Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel Full Length Article Energy and water optimization of an integrated bioethanol production process from molasses and sugarcane bagasse: A Colombian case Claudia Valderrama a, ⁎ , Viviana Quintero b , Viatcheslav Kafarov a a Chemical Engineering, Physicochemical Engineering Department, Industrial University of Santander, 9 Street #27, Bucaramanga, Santander, Colombia b Environmental engineering. Marina University. Calle 18 No. 34-104, Pasto, Nariño, Colombia ARTICLE INFO Keywords: Bioethanol Exergy analysis Heat integration Water integration Mixed-integer nonlinear programming ABSTRACT In the present paper, an integrated scheme of frst and second-generation bioethanol production is proposed to increase the yield and decreasing thermal energy and freshwater requirements. In this sense, an energy con- sumption reduction of the integrated process was evaluated through heat exchangers network integration, ap- plying mathematical programming. Then, to reduce freshwater consumption, streams with water disposal for re- use in the process was evaluated, formulating the problem as a mixed-integer nonlinear programming problem (MINLP). Bioethanol production from the integrated scheme increased at least 40% compared it with sugar- bioethanol production scheme. The heat exchanger network with the minimum annual cost was identifed. Around of 16% of freshwater consumption was minimized using a nonconvex nonlinear programming NLP. The integration of second-generation bioethanol to a sugar-bioethanol process could increase, the bioethanol pro- duction in Colombia, without an energy and water excessive consumption. 1. Introduction In Colombia the production of bioethanol is carried out in dis- tilleries attached to sugar mills, where 367 million liters of this biofuel was produced in 2017. In addition, approximately 6 million tons of bagasse were generated for the paper industry and cogeneration sys- tems. Where, it contributed about 1,48 GWh/year to the network [1]. Further, according to resolution 40,185 of 2018, the percentage of fuel alcohol mixture E10 was established for the transport sector which imply an increase in the demand for this biofuel [2]. It is a fact that worldwide there is a great interest in diversifying bioethanol production and technological eforts have been oriented towards the use of alternative sources for its production, such as lig- nocellulosic biomass. In tropical countries, such as Colombia, bagasse is a promising raw material for bioethanol production due their high yield 120 L/ton [3]. However, the bagasse-based ethanol involves high water consumption and it will also require the improvement of energy con- sumption on pretreatment and hydrolysis operation [4] as well as high production costs, which make this process low competitive with respect to the frst-generation scheme. In this sense, several authors have proposed strategies to integrate the process production of second-generation ethanol with frst genera- tion ethanol, taking advantage of common stages and secondary streams. This can be seen in the studies conducted by Dias et al. [4], Dias et al. [5], Lennarstsson et al. [6], Dias et al. [7], compared the individual processing schemes denominated frst and second genera- tion, with an integrated scheme; identifying that the latter presents higher bioethanol production, better environmental and economic in- dicators accompanied by an energy integration in the process. Furlan et al. [8], using optimization tools, applies the concept of biorefnery, using as raw material juice and sugarcane bagasse to obtain biofuels, steam and electric energy. In this work the availability of bagasse as a raw material for obtaining bioethanol and as a fuel for cogeneration was evaluated. Ensinas et al. [9] propose the integration of a 1st and 2nd generation process to obtain bioethanol, applying a thermo-eco- nomic optimization based on an evolutionary algorithm. The authors concluded that when more than 72% of the bagasse is destined to produce second-generation bioethanol the quantity of electricity gen- erated by cogeneration does not meet the process energy demand. The present paper aims to propose a conceptual scheme of frst- and second-generation bioethanol with de minimum energy and water consumption; mainly focused on the national scenario where frst- generation production involves a continuous fermentation that includes yeast recovery. The substrates used come from the sugar production and they are: B magma, molasses and clarifed juice, obtaining ethanol concentrations in the fermented wine between 9 and 11% (v/v) [10,11]. The integrated scheme development was carried out con- sidering two aspects. The frst one was raw materials integration; that is https://doi.org/10.1016/j.fuel.2019.116314 Received 23 April 2019; Received in revised form 16 August 2019; Accepted 27 September 2019 ⁎ Corresponding author. E-mail address: claudia2158086@correo.uis.edu.co (C. Valderrama). Fuel 260 (2020) 116314 0016-2361/ © 2019 Elsevier Ltd. All rights reserved. T