In Brave New World, what happens to dead bodies in the World State?
Every body is cremated. It's an idea that springs from the "everyone is equal and contributes equally to production" concept of the World State. Lenina and Henry discuss this while on their date, after Lenina inquires about the balconies she sees along the smoke stacks.
"Phosphorus recovery," explained Henry telegraphically. "On their way up the chimney the gases go through four separate treatments. P2O5 used to go right out of circulation every time they cremated some one. Now they recover over ninety-eight per cent of it. More than a kilo and a half per adult corpse. Which makes the best part of four hundred tons of phosphorus every year from England alone." Henry spoke with a happy pride, rejoicing whole-heartedly in the achievement, as though it had been his own. "Fine to think we can go on being socially useful even after we're dead. Making plants grow."
Lenina, meanwhile, had turned her eyes away and was looking perpendicularly downwards at the monorail station. "Fine," she agreed. "But queer that Alphas and Betas won't make any more plants grow than those nasty little Gammas and Deltas and Epsilons down there."
"All men are physico-chemically equal," said Henry sententiously. "Besides, even Epsilons perform indispensable services."
Lenina has no reaction to the Crematorium, apart from a strong sense of caste superiority. Henry reminds her that everyone, even an Epsilon, is essential to the health and stability of the World State. Thus, the phosphorus is recovered (at least 98% of it), and everyone continues being useful long after their deaths.
They are cremated and used to fertilize the ground. According to the people it helps keep the world beautiful.