Sustainability Atlas
Mobility & Built Environment·13 min read··...

Myth-busting sustainable aviation & shipping: separating hype from reality

what's working, what isn't, and what's next. Focus on a startup-to-enterprise scale story.

In 2024, global sustainable aviation fuel (SAF) production doubled to 1 million tonnes—yet this represented just 0.3% of total jet fuel consumption. Meanwhile, shipping saw alternative-fuel vessel orders surge 50% with 600 new orders, but the entire alternative-fuel fleet still comprises only 4.8% of global tonnage. These numbers reveal the uncomfortable truth about transport decarbonization: progress is real but the gap between ambition and reality remains vast. The aviation industry needs to scale SAF production from 1 million tonnes today to 40 million tonnes by 2035; shipping must retrofit or replace a 60,000-vessel global fleet running on heavy fuel oil. This article separates the genuine breakthroughs from the greenwashing, examining what's actually working in sustainable aviation and shipping—and what claims deserve more scrutiny.

Why It Matters

Aviation and maritime shipping together account for approximately 5-6% of global greenhouse gas emissions—a figure that understates their climate significance. Unlike road transport or electricity generation, these sectors have proven remarkably resistant to decarbonization. There are no viable battery-electric options for transoceanic flights or container ships: the energy density requirements exceed current battery technology by orders of magnitude. This means aviation and shipping will remain dependent on liquid or gaseous fuels for decades, making the transition to sustainable alternatives an urgent priority.

The International Maritime Organization (IMO) adopted its revised GHG Strategy in July 2023, targeting net-zero emissions "by or around" 2050, with checkpoints requiring at least 20% reduction by 2030 and 70% by 2040 compared to 2008 levels. For aviation, the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) entered its First Phase in 2024, requiring airlines to offset emissions growth above 85% of 2019 levels. The EU's ReFuelEU Aviation mandate now requires 2% SAF blending as of January 2025, escalating to 70% by 2050.

These regulatory frameworks create both compliance obligations and market opportunities. Organizations that move early on sustainable fuels and technologies position themselves for competitive advantage as carbon pricing mechanisms strengthen. Those that dismiss the transition as distant face escalating costs and stranded asset risks.

Key Concepts

Understanding sustainable aviation and shipping requires grasping several technical and regulatory foundations:

Sustainable Aviation Fuel (SAF) refers to aviation fuels produced from non-fossil sources that meet strict sustainability criteria. SAF achieves 50-80% lifecycle GHG reductions compared to conventional jet fuel, depending on the feedstock and production pathway. Currently, 11 production pathways are certified by ASTM International, with Hydroprocessed Esters and Fatty Acids (HEFA)—using waste oils, used cooking oil, and animal fats—comprising approximately 80% of production.

Green methanol and ammonia represent the leading alternative fuels for maritime shipping. Green methanol, produced from renewable hydrogen and captured CO2 or biomass, achieves 65-90% GHG reductions and can use adapted conventional engines. Green ammonia, produced from renewable hydrogen and nitrogen, offers 95% tank-to-wake emissions reduction but presents significant toxicity and handling challenges.

CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation) is ICAO's market-based mechanism requiring airlines to offset emissions growth through purchase of approved carbon credits or use of CORSIA Eligible Fuels. The scheme covers flights between 130 participating states as of January 2026.

IMO Net-Zero Framework, approved in April 2025, establishes mandatory GHG fuel standards and a carbon pricing mechanism for ships above 5,000 gross tonnage, with compliance starting in 2028. This framework will fundamentally reshape maritime fuel economics.

What's Working

SAF Production Scale-Up

The HEFA pathway has proven commercially viable at scale. Neste, the world's largest SAF producer, now operates 1.5 million tonnes of annual production capacity, with its Rotterdam refinery producing 500,000 tonnes of SAF since 2024. The company has secured offtake agreements with United Airlines, FedEx, Boeing, Air Canada, and Air New Zealand, demonstrating genuine market demand when supply exists.

In the United States, production capacity grew from 2,000 barrels per day in early 2024 to 30,000 barrels per day by late 2024, with Phillips 66's Rodeo facility and Diamond Green Diesel's Port Arthur plant coming online. The U.S. Energy Information Administration projects Other Biofuels production (primarily SAF) to double between 2024-2025, with an additional 20% growth forecast for 2026.

Methanol-Fueled Shipping

Maersk has proven that methanol propulsion works at commercial scale. The company deployed 7 large dual-fuel methanol vessels in 2024, with its flagship Ane Mærsk (16,000 TEU capacity) operating on the Asia-Europe route since January 2024. Maersk's 18-vessel methanol fleet order, combined with a 500,000 tonnes per year green methanol offtake agreement with Goldwind, demonstrates end-to-end supply chain development rather than isolated pilot projects.

The broader industry has followed: over 170 dual-fuel methanol vessels are now on order globally, with methanol emerging as the leading liquid alternative fuel choice. Lloyd's Register reports that 119 methanol vessel orders were placed in 2024 alone, outpacing all other alternative fuel categories.

Policy-Driven Investment

The EU's ReFuelEU Aviation mandate and the U.S. Inflation Reduction Act have catalyzed meaningful investment. The SAFFA (Sustainable Aviation Fuel Financing Alliance), anchored by Airbus with partners including Air France-KLM, BNP Paribas, and Qantas, deployed $200 million into SAF production projects. United Airlines expanded its Sustainable Flight Fund to approximately $200 million in July 2024. Boeing's Clear Sky initiative made its first investment in Firefly Green Fuels, targeting sewage-to-SAF conversion.

Metric202320242025 Target
Global SAF Production (million tonnes)0.51.01.9-2.1
SAF Share of Jet Fuel0.15%0.3%0.7%
Alternative-Fuel Vessel Orders400600750+
Methanol-Capable Ships in Operation<4060+120+
Green Methanol Projects Announced120170200+

What's Not Working

SAF Cost Premium Persistence

Despite production growth, SAF remains 3-10x more expensive than conventional jet fuel, with e-SAF (produced from renewable electricity) costing up to 12x more. Airlines paid $2.9 billion in premiums for 1.9 million tonnes of SAF in 2025. This cost gap shows no sign of closing without sustained policy support, as feedstock constraints and production economics limit price competitiveness.

The "HEFA tipping point" expected after 2030 presents a structural challenge: current SAF production depends heavily on waste oils and fats, but demand will outpace available feedstock. Diversification to Alcohol-to-Jet (AtJ), Fischer-Tropsch, and Power-to-Liquid pathways requires technology maturation and capital investment that market signals alone cannot provide.

Carbon Offset Quality Concerns

CORSIA's first phase requires airlines to purchase approximately 200 million eligible emissions units for 2024-2026 compliance, costing an estimated $4-5 billion. However, investigations by Carbon Market Watch and Seas At Risk have documented quality concerns with approved offset standards, questioning whether purchased credits represent genuine, additional emissions reductions. Airlines meeting CORSIA obligations through offsets rather than SAF adoption may face reputational and regulatory risks as scrutiny intensifies.

Ammonia Adoption Hesitation

While green ammonia offers superior emissions reduction potential, market adoption has stalled. Only 22 ammonia-fueled vessels were ordered in 2024, dropping to 5 in 2025. The acute toxicity of ammonia creates safety concerns for ports and public health authorities, with social license challenges emerging in port communities. The first ammonia-powered container ship (Yara Eyde) will not debut until 2026, leaving ammonia years behind methanol in commercial readiness.

Greenwashing and Voluntary Demand Weakness

Neste's Q3 2024 report highlighted "lower-than-expected voluntary SAF demand," revealing that corporate sustainability commitments have not translated into purchase orders at projected rates. IATA noted in December 2025 that SAF production growth rates are actually slowing despite absolute volume increases. Many corporate net-zero pledges rely on SAF availability projections that exceed plausible production scenarios.

Key Players

Established Leaders

Neste — Finland-based global leader in renewable fuels, producing 1.5 million tonnes of SAF annually with partnerships across major airlines worldwide. Targeting 6.8 million tonnes total renewable fuel capacity by 2027.

Maersk — Danish shipping giant operating the world's largest methanol-fueled container fleet, with Science-Based Targets validated by SBTi and a 2040 net-zero commitment. Policy-setting industry leader with 500,000 tonnes annual green methanol secured.

World Energy — Operates America's only commercial-scale SAF production facility, with 150 million gallons annual capacity and the largest publicly announced SAF agreement (1.5 billion gallons with United Airlines).

CMA CGM — French shipping conglomerate investing heavily in LNG and methanol-capable vessels, with dual-fuel orders across its fleet renewal program.

Emerging Startups

LanzaJet — Leading Alcohol-to-Jet technology developer converting ethanol to SAF, addressing the medium-term pathway gap between HEFA and Power-to-Liquid technologies.

Twelve — WEF Top Innovator 2024 developing carbon transformation technology to produce aviation fuel from CO2 captured directly from air.

Synhelion SA — Swiss startup producing synthetic fuels using concentrated solar energy, selected for WEF Sustainable Aviation Challenge 2024.

Firefly Green Fuels — UK-based startup converting sewage waste to SAF via hydrothermal liquefaction, claiming 90%+ lifecycle CO2 reduction. Backed by Boeing's Clear Sky fund.

Key Investors & Funders

SAFFA (Sustainable Aviation Fuel Financing Alliance) — $200 million fund anchored by Airbus with Air France-KLM, BNP Paribas, Qantas, and Mitsubishi HC Capital. First investment in Crysalis Biosciences.

United Airlines Ventures — Corporate venture arm operating ~$200 million Sustainable Flight Fund targeting SAF and alternative propulsion technologies.

Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping — Copenhagen-based nonprofit accelerating shipping decarbonization through technology development and industry collaboration.

Examples

Maersk's Methanol Fleet Deployment: Between January 2024 and late 2025, Maersk deployed its full order of 18 large dual-fuel methanol vessels, proving commercial viability of alternative fuel shipping at scale. The Ane Mærsk completed its maiden voyage on green methanol secured from European Energy's Danish e-methanol facility. Maersk's ECO Delivery Ocean product now enables customers including Primark to decarbonize supply chains using verified green fuel allocation. Critical success factors: long-term fuel offtake agreements signed before vessel delivery, engine technology partnership with MAN Energy Solutions, and premium pricing model that transfers costs to sustainability-conscious cargo owners.

Crysalis Biosciences SAF Plant: SAFFA's first investment supported Crysalis Biosciences' ethanol-to-SAF conversion facility in Illinois, which became operational in Q1 2024. The plant converts existing ethanol production to aviation fuel using Alcohol-to-Jet technology, demonstrating that SAF scale-up can leverage existing biofuel infrastructure rather than requiring entirely new supply chains. The Illinois SAF purchase credit provided additional economic incentive for production location selection.

CORSIA First Phase Implementation: Airlines subject to CORSIA offset requirements for 2024 emissions needed approximately 55 million carbon credits, with the Sectoral Growth Factor calculated at 0.154 following ICAO's baseline adjustment to 85% of 2019 emissions. Four carbon standards were approved for Phase 1 compliance: Gold Standard, Verra, Climate Action Reserve, and Global Carbon Council. Implementation challenges included delays in Letters of Authorization (LoA) from national authorities and questions about offset credit quality from environmental groups.

Action Checklist

  • Assess SAF procurement feasibility: Contact Neste, World Energy, or regional producers to understand pricing, availability, and book-and-claim mechanisms for your air freight emissions
  • Evaluate shipping carrier sustainability options: Request ECO Delivery or equivalent low-emission container transport quotes from Maersk, CMA CGM, or Hapag-Lloyd for Scope 3 emissions reduction
  • Map CORSIA and EU ETS exposure: Calculate your organization's aviation and maritime emissions under current and projected regulatory frameworks to quantify compliance cost scenarios
  • Join industry coalitions: Consider membership in Zero Emission Maritime Buyers Alliance (ZEMBA) or Cargo Owners for Zero Emission Vessels (coZEV) to aggregate demand and access green fuel offtake opportunities
  • Develop supplier engagement criteria: Incorporate SAF adoption rates and fuel pathway specifications into air cargo RFPs; add alternative fuel vessel requirements to ocean freight contracts
  • Build internal carbon pricing: Apply shadow carbon prices to transport decisions that reflect anticipated regulatory costs ($50-150/tonne) to internalize future compliance expenses

FAQ

Q: Is SAF actually better for the climate, or just expensive greenwashing? A: SAF achieves genuine lifecycle emissions reductions of 50-80% compared to fossil jet fuel when produced from certified sustainable feedstocks. However, the benefits depend entirely on feedstock sourcing and production pathway. HEFA-based SAF from waste oils performs well; SAF from palm oil or first-generation crops can have net negative climate impacts. Demand book-and-claim certificates specifying feedstock and certification standards (RSB, ISCC) rather than generic "SAF" claims.

Q: Should my company prioritize aviation or shipping decarbonization? A: The answer depends on your emissions profile and sector exposure. Shipping offers more near-term options with methanol-fueled vessels entering commercial operation, while SAF remains supply-constrained and expensive. However, aviation faces more immediate regulatory pressure through CORSIA and EU ETS. Analyze your Scope 3 transport emissions breakdown, then prioritize the sector with both material emissions impact and available decarbonization pathways.

Q: What's the realistic timeline for affordable sustainable transport fuels? A: Expect SAF to remain 2-3x fossil fuel prices through 2030, declining to 1.5-2x by 2035 as production scales and competition increases. Green methanol will likely reach cost parity with marine gas oil by 2028-2030 as carbon pricing mechanisms take effect. "Affordable" is relative: regulatory frameworks will increasingly internalize the climate costs of fossil fuels, making sustainable alternatives competitive by raising the baseline rather than lowering green premiums.

Q: Are carbon offsets a legitimate alternative to SAF and green shipping fuels? A: Offsets are a transitional mechanism, not an endpoint. CORSIA accepts offsets for compliance, but quality concerns persist across approved standards. Organizations relying primarily on offsets face reputational risk as investor and customer scrutiny intensifies. Best practice: use offsets for residual emissions after maximizing actual fuel switching, and preferentially select removal-based credits (biochar, DAC) over avoidance credits with additionality questions.

Q: How do I verify a shipping carrier's green fuel claims? A: Request fuel allocation certificates specifying methanol or other alternative fuel volumes, production pathway, and certification body. Legitimate green fuel claims should include mass balance chain of custody documentation from fuel supplier to vessel. Be skeptical of LNG claims marketed as "clean"—LNG reduces CO2 but methane slip during combustion can offset benefits. Maersk's ECO Delivery and similar products provide third-party verified fuel allocation documentation.

Sources

Topics

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