Waste of hops.

"Here, Stringers", said the Professor, "You'll be interested in this."

He waved at the far wall of his workroom, currently the target of the blinding glare of his triple laser digital projector.

"Say again, Professor?", It was rather difficult to hear over the whine and whirr of the motors which whirled the mirrors of the projector.

"Ah, yes, sorry about that", He threw a knifeswitch, and as the mirrors slowed and stopped, and our eyes readjusted to normal illumination, we could see that  he was holding out some papers.

"Yes", he continued, "I printed this out for you. It's a jolly interesting presentation on dry-hopping."

"So, here's someone who's actually done some measurements on what you get out of your hops in a model dry-hopping procedure. It's most educational. Now, Stringers, what sort of efficiency of extraction would you expect to be getting?"

We weren't quite sure what the Prof meant, and said so.

"Well", he continued, slowly, "If you were adding 10 kilos of smelly hops into a tank, how smelly would your beer end up?"

We supposed that would depend on how much smelly stuff from the hops got into the beer.

"Precisely!", said the Professor, "What percentage of the smelly chemicals added via the hops will be found in the finished beer."

He went on, "Of course, this will depend to a large extent on the solubility of the compound in water - beer's mainly water - as well as the detail of how the hop material is dispersed in the beer. So it's no surprise to see that, according to this piece of work, linalool is extracted with around 100% efficiency. It's an alcohol after all, with a reasonable solubility in water. Whereas other important smelly chemicals, myrcene for instance, are pretty much insoluble in water, so you'll not be surprised to see that less than 1% of what you put in makes it into the finished beer. The same thing seems to hold for caryophyllene, and humulene."

We were unsure, "But Prof, if we don't get much of these things out of dry-hopping, but we all love the  dry-hopped beers, surely it's because we don't miss them?"

The Prof nodded, "For sure Stringers, these poorly extracted chemicals have some much more soluble relatives, either naturally occurring in the hop, or produced in the brewing process, or as a result of yeast metabolism. But it seems to me that if you want, say, myrcene, in your beer, dry-hopping is a terribly inefficient way of going about it.

"And with hops the price they are, to say nothing of the environmental impacts of growing and transporting them, I wonder if it's something you should be giving more thought to?"