Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Comprehensive exergy analysis of a gas engine-equipped anaerobic digestion plant producing electricity and biofertilizer from organic fraction of municipal solid waste Mohamad Reza Barati a , Mortaza Aghbashlo a, ⁎ , Hossein Ghanavati b,c, ⁎ , Meisam Tabatabaei b,c, ⁎ , Mohammad Sharifi a , Ghasem Javadirad d , Ali Dadak a , Mohamad Mojarab Soufiyan a a Department of Mechanical Engineering of Agricultural Machinery, Faculty of Agricultural Engineering and Technology, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran b Biofuel Research Team (BRTeam), Karaj, Iran c Microbial Biotechnology Department, Agricultural Biotechnology Research Institute of Iran (ABRII), Agricultural Research, Extension, and Education Organization (AREEO), Karaj, Iran d Caspian Motor Technology (CaMoTec) Company, Iran ARTICLE INFO Keywords: Anaerobic digestion plant Biogas Biofertilizer Electric power Exergy Organic fraction of municipal solid waste ABSTRACT This study was devoted to comprehensively investigating the exergetic performance of a gas-engine equipped anaerobic digestion plant producing electric power as well as biofertilizer from organic fraction of municipal solid waste (OFMSW). The main aim of the current survey was to reveal the reasons and sources of thermo- dynamic losses occurring in the plant based on real operational data. The required data for the analysis were collected from a local OFMSW anaerobic digestion plant located in Tehran, Iran. After writing energy and exergy balances for all components of the plant, their exergetic performance parameters were measured individually. An attempt was also undertaken to quantify the contributions of the products to the overall exergetic efficiency of the plant. The exergetic value of the net electric power was determined at 1596.0 kW, while the chemical exergetic content of the biofertilizer was found to be 8758.3 kW. The overall exergetic efficiency of the plant was determined at 72.8%. The contributions of the electric power and the biofertilizer to the overall exergetic ef- ficiency of the plant were found to be 15.4% and 84.6%, respectively. Generally, the exergetic analysis presented herein could provide important guidelines and methodological blueprints for future investigations in order to develop thermodynamically-efficient and environmentally-benign waste-to-energy plants. 1. Introduction During the last decade, population growth, increased urbanization, rapid industrialization, and societal lifestyle changes have led to con- stant increases in municipal solid waste (MSW) production worldwide. Nowadays, the collection, processing, and disposal of MSW are the most challenging and sometimes controversial issues faced by local govern- ments around the world [1,2]. In general, MSW could potentially in- clude any or all of five different groups of wastes, i.e., biodegradable wastes, hazardous wastes, composite wastes, recyclable wastes, and inert waste [3]. Conventional waste disposal methods such as land- filling and dumping as the most widely-practiced low cost treatment approaches have been shown to be unsuitable and unsustainable due to land availability limitations in metropolitan cities as well as several environmental concerns such as gas emissions and leachate production. Therefore, there is an emergent need to shift towards environmentally, economically, and socially sound MSW tackling systems in order to ensure the protection of the public health and the environment. On the other hand, the organic fraction of MSW (OFMSW) can be regarded as a renewable source of energy to not only partially diminish non-renew- able energy consumption but also to slightly mitigate greenhouse gas emissions. In better words, a circular bioeconomy is expected to evolve progressively in the coming decades in order to address a range of sustainability-related challenges such as climate change, resource de- pletion, and expanding populations [4]. Today, various waste-to-energy options such as incineration, pyr- olysis, gasification, mechanical treatment, refuse-derived fuel, and anaerobic digestion are available for treating MSW in order to recover http://dx.doi.org/10.1016/j.enconman.2017.09.017 Received 1 June 2017; Received in revised form 10 August 2017; Accepted 7 September 2017 ⁎ Corresponding authors at: Biofuel Research Team (BRTeam), Karaj, Iran (H. Ghanavati, M. Tabatabaei). E-mail addresses: maghbashlo@ut.ac.ir (M. Aghbashlo), ghanavatih@abrii.ac.ir, ghanavatih@yahoo.com (H. Ghanavati), meisam_tab@yahoo.com, meisam_tabatabaei@abrii.ac.ir (M. Tabatabaei). Energy Conversion and Management 151 (2017) 753–763 0196-8904/ © 2017 Elsevier Ltd. All rights reserved. MARK