Recent trends of biodiesel production from animal fat wastes and associated production techniques Peter Adewale, Marie-Josée Dumont n , Michael Ngadi nn Department of Bioresource Engineering, McGill University, 21111 Lakeshore Rd., Ste-Anne-de-Bellevue, QC, Canada H9X 3V9 article info Article history: Received 27 May 2014 Received in revised form 14 January 2015 Accepted 8 February 2015 Keywords: Animal fat wastes Biodiesel Transesterification Production techniques Assisted-transesterification abstract Non-edible feedstocks such as animal fat wastes (AFWs) have recently increased in popularity as alternatives to vegetable oils in the production of biodiesel. They are low cost, mitigate environmental damage and increase the quality of the resultant biodiesel fuel (low NO x emissions, high Cetane number and oxidative stability). Therefore, AFWs are an excellent feedstock for biodiesel production. Here we provide a comprehensive review trends and techniques in biodiesel production from AFWs. A critical overview of homogeneous and heterogeneous (one- or two-step) catalytic transesterification of AFWs is presented. Similarly, enzyme-catalyzed transesterification and the application of supercritical fluids conversion techniques in the production of biodiesel from AFWs are thoroughly assessed. Finally, cutting edge advances in assisted transesterification processes for biodiesel production are critically reviewed. & 2015 Elsevier Ltd. All rights reserved. Contents 1. Introduction ........................................................................................................ 575 2. Non-edible feedstocks ................................................................................................ 576 2.1. Non-edible vegetable oils ....................................................................................... 576 2.2. Waste cooking oils ............................................................................................. 576 2.3. Animal fats ................................................................................................... 576 2.3.1. Chicken fat ............................................................................................ 578 2.3.2. Lard ................................................................................................. 579 2.3.3. Tallow................................................................................................ 579 2.3.4. Leather industry solid waste fat ........................................................................... 579 2.3.5. Fish oil ............................................................................................... 580 3. Biodiesel production techniques ........................................................................................ 580 3.1. Direct use and blending ........................................................................................ 580 3.2. Microemulsions ............................................................................................... 580 3.3. Pyrolysis ..................................................................................................... 581 3.4. Transesterification reaction techniques ............................................................................ 581 3.4.1. Homogeneous catalytic conversion of AFWs ................................................................. 582 3.4.2. Heterogeneous catalytic conversion of AFWs ................................................................. 582 3.4.3. Enzyme catalytic conversion of AFWs ...................................................................... 583 3.4.4. Supercritical non-catalytic conversion of AFWs ............................................................... 583 4. Assisted transesterification techniques ................................................................................... 584 4.1. Ultrasound-assisted technique ................................................................................... 584 4.2. Microwave-assisted technique ................................................................................... 584 Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/rser Renewable and Sustainable Energy Reviews http://dx.doi.org/10.1016/j.rser.2015.02.039 1364-0321/& 2015 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ1 514 398 7776; fax: þ1 514 398 8387. nn Corresponding author. Tel.: þ1 514 398 7779; fax: þ1 514 398 8387. E-mail addresses: marie-josee.dumont@mcgill.ca (M.-J. Dumont), michael.ngadi@mcgill.ca (M. Ngadi). Renewable and Sustainable Energy Reviews 45 (2015) 574–588