Introducing an exergy-based model for soil restoration: quantifying energy demands for SOC rebuilding

Soil degradation driven by human activities threatens ecosystem stability and agricultural productivity. This study introduces an exergy-based model to quantify the energy required to restore degraded soils (phenosoils) to their natural reference state (genosoils), focusing on Soil Organic Carbon (SOC) as a key indicator of restoration progress. SOC plays a crucial role in carbon storage, nutrient cycling, and soil functionality, making its recovery essential for sustainable land management. A mathematical model was developed to calculate the exergy required to restore SOC in degraded soils to levels characteristic of genosoils. The model, based on first-order kinetics, has three parameters: SOC gap, recovery rate constant (k), and energy cost per unit SOC increase (α). Results reveal significant variability in energy demands across management practices and soil types. Pedogenons (soil types) with large SOC gaps and low recovery rates exhibited the largest exergy demands, highlighting the need for long-term, energy-efficient management strategies. In an example calculation, organic amendment demonstrated lower exergy requirements compared to irrigated cotton-to-wheat rotations, while wheat-to-sorghum rotations in dry areas showed the highest energy efficiency. Sensitivity analysis identified recovery rates (k) as the dominant parameter influencing total exergy, followed by SOC gaps (ΔSOC), with energy cost per unit SOC increase (α) playing a secondary role. Optimizing k and managing ΔSOC are essential for achieving energy-efficient SOC restoration, while enhancements in α offer secondary benefits. The proposed model provides a robust tool for evaluating the energy demands of SOC restoration, offering actionable insights to optimize restoration efforts. Linking SOC dynamics to energy requirements enhances the development of sustainable soil management strategies and advances our understanding of energy-efficient approaches to soil restoration.