This is one most interesting fire starting techniques we have ever seen.
If you want to build your own lemon fire starter you will need the following materials.
A lemon or similarly acidic fruit
Galvanized nails, or another source of zinc
A Copper source
Steel wool and some tinder
If that seems like a difficult list to pack for a survival situation that’s because it is. This is mostly a very interesting proof of concept and there are many easier fire starting methods.
The energy used to start the fire comes from the chemical change in the zinc when it dissolves into the acid. The energy does not come from the lemon or potato. The zinc is oxidized inside the lemon, exchanging some of its electrons with the acid in order to reach a lower energy state, and the energy released provides the power. When the lemon battery is providing an electric current the metallic zinc at the surface of the zinc electrode is dissolving into the solution. This means you won’t be able to keep your lemon generating electricity for ever.
You can squeeze about 1 Volt out of a lemon battery
Begin by sticking copper fasteners into the fruit
Add some zinc nails
Connect the copper to the zinc on a diagonal
Attach one insulated wire to the free copper fastener and one to the free zinc nail
Touch the two wires to a piece of steel wool to create a short-circuit, and watch the steel wool heat up!