Exergy-Based Sustainability Assessment of Gold Mining in Colombia: A Comparative Analysis of Open-Pit and Alluvial Mining

Thermodynamic methods such as exergy analysis enable the evaluation of environmental load (environmental impacts) by quantifying entropy generation and exergy destruction associated with using renewable and non-renewable resources throughout a production system. Based on the principle that environmental impacts occur when exergy is dissipated into the environment, this study applies exergy analysis as a tool for assessing the sustainability of gold mining in Colombia. Two extraction technologies—open-pit and alluvial mining—are evaluated by calculating exergy efficiencies, cumulative exergy demand (CExD), and associated environmental impacts. The results reveal significant differences between the two methods: open-pit mining is heavily dependent on fossil fuels (53% of input exergy), with 99.62% of total exergy destroyed, resulting in an exergy efficiency of just 0.37% and a sustainability index (SI) of 1.00. In contrast, alluvial mining relies predominantly on water (94%), with 69% of input exergy destroyed, an exergy efficiency of 31%, and an SI of 1.46. Four strategies are proposed to reduce environmental burdens: improving efficiency, minimizing exergy losses, integrating renewable energy, and adopting circular economy principles. This study presents the first application of exergy analysis to comprehensively assess the exergy cost of gold production, from extraction through refining, casting, and molding, highlighting critical exergy hotspots and offering a thermodynamic foundation for optimizing resource use in mineral processing.