Bigger question; it there enough manganese anywhere on the planet to make this useful, or is this a specialty solution?
Manganese is the tenth most common element in the earth’s crust.
The ocean floors have metal nodules on them and under them with billions of tonnes worth we will never run out of manganese. As a note common zinc carbon AAA TO D cells have are actually zinc manganese cells the carbon is just the conductor it’s zinc and manganese oxide going to zinc oxide and manganese metal that powers those cells. As for fire I don’t think a discharged zinc carbon manganese cell has never burst into flames due to the now metallic manganese metal present in it.