In this talk I provide an overview of the environmental harm driven by software and how FOSS is well-positioned to address the issues. I will link the inherent values that come with a Free & Open Source Software license to sustainable software design, and I will present the various ways that Free Software aligns with the Blue Angel ecolabel. Finally, I will provide an overview of the current sustainability goal of KDE and the work of the KDE Eco initiative. This includes publishing the KDE Eco handbook, setting up a measurement lab for FOSS developers (KEcoLab), squashing hundreds of efficiency bugs, among others.