In this talk at the FOSDEM conference, the speaker discusses the environmental impact of the ICT sector and how free and open source software can help combat software-driven environmental harm. The speaker highlights the energy consumption and greenhouse gas emissions of the ICT sector, emphasizing the need for more efficient and sustainable software. They present data comparing the energy consumption of different software products and showcase how free and open source software, such as KDE, can contribute to energy savings and reduction of e-waste. The speaker also mentions the Blue Angel Eco Certification for software and how it recognizes the sustainability of free and open source software. They discuss the importance of user autonomy, uninstallability, modularity, continuity of support, offline capability, and freedom from advertising as key features of sustainable software. The speaker concludes by mentioning KDE's commitment to making sustainable software and invites others to join their community initiative.