The exergetic efficiency of agricultural processes, including the regeneration of soil

Agricultural processes are fundamental for providing food, yet they are significant consumers of energy. Detailed studies havequantified energy use in open-field agriculture across the European Union (EU) at a minimum of 1435 petajoules (PJ), equivalentto approximately 3.7% of the total EU energy consumption[1]. Additionally, the greenhouse gas emissions associated withagriculture pose a significant environmental concern. Beyond emissions, extensive farming exacerbates other critical issues, suchas soil degradation. In Europe, it is estimated that 60–70% of soils are in poor health, posing a serious risk to sustainable foodproduction and the essential ecosystem services that support human well-being. The financial burden of soil degradation across the EU is substantial, exceeding €50 billion each year [2]. The Life Cycle Assessment (LCA) approach is widely employed to evaluate the environmental impacts of agriculture, includingenergy consumption. However, LCA methods fail to account for soil quality and fertility, leading in some cases to more favourable results for intensive agricultural systems due to their higher yields per hectare (van der Werf et al., 2020). This oversight can disadvantage agroecological practices in comparative assessments, despite the fact that intensive agriculture frequently degrades soils to prioritize short-term production. However, assessing soil comprehensively is challenging due to the intricate interplay of physical, chemical, and biological parameters [3]. In previous studies, we quantified the costs associated with restoring soil fertility lost or degraded by agricultural activities [4], [5]. Soil fertility is often perceived as a free natural resource; however, when fertility is depleted, its restoration incurs long-term loss of efficiency and, thus, economic costs that are not explicitly recognized. To address this, the concept of exergy has been proposed as a tool to estimate the regeneration cost of soil. Exergy, which measures the energy available to perform useful work in a system, was applied to estimate the energy required to restore soil fertility. This approach considered the exergy embodied in a theoretical remediation and regeneration process, encompassing nutrient replenishment, organic matter restoration, sodicity correction, and soil acidification mitigation. This study aims to assess the efficiency of agricultural systems through a single metric. To achieve this, the exergy regenerationcost has been integrated into the ExROI (Exergy Return on Investment) index, resulting in the novel ExROIREGENERATIVE metric.Validation using data from various field trials will demonstrate the utility of this metric and underscore the importance of incorporating soil regeneration into assessments of agricultural efficiency.