Originally Posted by BigEd
IBUs are based on the alpha acid bittering compounds in hops.
And the oxidized beta acids, and (at much smaller levels) other compounds.
While other botanicals may provide bittering of some sort I don't think it is going to translate or cross reference to what humulus lupus does to beer.
I agree. IBU estimation is kind of a black art anyway, even when limited to hops that have known, measured levels of alpha/beta acids--heck, most of the formulas used by home brewers to estimate IBUs completely ignore beta acids even though those are certainly part of true measured IBUs.
Even measured IBUs don't capture anywhere near all bittering compounds, and I'd expect that most botanicals that provide bittering aren't contributing true IBUs even when they are providing a similar impact on flavor.
On deck: Little Bo Pils, Bretta Off Dead (Brett pale)
Secondary: Oude Bruin, Red Sky at Morning (Sour brown ale)
On tap: Saison Duphunk (sour), Amarillo Slim (IPA), Earl White (ginger/bergamot wit)
Bottled: Number 8 (Belgian Strong Dark Ale), Eternale (Barleywine), Ancho Villa (Ancho/pasilla/chocolate/cinnamon RIS), Oak smoked porter (1/2 maple bourbon oaked, 1/2 apple brandy oaked)