Cordova Biogas Digester
Science Fair Project by Ben Americus and Adam Zamudio
Abstract
Energy costs in rural Alaska are skyrocketing. We aim to reuse our food scraps as a resource to augment the use of propane to for heating and cooking. Right now digesters are used around the world, but contain warm loving mesophile bacteria that do not produce methane in colder climates that are found around Alaska. Psychrophilic bacteria that is found at the bottom of lakes all around Alaska and the northern areas of the world, is able to produce methane at cooler temperatures, but has not been tested before biogas digesters. We have found that to come to a conclusion about the effectiveness this bacterium, stable conditions for methane productions are required. If we are able to come to a conclusion about the use of these bacteria for biogas digesters, we may be able to make a serious difference on fuel costs around the world.
Background Information
Mesophiles found in warmer areas of the world, and used in traditional biogas digesters do not produce methane in colder climates.
Mesophiles-Warm area bacteria found in cows stomachs
Psychrophiles-cold Area bacteria found in Alaskan lake mud
Problem
Traditional (mesophile) biogas digesters don’t work in cold climates.
Question
Will cold loving Alaskan bacteria produce methane effectively in a traditional biogas digester?
Our Hypothesis
Phsycophiles will continue to produce methane inside a contained digestor system like they do at the bottom of a lake. This will extend the useable range of methane digestors to cold areas.
Control
One Mesophile digester kept in the warm 25 Celsius room acts as a control for the project as well as information provided by warm area projects around the world.
These Are the Supplies you need to make your very own Methane Digestor
-x1 40ft shipping container
-x18 1000 liter IBC plastic containers
-x18 pallets for digester support
-x3 five gallon containers of organic beet juice deicer
-x6 antifreeze/water pump systems
-Various sizes of PVC pipe, pipe fittings, and valves
-Sufficient lumbar to build partition and stack system for outside digestors
-Sufficient two inch foam insulation to cover all digesters and inside walls of shipping container.
Feeding and Food Processing
-x1 standard food processor
-x6 two liter plastic pitchers
-x2 garbage can for food collection and processing
-x10 five gallon buckets used for effluent collection and food scrap transportation
-x2 funnels
-x2 scales with measurements in kilograms
Data collection
-x6 paper notebooks
-x6 500ml beakers
-x6 flow meters
-x6 packets of litmus paper
-x1 dissolved oxygen test kit
-x6 multi-sensor thermometers
-x1 sample vial for each feeding day.
Setup for Methane Digestors
1. Place 40ft long shipping container in area with easy access
2. Insulate interior of shipping container with two inch insulation
3. Lay down inner pallets and place six plastic containers in groups of three
4. Fill plastic containers with various combinations of mud and manure with equal total volumes in each container
5. Build wooden partition halfway through container with access door
6. Cover exterior of digester with two-inch insulation with holes for effluent valve, feeding pipe, and methane expulsion valve.
7. Drill six half-inch holes through wall of shipping container.
8. Attach fittings for feeding, and effluent and methane collection to tanks
9. Set down six pallets on ground outside of shipping container that reflect positions of digesters inside of container
10. Place six plastic containers on pallets
11. Construct support system and place pallets on top of outside containers
12. Place remaining six plastic containers on top of higher pallets
13. Fill lower six containers with mixture of 2.5 gallons of beet juice and sufficient amount of water to fill 1000 liter tanks
14. Attach fluid pumping systems to stacks of outside containers.
15. Feed methane expulsion hoses through holes in wall of shipping container and attach to bottom outside plastic containers
Setup for Food Processing Station
1. Cut off top upper half of garbage can and cut hole at wide enough for food processor
2. Insert food processor to bottom of cut off garbage can
3. Attach food processor system to table with clearance off of ground for five gallon bucket
4. Place bucket under processing system for food slurry collection
Tri-weekly Data Collection
1. Use litmus paper to take ph measurements of effluent from each digester.
2. Test dissolved oxygen and oxidation reduction with electronic sensors
3. Record temperatures for each digester and room temperature.
Food Processing
1. Collect only waste food in plastic garbage bin
2. Separate six kilograms of food scraps into separate five-gallon bucket using scale to weigh food.
3. Fill separate five gallon bucket with six liters of water (six kilograms)
4. Add food to processor and begin grinding of food.
5. Add six liters of water into food while it is being ground.
6. Collect slurry of food and turn off food processor
7. Separate bucket of food slurry into six, two liter pitchers using multi-funnel system
8. Collect sub-sample of food slurry
9. Move six pitchers into shipping container.
Feeding
1. Close methane expulsion valve
2. Record Weight and volume of pitcher for each biogas digestor
3. Remove cap of feeding pipe and begin feeding of digestor with funnel
4. Open up effluent release valve and collect effluent in 500ml beakers
5. Record amount of effluent collected
6. Reopen methane expulsion valve for digestor
7. Repeat process until all digesteors are fed one pitcher and effluent is collected.
Our Observation
One of the first things we noticed on this project was the clogging of food during feeding. This may be caused by the viscosity of the food by the stratification of the food as it sits. Later in this project we noticed negative numbers on the flow meters attached to the digesters. We hypothesized that this air entering the digesters from outside may interfere with the ideal vacuum-like qualities required for food to be dragged down and turned into effluent.
Our Fix: This problem may be fixed by shutting off the methane release valve and blocking the flow of methane and air as the digesters are fed. During feeding, approximately two liters of food slurry are added to a closed system. When an equal volume of effluent is removed the system will work to achive equilibreum, and pull the food down the feeding tube.
The underlying observation we came to since the beginning of this project is that it is difficult to control the conditions of the digesters. This has led to troubles in the feeding process and overly acidic levels inside the digesters. The PH has been steadily dropping inhibiting the production of methane in some digestors.
Our Fix: By injecting a combination of baking soda and water into the digesters using a syringe-like device, we have attempted to lower the PH in the digesters creating better methane production conditions. Further data will be needed to reveal the effectiveness of this procedure.
So far the entire gas collection system has not worked for our project. This is caused by the cold temperatures that freeze the lower liquid filled tanks. During the spring and summer this aspect of the design can be fairly tested.
Our Fix: During the winter months we can add a larger amount of antifreeze to these tanks so they can operate year-round.
The 7th Digester
The six digesters in the container are held to rigorous scientific standards, with controlled amounts of feeding and the same design. A seventh digester was built using a different design more commonly used around the world. This separate smaller digester is not held to the same scientific standards that the other six are, but has been able to produce methane effectively since its creation. It does not require manual effluent release and better blocks outside air from entering the anaerobic conditions. This has led the Cordova Science Club to believe that the design used in this separate digester using the traditional design may be easier to implement and operate in household use than the design used in the six digesters in the container.
Our Conclusion
Because of unforeseen occurrences (the change in PH, the introduction of outside air through the flow meters, and the temperature influence on the gas collection system) we have not been able to assess the comparative effectiveness of psychrophilic, cold loving bacteria, versus mesophilic, warm loving bacteria, on biogas digesters in cold climates. We are currently taking steps to stabilize the PH of the digesters at seven, and reduce the introduction of outside air into the digesters.
FAQs
Q: What is Biogas?
A: Biogas is a flammable gas created by the bacterial breakdown of organic material. Biogas = 60% methane + 35% carbon dioxide + 5% other gases.
Q: Why test the methane digesters in Cordova, Alaska?
A: traditional biogas digesters used in warmer areas of the world contain mesophile bacteria. Our project uses variations of warm area mesophiles, and cold area psychrophiles that have not yet been tested for contained methane production. In Cordova there is the right connections within the community to support a project like this.
Q: Are their any experts working on this project that have worked with methane digesters in the past?
A: This project was overseen partly by T.H. Culhane, founder of solar cities a non-profit organization that has built systems like this in Egypt, Germany, and inner city LA. He is the inventor of the methane collection system that we will eventually come into play with our project.
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