“…In fact, various indicators have been used, often with the same meaning but different definition, or inversely, e.g. overall energy efficiency (Boustead and Hancock, 1979;Boustead, 2003); energy efficiency (ADEME, 2002); gross energy requirement and net energy requirement (Wilting 1996); energy requirement (Whitaker et al, 2010); overall energy balance (Armstrong et al, 2002); energy balance (Börjesson and Tufvesson, 2011); cumulative energy demand (Huijbregts et al, 2006); input/output energy balance, cumulative energy requirement, fossil energy requirement, and renewable energy requirement (Cherubini et al, 2009); net energy use, and energy substitution efficiency (Gnansounou et al, 2009); energy ratio (Liska and Cassman, 2008;Papong and Malakul, 2010); net energy yield (Liska and Cassman 2008); and energy return on investment 1 (Poldy, 2008). In particular, Sheehan et al (1998) have used the life-cycle energy efficiency (LCEE), defined as the ratio between the biofuel energy content and the biofuel GER:…”