How to decarbonise international shipping: Options for fuels, technologies and policies

•Assessment of fuels, efficiency measures and policies to decarbonise shipping.•LNG must be combined with various efficiency measures to meet 50% climate target.•Slow steaming and wind assistance are key efficiency measures to reduce fuel.•Hydrogen and biofuels are lower carbon, but highly variable supply chain emissions.•Longer term deep decarbonisation will require strong economic incentives.