"Hauling Ash" is the bain of our existences, ain't it?
I agree with Greg; fabricate another bin so you can do a quick swap and let 'er cool.
My stoker furnace grate empties into 17" square x 11" high (~2 ft3, ~15 gal) galvanized ash bins. Depending on how full I let them get, it's between 30 and 45# of ash coming out. (That's the yield from 180-250# of fuel input, so 15-20% by weight is my operating ash:fuel ratio. Because my unit is a stoker, the ash contains noticeable amounts of unburnt coal (which pissed me off last year but I'm over it now

), so FWIW that's a misleading number for evaluating the ash content of my fuel.)
Anyhow, last year, I used 3 mil contractor bags, into which I could dump two bins of ash. And it's not recyclable here, so it goes out with the regular trash. But 90# of ash in a plastic bag is, well,
a pain in the ash, so I think I'm going to go to cheaper bags this year and use one per bin-full.
I think we've kicked this around before, but what can be done with large quantities of coal ash? It's one thing if you're on a farm or have a gravel road that you can fill holes in, but does anybody know what our ancestors did with their ash when coal was commonly burnt in the cities?