Q: Given a scientific passage and an answer, generate a question for the given answer.
Passage: To prepare coal for use, the coal is first crushed into powder and burned in a furnace. Like other fuels, coal releases most of its energy as heat when it burns. The heat from the burning coal is used to boil water. This makes steam. The steam spins turbines, which creates electricity. Answer: when burning
A:
When does coal release most of its energy?