Just an FYI, ash has high alkalinity compared to normal soil. Adding it in moderation to your garden will probably have little to no ill effect. In fact, it is considered a fertilizer, according to the article cited below. However, if the alkalinity of the soil becomes too high (say after repeated dumping), it can cause the soil to become unforgiving for plant growth. So I guess the moral of the story is moderation. My family told me this long ago, but here is some citation just to be thorough (
http://www.hort.purdue.edu/ext/woodash.html).
Also, the reason that it wards off pests and insects is because of the alkalinity. This works just like liming horses out at pasture to ward off insects, hence why the chickens probably love rolling in it.
But I digress... I usually pour some water in the ash catch bucket the day after to make a thick slurry, then pour it into the next bag of trash.