Contents lists available at ScienceDirect Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser Membrane separation processes for dehydration of bioethanol from fermentation broths: Recent developments, challenges, and prospects Azqa Khalid a,1 , Muhammad Aslam b,1 , Muhammad Abdul Qyyum c , Abrar Faisal a , Asim Laeeq Khan b , Faisal Ahmed d , Moonyong Lee c , Jeonghwan Kim e , Nulee Jang f , In Seop Chang f, ⁎ , Aqeel Ahmed Bazmi d, ⁎ , Muhammad Yasin b, ⁎ a Department of Chemical Engineering, COMSATS University Islamabad (CUI), Lahore Campus, Defense Road, Off Raiwind Road, Lahore, Pakistan b Bioenergy & Environmental Sustainable Membrane Technology (BEST) Research Group, Department of Chemical Engineering, COMSATS University Islamabad (CUI), Lahore Campus, Defense Road, Off Raiwind Road, Lahore, Pakistan c School of Chemical Engineering, Yeungnam University, Gyeongsan 712-749, Republic of Korea d Process and Energy Systems Engineering Center-PRESTIGE, Department of Chemical Engineering, Department of Chemical Engineering, COMSATS University Islamabad (CUI), Lahore Campus, Defense Road, Off Raiwind Road, Lahore, Pakistan e Department of Environmental Engineering, Inha University, Namgu, Incheon, Republic of Korea f School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea ARTICLE INFO Keywords: Syngas fermentation Bioethanol Distillation Membrane separation Pervaporation ABSTRACT Bioethanol has garnered a great interest as a potential energy source, mainly due to its sustainable and green nature. Generally, bioethanol is produced through the microbial conversion of biomass and biomass derived syngas. However, the dehydration and purification steps for achieving fuel-grade ethanol from the microbial production process consume tremendous amounts of energy. This high energy consumption limits the feasibility of microbial ethanol production on the commercial scale. In this context, selection of an optimal technology for product separation is essential for successful commercialization of microbially produced bioethanol. This article presents the recent developments in dehydration and purification technologies for bioethanol production using distillation and membrane based separation. Distillation and pervaporation are analyzed on the basis of the overall energy requirement, consumption, and economics. Pervaporation-assisted distillation approaches are also examined from the perspective of process systems engineering, including factors affecting the system per- formance. Furthermore, the role of simulation in technological development along with available mathematical models is discussed, and commercial status of pervaporation based separation is presented. Finally, the current status of the existing technology, challenges, and future research directions are identified from the perspective of achieving process sustainability on the industrial scale. Economic comparison between distillation and different hybrid schemes revealed that integrating distillation with membrane based separation techniques reduce the bioethanol production cost. Moreover, hybrid schemes that combine distillation with pervaporation, and steam stripping with vapor permeation are proved to be the best combinations for the cheapest bioethanol production. 1. Introduction Global energy demand has continued to escalate as a result of im- proved standards of living and population growth. The global energy requirement is anticipated to rise by as much as 48% between 2012 and 2040 [1,2]. The primary energy source to fulfill these requirements is fossil fuel reserves. In recent years, research focus has shifted to finding alternate renewable energy resources. This search is mainly driven by: the uneven distribution of regional fossil fuel reserves, which makes the world highly dependent on oil- and gas-producing countries [3], poli- tical instability in the organization of Oil Producing Countries (OPEC) [4], expected depletion of fossil fuel [5], and CO 2 emissions from fossil fuel combustion. In order to reduce the dependence on petroleum, bioethanol produced from fermentation of first-generation feedstock e.g., watermelon, corn, wheat, barley, and sorghum has been in- troduced as an alternative to gasoline [6]. In 2015, the bioethanol produced from these feedstocks in the US alone accounted for 58% of global production, followed by production in Brazil, Canada, and China https://doi.org/10.1016/j.rser.2019.02.002 Received 16 September 2018; Received in revised form 9 January 2019; Accepted 3 February 2019 ⁎ Corresponding authors. E-mail addresses: ischang@gist.ac.kr (I.S. Chang), abazmi@cuilahore.edu.pk (A.A. Bazmi), myasin@cuilahore.edu.pk (M. Yasin). 1 First co-authors. Renewable and Sustainable Energy Reviews 105 (2019) 427–443 1364-0321/ © 2019 Elsevier Ltd. All rights reserved. T