Waste animal fats as feedstock for biodiesel production using non-catalytic supercritical alcohol transesterification: A perspective by the PRISMA methodology

© 2022 International Energy InitiativeGlobal warming and fossil fuel depletion have boosted the search for alternative and renewable fuels with a low environmental impact. Biodiesel exhibits many advantages over conventional diesel including the possibility of being produced from renewable sources such as waste oils and fats. Specifically, waste animal fats are receiving increased attention as an alternative to vegetable oils for biodiesel production. This low-cost feedstock allows the mitigation of environmental pollution and can also improve biodiesel features by increasing cetane number and enhancing oxidative stability. Among the different technologies available for biodiesel production, supercritical processes offer important advantages over conventional catalytic transesterification in terms of process efficiency and reaction time. According to the increasing interest and number of research articles published in this field in the last years, this work focuses on the systematic review of the technology by using the Systematic Reviews and Meta-Analysis (PRISMA) methodology. This work describes the state of the art of non-catalytic supercritical production of biodiesel using animal fats as a feedstock and discusses the key aspects of the process such as the type of fat used, operation variables including reaction time, temperature, solvent excess, pressure, and solvent excess, and the final properties of the synthesized biodiesel.