Regeneration costs of topsoil fertility: An exergy indicator of agricultural impacts

In recent years, heightened environmental concerns linked to agriculture have surged, with soil degradation standing out as a global issue. However, prevailing sustainability assessment methodologies in agriculture often overlook soil systems due to their intricate nature. This study aims to develop a methodology for evaluating soil degradation in agricultural practices using exergy regeneration costs. These costs determine the exergy required to restore soil fertility to pre-harvest levels. The methodology covers key soil factors like nutrients, organic matter, and prevalent issues like salinity, acidification, and erosion. For each of these factors, exergy regeneration costs are determined based on the energy needed to execute an optimal process for reverting the soil to its original or ideal state. The methodology has been applied to data from agricultural trials, showing that the calculated soil replacement cost is significantly higher compared to one of the most energy-demanding processes in agriculture, the use of urea. This demonstrates that agricultural soil degradation needs to be quantified for a correct evaluation of agricultural practices and their sustainability.