In this talk we will explore the environmental footprint of cryptocurrencies. We will estimate the energy consumption of cryptocurrency mining, and the corresponding impact on climate change. By doing so, we will dive into consensus algorithms that are used in different cryptocurrencies. We will compare our results with other estimates from scientific literature, and show that estimates in some scientific papers are rather unrealistic. We will end the talk by discussing ongoing initiatives in the world to make cryptocurrency mining ‘greener’, either by legislation or by adopting renewable energy sources. During the talk, we will suggest various research topics that students may explore in a research internship or graduation project.