The base of most mixes here in NSW Australia where there are about 90 orchid societies is treated/composted radiata pine bark.
Raw bark needs some treatment and there is the trend to use materials that do not decay readily in warmer/humid climates. Lava rock is a good base material for such places.
Also depends on which orchids you wish to grow.

If you have some on hand you should try it. People have use some off the wall stuff with success. Other variables will kick in such as watering, type of pot, solar exposure...I would not use it because I've found a comfort zone with what I do. You won't know until you try.