I ask hundreds of why? questions every day and most don’t stick around for long. But last month I had one that stuck. The question was:
‘Why do brewers import bittering hops?’
The UK breweries I have worked in have used various hop varieties as our core bittering hops. German, UK and US hops.
Why do we buy the bittering hops we choose? How significant is the impact on overall flavour? What is their contribution to your breweries carbon footprint?
Let's find out.
I would like to create another metric to help brewers decide which bittering hop to chose. I have a concept to do this by creating a kg of CO2e per % of alpha for the ‘traditional’ bittering hops from the top 3 markets, US, German & UK.
So the plan is to:
1. Identify decision factors in bittering hop selection
4. Conclusions
1. Identify decision factors in bittering hop selection
Alpha Acids
The importance of the alpha acid isomerisation in brewing has been widely documented and is well understood. Naturally the alpha acid content (%) is therefore the essential driver on bittering hop choice – even though we on average only isomerise 30% of the available alpha acids.
Most ‘macro’ or larger craft breweries buy their bittering hops on kilos of alpha rather than kilos of hops @ a specific alpha. It’s absolutely logical. Unlike aroma hops you for bittering you are likely exclusively looking at the alpha acid, so why buy on a static kg value with a fluctuating alpha acid % every year when it’s actually the alpha acid content you are using? Why should you, the purchasers see the damage of a lower alpha yield year? Instead, you should buy on the premise of kilos of alpha.
Price
Of course, price is next in line. The price of hops varies widely brewery to brewery on a bunch of factors:
Economies of Scale
Hop Variety Preference
Storage capabilities
Relationship with supplier
Geographical Location
Considering those variables I don't see the need to discuss the price of hops as a decision maker in this article.
Age of Hops
Another great decision factor is age of hops – or more accurately age of hops vs storage conditions. Alpha acids are the most susceptible to degradation in poor storage conditions. Luckily there is the ‘Hop Storage Index’ (HSI) that helps you understand this effect. Further reading on this is supplied below. Whenever your changing years/suppliers of bittering hops its essential you measure your wort IBU’s (either internally or externally).
What else matters?
Beta Acids? Co-humulone?
There is some historic belief that the Cohumulone level play an important role in the presentation of bitterness to the palate. The origins came from a 1950’s study by Lloyd Rigby and is even acknowledged in the ICONIC ‘Technology Brewing and Malting’ by Wolfgang Kunze but this belief has widely been disregarded.
Beta-Acids also pop up in conversations. They are not soluble nor can they be isomerised so directly do not contribute. However, they do oxidise in storage and can impart bitterness, but for the sake of this article they will be ignored.
This is 100% my opinion but ultimately if you’re producing and style of beer where the dry hop rate is between 4+ grams p/l your concerns over cohumulone and beta acids effects on the presentation of bitterness are pretty much irrelevant.
From my experience where you add your bittering hops do play an important role in the presentation of bitterness (first wort hopping). But again, this importance is negatively correlated with the amount of dry hops you are adding.
2. Assess current top global options that fit these factors
United States
Columbus, Tomahawk and Zeus are all similar bittering hops grown in America. So similar they are often grouped and sold together under the acronym CTZ. Alpha Acid % Ranges from 15-17.5%.
Germany
Magnum and Herkules are the popular bittering hops. Magnum ranges from 10-14%. And Herkules ranges from 16-17.5% . So you can see why they have been replacing magnum with herkules in Germany for some time.
UK
Admiral is the primo bittering hop in the UK. 12-18% alpha can be achieved.
Will Rodgers of Charles Faram gave this comment when he kindly replied to my messages asking for him for historical statistics on UK bittering varieties, it’s a slight sidetrack but super interesting:
“There are still newer varieties in development which should produce consistently 14-18% Alpha and correspondingly high Beta and Oil contents. The issue with breeding for high alpha is that currently the gene/s for high alpha are closely linked to the gene/s for powdery mildew susceptibility. In the UK this is a major problem with our maritime climate as Powdery mildew loves our climate.
The varieties we have are growable, but if you were to try to grow Herkules or some of the US high alpha varieties (CTZs etc) whilst we would achieve higher alphas, we would lose crops regularly to Powdery mildew, we would also risk other varieties less susceptible and risk selecting a new super strain of Powdery mildew!” Will Rodgers of Charles FaramSo here’s the start of the table we will continue to add to during the article.
Name of Hop | Country of Origin | Alpha Acid % (avg) |
CTZ | USA | 16% |
Magnum | Germany | 12% |
Herkules | Germnay | 15% |
Admiral | UK | 15% |
*values taken from YCH, Barth Haas & Charles Faram respectively
Word Count Saving Honourable Mentions
Nugget (US), Northern Brewer (Germany), Target (UK)
Is high alpha the best?
Naturally the answer is yes, but if you’re looking for 20-35 IBUs and adding sizable grams p/l in the Whirlpool for flavour and aroma you leave little room for IBU contribution from your bittering hops. So you could end up leaving a <0.1 grams p/l of bittering addition which can lead to boil overs (wort kettle design pending) and a different bitterness perception. We will continue assuming high alpha IS best, but it’s good to assess if that is right for your brewery.
3. kg of CO2e per kg of hop by country of origin
What is kg CO2e?
How do you quantify and compare global warming potential of activities with a standard unit of measurement? Kilos of CO2 equivalent is the answer.
Every Green House Gas (GHG) is expressed as kg of CO2e by multiplying the amount of the specific GHG by its Global Warming Potential. See chart from Ecometrica below
The common example is 1kg of Methane has 25kg of CO2e.
kg of CO2e per kg of hops
As you can totally imagine, measuring and calculating a kg of CO2e value per kg for hops is an absolute monster task. Let alone to then calculate that by variety. Hop farmers/merchants/cooperatives are working very well to get these figures and some do exist. These are the most reliable figures available.
UK Hops 4kg CO2e per kg of hops *Carbon Cloud
Germany 3.2kg CO2e per kg of hops *Barth Haas
US 3.5kg CO2e per kg of hops *Yakima Chief Hops
*It’s important to emphasise these are estimates rather than truths and we need to treat this as initial investigations. Furthermore, all of these figures are for whole cone, so for the purpose of this we will have assume an equal kg co2e contribution for pelletising across all countries. As better data becomes available, I will revisit this topic and perhaps portray a more accurate reality. Nonetheless.
Fertilisers/pesticides, energy for drying/cooling & farming equipment are the biggest contribution factors to a hop growers carbon footprint.
And it looks like UK’s CO2e is the highest which I speculate is down to yields (the aforementioned powdery mildew issues), infrastructure and technology being generally inferior to the German and US farmers.
Import kg of CO2e
But when considering the total kg CO2e of hops we must account for the importing transport, hops will need to be transported in a refrigerated container (lovingly called reefer containers) and if you’re purchasing in the UK this could be travelling some pretty serious distance. So let's look at the transport kg of CO2e.
We will have to make some more assumptions, but I think these are fair. We will assume:
The brewery is based in the UK and requires no transport as we are only evaluating importing (not the domestic route travels).
A full 20ft container holds 10000kg of t90 pellets
A travel route that comes up as most popular on this site www.routescanner.com
A reefer container uses between 15-35% more CO2e than its ambient compadre (I will take the middle value of 25%) (Chat GPT)
Reefer shipping companies were approached, all declined to respond.
The Route Scanner quotes look like this
Yakima to London – 1942 kg CO2e/TEU
Germany to London – 370 kg CO2e/TEU
*TEU = Twenty Foot Container Equivalent Unit
Lets increase the numbers by 25% (to account for the reefer container) Divide it by the amount of that can fit into a 20ft Container 10000kg and add that into the table.
Name of Hop | Country of Origin | kg of CO2e per kg of hops | kg of CO2e per kg of hops transported | Total kg CO2e | Alpha % | kg CO2e per alpha % |
CTZ | USA | 3.5 | 0.25 | 3.75 | 16% | 0.23 |
Magnum | Germany | 3.2 | 0.046 | 3.25 | 12% | 0.27 |
Herkules | Germany | 3.2 | 0.046 | 3.25 | 15% | 0.22 |
Admiral | UK | 4 | 0 | 4 | 15% | 0.27 |
Super interesting to see the fairly insignificant contribution to the overall kg of CO2e per kg of hops transport has, even if the journey is long and cold.
As discussed at the start we should be buying in kilos of alpha rather than kilos of hops, therefore I created a 'kg of CO2e per 1% of alpha' column to compare the varieties.
If the alpha was to change then obviously this would largely impact this table and my decision making also. It could be a good take-away not to handcuff yourself to a variety of bittering hop. Instead look for the most favourable alpha%/price/CO2e ratio on the market.
4. Assessment of the environmental impact of bittering hops
I set out to discover why brewers import bittering hops as there could be an negative environmental impact in doing so. What I have actually discovered is that the country of origin goes some way in negating the transport impact. However, due to the difficulty in measuring the kg CO2e per kg of hops value for their respective country of origin and the scarcity of independent data on this matter I cannot definitively answer the question.
On a personal level, I felt this excersise quite eye-opening. It's partly engrained in our minds that transport is the devil of sustainability when in fact more often its the production of the good that is being transported that is creating a greater negative impact. Of course, this is not to say ignore transport reductions (especially as it is what we as the consumer have the biggest control over) but perhaps we should be challenging suppliers more to reduce their impact as much as we challenge ourselves.
Much love all!
Chris
Special Thanks To:
Will Rodgers - Charles Faram
Jack Teagle - Yakima Chief Hops
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