From 1 January 2025, for ships trading in or to/from the EU/ EEA irrespective of flag, the annual average GHG intensity of energy used on board needs to be below a defined level. The GHG intensity is measured as GHG emissions per energy unit (gCO2e/MJ) and includes carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O).
https://www.dnv.com/news/fueleu-maritime-how-to-prepare-for-compliance/