Fatemeh Parvizi

Sustainable Aviation Fuel (SAF) is appearing as a critical solution to decrease greenhouse gas emissions from the aviation sector, which is heavily reliant on fossil-based fuels, by providing (through the adoption of) low-carbon, renewable fuels compatible with current engines. This paper describes the situation of SAF developments in total, in terms of their production methods, emerging technologies, and challenges. The paper first presents the principal pathways of SAF, including bio-based and power-to-liquid (PtL) technologies. Bio-based SAF, derived from biomass such as oilseed crops, agricultural residues, and waste oil, has played a basic role in the development of sustainable fuel. Although it stands out due to its technological readiness and low carbon emissions, particularly apparent in the Hydroprocessed Esters and Fatty Acids (HEFA) pathway, its widespread use has limited its application due to sustainability concerns associated with biomass resources, land use change environmental issues and competition with the food industries. The PtL technologies differ as they convert renewable electric energy to liquid hydrocarbons using water electrolysis and carbon capture as pathways to offer a new way of producing low-carbon fuels with potentially better benefits for environmental impacts. Yet, the high capital cost and technological complexities currently restrict PtL’s commercial feasibility. Achieving large-scale production and ensuring a continuous renewable energy supply also pose ongoing challenges. A main focus of the paper is the methanol-to-jet (MTJ) pathway, where methanol is reacted as an intermediate and converted to jet fuel through the methanol-to-olefins (MTO) pathway and subsequent olefin oligomerization and hydroprocessing. The MTJ pathway has the added bonus of feedstock flexibility, including renewable methanol that can be produced from biomass in addition to green electricity. Furthermore, the MTJ pathway can produce sustainable aviation fuel that meets international fuel specifications and reduces CO2 emissions. The paper further explores the integration of SAF production with renewable energy systems and outlines how this integrated approach can form the basis of a more sustainable and financially viable industry. This is based on life cycle assessments (LCA) and techno-economic assessments (TEA) to quantify environmental impacts and main cost factors. In summary, SAF plays an essential role in achieving a sustainable and low-carbon aviation future. The MTJ pathway, among others, is highlighted as a practical, scalable, and cost-effective approach that can significantly support worldwide climate goals. Continued research, industrial collaboration, and strong policy supports are needed to address the associated challenges with feedstock sustainability, process efficiency, and regulatory alignment.