An Environmental Impact Assessment Framework for Ammonia and Methanol as Future Marine Fuels in Singapore Coastal Waters

As one of the world’s largest bunkering hubs, Singapore is actively preparing for the transition to low- and zero-carbon marine fuels such as ammonia and methanol. While these fuels offer distinct decarbonisation benefits, their use raises environmental safety concerns in the densely trafficked and ecologically sensitive waters of the Singapore Strait. Unlike conventional oil fuels, spills of ammonia and methanol behave primarily as dissolved plumes, with distinct physicochemical behaviour and toxicity pathways that challenge current environmental impact assessment (EIA) and spill response practices.

This study proposes an integrated EIA framework tailored to upcoming low-carbon fuels in Singapore’s coastal waters. Drawing on international practice, the local regulatory context, and scientific evidence, the framework integrates hazard identification, hydrodynamic and water quality modelling of spill scenarios, ecotoxicological risk assessment, and spatial sensitivity mapping of key marine receptors, including coral reefs, mangroves, aquaculture zones, and coastal water intakes. Ammonia and methanol are evaluated within the same framework to illustrate fuel-specific risks: methanol presents short-term toxicity risks despite rapid biodegradation, whereas ammonia exhibits both acute and chronic toxicity with complex speciation dynamics under tropical conditions.