Design of Scalable Biogas Digester for the Developing World
By: Tiffany Cheng, Thomas DavisDawn Schmidt, Kyle Schroeder, Andrew Wu
BME 2721/21/10
Advisors:Dr. Dave Owens – Owen Graduate School of Management Dr. Paul King – Vanderbilt University School of Engineering
Meet the Rezas• 6 members
– Two parents, four children• 1 cow• Make $60 per month• Spend $10 on petroleum fuel per
month• Spend 2 weeks per year collecting
additional fuel• Interested in neighbor’s biogas
digester• To improve their standard of living
1kg manure 360L of biogas (~enough to cook for 1 person for 1 day)
(Saubolle & Bachmann, 1983)
What is a BioGas Digester?
Neighbor’s Digester
• Cost $200• Expensive materials• Hard to install• Requires specialist
Design Criteria:
• Costs $80 or less• Produces 2800 liters of biogas/day
– 15,000 Kcal– Cooks for 6 people
• Lasts at least 5 years• Easy to install
Design Method
Design Method
Biogas Digesters Worldwide
http://www.snisd.org.cn/images/05126b.JPGhttp://www.water-technology.net/projects/reading_sewage/images/Island-Road-2.jpg
Floating Drum Egg Shaped
http://www.saintsfarm.org/photos/biogas_digester_2_large.jpg http://www.inforse.dk/asia/images/M_III_biogas3.jpg
Plastic Bag Fixed Dome
Our Full-Scale Designs
Brick Design• Masonry and cement• Readily available materials• Requires sealant
Plastic Design• Polyethylene• Easier to install• Mass producible
http://www.journeytoforever.org/biofuel_library/methane_nepal.html
Selection Matrix:Material for Digester
Testing Prototypes
Testing the effects of:• Stirring• Heating by compost• Changing material type
– Brick– Plastic
10.1u (add 0.1u)
10.2u (add 0.1u)
3.5uV = 151.37u3
V = 825u3
Dome
Wall
Floor
Brick Prototype
10.1u (add 0.1u)
10.2u (add 0.1u)
1.5uV = 151.64u3
V = 825u3
4.2u
Plastic Prototype (Bucket)
Future Work Timeline
• Talk to technicians and receive feedback from Bangladesh (Pricing) – Jan 21-Jan 28
• Determine thickness of plastic– Jan 29-Feb 4
• Obtain materials and site location– Jan 29- Feb 4
• Detail design of prototypes– Feb 5-Feb 11
Cont.
• Build prototypes for testing– Feb 12-Feb 18
• Begin digestion– Feb 19- March 4
• Detail the design of full scale digester– Feb 19-March 4
• Obtain experimental data– Feb 19-March 4
Additional Citations
• Saubolle, B., & Bachmann, A. (1983). Fuel Gas from Cowdung. Kathmandu: Sahayogi Press.
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