As technologies progress in data centres, older-generation servers are often replaced by more energy-efficient ones. As a result of this trend, the problem of electronic waste is exacerbated. This extended abstract discusses a few recent insights about sustainable data centres. Then, it presents an ongoing approach to extend the lifetime of old-generation servers in data centres and reducing the amount of brown energy and water needed for cooling. CCS CONCEPTS • Computer systems organization → Architectures; Other architectures; Heterogeneous (hybrid) systems.