Very interesting. I wonder how the costs compare, coal ash vs. volcanic ash for the same industrial use.
Mostly it’s a way of disposing of something considered all too plentiful, otherwise transportation becomes the primary factor.
Coal has other attributes to recommend against its common usage, but we have so much of it! It would be a shame, economically, if we did not use it to our best advantage while we can.
Eventually, the push that should get nuclear properly implemented may be the promise to use its abundant excess of energy to clean up the leavings of previous techniques, like coal.