This one is tricky - as science cannot seem to identify glycerol within the confines of any particular macronutrient. Is it a carb? Is it a precursor to fat? It's hard to say.
In any case, glycerol (chemically identical to glycerine) contains something like 4.32 calories per gram - so it does have an impact in terms of calculating daily totals. It became all the rage in the low-carb world when it was found to have very little effect on insulin levels.
For our purposes, I'd say glycerol is most useful in terms of its hydrating/dehydrating properties. It holds onto water very well - and may be useful precontest (i.e., immediately before stepping on stage, or, perhaps, simply onto the beach) for drawing out subcutaneous water (in other words, it'll help you look more ripped). Be wary of cramping.