The House Rabbit Society recommends organic litters made from alfalfa, oat, citrus or paper. (tampabayvets.net)
Essential supplies for all indoor rabbit habitats include: a litter box with organic litter (do not use softwood shavings such as pine or cedar), water bottle or bowl, feed bowl, hay, and toys. (svg-vets.com)
Generally, organic litter types such as alfalfa, oat, citrus and paper make the best litters as they are absorbent and safe for your bunny to nibble on. (petsmagazine.com.sg)