An assessment of decarbonisation pathways for intercontinental deep-sea shipping using power-to-X fuels

Shipping corridors act as the arteries of the global economy. The maritime shipping sector is also a major source of greenhouse gas emissions, accounting for 2.9% of the global total. The international nature of the shipping sector, combined with issues surrounding the use of battery technology means that these emissions are considered difficult to eliminate. This work explores the transition to renewable fuels by examining the use of electrofuels (in the form of liquid hydrogen, methane, methanol, ammonia, and Fischer-Tropsch fuel) to decarbonise large container ships from a technical, economic, and environmental perspective. For an equivalent range to current fossil fuel vessels, the cargo capacity of vessels powered by electrofuels decreases by between 3% and 16% depending on the fuel of choice due to the lower energy density compared with conventional marine fuels. If vessel operators are willing to sacrifice range, cargo space can be preserved by downsizing onboard energy storage which necessitates more frequent refuelling. For a realistic green hydrogen cost of €3.5/kg (10.5 €c/kWh) in 2030, the use of electrofuels in the shipping sector results in an increase in the total cost of ownership of between 124% and 731%, with liquid hydrogen in an internal combustion engine being the most expensive and methanol in an internal combustion engine resulting in the lowest cost increase. Despite this, we find that the increased transportation costs of some consumer goods to be relatively small, adding for example less than €3.27 to the cost of a laptop. In general, fuels which do not require cryogenic storage and can be used in internal combustion engines result in the lowest cost increases. For policymakers, reducing the environmental impact of the shipping sector is a key priority. The use of liquid hydrogen, which results in the largest cost increase, offers a 70% reduction in GHG emissions for an electricity carbon intensity of 80 gCO2e/kWh, which is the greatest reduction of all fuels assessed in this work. A minimum carbon price of €400/tCO2 is required to allow these fuels to reach parity with conventional shipping operations. To meet European Union emissions reductions targets, electricity with an emissions intensity below 40 gCO2e/kWh is required, which suggests that for electrofuels to be truly sustainable, direct connection with a source of renewable electricity is required.