1) filter it, filter it, and filter it. Maybe do a hot water wash, to get acids/salts out of the fat.
2) be very sure your plan for starting & stopping on regular diesel, is fool proof. All you need to make your day is trying to cold start with lard in the injector.
I don't know if lard needs to melt the whole tank, for each run cycle, otherwise, is there a problem with lots of incomplete cycles "distilling" the low temp melt out of the tank, leaving only high temp lard in it ?