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
Table of Contents
I. Introduction……………………………………………………………………...A. Current Process……………………………………………………………...
B. Our Process………………………………………………………………….
II. 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……………………………………………...
III. Results…………………………………………………………………………...
IV. Works Cited…………………………………………………………………….. / 3
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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.
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
Waste Free Brewery
AIChE Student Chapter
Rowan College of Engineering
Revised 10/30/99
Module Outline
Week 1: Fermentation Process (Class Activity)
Week 2: Yeast Filtration using Microfiltration/ Start BOD Testing
Week 3: 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
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.
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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Waste Free Brewery
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:
Figure 2
Flux =
Ksolv = Solvent Permeability
tm = Membrane Thickness
DP = 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.
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.
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: