After mixing in motor oil I would notify the EPA of my intent to burn it. The EPA will send a 47 page regulation on the needed permits and process to legally burn the mix. You will probably have to wait for the "dark of the moon" and the availability of certified govt. inspectors to insure all the proper forms and permits are in place.
It appears that cabin fever has set in early this year. As long as your loads don't exceed the max for the faster of the 2 powders it should be safe if not optimal. Or just pour in on the flowers.