The advanced biofuel from microalgae, as manufactured by the Spanish company AlgaEnergy, has a reduced carbon lifecycle because growing algae, as plants they are, they absorbe CO2 from the atmosphere which is incorporated into the final fuel.
This is a logical change in the navy, which has gone from the sails to coal, then petrol, then to nuclear and now to biofuels, always with an advance on the private sector and merchant marine. Although nowadays biofuels are far more expensive, they will be cheaper in the long run than fossil fuels.