Table 1.

Comparison of Novel Propulsion Options

Technology	Pros	Cons
Nuclear propulsion	•Very high energy density •Absence of CO2, CH4, NOx, SOx, particulate matter and other emissions	•Public safety concerns •Long-term storage of radioactive wastes
Fuel cells	•Zero emissions at point of use if hydrogen used •Suitable for large ships on longer missions	•Production of renewable hydrogen and its secure on-board storage still in development •Unsuitable for small vessels with high power requirements
Batteries	•Clean and flexible operation •Capitalize on global renewable electrification trends	•Low energy density (<240 kWh/kg, ~0.09 kWh/L) lead to volume and mass constraints •Relatively high costs and short lifetimes
Ammonia	•Well-developed global production and distribution infrastructure •Non-carbonaceous fuel	•Present production highly carbon intensive •Highly toxic
Biofuels	•More compatible with present shipping infrastructure than other options •High level of GHG mitigation	•Competition from road, aviation, and petrochemical sectors •Fragmentation due to wide range of feedstock and fuels