Waste Free Brewery
Pollution, whether it is water, air or noise pollution, has always been the drawback of many
large and profitable industries. With an increase in environmental awareness and strict EPA
regulations, the drive for improved technologies is becoming greater. The brewing industry, once
thought to be harmless, is also considered a risk to our environment. Breweries have a high BOD
(Biochemical Oxygen Demand) level in their effluent streams. The cause of this is the use of yeast
in the fermentation process. The Rowan University student chapter AIChE has sought out an
economical and efficient way of dealing with this problem. By using microfiltration, yeast can be
separated from the beer allowing the yeast to be recycled in the process or sold for alternative usage.
The bench-scale model of the brewery process allows the student to understand the reaction taking
place during fermentation, separation using size distribution, and a look at BOD testing and the
environmental concerns it presents. The student can also view the economics of this separation, the
loss of raw material will be minimized and the cost of high BOD levels due to water treatment
charges decrease.
Rowan University
Team Members:
Brian Dericks
William Cardone
Jason Russell
Daniel Sweeney
Brad Tyers
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Table of Contents
I.
II.
III.
IV.
Introduction……………………………………………………………………...
A. Current Process……………………………………………………………...
B. Our Process………………………………………………………………….
Laboratory Experiment………………………………………………………….
A. Fermentation Process………………………………………………………..
1. Objectives…………………………………………………………….
2. Theory………………………………………………………………..
3. Equipment……………………………………………………………
4. Experimental Procedure…………………………………….………..
B. Yeast Filtration………………………………………………………………
1. Objectives…………………………………………………………….
2. Theory………………………………………………………………..
3. Equipment……………………………………………………………
4. Experimental Procedure……………………………………………...
C. Biochemical Oxygen Demand (BOD) Test………………………………….
1. Objectives…………………………………………………………….
2. Theory………………………………………………………………..
3. Equipment……………………………………………………………
4. Experimental Procedure……………………………………………...
Results…………………………………………………………………………...
Works Cited……………………………………………………………………..
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3
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4-10
4-6
4
4-5
6
6
7-8
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8
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9-10
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9
10
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11-13
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Introduction
The goal of the experiment is to show students how environmental improvement may be
applied to processes in today's field of chemical engineering. This is the case with breweries
throughout the world. In the brewing process, many effluents are released that contain yeast, which
increase the BOD (Biochemical Oxygen Demand) level. Our experiment is designed to replicate the
brewing process and extract the yeast to be recycled or sold for alternative use. This will drastically
reduce the BOD level and save money for the brewery. The following is a comparison between the
current process of recycling yeast and ours.
Current Process:
Once fermentation is complete there is a large amount of particulate on the bottom called
trub. The trub consists of three levels: two levels of sludge (low concentration yeast, high
concentration waste) and one level of yeast. In order to reuse the yeast, the sludge is released into
the effluent stream while the yeast is placed in a storage tank. Unfortunately, the sludge contains a
large amount of yeast that is released to the environment.
Beer
Sludge
Yeast
Sludge
Our Process:
The experiment is designed to recycle the yeast used in brewing beer by separating the yeast
from the sludge and the beer. Many of the sludge particles are larger than the yeast cells. This
allows us to filter the sludge out using a 3-5 micron filter. The yeast is then separated from the beer
and sugar using microfiltration. The microfilter allows the beer through the membrane while
concentrating the yeast. In production, the yeast would be put in a storage tank at 40ºF until used
once again for fermentation.
Particle Filter
Microfiltration
Beer
Filtered Beer
Trub
Waste Free Brewery
Concentrated
Yeast
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Waste Free Brewery
AIChE Student Chapter
Rowan College of Engineering
Revised 10/30/99
Module Outline
Week 1:
Week 2:
Week 3:
Fermentation Process (Class Activity)
Yeast Filtration using Microfiltration/ Start BOD Testing
Review BOD results
Fermentation Process
Objectives
1. Reproduce the fermentation process of a brewery.
2. Understand how biochemical reactions take place.
3. Understand the life cycle and growth of yeast.
Theory
“Yeast fungus cells are incredible little creatures that eat, drink, and create waste just like
other organisms. Fortunately, they like to eat and drink the sugars, proteins, and water in the wort,
and the waste they produce is alcohol.” (Janson, 37) This is the process called fermentation, a
bioreaction that allows the yeast cells to form ethanol. The amount of sugar, oxygen, and type of
yeast present determine the strength and flavor. A brewer’s job is to combine the ingredients that
create the perfect environment for the yeast cell to flourish and grow. Fermentation will last from
ten days to several months (depending on the type of beer being brewed). During this time, the
yeast cells will disperse themselves throughout the fermenter converting all the sugar to alcohol and
all of the oxygen to carbon dioxide. The life cycle and growth of the yeast can be shown in four
stages. (See Figure 1)
Figure 1
Yeast Activity Graph
80
70
Sedimentation
60
Anaerobic Cycle
Yeast Count
(millions of cells 50
per milliliter)
During Suspension
40
30
20
10
Aerobic Cycle
0
0
1
2
3
4
5
6
Time (days)
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Pre-aerobic Cycle or Initial Preparation
This is when the cells “wake up” and begin to utilize their environment. Many ale and lager
yeast cells are dried and packaged. When the cells are reintroduced to water, sugar and oxygen, they
need to start preparing themselves for fermentation. The length of time this process takes depends
on how healthy the yeast cells are.
Aerobic Cycle
The yeast cells get fifteen times as much energy from oxygen than sugar. Aerating the wort
is important because it increases the amount of dissolved oxygen therefore allowing the yeast to
create more energy to facilitate growth and reproduction. During this time, no alcohol is made and
the sugars are converted to carbon dioxide and water.
Anaerobic Cycle
Now the yeast is suspended and optimally dispersed throughout the beer. The yeast
continues to grow and multiply during this cycle. Since the oxygen is all gone, ethanol production
begins and carbon dioxide is purged. For every carbon dioxide molecule formed, a molecule of
ethanol is formed. This accounts for the large amount of activity observed during this period.
Sedimentation
At the beginning of sedimentation, yeast growth ceases and flocculation begins. The yeast
activity will slow down gradually and a large amount of sediment will appear on the bottom of the
fermenter. Once sedimentation is finished, the beer will appear relatively clear.
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Equipment Needed
1. 5 gallon glass carboy or 5 gallon painter’s bucket with air tight lid (drill a hole in lid and attach ¼”
tubing)
2. ¼” rubber tubing with rubber stopper
3. 500 mL beaker
4. 6 lb. malt extract
5. 1 package ale yeast
6. 5 gallons of water
Experimental Procedure
1. Safety
1.1. Review the procedure and safety analysis with your instructor.
1.2. Caution! Fermentation is a dangerous process if proper preparation is not addressed. When an
aerobic bioreaction is taking place, carbon dioxide is given off. If the carbon dioxide is not vented
off, the fermenter will increase in pressure and possibly build up more pressure then the fermenter
is designed to handle. To prevent this, a ¼” tube is attached to allow the CO2 to vent.
1.3. Hot fluids will be used in the experiment, wear gloves.
1.4. Eye protection and apron are also advised.
2. Sanitation
2.1. Fill carboy or bucket with warm water and ½ cup bleach. This is done to disinfect the apparatus to
prevent contamination from outside bacteria. Breweries also do this step to prevent off-flavors in
their beer.
2.2. Also sanitize tubing, rubber stopper, and beaker.
2.3. Rinse everything with warm water to be sure there is no residual bleach.
3. Making the wort
3.1. Boil 1-2 gallons of water on a hot plate or stove (if one is available).
3.2. Once the water is boiling, add the malt extract slowly while stirring continuously.
3.3. Allow the wort to boil for at least 20 minutes. This is enough time to allow the starches to form
sugars in the solution. We will not be using hops or any other aroma or flavor ingredients, as they
are not necessary for the experiment.
4. Cooling the wort (Optional)
4.1. If you would like to incorporate heat transfer into the lab, a cooling coil could be used to cool the
wort. This is done by taking a long piece of soft copper tubing (about 10 feet long). Coil it up and
immerse it in the wort. Run cold water through the tubing until the heat from the wort has transfer
to the water.
5. Prepare the fermenter
5.1. While the wort is cooling off, add the remaining water to the carboy or bucket.
5.2. Once the wort is cooled to about 150F, add the wort to the water.
5.3. Mix and agitate the unfermented beer. This done to aerate the beer since oxygen is needed for the
reaction.
5.4. Sprinkle the yeast onto the beer and attach lid or rubber stopper.
5.5. Allow the ¼” tubing to run into the 500 mL beaker filled with water.
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Yeast Filtration
Objectives
1. Understand microfiltration and its driving force.
2. To filter the insoluble particles out of beer without removing the yeast.
3. To concentrate the yeast, by removing it from the beer.
Theory
Microfiltration consists of porous membranes, which
operate like a molecular sieve. The membranes are designed with
a molecular weight cut-off. In Figure 2, we see that small particles
with low molecular weight are able to pass through the membrane,
while large particles (ex. yeast) continue to follow the flow on the
feed side. The driving force that allows the particle to flow
through the porous membrane is the change in pressure. The
pressure on the feed side may range from 10-100 psi, while the
pressure on the permeate side may only be atmospheric. This
change in pressure allows the small particles to make their way to
the permeate side.
The flux through the membrane can be written as:
FEED
PERMEATE
P
Figure 2
Flux =
K
TranferRat e
 solv (P)
TransferArea
tm
Ksolv = Solvent Permeability
tm = Membrane Thickness
P = Change in Pressure
High fluxes are desirable since the transfer area required will be decreased. This means obtaining
and sustaining a high driving force across the membrane. The membrane must be mechanically strong to
withstand these high pressures. Unfortunately, mechanical strength is achieved by increasing the
membrane thickness, which correspondingly lowers the flux. This is why we have chosen a microfilter
made of a strong material such as polypropylene or polytetraflouroethylene. The pressure exerted on the
membrane will depend on the manufacturer’s specification and the pump used specifically for the
membrane.
In our case we are removing the beer from the yeast. Pumping the fermented beer through a
microfiltration system, allowing the small particles (ex. sugars, ethanol, and water) to permeate through
the membrane, does this. The large particles will remain in the solution and be reintroduced into the feed
stream. This cycle will continue until the yeast has been concentrated enough.
FEED
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CONCENTRATE
PERMEATE
(Filtered Beer)
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Equipment Needed
1. Prefilter (3-5 micron) with centrifugal pump
2. Microfilter (0.45 – 0.8) micron polypropylene or polytetraflouroethylene membrane) with pump
3. One gallon container
Experimental Procedure
1. Safety
1.1. Review the procedure and safety analysis with your instructor.
1.2. Eye protection and apron required
1.3. An electrical hazard is present
2. Sanitation
2.1. Be sure the containers are sanitary by cleaning with hot water and soap or a small amount of bleach in
water.
2.2. Rinse everything with warm water to be sure there is no residual bleach or soap.
3. Prepare fermented beer for filtration
3.1. Measure 1 gallon of fermented beer. The beer used for sampling can be decanted from the top without
disturbing the sediment or the sediment can be stirred slowly into solution. The choice depends on the
method of yeast recovery planned.
3.2. Measure ½ gallon sample to be used in the BOD test. Do not filter this sample. This will be used for
comparison before and after filtration.
3.3. If the sediment has been stirred into solution, the large particulate or sludge will need to be removed by
running the sample through a 3-5 micron filter. This will remove the particulate without disturbing the
yeast.
4. Microfilter the beer to concentrate the yeast
4.1. Pour the beer into the container designed to hook up the microfilter. If there is not one available, place
the input and output hoses from the microfiltration system into the beer. Be sure the hoses are both
immersed in the beer to prevent agitation and aeration.
4.2. Turn on the pump.
4.3. Allow the beer to be filtered until the volume of the beer is 10% its original volume.
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Biochemical Oxygen Demand (BOD) Test
Objective
1. To measure the BOD of the yeast concentrate, the filtered beer and the original beer.
2. To understand the cause of BOD and relate the BOD to the concentration of yeast.
3. To understand the environmental problem BOD presents.
Theory
Biochemical Oxygen Demand (BOD) is a measurement of how much and at what rate a
biochemical reaction uses oxygen to oxidize organic matter. The higher the BOD reading, the more
oxygen is being used by the bacteria in the sample. This is the major problem yeast creates in breweries.
They are beneficial to the fermentation process but once they leave the brewery the biochemical reaction
continues. It deprives water of oxygen, which is needed for the plant and animals that live in the ponds
and rivers. There are three different ways that breweries can deal with this problem. They can pay the
high water treatment rates and have the Water Company clean the water; they can kill off the yeast by
pasteurizing the beer and the trub, or use a microfiltration process that will allow the breweries to recycle
the yeast.
To understand if microfiltration is working, we need to measure the BOD. This is done by a using
a BODTrak Instrument. The BOD instrument works by measuring the amount of oxygen consumed. A
measured sample is placed in a sample bottle and the instrument introduces air (21% oxygen) to the bottle.
A stir bar is used to help transfer the oxygen to the sample and the yeast or bacteria uses the oxygen to
oxidize the organic matter within the sample bottles. As the air pressure decreases due to consumption,
the pressure change is converted to mg/L BOD. There are lithium hydroxide crystals present in the bottle,
which remove the carbon dioxide that is produced by the bacteria.
In order to understand how the BOD is affected by the concentration of yeast the following
equation is used:
Rate of BOD formation =
x
Yobs
=
x
Yobs
(Bailey, 939)
x = Concentration of Yeast
 = Maximum Specific Growth Rate
Yobs = Observed Stoichiometry
c = Minimum Cell Age
The following assumptions for beer should be made for ale yeast (Saccharomyces cerevisiae):
Yobs = 0.50 grams of yeast cell / grams of oxygen
 = 2.2 day-1
Waste Free Brewery
(Bailey, 284)
(Nova, 272)
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Equipment
1. BODTrak Instrument
2. Graduated Cylinders (100 mL, 1000mL)
3. Pipet
4. Beer Samples
Procedure
1. Safety
1.1. Review the procedure and safety analysis with your instructor.
1.2. Lithium Hydroxide is a strong alkaline and irritating to the skin and eyes.
1.3. Eye protection, apron, and latex gloves required
1.4. An electrical hazard is present.
2. Sample Preparation
2.1. Using a clean graduated cylinder and pipet, dilute the three samples: 20 parts water to 1 part sample
2.2. Measure 95 mL of each sample and pour in labeled sample bottle.
2.3. Place a 3.8-cm (1-1/2”) magnetic stir bar in each sample bottle.
2.4. Add the contents of one BOD nutrient Buffer Pillow to each bottle for optimum growth.
2.5. Apply stopcock grease to the seal lip of each bottle and to the top of each seal cup.
2.6. Place a seal cup in the neck of each bottle.
2.7. Using a funnel, add the contents of one Lithium Hydroxide Powder Pillow to each seal cup. Do not
allow lithium hydroxide particles to fall into the sample!
3. BODTrak Test Procedure
3.1. Place the bottles on the chassis of the BODTrak. Connect the appropriate tube to the sample bottle and
firmly tighten the cap.
3.2. Place the instrument in the incubator. Start the instrument.
3.3. Make sure all stir bars are rotating. If the stir bar slides to the side of the bottle, lift the bottle off the unit
and gently replace. Do not start the channel until the stir bar is rotating properly.
3.4. Select test duration and range of concentration for each bottle.
3.5. To start a test, press the channel number corresponding to the bottle.
4. BOD Results
4.1. Read the BOD results directly from the BODTrak display by pressing the key corresponding to each
sample.
4.2. Using Microsoft Excel, plot the data and find the rate of BOD formation by using a trend-line. This
information will be used to find the concentration and rate of growth of the yeast.
4.3. Be sure to clean bottles. Use a brush and hot soapy water to clean all bottles, stir bars, and seal cups.
Rinse thoroughly with distilled water.
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Results
When conducting this experiment, the goal should be known. Our goal is to see if the yeast has
been filtered out and how well it has been filtered. This is determined by the BOD results. If the BOD is
high, the concentration of yeast is high. In the filtered beer sample, there should be little to no BOD
present. In the concentrated yeast sample, the BOD should be high.
The experiment focused on two variables: amount of yeast and dilution of sample. The first time
the experiment was conducted, two times the amount of yeast was used. The BOD test results were
inconclusive, in other words “off the charts”. Our beer sample showed little signs of oxygen demand.
The next time we decided to use the correct amount of yeast but also dilute the samples for the BOD test.
After filtration, we diluted the samples 1 to 1, 10 to 1, 20 to 1, and 100 parts water to 1 part sample. We
found that diluting the samples 20 parts water to 1 part sample gave the most consistent results. In each
dilution we still saw the same trend, high BOD in the concentrated yeast, less BOD in the unfiltered beer
and little oxygen demand in the filtered beer. We chose to run the experiment again to see how consistent
our results can be. This time we used the correct amount of yeast, and only diluted the samples 20 to 1.
We received the same results.
Future Experiments:
Unfortunately, the experiment takes a long time to run. This did not allow us much time to receive
numerous data. There are also a few different variables and other approaches to the problem that may
have been made. For example, the volume of the batch being filtered can be changed. Instead of only
filtering one gallons of beer, the entire five gallons of beer can be filtered. We predict that this will
dramatically increase the difference in BOD results from the unfiltered beer and the concentrated yeast.
Another variable is the volume of the fermented batch. You could increase or decrease the volume of beer
being filtered and see how feasible microfiltration is for large-scale or small-scale fermentation. Samples
from a real brewery might create different results also. The variations to this experiment may be
unlimited when you begin to consider the many different strains of yeast that can be used and whether or
not taste of the beer is affected.
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Results for 20 to 1 Dilution
BOD Results
18000
16000
14000
BOD (mg/L)
12000
Initial
10000
Concentrate
8000
Filtered
6000
4000
2000
0
0
0.5
1
1.5
2
2.5
3
3.5
4
Time (days)
Yeast Concentration
1400
Concentration (mg/L)
1200
1000
Concentrate
800
Initial
Filtered
600
400
200
0
0
0.5
1
1.5
2
2.5
3
3.5
4
Time (days)
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Example Results
Fermented Beer
Time
(days)
BOD (mg/L)
Diluted BOD Actual Trendline Fit Concentration of Yeast Cells
BOD
0.5
30
600
1127.18
512.35
1.0
124
2480
4646.50
1056.02
1.5
494
9880
7593.48
1150.53
2.0
580 11600
9968.10
1132.74
2.5
712 14240
11770.38
1070.03
3.0
724 14480
13000.30
984.87
3.5
760 15200
13657.88
886.88
4.0
694 13880
13743.10
780.86
4.5
768 15360
13255.98
669.49
5.0
618 12360
12196.50
554.39
5.5
634 12680
10564.68
436.56
Concentrated Yeast
Time
(days)
BOD (mg/L)
Diluted BOD Actual Trendline Fit Concentration of Yeast Cells
BOD
0.5
18
360
381.78
173.53
1.0
208
4160
4633.10
1052.98
1.5
460
9200
8185.98
1240.30
2.0
476
9520
11040.40
1254.59
2.5
616 12320
13196.38
1199.67
3.0
702 14040
14653.90
1110.14
3.5
680 13600
15412.98
1000.84
4.0
624 12480
15473.60
879.18
4.5
694 13880
14835.78
749.28
5.0
506 10120
13499.50
613.61
5.5
526 10520
11464.78
473.75
6.0
484
9680
8731.60
330.74
Filtered Beer
Time
(days)
BOD (mg/L)
Diluted BOD Actual No Trendline
BOD
0.5
58
116
1.0
34
68
1.5
32
64
2.0
28
56
2.5
76
152
3.0
216
432
3.5
430
860
4.0
532
1064
4.5
720
1440
5.0
574
1148
5.5
620
1240
Waste Free Brewery
Concentration of Yeast Cells
52.73
15.45
9.70
6.36
13.82
32.73
55.84
60.45
72.73
52.18
51.24
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Works Cited
Bailey, and Ollis D. Biochemical Engineering Fundamentals 2nd ed. NewYork: McGraw-Hill, Inc. 1986.
Bamforth, Charles. Tap Into The Art And Science Of Brewing. New York, NY: Plenum Press, 1998.
Janson Ph.D, Lee W. Brew Chem 101. Pownal, Vermont: Storey Publishing, 1996.
Nova, Prokop, and B. Sikyta, eds. Advances in Microbial Engineering. New York, NY: John Wiley and
Sons Inc., 1973.
Papazian, Charlie. The New Complete Joy of Home Brewing. New York, NY: Avon Books, 1991.
Wankat, Philip C. Rate-Controlled Separations. Glasgow, UK: Blackie Academic & Professional, 1996.
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