The shipping industry is beginning to evaluate ammonia as a potential "bunker fuel," a carbon-free alternative to the heavy fuel oil (HFO) used in maritime transport. International trade associations are leading the effort to decarbonize the sector, in alignment with targets set by the Paris Climate Agreement. Their immediate challenge is simple to state but hard to solve: "ambitious CO2 reduction objectives will only be achievable with alternative marine fuels which do not yet exist." In the long-term, however researchers recognize that "fuel cell-powered ships are likely to dominate, drawing their energy from fuels such as hydrogen and ammonia."