Sorry. I chuckled a little bit when I saw that picture. I can just imagine you lifting the bag and just catching the edge of the barrel with it. Splat!
If you have room, a compost pile can be pretty useful.
Shame on you for throwing the grains out anyway. Compost them, feed the deer, find someone with horses, make dog biscuits, make bread, ANYTHING! No reason to throw them out. Especially in a plastic bag.