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ChristinaS1

Reusing spent dry hops for bittering

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I receive Stan Hieronymous' "Hop Queries" in my email in which he shares news of the latest hop research. In the most recent issue he reported on experiments being done on reusing dry hops for bittering. I don't think Stan would mind me copying what he said here on the forum. Interestingly he mentions research by Dr. Tom Shellhammer, whose other research has been discussed in other threads recently:

“An Overview of Sustainability Challenges in Beer Production, and the Carbon Footprint of Hops Production” in the Technical Quarterly should be required reading for every brewery operator. The paper by Dean Hauser and Tom Shellhammer at Oregon State University examines CO2 emissions that result from hop production, the main sources being agricultural machinery, irrigation, fertilizer, soil, pesticides and kilning. Traditional literature reports the impact of hops are negligible compared to barley, because the world’s largest breweries often use less than 1 gram of hops per liter in producing their most popular brands. Craft brewers, on the other hand, add between 6 and 7 grams per liter, on average. They may use more than 25 grams per liter in highly hopped beers.  
 
Hauser previously conducted research that revealed just how much punch is left in dry hops after brewers are done with them (Hop Queries Vol. 2, No. 10). When I asked him about this, he replied, “The reuse of spent hops in particular could provide smaller-scale brewers (who often use more energy and water to produce their product) with a way to mitigate their impact, while at the same time providing a novel, potentially more sustainable product that may differentiate them in a rather saturated market.” 
 
He followed that first study with additional research reported in Brewing Science (subscription required). In this experiment, utilization was higher for spent dry hops than pelletized hops. “From a sensory perspective, although the spent dry-hop bittered beers were significantly more bitter, no consumer preference was found in terms of aroma, overall, or bitterness liking between the two sets of beers.”
 
His paper acknowledged the challenges of reuse on a larger scale. However, on a smaller scale there is this.
 
Reusing hops II: A case study
For Josh Chapman at Black Narrows Brewing in Chincoteague Island, Virginia, Hauser’s initial research was a “light bulb moment.” Black Narrows has a five-barrel brewing system, and he is constantly aware of how much more proportionally he spends on hops because he buys in small quantities. In addition, “not getting the most out of our ingredients is wasteful both in practice and ethos.”
 
What resulted was a beer he calls Cruisin’ the J. Chincoteague is a small island, covering only seven square miles, and the story goes that back in day for Friday night fun locals would meet at the town marina, drive down Main Street, hang a right at Beach Road, take it to a roundabout, then head back to the town marina. The route loosely resembled a J, and a tradition called “cruisin’ the J” was born. Chapman figured a low ABV beer seemed perfect for a Friday night on the town.
 
He outlined the process he uses, and the thinking behind it, in an email. I’ve left it in “brewer code” – something I would never do in a blog post or print – because I figure subscribers speak the same language.
 
* Did some back of napkin brewing theory jotting and everything seemed to point to the following: If beer transferred from FV to brite is clean, and then from brite to keg is clean, and then from keg to draft/can is clean, then what’s in the FV should be “clean” as far as ingredient integrity is concerned. Add to that the fact that if contamination/quality degradation were present it’d show most often in the yeast, which I cone to cone pitch. It stood to reason that those dry hops were ripe for stripping more aroma/oils from.  
 
* Figured I’d start with something mixed-ferm/brett so the margin for error was less re finished beer. We do a mosaic dry-hopped mixed culture saison w/ sacch and three brett strains. First run takes about three-ish months, with one month on dry hops at .5#/bbl [note: that’s about 2 grams per liter]. On transfer day, I brewed the same wort, and knocked out directly into the tank on the spent hops/yeast combo. Within two weeks I’d say we had roughly 85%-90% the same beer as the first iteration that took three months. With the amount of trub/hops/yeast/beer I left in the FV, I missed my target OG by about 4 points, because I didn’t take into account that on the hot side that I’d basically be diluting the wort.
 
* The second hop runnings saison took about a month and ended up needing a dry hopping of .2#/bbl touch up to meet the aromatic/flavor profile of the first beer. Fantastic proof of concept brew and helped dial in how we’d handle the concept from there on.
 
* Recognizing that both hop and wort targets would be slightly lowered due to both the roughly 30% initial dry hop utilization and the spent beer/yeast in the tank, it made the most sense to take our most hop-forward IPA and brew a pale or session on the seconds.
 
* Four Mouths (our house IPA) is a combo of 2:1 Mosaic/El Dorado to Hallertau Blanc/Callista. 1#/bbl at whirlpool, then 3.5#/bbl at dry hop. 90/10 English Pale Malt (Murphy & Rude Malthouse, VA)/Flaked Oats. English Ale yeast, roughly 1.056 OG, 6.8% ABV beer.
 
* On transfer day, knocked out a target 1.042 OG wort, 1#/bbl whirlpool hops (Blanc) into the spent Four Mouths tank. OG became 1.038 after knockout (anticipated per the saison test). Didn't dry hop at all, and post racking/carb beer had a wonderfully aromatic, soft bitterness. A very cohesive 4.65% pale ale. I didn't call it a session IPA, because it wasn’t hop forward enough in my opinion to qualify.
 
* It was the fastest selling beer we’ve ever had. I think the combo of enticing aromatics and ease of drinkability make it incredibly accessible. We’re at the point now where whenever we brew Four Mouths, we know that on racking day we’re brewing Cruisin’ right on top of it, and you’d be stunned by how many folks are always asking when Cruisin’ is coming back, because it’s beating the IPA off the taps."

So, has anyone on the forum tried reusing spent dry hops to bitter their next brew? 

Cheers,

Christina.
 

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9 hours ago, ChristinaS1 said:

So, has anyone on the forum tried reusing spent dry hops to bitter their next brew? 

No i haven't.

I guess in a commercial brewery it makes sense from a financial perspective.

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I'd heard of this idea before but as I homebrewer I wasn't sure how the IBU would be accurately determined in a subsequent brew?  I assumed you'd just punch in the weight of the dry-hop pulp used from the previous batch and calculate as per usual?   But if it was say a dry-hop combo, accounting for the different AA% ratio in the dry hop pulp could get tricky.  I guess you'd have to give it a good mix to make sure there was an even distribution...        

Edited by BlackSands

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Very interesting.  I have often thought how much nicer my garbage bin smells when I have chucked the spent dry hops into it.  It seems such a waste.  I guess if there are remnant goodness in the hops it makes sense that you could get something out of them.  Something like the second brew as described in the article.

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8 minutes ago, Shamus O'Sean said:

 I guess if there are remnant goodness in the hops it makes sense that you could get something out of them.  

Well, theoretically, because the hops haven't actually been boiled the alpha acids should still be largely intact so from a bittering point of view they would presumably still be similar to virgin hops.  

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I thought there were some breweries in the US already doing this. With the amount of dry hops that was going into these IPAs and the likes they would take them out of the bags or what ever they used to contain them while dry hopping, then dry them and bang them in the next brew for the bittering run. It was looking to be quite a savings for them even when involving the process of having to re-dry and store accordingly. And the best part was there was no negative effect on the quality of the beer.

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@Bladeca Re-dry the hops? Where did you read that?....Freezing them sounds more hygienic.

@BlackSands The guy from Black Narrows Brewing estimated about a 30% loss from the initial dry hop utilization. They only added a whirlpool addition to the second / session brew. 

Cheers,

Christina

Edited by ChristinaS1
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@ChristinaS1 It was a while ago that I came across the article and it wasn't overly detailed. Didn't give the process of drying or what ever they did other than saying something to the effect of they collect the dry hops and process it to not store it wet. This was the excess that wasn't going to be used immediately.

I don't even recall where I saw the article, it most likely was a feed on my phone on things some of the commercial brewers were doing. It was only a benefit to those using a lot of hops in their beers. Not something of any use for the home brewer as the quantities we use to give the bitterness charge is not worth the effort if we aren't doing a brew as we pull the dry hops out of the fermenter.

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