This is an old-fashioned furnace; you burn combustible objects in it, and you get power from its built-in turbine system, as well as heat for the environment. These are typically not very impressive in terms of power generated, but are commonly used in mining outposts and other isolated bases in order to heat them inexpensively, especially when quantities of char ore or other flammables are available.

The furnace occasionally needs to be cleaned of buildups of non-combustible material; throwing in non-combustible or less-than-combustible items will obviously cause buildups to occur more quickly. Throwing a body in a furnace will eventually reduce it to ash, although it will take a fairly long while to entirely burn the body and anyone who cleans the furnace will note the presence of a corpse or its remnants if the fire isn't hot enough.

While not commonly found on modern starships, one repurposed use for these furnaces is in the crematorium industry, when bodies need to be disposed of, and the incineration industry, where garbage goes to be burned and whatever survives that is salvaged for recyclable objects. It is also a good way of getting rid of xenocreatures that are not immune to extreme heat in general.