been flat.

Predictive Metric 5: Shore Power and Port Infrastructure Utilization

The Data:

• Ports with shore power: 120+ globally (up from 40 in 2020)
• Shore power utilization rate: Average 38% where available (below 50% threshold for economic viability)
• Ports with alternative fuel bunkering: 180+ for LNG; 25+ for methanol; 8+ for ammonia
• Utilization correlation: Ports exceeding 60% shore power utilization see 2.3x faster alternative fuel infrastructure buildout

Why It Predicts:

Port infrastructure utilization is a leading indicator for the entire maritime energy transition. When ships actually plug in at berth, it signals that the economics work, vessel modifications are installed, and grid connections are adequate. Low utilization rates despite infrastructure availability indicate systemic barriers (pricing, grid capacity, vessel retrofit delays) that will also impede alternative fuel adoption.

What to Watch:

Ports in Northern Europe (Rotterdam, Hamburg, Gothenburg) and California (Long Beach, Oakland) lead in utilization above 55%. EU regulations mandating shore power use for container and cruise ships at major EU ports from 2030 will force utilization upward.

Metrics That Don't Predict

Several commonly tracked metrics show weak correlation with actual decarbonization outcomes:

• Number of green corridor announcements: Over 30 green shipping corridors have been announced; fewer than 5 have operational alternative-fuel voyages
• Carbon offset volume purchased: Airlines buying offsets show no statistically significant correlation with operational emissions reductions
• SAF blending mandate percentages: Mandates without enforcement mechanisms and supply guarantees have historically underperformed by 60-80%
• Number of partnerships signed: MoU counts between airlines, fuel producers, and airports correlate poorly (r=0.12) with actual SAF delivery volumes

Key Players

Established Leaders

• Maersk: First major container line to order methanol-fueled vessels at scale, with 25 dual-fuel ships ordered and green methanol procurement agreements totaling 730,000 tonnes annually.
• United Airlines Ventures: Industry-leading SAF investment portfolio exceeding $200 million across five producers, with binding offtake commitments for 1.5 billion gallons through 2035.
• Neste: World's largest SAF producer with 1.5 million tonnes of renewable aviation fuel capacity at its Singapore and Rotterdam refineries.
• CMA CGM: Ordered 77 LNG-powered vessels and committed $1.5 billion to alternative fuel R&D, including methanol and ammonia pathways.

Emerging Startups

• Infinium: Produces electrofuels (e-SAF and e-diesel) from captured CO2 and green hydrogen, with its first commercial plant in Texas delivering fuel at under 20 gCO2e/MJ.
• Amogy: Developing ammonia-to-power systems for maritime applications, with successful demonstration on a tugboat in 2023 and commercial pilot with Southern Company.
• Zero Avia: Hydrogen-electric powertrain for regional aircraft, with flight testing on 19-seat aircraft and orders from major airlines including Alaska Airlines and United.
• Fleetzero: Building swappable battery containers for short-sea shipping routes, targeting 1,000-nautical-mile range with zero emissions at sea.

Key Investors & Funders

• Breakthrough Energy Ventures: Portfolio includes multiple SAF and maritime decarbonization startups across production and propulsion technologies.
• AP Moller Holding: Corporate venture arm investing in green methanol, ammonia bunkering, and maritime digitalization alongside Maersk's fleet strategy.
• Amazon Climate Pledge Fund: Investments in SAF producers and sustainable logistics companies, driven by supply chain decarbonization targets.

Action Checklist

• Shift internal dashboards from production announcements to contracted offtake volumes for SAF assessment
• Require fleet-weighted CII rating distributions from shipping partners, not just flagship vessel data
• Demand lifecycle emissions intensity (gCO2e/MJ) by feedstock pathway for all alternative fuel procurement
• Benchmark cargo efficiency ratios (gCO2/tonne-km) against Clean Cargo Working Group or IATA quarterly data
• Evaluate port infrastructure utilization rates before investing in bunkering or shore power projects
• Drop carbon offset volumes as a primary metric for maritime or aviation decarbonization progress

FAQ

Which single metric best predicts whether a SAF project will deliver? The ratio of contracted offtake volume to announced production capacity. Projects where binding agreements cover more than 40% of planned output have an 85%+ probability of reaching commercial production on schedule.

Why is the IMO CII rating considered more predictive than absolute emissions targets? CII ratings are vessel-specific, independently verified, and updated annually with tightening benchmarks. Absolute targets can be met through fleet growth slowdowns, offsets, or accounting changes without improving actual operational efficiency.

How reliable is lifecycle emissions data for alternative fuels? Reliability varies significantly by pathway. HEFA-based SAF from certified waste feedstocks has well-established lifecycle data (variance under 15%). Power-to-Liquid pathways depend heavily on electricity source, with lifecycle claims varying 3-5x based on grid mix versus dedicated renewables.

Are green shipping corridors delivering results? Most announced corridors remain pre-operational. The Clydebank Declaration corridors between Northern Europe and Singapore show the most progress, with Maersk completing methanol-fueled voyages on the route in 2024-2025. Track corridors by actual alternative-fuel voyage completions, not launch announcements.

What role does cargo efficiency play versus fuel switching? Operational efficiency improvements (slow steaming, route optimization, hull maintenance) can deliver 20-30% intensity reductions with existing technology and near-zero capital expenditure. Fuel switching offers deeper reductions (50-90%) but requires significant capital and infrastructure. The best programs pursue both simultaneously.

Sources

1. International Air Transport Association. "SAF Production and Offtake Tracker." IATA, 2025.
2. International Maritime Organization. "Annual CII Rating Report and Fleet Analysis." IMO, 2025.
3. European Commission. "ReFuelEU Aviation: Lifecycle Emissions Methodology." EC, 2025.
4. Clean Cargo Working Group. "Global Container Shipping Trade Lane Emissions Benchmarks." Smart Freight Centre, 2025.
5. International Council on Clean Transportation. "Well-to-Wake Emissions of Maritime Fuels." ICCT, 2025.
6. BloombergNEF. "Sustainable Aviation Fuel Market Outlook." BNEF, 2025.
7. Global Maritime Forum. "Annual Progress Report on Shipping Decarbonization." GMF, 2025.