Efficiency: Why and What You Need to Know

Ok, so you already saw the prequel to this post The Yeast Starter. The good news is that the 2000ml yeast starter was sufficient in handling the fermentation associated with this Belgian Dubbel/Trippel Chimay Clone. The funny thing is that on brewday we overshot our OG and ended with a higher gravity than anticipated.

This is due to several factors:

1.) Set my efficiency too low at 75%.

2.) Increased the grain bill to make up for an anticipated lower efficiency at 68%.

3.) Increased Dark Belgian Candi Sugar to make up for an anticipated lower efficiency at 68%.

4.) Boiled hot an heavy and evaporated too much water.

So basically, while this beer is going to be great, it taught me that I still have to determine my efficiency on my system. I'd be happy by all means with an efficiency in the 80 percentile, but would be astonished and dumbfounded if I could get an efficiency in the 90 percentile.

Efficiency is determined by calculating the total grains available for brewday and calculating how many possible fermentables were converted. Evaporation rate also plays a factor in the calculation. Essentially, if I set my evaporation rate at 9% per hour and boil off exactly 9% per hour; and if I have 30 pounds of grains and extract all the possible sugars from these grains, then I have 100% efficiency. It raises a good question that I'd like to know the answer for. What are commercial brewery efficiencies like? I'd be willing to bet they get 85-94% efficiency (possibly more), while homebrewers get anywhere from 60-90% efficiency, depending on the setup and equipment used.

I thought my efficiency would be determined over the last 5 batches, but the factors keep changing batch after batch. Number one being, I brew something different and a different quantity every time. I will do a dry run with evaporation rate. I will transfer water to the boil kettle at 150F as that is a safe mash temp and begin to boil. The second the first bubbly boil rises I will record how many turns my propane regulator is open and determine my true boil off at 60 minutes and 90 minutes being that these are the two most common boil times. This will assist me in my entire 'brewhouse efficiency.' Then I will do a cheap 1 gallon batch of just 2-row pale malt to see what my yield is, by calculating the mash/sparge process to my preboil gravity. This will determine my mash efficiency.

By default, Beersmith (the software I use to handle all my brewing calculations) is set at a 75% efficiency. Therefore, the grain bill, water quantities, etc is assuming a 75% efficiency. If I undershoot that 75% efficiency, then I have a beer with lower alcohol content than intended. Yep, that would be very disappointing. However, If I overshot the default 75% efficiency, then I would have a stronger beer. While that doesn't seem bad at all, it has its consequences. It actually tells me that I depending more on chance than pure science. Proper note taking allows one to make the same beer over and over again, just the way that one Budweiser batch after the other taste exactly the same. If you have various factors on different brewdays, its harder to replicate that. The more you control, the better off you are. The more you leave up to chance, the more risk you ensue.

So, let's take a look at what happened to me on this particular brewday.

We will look at Target Volume, Efficiency into Boiler, and Actual Volume Efficiency.


Brewhouse Efficiency Based on Target Volume

Actual OG: 1.083
Estimated OG: 1.075
Brewhouse Efficiency: 75.00%
Actual Efficiency: 84.56%




Efficiency Into Boiler

Volume into Boiler: 13.27 gallons
Planned Boil Volume: 13.27%
OG into Boiler: 1.067
Estimated OG into Boiler: 1.067
Efficiency into Boiler: 78.09%


Efficiency Into Fermenter

Actual Batch Volume: 9.50 gallons
Planned Volume: 11.50 gallons
Efficiency calculated from Volume: 68.16%


So, after reviewing the above, you will see I overshot OG by overcompensating my grain bill. I hit my OG into the boiler and the 13.27 as planned so I ended up with 78.09% efficiency. That's great. Where I failed is the efficiency into the fermenter because I planned for 11.50 gallons but only ended up with 9.50 so I had a 68.16% efficiency. That means I definately boiled off too much. I had the flame set too high. Once I determine my evaporation rate, it looks like my brewhouse efficiency would be 84.56%. That'll be something to be proud of. I'll send updates once I work on that.

Once I do that, I can set beersmith to calculate everything from grain bill to hop quantities to water needed to everything else at 85% and won't have to adjust anything. Like I said earlier, I assumed a 68% efficiency so I added more grains and more belgian candi sugar, and as a result ended up with an 84.56% efficiency in regards to Alcohol Content but underscored in regards to my final volume at 68.16%. I was supposed to have 11.50 gallons of beer to ferment, but ended up with 9.50 gallons.

Going back to the fact that I need to take good notes correlates with the fact that I am relying on chance. If this beer turns out phenomenal, I'll never be able to duplicate it without some sort of noticeable difference in character and taste, unless by chance I end up with all the same gravities and efficiencies mentioned above.

So now you know what Efficiency is when discussed in the homebrew community. By now, you should have some better understanding of how it affects your brewing process. Essentially, it affects the cost of the beer if you have to buy more grains than what would be needed on a more efficient system. You can utilize less of every ingredient with better efficiency and end up with more beer at the end of the day if you do it right. Needless to say, I am disappointed because I could have/should have had this all determined months ago. I have some work ahead of me and will report back.

Two new discussions in the works: 1.) The Chimay Clone Outcome and 2.) Using pumps and how to prevent wasted time from day 1.

VIDEO LINK: Just a quick shot at the brewing process. At this point, the mash tun (middle keg) is steeping 30 pounds of grains in 8 gallons of water at 149F. The HLT (right keg) is filled with 9 gallons of water and is in the process of being heated to 167F to use for sparging.

http://www.youtube.com/watch?v=MmwlmxfPmZs

Teaser: The Chimay Clone finished fermenting out at 1.008 from 1.083. Subtract 1.008 from 1.083 and multiply by 131 to get ABV. In this case, we're looking at a 9.82% beer. One and buzzed, two and drunk, three and you'll regret it.