I have a Bis 1.2 insert in which I have always burned hardwood, but this year I was thinking of using compressed sawdust (no paraffin) ecologs. The Bis has a grate and an ash pan about 3 inches deep. I was wondering if I should continue to empty the ash pan regularly, let it fill up and burn the ecologs on top of the ashes and grate, or remove the grate completely, and replace the pan with refractory bricks.