Critical review on energy balance of agricultural systems

The increased cost of fossil fuels and greenhouse gas emissions has attracted the interest of many researchers to study energy use in agricultural systems. Even though energy balance is the customary method used to evaluate and compare the performance of agricultural systems in terms of energy, a variety of methodological approaches and coeffi cients are the source of confusion and misleading conclusions. In this review, the problems and inconstancies attributed to the use of inappropriate and obsolete data, unclear boundary systems, and diffi culties in obtaining representative data are discussed. The methodological procedure to compute energy balance in agricultural systems is presented briefly. Then the inconsistencies and causes of variability in the principal operating factors of energy balance studies are discussed. Examples are given from the literature where controversial, incomplete, and inappropriate data are used. Also the diffi culties in obtaining reliable data and defi ning the boundary systems are highlighted. The identifi ed problems with the methodology and the data included in the computations of energy coeffi cients should serve as a starting point toward a better understanding of energy flows in agricultural systems and toward an agreed methodology for complete and sound energy balance studies.