Different pretreatment technologies of lignocellulosic biomass for bioethanol production: An overview Shahabaldin Rezania a, * , Bahareh Oryani b , Jinwoo Cho a , Amirreza Talaiekhozani c , Farzaneh Sabbagh d , Beshare Hashemi e , Parveen Fatemeh Rupani f , Ali Akbar Mohammadi g, ** a Department of Environment and Energy, Sejong University, Seoul, 05006, South Korea b Technology Management, Economics and Policy Program, College of Engineering, Seoul National University,1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea c Department of Civil Engineering, Jami Institute of Technology, Isfahan, Iran d Department of Biotechnology, Faculty of Biological Science, Alzahra University, Tehran, Iran e Department of Chemistry, Razi University, Kermanshah, Iran f School of Energy and Power Engineering, Jiangsu University, Zhenjiang, Jiangsu, 212100, PR China g Department of Environmental Health Engineering, Neyshabur University of Medical Sciences, Neyshabur, Iran article info Article history: Received 14 June 2019 Received in revised form 25 February 2020 Accepted 22 March 2020 Available online 29 March 2020 Keywords: Lignocellulosic biomass Bioethanol production Biological pretreatment Chemical pretreatment Physical pretreatment abstract Regarding the supply of fossil fuels, greenhouse gasses emission, global warming, and increasing fuel price; there is a need to find alternative energy resources, which are renewable, environmentally sus- tainable, and economically viable. Agro-industrial biomass such as sugarcane bagasse, rice and wheat straw, corn stover, and switchgrass, named as lignocellulosic biomass (LCB) which is inexpensive, abundant, renewable, and provides a unique natural resource for large-scale and cost-effective bio-en- ergy production. During the production of biofuels, pretreatment is a necessary step due to the recal- citrant structure of LCB. Various pretreatment methods were employed with a different mechanism of action, feasibility, and practicability to produce high yield biofuels. Since many years ago, the develop- ment of an effective pretreatment method has been challenging due to the existence of barriers and obstacles. Besides, each pretreatment method has its advantage and disadvantage, which should be investigated to obtain a higher yield of bioethanol. In this paper, the recent findings regarding the application of various pretreatment techniques such as chemical, physical and biological methods for bioethanol production from LCBs have been reviewed. The limitations of the mentioned methods based on the existing barriers were explained, and the future recommendations were discussed. © 2020 Elsevier Ltd. All rights reserved. 1. Introduction Energy plays a crucial role in economic development, human, and social improvements [1,2]. However, concerns about the depletion of fossil fuels and the increasing rate of energy con- sumption and industrialization, have encouraged the researchers to find alternative energy sources [3,4]. Owing to a reliable supply of required fuels for transportation and environmental pollution, cellulose-based fuel is an answer to the current issues [5]. Besides, the generated agricultural waste, through or after agricultural crop processing is a kind of renewable and lignocellulose-rich biomass resource [6]. It should be noted that agricultural wastes do not need land, water, and energy requirements and are not directly associ- ated with food security for conversion to energy [7]. Lignocellulosic waste is a kind of agro-industrial biomass, which is available at a reasonable price categorized as a renewable source. Generally, lignocellulose biomass (LCB) can be categorized into four main sources: agricultural and forest residues, energy crops, and cellu- losic wastes. As a wide category of biomass, agro-industrial biomass incorporates both the food-based and the non-food-based portions of crops [8]. Globally, wheat, maize, rice, and sugarcane are the major cultivated crops which use as feedstock to produce the LCBs * Corresponding author. ** Corresponding author. E-mail addresses: shahab.rezania@sejong.ac.kr, Shahab_rezania89@yahoo.com (S. Rezania), mohammadi.eng73@gmail.com, mohammadia3@nums.ac.ir (A.A. Mohammadi). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy https://doi.org/10.1016/j.energy.2020.117457 0360-5442/© 2020 Elsevier Ltd. All rights reserved. Energy 199 (2020) 117457