This chapter presents a synthesis of key concepts concerning the potential application of in situ leaching processes for direct and indirect resource recovery (with emphasis on metals) from wastes. The global stocks of industrial and mining wastes (IMWs) run into the billions of tonnes and will continue to accumulate in response to unabating global economic growth and consumption. Circular economy (CE) discourse to date generally emphasises recycling of post-consumer goods rather than resource recovery from IMWs even though they comprise very large, albeit dilute, stocks of metals. Because the metal contents of many of these wastes are (by definition) lower than corresponding ore grades, greater energy (or exergy) expenditure is required to win metals from these sources. Since the majority of metal recovery processes are driven by fossil fuels, this also implies greater carbon footprints and other detrimental consequences to natural capital. Thus, the application of conventional pyrometallurgical and hydrometallurgical processes for recovering metals from wastes must be closely scrutinised with respect to sustainability. More energy efficient processes and/or those that utilise non-fossil energy are required. Herein we explore key concepts in the potential application of low-intensity in situ leaching processes.