Today, Information & Communications Technology accounts for 2-3% of global CO2 emissions, on a par with the aviation industry. If nothing changes, by 2050 it's estimated this number will rise to over 30%. Often overlooked is the crucial role of software. It is software which determines hardware's energy consumption, and for how long devices remain in use. That software design can drive environmental harm is still largely unknown to much of the population, let alone that users can already do something about it with Free Software.

In early 2023 KDE published the handbook "Applying The Blue Angel Criteria To Free Software", the culmination of a 21-month project funded by the German government. The handbook presents the whys, whats, and hows for certifying software as sustainable with the Blue Angel ecolabel. In this talk I will provide an overview of the environmental harm driven by software and how Free Software 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, squashing hundreds of efficiency bugs, supporting the sustainability objectives of the FOSS Nigeria project "Renew V", among others.