"This handy device allows you to destroy any excess items in your inventory and gain fuel for the generator in exchange."
Beside coals, you can virtually burn any item before you get Recycler Plant to deal with junky items. Some items recommended for burning in Incinerator are powder, butter and soap, so considering spare them instead of taking for showering. In case of powder, it's much cheaper than gasoline and might not be used in early game. You may not want to burn gasoline in Incinerator as it only gives one hour of power, whereas it may fuel up a day in Generator.
Instead of using graves, human corpses can be cremated in the incinerator, providing a cost-free method of disposing bodies in the shelter. Pet corpses can also be incinerated.