Technical and Regulatory Evaluation of 1G-Ethanol Synthesis and Use in Marine Engines Under EU Fuel Policy Requirements

The European Commission’s decision to establish a 10% v/v volumetric ethanol cap in gasoline (E10) under Renewable Energy Directive II (RED II), further reinforced by the stricter sustainability criteria introduced in RED III, marks a critical turning point for the global ethanol industry. By 2023, worldwide ethanol production reached approximately 116–118 bn liters annually, with the United States dominating at 52% and Brazil contributing about 28%. First-generation (1G) ethanol is increasingly constrained in its expansion within the road transport sector, necessitating the identification of alternative markets to absorb surplus volumes. RED III emphasizes the deployment of advanced biofuels and renewable fuels of non-biological origin (RFNBOs), mandating either a 14.5% reduction in greenhouse gas emissions or a 29% renewable energy share by 2030, thereby encouraging sectoral diversification. The maritime sector emerges as a promising outlet to accommodate surplus ethanol. However, regulatory inconsistencies persist: ReFuel EU excludes crop-based biofuels, while Fuel EU Maritime permits certified options. Aviation remains limited to advanced biofuels. Meanwhile, IMO policies, including MEPC 83 and 84, introduce emissions pricing and lifecycle assessment frameworks, promoting low-emission fuels without clearly recognizing ethanol’s competitiveness. This study evaluates ethanol utilization in marine engines under these constraints.