Fossil-free maritime fuels

As part of the 2023 IMO Strategy on Reduction of GHG Emissions from Ships, the IMO has recently announced changes that will transform maritime fuels. By 2030 the Carbon Intensity of international shipping is targeted to decline by at least 40% compared to 2008 levels.

The intent is not to eliminate Carbon from maritime fuels, nor to prohibit the use of hydrocarbons. But the carbon intensity must be considered in the life cycle analysis of the fuel. For example, burning bio-diesel emits CO2 but does not emit fresh fossil CO2 to the atmosphere. Instead, it puts CO2 back into the atmosphere that a plant has previously removed.

Metrology for methanol

Methanol-ready ship orders have been on the increase since 2020. Methanol burns in a similar way to diesel meaning that engines can easily be built to accommodate both fuels. Storage of liquid methanol on board can be achieved in the same tanks that are used for heavy fuel oil. So, building a ‘methanol-read’ ship adds only marginal cost.

Methanol ready ships can operate with traditional fossil fuels today and transition to a lower carbon fuel when the bunkering infrastructure is more developed and the economics are more favourable.

As part of the fuel transition, the emissions monitoring systems must either be changed or built to be methanol ready from day-1. For example, methanol combustion is lean in particulate emissions but can result in methanol slip or formaldehyde production. The implication is that the gas metrology and instrumentation requirements will also transition.

An additional gas-measurement challenge is within the engine itself. Sensors are used to feed data to the engine management system. A common control loop is to measure the amount of partially combusted molecules to fine-tune the fuel air ratio. In the case of heavy fuel oil measuring CO would be appropriate. In the case of methanol as a fuel, methanol slip or formaldehyde may be a more appropriate control variable for the fuel/air ratio.

Fossil carbon, recycled carbon and biogenic carbon

Methanol contains carbon and yields CO2 when burned in the ship’s engine. However, it can be built from biogenic carbon in which case the emissions are CO2-neutral.

Alternatively, fossil CO2 can be captured from industrial or power generation emissions and can be recycled into methanol molecules. Whilst the full life cycle here does result in fossil CO2 emissions to the atmosphere, they have occurred only once not twice. This represents a reduction in the net CO2 emissions.

CO2 sourcing from waste to energy plants that burn municipal solid waste is also possible. In this case, the CO2 will be partially fossil-based (from burning plastics and synthetic fabrics) and partially biogenic (from burning cotton and wool fabrics, leather, wood, food scraps and paper).

Achieving zero CO2 emissions in 2030 and 2040 is a big ask. A significant reduction in CO2 emissions by using recycled CO2 fuels is a major step in the right direction. In the EU, the rules around renewable fuels of non-biological origin allow renewable methanol to be built using CO2 from power generation emissions until the end of 2035. If the CO2 is captured from industrial fossil CO2 emissions, it can be used to build renewable methanol until the end of 2039.

A metrological challenge related to the use of methanol in fuels is to accurately establish the amount of the CO2 that is biogenic and the amount that is of fossil origin. A potential technique to determine this is to speciate between 12C and 14C isotopes in the fuel, or the CO2 emissions from combustion of the fuel. The presence of 12C in fossil fuels is much lower than in biogenic CO2 because the radioactive C-14 isotope has decayed over millions of years to the C-12 isotope.

EURAMET Maritime metrology project

Ajoy Ramalingam, a Research Scientist at the PTB in Germany is the Project Coordinator for the MaritimeMET initiative that is funded by the European Partnership on Metrology and co-financed from the European Union’s Horizon Europe Research and Innovation Programme and by the Participating States. “MaritimeMET covers Metrology for green maritime shipping: Emission control through traceable measurements and machine learning approaches”, he confirms.

“Our work focuses on the future metrological needs of ‘Power to X’ fuels such as ammonia and methanol. We believe these fuels will play an increasingly important role in shipping and we therefore want to ensure that the gas metrology and other physical property measurement capabilities are ready to support the energy transition.”

On the 3rd of June 2025 from 10am to 11am CEST (Central European Summer Time) the MaritimeMET project team will be hosting a webinar looking into ammonia and methanol as emerging clean fuels and the gas metrology challenges associate with their introduction.

“We are delighted that Mr Stephen B. Harrison of sbh4 consulting will make a presentation and take an extended Q&A session for this webinar,” says Ramalingam. “And, of course, we are looking forward to welcoming participants from metrological institutes, gas analyser and sensor OEMs, engine developers and shipping operators. See you there!”

Registration for the webinar is free of charge. Please see here.