Title: Exergy analysis of the valorisation of rice straw for energy purposes with a life cycle approach: rice production in Cuba

Authors: Edelvy Bravo Amarante; Ralf Kiran Schulz; Osvaldo Romero Romero; Eduardo Julio Lopez Bastida; Yenima Martínez Castro; Alberto E. Calvo González; Leonor Patricia Guereca Hernández

Addresses: Center for Studies on Energy and Industrial Processes (CEEPI), University of Sancti Spíritus 'José Martí Pérez', Cuba ' Institute of Professional Training (IBB), University of Kassel, Germany ' Center for Studies on Energy and Industrial Processes (CEEPI), University of Sancti Spíritus 'José Martí Pérez', Cuba ' Center for the Study of Energy and Environment, University of Cienfuegos, Cuba ' Center for Studies on Energy and Industrial Processes (CEEPI), University of Sancti Spíritus 'José Martí Pérez', Cuba ' Faculty of Mechanical Engineering, Technological University of Havana 'Jose Antonio Echevarria', Cuba ' Institute of Engineering, National University of Mexico, Mexico

Abstract: In this paper, the exergy analysis methodology is used to analyse four alternatives for the valorisation of rice straw for energy purposes in Cuba. The exergy input and output of the product (%), the exergy destroyed (MJ) and the exergetic efficiency (%) are calculated. The exergetic efficiency increases in the three alternatives where rice straw is valorised for energetic purposes. In alternative 4, where it is considered the production of biomethane (to replace 60% of the diesel fuel for harvesting and transportation of products) and electricity via biogas, the exergetic efficiency reaches values of 66.6%. The exergy flow contained in the product increases from 13.2% to 21.9%. The increase in exergy flow in the final product also represents a reduction in greenhouse gas emissions as emissions are avoided by generating the same amount of electricity in a thermal power plant. Alternative 4 also achieves the highest sustainability index (2.994). The cumulative exergy consumption in greenhouse gases (CExCGEI), a new indicator that considers the accumulated exergy that is destroyed in greenhouse gases, is proposed.

Keywords: exergy; wastes; rice straw; biogas; sustainability; renewable energy; Cuba.

DOI: 10.1504/IJEX.2019.104101

International Journal of Exergy, 2019 Vol.30 No.4, pp.338 - 359

Received: 09 Oct 2018
Accepted: 16 Jul 2019
Published online: 13 Dec 2019 *

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