Life cycle environmental analysis of ‘drop in’ alternative aviation fuels: a review

Alternative aviation fuels possess significant potential to reduce the environmental burdens of the aviation industry. This review critically explores the application of the Life Cycle Assessment Methodology to the assessment of alternative aviation fuels, highlighting critical issues associated with implementing Life Cycle Assessment, such as the regulatory policy, functional unit selection, key system boundaries and the selection of the appropriate allocation methods. Critically distinct from other reviews on aviation fuels, a full, detailed analysis of the 37 Lifecycle Assessment studies currently available is critically evaluated over the past decade, supported by the additional background literature. For the first time, it brings together the assessment of sustainable feedstocks, processes and impact methods on the assessment of the jet fuel fraction. Significantly, the results highlight a lack of assessment into other characterisation factors within the Life Cycle Impact Assessment phase, leading to an over reliance on Global Warming Potentials and high uncertainty during production and combustion of the aircraft at high altitudes. Future perspectives on the next generation of aviation fuels from novel feedstocks are explored, leading to recommendations for applying endpoint damage assessment categories to these studies.