Renewable Ammonia for a Sustainable Energy Future: the Case of Maritime Transportation

The energy sector is responsible for 75% of greenhouse gas emissions. We therefore want to reduce carbon dioxide emissions to reach net zero by 2050. The transition to an energy sector dominated by renewable sources also requires an appropriate growth of storage systems that make up for the difference between demand and production of electricity. The use of ammonia as an energy carrier can facilitate the energy transition. The high energy density, the ease of storage and transport, make it a very promising energy carrier. In addition, ammonia produced from renewable sources, i.e. water, air and renewable energy, could also be used for other applications: transport fuel, hydrogen carrier, long-term energy storage system, etc. Consequently, ammonia could play a crucial role in the decarbonization of several sectors, especially the naval sector. There are still several technological, economic and political challenges to be addressed for the production and use of ammonia produced from renewable sources. In this work, two different ammonia production processes were simulated: the traditional one, i.e., the Haber-Bosh process using methane as raw material and a novel one based on green hydrogen production via electrolysis. Starting from the material and energy balances obtained by process simulation, CAPEX and OPEX were calculated and three indicators assessing sustainability performance have been evaluated. Well-established indicators, such as Energy Return On Energy Invested (EROEI), the Levelized Cost of Ammonia (LCOA), and the Life Cycle Assessment (LCA), allowed the comparison between the different processes simulated from an energetic, economic, and environmental viewpoint, respectively. The indicators’ outcomes indicate that the most convenient process in terms of energetic performance is the green hydrogen-based with electrical energy obtained from a green energy mix, counterbalanced by a higher cost of ammonia produced via green hydrogen. Environmental assessment highlighted that a trade-off must be found in order to select the most environmentally friendly production pathway.