E-fuels represent a crucial technology for transitioning to fossil-free energy systems, driven by the need to eliminate dependence on fossil fuels, which are major environmental pollutants. This study investigates the production of carbon-neutral synthetic fuels, focusing on e-hydrogen (e-H₂) generated from water electrolysis using renewable electricity and carbon dioxide (CO₂) captured from industrial sites or the air (CCUS, DAC). E-H₂ can be converted into various e-fuels (e-methane, e-methanol, e-DME/OME, e-diesel/kerosene/gasoline) or combined with nitrogen to produce e-ammonia. These e-fuels serve as efficient energy carriers that can be stored, transported, and utilized across different energy sectors, including transportation and industry. The first objective is to establish a clear framework encompassing the required feedstocks and production technologies, such as water electrolysis, carbon capture, and nitrogen production techniques, followed by an analysis of e-fuel synthesis technologies. The second objective is to evaluate these technologies’ technological maturity and sustainability, comparing energy conversion efficiency and greenhouse gas emissions with their electric counterparts. The sustainability of e-fuels hinges on using renewable electricity. Challenges and future prospects of an energy system based on e-fuels are discussed, aiming to inform the debate on e-fuels’ role in reducing fossil fuel dependency.

Understanding the structural drivers of global CO₂ emissions is essential for designing effective climate-mitigation strategies and for supporting progress toward Sustainable Development Goal 13 (SDG 13—Climate Action). This study applies the Kaya Identity-based decomposition approach to quantify how population, gross domestic product per capita, energy intensity, and emission intensity jointly shape long-term emission dynamics. Using harmonized historical datasets for the period 1990–2020, the analysis compares global trends with country-level trajectories in major emitting regions, including China, India, the United States, the European Union, and Russia. Results indicate that although energy and emission intensity have improved in several regions, these gains remain insufficient to offset the combined effects of population growth and rising economic output, leading to continued increases in global emissions. Significant asymmetries emerge across countries in terms of development stages, historical responsibility, and capacity for decarbonization, raising important considerations for climate equity. Overall, the Kaya decomposition provides a transparent diagnostic framework for identifying policy-sensitive levers, particularly energy intensity and carbon intensity, and for highlighting where mitigation efforts are most urgently needed to advance progress toward SDG 13.