incinerate
To burn something completely until only ash is left.
To incinerate means to burn something completely until almost nothing remains but ash. When hospitals incinerate medical waste, they use extremely hot furnaces that turn bandages, needles, and other materials into harmless ash. When a city incinerates garbage at a waste facility, powerful flames reduce tons of trash to a tiny fraction of its original size.
That complete destruction is what makes incineration different from ordinary burning. A campfire might char a log or burn it partway, but an incinerator (a special furnace built for this purpose) burns things so thoroughly that only fine ash and gases remain.
Scientists studying volcanoes sometimes describe how intense heat can incinerate everything in its path. The word suggests total destruction by fire: burning or scorching something so completely that it's reduced to almost nothing. When you hear that a forest fire incinerated a building, it means the flames were so hot and so complete that the structure was utterly consumed, leaving only ash and debris behind.