What problems do liquid fuels pose which solid fuels don't?

Think of the "SAFETY" reasons. I will use Ethanol as an example. If you opened an ethanol bottle there is most of the time a safety bottle top. But if there was'nt one then if someone accidentally knocked you. Then you could spill the Ethanol everywhere. So one of the reasons SPILLAGES. Another reason in this case Ethanol is a flammable substance. Do not get me wrong but I know that not all liquid fuels are flammable.It is the fumes of Liquid fuels that are flammable instead of the fluid. But if you opened a Ethanol bottle and a source of fire was lit nearby. (Example a Bunsen Burner). Then the Ethanol might start to burn and cause a fire. So another reason FLAMMABLE.These are two problems that liquid fuels cause that solid fuels do not. I tried my hardest to detail them and make it understandable :)