Decarbonization, Emissions and Alternative Fuels

This portal covers emissions and the move away from fossil fuel: MARPOL Annex VI air-pollution limits, EEDI, EEXI and CII, SEEMP, the IMO GHG strategy and the mid-term measure, the EU ETS and FuelEU Maritime, alternative fuels (LNG, methanol, ammonia, hydrogen, biofuels), well-to-wake accounting, onboard carbon capture, wind assistance and energy-efficiency technology.

The instruments are MARPOL Annex VI and the MEPC resolutions under it, the 2023 IMO GHG Strategy, the EU ETS under Directive 2003/87/EC as amended, and FuelEU Maritime under Regulation (EU) 2023/1805.

Engine design belongs to Marine Engineering and Propulsion. The IMO mid-term (Net-Zero) measure was adjourned in October 2025, so articles here state its status with a date.

Start here

IMO Net-Zero Framework: Draft MARPOL Annex VI Chapter 5
The IMO Net-Zero Framework is the draft MARPOL Annex VI Chapter 5 fuel-intensity standard and GHG pricing regime approved at MEPC 83 in 2025 and not yet adopted.
EU ETS Maritime Scope and Phase-In, 2024 to 2030
Which ships, voyages and gases the EU ETS covers for shipping under Directive 2003/87/EC, the 40, 70 and 100 percent phase-in, and the 2030 derogations.
FuelEU Compliance Balance: Banking, Borrowing, Pooling
How FuelEU Maritime turns a ship's GHG intensity into a compliance balance, and the Article 20 banking and borrowing and Article 21 pooling rules that settle it.
Exhaust gas cleaning system (EGCS): marine SOx scrubbers
An exhaust gas cleaning system (EGCS) is a shipboard SOx scrubber accepted under MARPOL Annex VI Reg.4 as equivalent to meeting the Reg.14 sulphur limits.
Slow Steaming: speed, fuel and carbon intensity
Slow steaming runs a ship below design speed to cut fuel. The speed-power law, the optimum speed, the engine limits, the charter clauses and the CII effect.
Hydrogen Marine Fuel Cells: Types, Rules and Projects
Marine hydrogen fuel cells: PEM, SOFC and MCFC types, MSC.1/Circ.1647 fuel cell power installation rules, class notations, integration and vessel projects.
Mediterranean SECA: the 0.10% Sulphur ECA Since May 2025
The Mediterranean Sea Emission Control Area under MARPOL Annex VI: MEPC.361(79), the 0.10% sulphur limit since 1 May 2025, its boundaries and compliance routes.
FONAR and BDN: Sulphur Compliance Evidence at PSC
How the bunker delivery note, MARPOL sample and FONAR form the sulphur compliance evidence a PSC officer checks under MARPOL Annex VI Regulations 14 and 18.

All articles in this portal

100 articles, plus 89 in preparation.