Research Paper Energy demand and greenhouse gases emissions in the life cycle of tractors Edemilson J. Mantoam a , Thiago L. Romanelli b,* , Leandro M. Gimenez c a Case Industry, Brazil b Laboratory of Systemic Management and Sustainability, Department of Biosystems Engineering, “Luiz de Queiroz” College of Agriculture, University of Sao Paulo, Brazil c Department of Biosystems Engineering, “Luiz de Queiroz” College of Agriculture, University of Sao Paulo, Brazil article info Article history: Received 9 February 2016 Received in revised form 29 August 2016 Accepted 31 August 2016 Keywords: Material flow Energy analysis Inventory Embodied energy Sustainability Energy supply and global warming are two of the main challenges of 21st century. To produce food to satisfy the increasing world population requires using more assets, more energy and emitting more greenhouse gases. Studies approaching embodied energy into and greenhouse gas emissions from agricultural machinery are rare. This study deter- mined the energy demand and greenhouse gas emissions in the life cycle of tractors. Four tractors with distinct power levels were evaluated: 55 kW (T1); 90 kW (T2); 172 kW (T3) and 246 kW (T4). Life cycles considered were obtained from three different sources. Con- sumption of the direct inputs used in the assembly phase and of the input used in the maintenance phase were accounted. The results presented higher embodied energy and emissions in life cycle than are found in the literature. The following indicators were determined: T1, 122.7 MJ kg À1 and 5.7 kg [CO 2 eq.] kg À1 ; T2, 91.2 MJ kg À1 and 4.2 kg [CO 2 eq.] kg À1 ; T3, 85.2 MJ kg À1 and 3.8 kg [CO 2 eq.] kg À1 ; and T4, 71.9 MJ kg À1 and 3.3 kg [CO 2 eq.] kg À1 . The hypothesis that more powerful tractors would require less energy and emit less greenhouse gas per functional unit (mass and power) was proved. Tractor (T4) has 313.2% more mass than (T1), but it required 70.6% less energy and 72.7% less GHG per unit mass, or 84.7% less energy and 87.7% less GHG per unit engine power than T1. For further use in modelling, equations were provided to determine energy demand and emission associated with either engine power or tractor mass. © 2016 IAgrE. Published by Elsevier Ltd. All rights reserved. 1. Introduction Energy is vital for the development of economies and societies, being mandatory to transform natural resources into goods and to provide services (Hinrichs & Kleinbach, 2009). Besides, its demand has increased globally (Abubakar & Umar, 2006). Current energy production chains are insufficient to meet the population's needs (AGECC, 2010). For instance, the growing demand for food and energy production, threatens water availability making ecosystems vulnerable (J ^ agerskog et al., 2014). Due to the growing environmental concerns about energy use and greenhouse gas emissions (GHG) in recent years, the global demand for renewable * Corresponding author. Av. Padua Dias, 11, Department of Biosystem Engineering, C.P 09, Piracicaba, SP, 13418-900, Brazil. Fax: þ55 19 34478571. E-mail address: romanelli@usp.br (T.L. Romanelli). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/issn/15375110 biosystems engineering 151 (2016) 158 e170 http://dx.doi.org/10.1016/j.biosystemseng.2016.08.028 1537-5110/© 2016 IAgrE. Published by Elsevier Ltd. All rights reserved.