Comparative Thermodynamic Assessment of Renewable Production Pathway Efficiencies for Methane, Methanol, and Ammonia Fuels

Abstract The use of alternative fuels such as methane, methanol, and ammonia is quintessential for the shipping decarbonization. However, to minimize their carbon footprint and achieve net-zero targets, these fuels’ production must involve energy from renewable sources. This study aims to perform a comparative thermodynamic assessment of methane, methanol, and ammonia production pathways using renewable energy, determining the efficiencies of the renewable electric power conversion to chemical fuel power. The methodological approach defines the fuels production process boundaries and considers both electrical and thermal power demands to identify the dominant sources of irreversibility. A thermodynamic approach is applied considering the e-fuel production of 1,000 kg, along with the inflows of energy, compounds, and chemical reactions for each e-fuel. The required input parameters for the involved chemical conversion processes are identified by thorough literature review. The results demonstrate that the second-law efficiency for e-methane, e-methanol, and e-ammonia production is 29.2%, 32.7%. and 30.9%, respectively. Most irreversibilities occur due to the electrolysis required to produce the hydrogen feedstock. The derived results are used to discuss the e-fuels’ suitability for shipping, supporting system optimization, and evidence-based decision-making for maritime decarbonization strategies, while informing stakeholders and policy makers, hence providing, to the best of our knowledge, a first-of-its-kind input to policymakers pertaining to e-fuels production insights.