With the recent changes to the flaming hal (which was needed) I think a remote grinder, say a rock tumbler, would be a nice alternative. Like the meat collector and butterfly milker it would grind rocks you put in slowly over time, so overall you would save energy, just at the cost of time. There could be a limit of ore put in and a limit per household so that people don't stack a bunch of ore in them and only log in once a week to check.