Healthy Regenerative Lifestyle
Anaerobic digesters breakdown organic materials into fertilizer and methane gas. In its simplest form, a digester can help with breaking down the waste around the yard or farm and produce a rich fertilizer. This can be done with a 55-gal drum and a bicycle inner tube.
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Anaerobic Methane Digester
by David Proctor
November 30, 2017
Urban Farm Lifestyle Magazine Published Weekly
One of the first digesters I read about was in Mother Earth News, it was made from a 55-gallon drum with another drum inverted into it. A loose seal was made by putting a bicycle tire innertube around the inverted drum and then pumped up to close the gap between the two drums. As the waste material would decompose, the inverted drum would fill with gas.
The inverted drum would need to have as much air removed as possible. This was done by have a siphoning valve on top of the drum to bleed the gas off. Methane gas would later be routed into a storage container. The gas pressure can be seen by the expansion or movement of water through a manometer. The manometer is placed on the storage container or on top of the digester.
A manometer is a piece of glass tubing that is bent in a “U” shape. The tube is then place in another sealed hole on top of the inverted drum. With water inside the glass tube, the water will move as the gas pressure increases. If the pressure becomes too great, the water will come out the end and vent the digester.
One of the things I learned when I built my first methane digester was that temperature is critical. I was taking chemistry in college when I came up with the idea of producing methane gas as an extra credit project over Christmas break.
I made my manometer in lab class. I used a two hole rubber plug that I inserted the manometer into with the help of glycerin to lubricate the glass. I then inserted another glass tube into the two-hole plug, this tube would be attached to my digester.
When I made it home on Christmas break, I went with my dad out to a dairy farm. The farmer was more than happy for me to shovel up some fresh cow manure. This was placed in a sealed container.
A milk dispenser bag that I aquired from the kitchen area at school before I left, was used to collect gas. The two-hole stopper fit into the top of the collection bag and a hose ran to my bucket of poop.
With it being winter or really anytime of the year, the bucket of poop was not allowed in the house. This meant it had to stay in the garage.
I went back to school after break, and took my collection bag with me. My chemistry professor, Dr. Dixon, took a sample from the collection bag so we could test for methane. We used a gas chromatograph that would measure any trace elements in the sample.
Sorry to say, no methane was recorded. He still gave me extra credit. I guess he figured if I was crazy enough to go home on Christmas break and shovel poop for an experiment, I should get something for my effort. I always did like Dr. Dixon.
The container needed to be at least 80 degrees Fahrenheit. The garage was at best in the 40-degree range. That is how I learned about temperature and gas production.
These small type digesters can be used to breakdown yard waste, food scraps and is great for backyard chicken manure waste. The main thing to remember is the temperature range needs to be between 68 to 113 F for the digester to work well.
If you would like to read one of the articles from Mother Earth News on building a methane digester, click on this link:
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Floating Drum Anaerobic Digester 2:37
Methane is an explosive gas. One of the most dangerous times in handling the gas is when it comes in contact with oxygen. Purge any containers of oxygen before storing methane in them.
“Anaerobic Digestion (AD).” EPA, Environmental Protection Agency, 2 Mar. 2017, www.epa.gov/anaerobic-digestion.
Publications, Inc. Ogden. “Homemade Natural Gas: The MOTHER EARTH NEWS Methane Digester – Renewable Energy.” Mother Earth News, www.motherearthnews.com/renewable-energy/homemade-natural-gas-methane-production-zmaz74zhol.
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