Why not eat them? We're not burning cows for fuel are we. Eating the bunnies instead of other meat would save more energy than burning them.
Seems more sensible than rounding the animals up en-masse and dumping them in an incinerator.
It was once common to eat them in Sydney; in fact my dad tells of a rabbit man that would sell them door-to-door when he was growing up. It was so common that they named the Rugby League team in the area after the tasty critters (the South Sydney Rabbitohs).
Just further demonstrates the benefits of being cute.