Could You Build a Banana-Powered Generator?
Interesting thought experiment. However,
I am assuming the energy from the beta decay and electron capture don’t matter. Maybe they really do matter, but antimatter energy is cooler.
The reactions actually release more energy than the 1.02 MeV of annihilation, and since charged particles release their energy as they travel through a material, you’re going to capture much of this energy (not the neutrino energy, though) so it turns out this is a bad assumption, given that only 1 in 10^5 decays give you a positron.
Assuming a typical banana is 200 g, and contains about 75% moisture, you can assume to obtain about 1 MJ of combustion energy from it, if you would be able to burn it. You could easily get a good 400 kJ of electricity from it in a normal powerplant.
Unfortunately, at room temperature bananas turn to sugary pulp quicker than they dry… and they won’t burn well when still moist. Biomass dryers may not be suited for chopped-up banana because of the soft core of the banana and may not effectively dry the whole banana through its tough skin, so your best option might be to pulp it, ferment its inside to ethanol, and distill the ethanol to a fuel. Then filter off the residue, and dry and burn that.
But that is if you are in a hurry. If you have time to wait 1,400,000,000,000,000 years, the option to use its natural nuclear decay, producing 9 x 10^-18 W might be more efficient!
Or you can just eat it.