An overview on bioethanol production from lignocellulosic feedstocks Manju Toor a, 1 , Smita S. Kumar a, 1 , Sandeep K. Malyan b , Narsi R. Bishnoi a , Thangavel Mathimani c , Karthik Rajendran d , Arivalagan Pugazhendhi e, * a Department of Environmental Science and Engineering, Guru Jambheshwar University of Science and Technology, Hisar,125 001, Haryana, India b Institute for Soil, Water, and Environmental Sciences, The Volcani Center, Agricultural Research Organization (ARO), Rishon LeZion - 7505101, Israel c Department of Energy and Environment, National Institute of Technology, Tiruchirappalli - 620 015, Tamil Nadu, India d Department of Environmental Science, SRM University-AP, Amaravati, Andhra Pradesh - 522502, India e Innovative Green Product Synthesis and Renewable Environment Development Research Group, Faculty of Environment and Labour Safety, Ton Duc Thang University, Ho Chi Minh City, Viet Nam highlights  Various ethanol production processes with their advantages and shortcomings.  Singlepot biorefineries, combined bioprocessing, bioenergy with carbon capture are promising.  Bioconversion process in bioethanol production.  This review focused on lucrative bioethanol production and the remedial solutions. article info Article history: Received 1 April 2019 Received in revised form 25 September 2019 Accepted 5 October 2019 Available online 9 October 2019 Handling Editor: Veeriah (Jega) Jegatheesan Keywords: Lignocellulosic Bioethanol Fermentation Saccharification Microorganism abstract Lignocellulosic ethanol has been proposed as a green alternative to fossil fuels for many decades. However, commercialization of lignocellulosic ethanol faces major hurdles including pretreatment, efficient sugar release and fermentation. Several processes were developed to overcome these challenges e.g. simultaneous saccharification and fermentation (SSF). This review highlights the various ethanol production processes with their advantages and shortcomings. Recent technologies such as singlepot biorefineries, combined bioprocessing, and bioenergy systems with carbon capture are promising. However, these technologies have a lower technology readiness level (TRL), implying that additional efforts are necessary before being evaluated for commercial availability. Solving energy needs is not only a technological solution and interlinkage of various factors needs to be assessed beyond technology development. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction Depriving fossil fuels are the primary energy sources worldwide. Fossil fuels are non-renewable resources primarily responsible for the increased carbon dioxide (CO 2 ) level in the environment and associated climate changes (Barreto, 2018; Saravanan et al., 2018). Declining petroleum reservoir and its negative impacts on the environment have raised interest in exploring alternative resources for energy (Bhatia et al., 2012; Mussatto, 2016). Various alternative resources such as solar, geothermal, hydro and wind are available. Among the resources, solar energy or solar fuels, a rapidly growing technology, considered as the prospective technology to avert en- ergy and environmental issues (Reshma et al., 2017). In addition to the above mentioned renewable energy sources, biofuels are perceived as a discrete type of alternative and viable renewable energy due to their non-toxic, biodegradable, and carbon neutral features (Koley et al., 2018; Mathimani and Mallick, 2019). Different kinds of biofuels exist in the market as well as under development, for example, biogas, biodiesel, biohydrogen and biobutanol (Lee, 2016; Saravanan et al., 2018). Yet, the predominant one is un- doubtedly ethanol (Naik et al., 2010; Ibrahim et al., 2018). Bioethanol is being used as a fuel since 1826. S. Morey was the * Corresponding author. E-mail address: arivalagan.pugazhendhi@tdtu.edu.vn (A. Pugazhendhi). 1 The authors contributed equally as first author to this work. Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere https://doi.org/10.1016/j.chemosphere.2019.125080 0045-6535/© 2019 Elsevier Ltd. All rights reserved. Chemosphere 242 (2020) 125080