Vienna designers Mischer’Traxler, also of Automatic Cake Decorator fame, used 700 used Nespresso coffee capsules, coffee grounds, strips of copper and salt water to create these coffee powered batteries. The batteries were used to power clocks at the 2010 Vienna Design Week. Six of the batteries connected together are enough to power a tiny clock. The whole collection of batteries would just about power a small radio.
So while coffee powered batteries might not be an option for any sort of practical alternative power source, it’s surely a lot safer and tastier than alkaline.