Earlier this year a video appeared online purportedly showing how you could turn a lemon into a simple battery and then use it to start a fire by igniting a piece of steel wool. Uh no, that’s where the science falls apart.
The two even substituted a giant pineapple for the lemon and were still unable to generate enough power to start their fire. You need about two AA batteries worth of electricity to ignite steel wool. That would end up requiring an entire bag of lemons to be wired up in series.
So don’t bother packing a lemon as part of your emergency supplies for the next time the power goes out. Just toss a box of matches in there and save yourself a lot of trouble.