This editorial piece emphasizes the importance of low-carbon, synthetic electro-fuels (e-fuels) in decarbonizing transport, which complements other decarbonization measures, including efficiency improvements, vehicle electrification and hybridization, as well as bio-based renewable fuels. Given the stringency of the emissions legislations worldwide, and the desire for many countries to achieve net-zero CO2 emissions by 2050, synthetic electro-fuels, produced using renewable electricity, water and captured CO2, has the potential to deliver significant CO2 reductions. When e-fuels are designed to be chemically similar to conventional fuels, they can be compatible with existing vehicles and infrastructure. Therefore, e-fuels can be a drop-in solution to facilitate an accelerated decarbonization of the existing legacy fleet as well as next generation IC engines. Furthermore, e-fuels could unlock greater penetration of renewable electricity into the transport sector by enabling international trade of renewable electricity in the form of liquid energy carriers. This is particularly useful for matching lower cost renewable electricity producers from regions with high solar irradiation and wind potential, with existing and growing energy demand centers globally that have limited renewable electricity generation potentials. The paper highlights the potential of several e-fuels: hydrogen, ammonia, e-gasoline, alcohols, DMC, paraffinic fuels, OMEx (DME), and their use in internal combustion engines, considering both spark-ignition and compression-ignition combustion, with an insight on dual-fuel and reactivity-controlled CI combustion modes. Advantages in terms of combustion efficiency and pollutant emissions are also comprehensively discussed, together with the challenges related to their use and production. Finally, the paper remarks the importance of Life-Cycle-Assessment (LCA) to assess the climate change mitigation potential of alternative fuels and powertrains. LCA studies reveal that there is no silver-bullet to decarbonizing transport, neither fuels nor powertrain technologies, since the CO2 reduction potential of these technologies is highly dependent on how they are produced and operated throughout their entire life cycles.
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