Techno-economic competitiveness of renewable fuel alternatives in the marine sector

The maritime sector accounts for almost 3% of global greenhouse gas emissions and is under increasing pressure to decarbonise rapidly. Renewable fuels represent a promising pathway for decarbonisation, but their high costs hinder adoption. Carbon Capture and Storage (CCS) can further augment marine fuel decarbonisation but adds to the cost. This work presents a harmonised cost comparison of four promising renewable carbon fuels (methanol, dimethyl ether (DME), liquefied natural gas (LNG) and bio-oil) produced either from routes utilising biomass (biofuels, including CCS) or CO2 (e-fuels). The differing technology status of the fuel production routes has been accounted for using the RAND Corporation method to estimate the cost of pioneer plants. Additionally, the impact of different levels of carbon taxation (15 or 140 €/t CO2) on the economic viability of the alternative fuels has been examined. None of the renewable fuels were found to be close to the incumbent fuels without carbon taxation, which needs to be considerable to adequately bridge the cost gap. Methanol and DME produced using point CO2 capture are the lowest cost choices if full scale sale of the oxygen by-product is considered. The biofuel routes remain at a premium to the existing fuels, while the direct air capture (DAC)-based fuels are the most expensive among the options studied, besides requiring completely renewable electricity for their carbon footprint to not exceed that of fossil fuels. Renewable LNG has a particularly high cost gap, bringing its status as a potential bridging fuel into doubt.