Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Fe 2 O 3 nanocatalyst aided transesterification for biodiesel production from lipid-intact wet microalgal biomass: A biorefinery approach Srijoni Banerjee a , Swagatika Rout b , Sanjukta Banerjee c , Arnab Atta d , Debabrata Das c, ⁎ a Advance Technology Development Center, Indian Institute of Technology, Kharagpur 721302, India b P K Sinha Centre for Bioenergy, Indian Institute of Technology, Kharagpur 721302, India c Department of Biotechnology, Indian Institute of Technology, Kharagpur 721302, India d Department of Chemical Engineering, Indian Institute of Technology, Kharagpur 721302, India ARTICLE INFO Keywords: Transesterification Microalgal biomass Biodiesel Nanocatalyst Biorefinery ABSTRACT Biodiesel production from non-edible feedstock such as microalgae is gaining importance in present day, as they do not interfere with global food economy in addition to higher photosynthetic efficiency as compared to plants. Fresh water grown Neochloris oleoabundans UTEX 1185 is considered as a potential source for biodiesel pro- duction. The present study investigated different direct lipid extraction process from wet microalgal biomass through autoclaving, microwave, and ultrasonication pretreatments. Autoclave treatment showed a higher ef- ficiency for lipid extraction as compared to other two pretreatments. Furthermore, transesterification process was carried out in presence of Fe 2 O 3 catalyst and compared with conventional acid (HCl) and base (NaOH) catalysts. Fe 2 O 3 nanoparticles used were synthesized from extract of Hibiscus rosa-sinensis by green procedure. The synthesized Fe 2 O 3 catalyst played an important role in improving the biodiesel yield up to 81%, which is higher than that obtained with HCl (64%) and NaOH (48%). Thereafter transesterification process parameter like catalyst content, reaction temperature and reaction time were optimized and finally 86% biodiesel yield was obtained. Fatty acid methyl esters (FAME) profile analysis and fuel properties revealed the suitability of algal lipid for biodiesel production. 20.2% w/w of carbohydrate present in lipid extracted microalgal biomass was further converted into biohydrogen by dark fermentation and bioethanol under anaerobic condition using acidogenic mixed consortia and Saccharomyces cerevisiae (INVSC-1), respectively. The life cycle assessment study of the overall process was also done. 1. Introduction Continuous use of fossil fuels over the last few decades and its im- pact on environment, has compelled the world to focus on finding al- ternative fuels [1,2]. Biodiesel is considered as one of the most pro- mising alternative fuels. Biodiesel is renewable, environment friendly, biodegradable and produces less CO, CO 2 , hydrocarbons, NO X and SO X as compared to conventional diesel [3]. Biodiesel production from microalgal biomass is one of the encouraging routes for renewable fuel production. Microalgae is considered as a third generation feedstock for biofuel production which has higher photosynthetic efficiency and growth rate than plants. Microalgae can sequester CO 2 from the at- mosphere which makes microalgal biodiesel production a carbon neu- tral process [4,5]. Therefore it is desirable to increase not only the biodiesel production but also other types of renewable energy resources [6]. To become a more viable alternative fuel, biodiesel must compete economically with conventional diesel [6–9]. Microalgal harvesting and oil extraction account up to 90% of the total energy cost [10]. Tradi- tionally biodiesel production from microalgal biomass involves pre- processing steps. Firstly harvested wet microalgal biomass has to be dried and then algal lipid has to be extracted from the dried biomass using organic solvents (methanol and chloroform) [11]. Subsequently the extracted lipid has to be transesterified using methanol in acidic or alkaline conditions with or without nanoparticle as catalyst, and finally the purification of the biodiesel is performed by hexane and water. However, as microalgal cell wall is very rigid, and consists of multiple layers, cell wall disruption and intracellular lipid extraction are key steps in microalgal biodiesel production process. Cell wall disruption methods and extraction solvents decide the efficiency of the oil ex- traction from microalgae. Additionally intracellular oil extraction is an energetically demanding process [12]. Consequently advanced pro- cesses of oil extraction from wet microalgal biomass have been https://doi.org/10.1016/j.enconman.2019.05.060 Received 7 March 2019; Received in revised form 10 May 2019; Accepted 19 May 2019 ⁎ Corresponding author. E-mail address: ddas.iitkgp@gmail.com (D. Das). Energy Conversion and Management 195 (2019) 844–853 Available online 29 May 2019 0196-8904/ © 2019 Elsevier Ltd. All rights reserved. T