system
Given the following post, respond as if you're commenting on Reddit:
human
Why isn't waste just melted down and poured inside a volcano.

Wouldn't the lava just nom nom it all?
gpt
A lot of materials would burn, not melt. Some trash is burned, in incinerators. In fact, trash-burning incinerators are used as a source of heat for apartment buildings in some places! However, not all trash is safe to burn.

Fire is a chemical reaction that combines oxygen with whatever material is burning, and produces smoke and ash and other leftovers. Exactly what chemicals are produced in the smoke depends on what you burn. Some trash, such as dead batteries, can produce smoke that is poisonous. Even smoke and ash that do not contain directly harmful chemicals still pollutes the environment by making your air dirtier and contributes to global warming.