Background
Why WtW matters
Marine fuels were historically regulated only on the basis of their tank-to-wake (TtW) emissions: the CO2, CH4 and N2O emitted at the funnel from combustion and slip. The TtW basis is the foundation of the IMO Data Collection System (IMO DCS) and was the basis of the original Carbon Intensity Indicator (CII). The TtW basis treats all fuels as equivalent to their direct combustion emissions; for example, LNG as marine fuel has approximately 25% lower TtW CO2 intensity than HFO, and a renewable methanol and a fossil methanol both have the same TtW CO2 intensity (because they are chemically identical at the point of combustion).
The TtW basis fails to capture two important distinctions:
- Upstream emissions: producing LNG involves significant methane leakage (typically 0.5 to 5% of the gas produced, depending on the production region) and significant CO2 emissions from compression and liquefaction; the WtT contribution to LNG WtW intensity is approximately 15 to 30 g-CO2eq/MJ, comparable in magnitude to the TtW saving over HFO. Producing renewable methanol from green hydrogen and captured CO2 has near-zero upstream emissions; producing fossil methanol from natural gas has significant upstream emissions.
- Renewability and additionality: a biomass-derived fuel that displaces fossil fuel reduces atmospheric CO2 only to the extent that the biomass would have been planted and grown specifically to produce the fuel (the “additionality” criterion). A fuel produced from renewable electricity is renewable only if the electricity is genuinely incremental to what would otherwise have been produced.
The introduction of the WtW basis in the FuelEU Maritime Regulation (in force January 2025) and in the IMO Net-Zero Framework GFI standard (in force 2027) brings marine fuel regulation into line with land-based transport (where WtW analysis under EU RED has been mandatory since 2009).
Definitions and the system boundary
Well-to-wake (WtW) = well-to-tank (WtT) + tank-to-wake (TtW).
The WtT boundary covers all GHG emissions from feedstock extraction or production, through fuel processing and refining, to delivery to the bunker tanker (or to the vessel directly). For a fossil fuel, WtT covers crude extraction, transport to refinery, refining, transport to bunker. For a biofuel, WtT covers feedstock cultivation (or waste collection), transport to processing plant, processing, and transport to bunker.
The TtW boundary covers all GHG emissions from combustion of the fuel in the engine, including any unburned fuel released as slip (methane slip for LNG and methanol; ammonia slip for ammonia as marine fuel; ethanol slip is theoretically possible but economically negligible) and the CO2 from any pilot fuel for dual-fuel engines.
For biofuels, the TtW CO2 emission is conventionally counted as zero (the carbon released by combustion was originally absorbed from the atmosphere by photosynthesis), so the WtW intensity of a biofuel equals its WtT intensity. This convention is challenged by the Indirect Land-Use Change (ILUC) literature, which argues that diversion of land or biomass to fuel production indirectly causes additional CO2 emissions from forest clearance or grassland conversion elsewhere; the EU RED applies an ILUC additivity factor for some feedstock categories.
Global warming potentials and the AR5 100-year basis
GHG emissions of different gases are normalised to a CO2-equivalent basis using global warming potentials (GWPs). The IPCC publishes successive revisions of GWP values; the relevant set for marine fuel regulation is the IPCC AR5 (Fifth Assessment Report) 100-year GWPs:
- CO2: GWP = 1 (by definition).
- CH4: GWP = 28 (without climate-carbon feedback) or 34 (with climate-carbon feedback, the “GWP-100 with feedback”). The FuelEU Maritime Regulation and the IMO Net-Zero Framework adopt GWP-100 = 28. Some voluntary schemes (e.g. some Sea Cargo Charter formulations) use the higher value.
- N2O: GWP = 265 (without feedback) or 298 (with feedback). FuelEU and IMO Net-Zero Framework adopt GWP-100 = 265.
The choice of GWP-100 rather than GWP-20 (a 20-year integration period in which the GWP of CH4 is 84 to 87 instead of 28) is an important policy choice. Because methane has a relatively short atmospheric lifetime (approximately 12 years), the choice of integration period significantly affects the ranking of fuels: under GWP-20, LNG has a higher WtW intensity than HFO if methane slip and methane leakage are significant; under GWP-100, LNG remains lower than HFO under typical leakage assumptions.
The GWP* metric (a modified GWP that better reflects the climate-temperature impact of short-lived gases relative to long-lived ones) is increasingly cited in academic literature but is not used in the FuelEU or IMO Net-Zero Framework regulatory framework.
The fossil baseline and reduction trajectories
FuelEU Maritime fossil baseline
The FuelEU Maritime Regulation specifies a fossil baseline of 91.16 g-CO2eq/MJ, derived from a weighted average of the WtW intensity of the dominant marine fuels in 2020 (HFO, VLSFO, LSMGO and MGO). The reduction trajectory (relative to this baseline) is:
| Period | Reduction vs baseline | Maximum WtW intensity |
|---|---|---|
| 2025 to 2029 | -2.0% | 89.34 g-CO2eq/MJ |
| 2030 to 2034 | -6.0% | 85.69 g-CO2eq/MJ |
| 2035 to 2039 | -14.5% | 77.94 g-CO2eq/MJ |
| 2040 to 2044 | -31.0% | 62.90 g-CO2eq/MJ |
| 2045 to 2049 | -62.0% | 34.64 g-CO2eq/MJ |
| 2050 onwards | -80.0% | 18.23 g-CO2eq/MJ |
Compliance is on a per-vessel-per-calendar-year basis. Non-compliance triggers a pooling, multiplier and penalty regime in which the company can either pay the penalty (currently EUR 2,400 per t VLSFO-equivalent of compliance deficit) or pool the deficit with other compliant vessels in the same company or via a multi-company pooling agreement.
IMO Net-Zero Framework GFI baseline
The IMO Net-Zero Framework, adopted at MEPC 83 in April 2025, specifies a fossil baseline of approximately 93.3 g-CO2eq/MJ (slightly different from FuelEU due to a different fossil-fuel weighting). The reduction trajectory (relative to this baseline) is:
| Period | Reduction vs baseline | Direct compliance threshold | Indirect compliance threshold |
|---|---|---|---|
| 2027 to 2029 | -4 to -8% | -8% | -17% |
| 2030 to 2034 | -8 to -19% | -17% | -30% |
| 2035 onwards | -19 to -65% | -30% to -65% | -43% to -77% |
A vessel meeting the direct compliance threshold has zero GFI deficit; a vessel between the direct and indirect thresholds has a Tier 1 remedial unit liability; a vessel above the indirect threshold has both Tier 1 and Tier 2 remedial unit liability. The remedial-unit pricing is set by an IMO-administered fund, with prices in the order of USD 100 to USD 380 per t CO2eq of deficit by 2030 (subject to MEPC review).
EU RED III shipping target
The EU Renewable Energy Directive Recast (RED III) Article 25 specifies that a minimum of 1.0% of marine fuel energy sold to ships in EU ports must be from Renewable Fuels of Non-Biological Origin (RFNBO) by 2030, rising to higher percentages thereafter. RFNBO is a defined category that requires:
- The fuel must be produced from renewable electricity, with strict additionality and temporal correlation criteria (the renewable electricity must be matched on an hourly basis from new renewable installations).
- The fuel must achieve at least 70% GHG savings compared to the fossil comparator (95.6 g-CO2eq/MJ for marine fuel), corresponding to a maximum WtW intensity of approximately 28.7 g-CO2eq/MJ.
Eligible RFNBO marine fuels include: green hydrogen, green ammonia (from green hydrogen), e-methanol (from green hydrogen + captured CO2), e-LNG (from green hydrogen + captured CO2). See RFNBO under EU rules for the full eligibility framework.
WtW intensity by fuel type
Conventional fossil fuels
| Fuel | WtT (g-CO2eq/MJ) | TtW (g-CO2eq/MJ) | WtW (g-CO2eq/MJ) |
|---|---|---|---|
| HFO (residual fuel oil) | 13.5 | 79.5 | 93.0 |
| VLSFO (very-low-sulphur fuel oil) | 14.0 | 78.5 | 92.5 |
| LSMGO (low-sulphur marine gas oil) | 16.5 | 75.5 | 92.0 |
| MGO (marine gas oil) | 14.0 | 76.0 | 90.0 |
| LNG, SI engine (no slip) | 18.5 | 56.0 | 74.5 |
| LNG, HPDF (low slip) | 18.5 | 60.0 | 78.5 |
| LNG, LBSI (medium slip) | 18.5 | 70.0 | 88.5 |
| LNG, LPSI (high slip) | 18.5 | 80.0 | 98.5 |
The values above are representative central estimates from the FuelEU Maritime Annex II default values (Annex II provides a tabulated set of default WtW intensities for use in compliance calculations where no certified bunker delivery note is available). Annex II is updated periodically by the European Commission as the Joint Research Centre (JRC) refines the default values.
LNG WtW intensity depends critically on the engine type and methane slip rate:
- Spark-ignition (SI) engines (Wartsila DF, Caterpillar 3500 series): no methane slip in normal operation; lowest WtW intensity.
- High-pressure dual-fuel (HPDF) engines (MAN ME-GI, Win GD X-DF): low slip (typically 0.2 to 0.5% of fuel); low WtW intensity.
- Low-pressure dual-fuel slow-speed (LBSI) engines (Win GD RT-flex DF, MAN ME-LGI): medium slip (typically 1.0 to 2.5% of fuel).
- Low-pressure spark-ignition (LPSI) engines (Wartsila 50DF generation 1, Caterpillar 3600 series): higher slip (typically 2.5 to 5.0% of fuel); the slip can be sufficient to make LNG WtW intensity comparable to or higher than HFO. This was the principal “methane slip” controversy of the early 2020s.
See methane slip from LNG dual-fuel for a comprehensive treatment.
Methanol
| Methanol pathway | WtT (g-CO2eq/MJ) | TtW (g-CO2eq/MJ) | WtW (g-CO2eq/MJ) |
|---|---|---|---|
| Fossil methanol (from natural gas, no CCS) | 31.3 | 69.1 | 100.4 |
| Fossil methanol (from natural gas, with CCS) | 18.5 | 69.1 | 87.6 |
| Bio-methanol (from waste wood, no CCS) | 8.0 | 0 | 8.0 |
| Bio-methanol (from forest residues, no CCS) | 12.0 | 0 | 12.0 |
| E-methanol (RFNBO, hourly-matched renewable electricity) | 5.0 | 0 | 5.0 |
| E-methanol (with low-carbon hydrogen, e.g. nuclear) | 7.5 | 0 | 7.5 |
Methanol can therefore range from higher WtW intensity than HFO (fossil methanol from natural gas) to near-zero WtW intensity (e-methanol with strict RFNBO accounting). The economic and regulatory value of a methanol bunker is highly dependent on the certified production pathway. See methanol as marine fuel for the full pathway analysis.
Ammonia
| Ammonia pathway | WtT (g-CO2eq/MJ) | TtW (g-CO2eq/MJ) | WtW (g-CO2eq/MJ) |
|---|---|---|---|
| Grey ammonia (from natural gas, no CCS) | 121.0 | 0 (CO2) + N2O slip | 121 to 130 |
| Blue ammonia (from natural gas, with CCS) | 25.0 | 0 (CO2) + N2O slip | 25 to 35 |
| Green ammonia (RFNBO from renewable hydrogen) | 5.0 | 0 (CO2) + N2O slip | 5 to 15 |
Ammonia TtW intensity is dominated by N2O slip from the engine, which has a GWP of 265. A 1% N2O slip rate (calculated as N2O emitted per N2O equivalent burned) translates to approximately 6.6 g-CO2eq/MJ of TtW intensity, comparable in magnitude to the WtT intensity of green ammonia. Engine manufacturers (MAN Energy Solutions, Wartsila, Win GD) are actively developing N2O catalysts and combustion strategies to minimise N2O slip; current commercial ammonia engines (2024) achieve approximately 0.05 to 0.5% N2O slip. See ammonia as marine fuel and N2O emissions from marine engines for full analyses.
Biofuels
| Biofuel pathway | WtT (g-CO2eq/MJ) | TtW (g-CO2eq/MJ) | WtW (g-CO2eq/MJ) |
|---|---|---|---|
| FAME from used cooking oil (UCO) | 14.9 | 0 | 14.9 |
| FAME from palm oil (with ILUC) | 56 to 73 | 0 | 56 to 73 |
| HVO from waste fats (Annex IX A feedstock) | 9.4 | 0 | 9.4 |
| HVO from energy crops (with ILUC) | 50 to 70 | 0 | 50 to 70 |
| Biodiesel B30 blend with VLSFO | (weighted) | (weighted) | 70 to 80 |
Biofuel WtW intensity depends critically on the feedstock and the ILUC accounting:
- Annex IX Part A feedstocks (waste cooking oil, animal fats Cat 1/2, lignocellulosic biomass, palm oil mill effluent): low WtW intensity (typically 5 to 20 g-CO2eq/MJ); double-counted under FuelEU Maritime (each MJ counts as 2 MJ for compliance).
- Annex IX Part B feedstocks (used cooking oil, animal fats Cat 3, molasses): moderate WtW intensity; capped at a fleet-wide share of bio-feedstock.
- Food and feed crops (rapeseed, soya, palm, maize, sugar beet, sugar cane): high WtW intensity due to ILUC; maximum 7% share of EU transport energy under RED III; further restricted for marine.
See biofuels in shipping and RFNBO under EU rules for full treatments.
Hydrogen
| Hydrogen pathway | WtT (g-CO2eq/MJ) | TtW (g-CO2eq/MJ) | WtW (g-CO2eq/MJ) |
|---|---|---|---|
| Grey hydrogen (from natural gas, no CCS) | 99.0 | 0 + N2O slip | 99 to 105 |
| Blue hydrogen (from natural gas, with CCS) | 30.0 | 0 + N2O slip | 30 to 35 |
| Green hydrogen (RFNBO from renewable electricity) | 3.0 | 0 + N2O slip | 3 to 10 |
Hydrogen WtW analysis is similar in structure to ammonia (which is itself produced from hydrogen); the principal differences are the absence of the ammonia synthesis step and the lower theoretical N2O slip rate (because hydrogen contains no nitrogen).
Captured CO2 and OCC
Onboard carbon capture (OCC) interacts with WtW analysis as follows: the captured CO2 is excluded from the TtW intensity provided it is permanently stored or utilised in a way that does not subsequently re-release the CO2. A 70% capture rate on HFO combustion reduces the effective TtW CO2 from approximately 79.5 g-CO2eq/MJ to approximately 23.9 g-CO2eq/MJ, with the WtW intensity falling from approximately 93 to approximately 37 g-CO2eq/MJ (after accounting for the energy penalty of the capture system).
Calculation methodology
FuelEU Maritime calculation
Under FuelEU Maritime, the annual GHG intensity of energy used onboard is calculated as:
$$ GHG_{intensity} = \frac{\sum_i E_i \cdot WtW_i}{\sum_i E_i} $$where $E_i$ is the energy of fuel category $i$ used by the vessel (in MJ) and $WtW_i$ is the WtW intensity of fuel category $i$ (in g-CO2eq/MJ). The sum is over all fuel categories used by the vessel during the calendar year.
The WtW intensity values are taken from:
- Bunker delivery note (BDN) certified values if available and traceable.
- FuelEU Annex II default values if certified BDN values are not available.
For RFNBO fuels, a multiplier of 2 is applied to the energy (each MJ of RFNBO counts as 2 MJ for compliance), with the multiplier applying through 2034. For onshore power supply at berth, the energy is counted at zero g-CO2eq/MJ (where the shore power is from the EU electricity grid, with appropriate residual mix accounting).
The compliance check is: $GHG_{intensity}$ is compared to the maximum permitted intensity for the calendar year (e.g. 89.34 g-CO2eq/MJ in 2025); if the vessel exceeds the maximum, a compliance deficit is calculated as:
$$ Deficit = \sum_i E_i \cdot (GHG_{intensity} - GHG_{max}) $$The deficit can be:
- Pooled with surplus from other vessels in the same company or via a third-party pooling agreement.
- Banked for use against a future-year deficit.
- Penalised at EUR 2,400 per t VLSFO-equivalent (the default penalty rate, increasing by 10% per consecutive year of non-compliance).
See FuelEU penalties, pooling and multipliers for the full mechanic.
IMO Net-Zero Framework GFI calculation
The IMO Net-Zero Framework GFI calculation is structurally similar to the FuelEU Maritime calculation but with different default values, different multipliers and a different penalty / remedial-unit mechanic.
The vessel’s annual GFI is:
$$ GFI = \frac{\sum_i E_i \cdot WtW_i}{\sum_i E_i} $$Compliance is tested against two thresholds: a direct compliance threshold and an indirect compliance threshold. A vessel meeting the direct compliance threshold has no liability. A vessel between the direct and indirect thresholds has a Tier 1 remedial unit liability, calculated as the deficit at a Tier 1 price (set by the IMO Fund). A vessel above the indirect threshold has additional Tier 2 remedial unit liability at a higher Tier 2 price.
The remedial units can be:
- Surrendered as actual emission reductions from a low-carbon fuel use elsewhere, evidenced by certified credits.
- Purchased from the IMO Fund at the Tier 1 / Tier 2 prices.
- Banked for future use within prescribed limits.
The IMO Net-Zero Framework GFI compliance interacts with FuelEU Maritime compliance for vessels operating in EU ports: the EU has indicated it will treat IMO Tier 1 / Tier 2 remedial unit surrender as evidence of FuelEU compliance, but the detail is yet to be confirmed.
JRC and IPCC default values
The principal source of WtW default values for FuelEU is the JRC (Joint Research Centre) of the European Commission, which maintains a comprehensive WtW analysis for all common transport fuel pathways. The JRC values feed into FuelEU Annex II.
The principal source of WtW default values for IMO Net-Zero Framework is the IMO Life Cycle Assessment Guidelines for Marine Fuels, adopted as MEPC.391 (in development through 2025). The IMO LCA Guidelines draw on JRC, IPCC, GREET (Argonne National Laboratory), Ecoinvent and other recognised LCA data sources.
For owners and charterers seeking to establish a non-default WtW value for a specific fuel batch, the principal certifiers are:
- ISCC EU (International Sustainability and Carbon Certification): the dominant certifier for EU RED-compliant biofuels.
- REDcert: an alternative EU RED certifier.
- Bonsucro: a sugar-cane specific certifier.
- Roundtable on Sustainable Biomaterials (RSB): a multi-feedstock certifier.
- Argus, Platts, S&P Global: index providers for certified fuel WtW intensity.
Key uncertainties and policy debates
Methane slip measurement
The actual in-service methane slip rate of LNG dual-fuel engines is a major source of uncertainty in WtW intensity estimates. Engine bench tests typically give lower slip rates than in-service measurements (because bench tests use clean fuel, optimised injection timing and steady-state load); in-service measurements are confounded by load variation, fuel composition variation and engine wear. The FuelEU Annex II default values use representative averages from a large in-service measurement campaign coordinated by SEA-LNG and the JRC; individual vessels can establish a vessel-specific value through certified continuous emission monitoring.
N2O slip from ammonia engines
The N2O slip rate from ammonia engines is currently poorly characterised because so few commercial ammonia engines are in operation. Initial estimates from engine manufacturer bench tests give 0.05 to 0.5% N2O slip; in-service validation data are expected from approximately 2026 to 2028 as the first commercial ammonia engines accumulate operating hours.
ILUC and biofuel sustainability
The ILUC accounting for biofuels is contested. The EU RED III applies an ILUC factor for some feedstock categories (e.g. palm oil) that effectively renders them ineligible for compliance counting; for other categories, the ILUC value is zero or low. Recent academic literature challenges several of the EU ILUC values and argues for a more granular spatial accounting; the EU has indicated it will review the ILUC framework periodically.
Hourly matching of renewable electricity
The RFNBO definition requires hourly matching of renewable electricity to hydrogen production, with the renewable electricity coming from new (additional) renewable installations within geographical proximity to the hydrogen plant. The hourly matching requirement is significantly stricter than monthly or annual matching and substantially raises the cost of compliant RFNBO production. The framework has been challenged by hydrogen industry groups arguing for monthly matching; the EU has so far retained the hourly requirement.
Black carbon and Arctic considerations
The WtW framework focuses on long-lived greenhouse gases (CO2, CH4, N2O) but excludes short-lived climate forcers (SLCFs) such as black carbon, which has a particularly high regional warming impact in the Arctic. The IMO is developing separate measures for black carbon control on Arctic routes. See black carbon and Arctic shipping for a comprehensive treatment.
Implications for owners, charterers and insurers
Owners
Vessel owners must understand WtW intensity to make informed bunkering, engine specification and retrofit decisions. The optimum strategy depends on the vessel’s trading pattern (FuelEU and EU ETS exposure) and on the residual life of the vessel (for IMO Net-Zero Framework compliance from 2027).
Charterers
Charterers in long-term time charters increasingly require BIMCO CII clauses and equivalent FuelEU clauses that allocate the regulatory cost of WtW non-compliance between owner and charterer. Spot voyage charterers face a more diffuse regulatory cost passthrough.
Insurers
Marine insurers (P&I clubs and hull underwriters) have begun incorporating WtW intensity into risk assessment for Poseidon Principles and Sea Cargo Charter signatories, and into climate-transition disclosures.
Banks and financiers
Ship-finance banks signed up to the Poseidon Principles report annual portfolio WtW intensity against a science-based reference trajectory; vessels with high WtW intensity contribute negatively to the bank’s portfolio score.
See also
Regulatory and reporting frameworks
- MARPOL Annex VI
- IMO Net-Zero Framework
- IMO GHG Strategy
- EEXI, EPL and ShaPoLi
- SEEMP I, II, III
- CII corrective action plan
- EU MRV Regulation
- EU ETS for shipping
- FuelEU Maritime
- FuelEU penalties, pooling and multipliers
- UK ETS for shipping
- China DCS
- IMO DCS vs EU MRV
- CARB at-berth rule
- Emission control areas
- NOx Tier I, II, III
- IMO 2020 sulphur cap
- RFNBO under EU rules
Voluntary frameworks
- Poseidon Principles
- Sea Cargo Charter
- RightShip GHG Rating
- Green Shipping Corridors
- BIMCO CII clauses
- EUA market mechanics for shipping
- Voluntary carbon credits in shipping
Marine fuels
- LNG as marine fuel
- LNG fuel system
- Methanol as marine fuel
- Ammonia as marine fuel
- Biofuels in shipping
- Heavy fuel oil
- Marine gas oil
- Methane slip from LNG dual-fuel
- N2O emissions from marine engines
- Black carbon and Arctic shipping
Operational and technical efficiency
- Wind-assisted propulsion
- Air lubrication systems
- Just-in-time arrival
- Weather routing
- Trim optimisation
- Slow steaming
- Bulbous bow retrofits
- Energy-saving devices
- Battery-hybrid propulsion
- Onboard carbon capture
- Cold ironing / shore power
Engines and machinery
Hydrostatics and stability
- Hull form design
- Block coefficient
- Hydrostatics and Bonjean curves
- Trim and list
- Metacentric height
- Free surface effect
- Intact stability
- Damage stability
- Ship resistance and powering
Conventions, codes and class
- SOLAS Convention
- MARPOL Convention
- Ballast Water Management Convention
- Hong Kong Convention
- COLREGs Convention
- ISM Code
- ISPS Code
- Classification society
Calculators
- WtW intensity calculator
- FuelEU intensity calculator
- GFI compliance calculator
- Methane slip GWP calculator
- Biofuel ILUC calculator
- SEEMP Measures Combined calculator
- EEXI Required calculator
- CII Attained calculator
- Calculator catalogue
References
- IMO Resolution MEPC.391 (in adoption 2025): Life Cycle Assessment Guidelines for Marine Fuels. International Maritime Organization, 2025.
- IMO Resolution MEPC.328(76): 2021 Revised MARPOL Annex VI. International Maritime Organization, 2021.
- IMO Resolution adopted MEPC 83 (April 2025): IMO Net-Zero Framework. International Maritime Organization, 2025.
- Regulation (EU) 2023/1805 of the European Parliament and of the Council of 13 September 2023 on the use of renewable and low-carbon fuels in maritime transport (FuelEU Maritime). Official Journal of the EU, 2023.
- Regulation (EU) 2023/959 of the European Parliament and of the Council of 10 May 2023 amending Directive 2003/87/EC (EU ETS Maritime). Official Journal of the EU, 2023.
- Directive (EU) 2023/2413 of the European Parliament and of the Council of 18 October 2023 amending Directive (EU) 2018/2001 (RED III). Official Journal of the EU, 2023.
- Joint Research Centre (JRC). Well-to-Wheels Analysis of Future Automotive Fuels and Powertrains in the European Context (JEC WTW Report v5). European Commission JRC, 2020.
- Argonne National Laboratory. GREET Model: Marine Module. Argonne National Laboratory, 2023.
- IPCC. Fifth Assessment Report (AR5) Working Group I: Climate Change 2013 - The Physical Science Basis. Intergovernmental Panel on Climate Change, 2013.
- DNV. Maritime Forecast to 2050. DNV Energy Transition Outlook, 2023.
- ICCT. Greenhouse gas emissions from global shipping, 2013 to 2015. International Council on Clean Transportation, 2017.
Further reading
- IRENA. A pathway to decarbonise the shipping sector by 2050. International Renewable Energy Agency, 2021.
- ICCT. The cost of zero-emission ships and shipping. International Council on Clean Transportation, 2022.
- ICS. Catalysing the Fourth Propulsion Revolution. International Chamber of Shipping, 2022.
- SEA-LNG. LNG as a Marine Fuel - The Investment Opportunity. SEA-LNG, 2023.
- Methanol Institute. Methanol as a Marine Fuel. Methanol Institute, 2023.
- World Bank. The Role of LNG in the Transition Toward Low and Zero Carbon Shipping. World Bank Group, 2021.