Final answer:
Captain Beatty is the character who said this quote, revealing his contempt for books and practical nature.
Step-by-step explanation:
The character who said, "You're a burden. And fire will lift you off my shoulders, clear, quick, sure; nothing to rot later. Antibiotic, aseptic, practical" is Captain Beatty. This quote is from the novel 'Fahrenheit 451' by Ray Bradbury. It reveals Captain Beatty's contempt for books and his belief that they are burdensome and should be destroyed. It also illustrates his practical and cold-hearted nature.