Another use for wood ash is as a fertilizer and soil amendment.

Wood ash contains calcium, phosphorus and potassium. On a bag of commercial fertilizer the contents will be listed as N-P-K
(% Nitrogen - % Phosphorus - % Potassium). Typical wood ash is about a 0-.5-2 to 0-1-3 fertilizer, i.e. almost no nitrogen, .5-1% phosphorus, and 2-3% potassium. Potassium levels are sometimes even higher.

Wood ash will increase soil pH. So, on acid soils, wood ash can be used like lime. Agricultural lime (calcium carbonate) is about 31% calcium. Wood ash is 10-20% calcium. A pound of wood ash is about equal to 1/2 pound of lime (more or less).

Mineral content of wood ash varies greatly depending on the type of wood,location where it was harvested and how it was burned, but above values are fairly typical.

If you have acid soil that is low in potassium, when you clean out the fireplace, spread it on your garden.