Home Cookin' With Homemade Biogas Energy

Learn to build a DIY anaerobic digester to turn biomass into clean, renewable biogas energy.

| 03/01/2013

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    Feed the Biogas Digester: Biodigesters trap the methane gas from decomposing organic waste, such as manure and table scraps, and use it for producing electricity or cooking fuel. Methane is composed of carbon and hydrogen — CH4. It has an octane rating of 110 and produces about 1,000 Btu of heat per cubic foot of gas.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    This biogas-powered cooking stove receives the fuel for its steady flame from methane captured in the biodigester.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    Maitreya resident Christa Stark loads kitchen scraps into the biodigester.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    Stirring the table scraps into the muck of the biodigester exposes them to active methanogenic bacteria.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    The Maitreya Ecovillage biodigester turns 15 pounds of kitchen scraps and garden clippings into a day's worth of cooking fuel for the community's kitchen.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    Kitchen scraps become a slurry in the feeding chamber, eventually sinking into the digester where their subsequent methane production is utilized to produce cooking fuel.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    As the biomass decomposes, methane and carbon dioxide are created, inflating the rubber bladder to create pressure.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    Cleaning up and adding water to replace what is drawn off as liquid compost.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    The outer forms of the biodigester are reinforced to withstand the pressures of poured concrete.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    The interior forms of the biodigester are shown here, with floor and wall reinforcements visible.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    The finished concrete pour, with rubber bladder in place.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    Details of the frame, gasket and rubber bladder assembly are shown here.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    Rigid foamboard is used to insulate the tank and help maintain the correct temperature for the bacteria.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    At the output, the nitrogen-rich liquid fertilizer is extracted from the digester, which produces 5 to 10 gallons per day.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    The liquid fertilizer can be added directly to plants or covered with dirt or mulch to keep beneficial ammonia in the soil.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com
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    The liquid fertilizer can be added directly to plants or covered with dirt or mulch to keep beneficial ammonia in the soil.
    Photo ©2013 Isaac Marquez, marquezarts@gmail.com

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The following article is posted with permission ©2013 Home Power Inc. Visit www.HomePower.com for information on renewable energy projects for your farm or home.

About five years ago, writer and renewable energy aficionado Warren Weismann was researching ancient Greece for his novel when he stumbled across information that the Greeks had built anaerobic digesters to produce methane. He then read about similar archaeological evidence in ancient Syria and China. But it was the modern biogas boom in China that got him most excited and distracted him from his writing career: Tens of millions of home-scale biodigesters have been built in China over the last century, with the pace of construction still accelerating. Warren wanted one for himself.  

After a few years of further research, including conversations with colleagues in India and Nepal, where small-scale biogas production is prevalent, Warren modified traditional designs to create a plan for his own 700-gallon biodigester. He was living at Maitreya Ecovillage, a threeblock community and green-building-oriented neighborhood near downtown Eugene, Oregon. After building his first biodigester last year, he’s become increasingly excited about the possibilities for home-scale biogas, and has established Hestia Home Biogas to build biodigesters locally and consult on biodigesters across the globe.

Back from Obscurity

Biogas has been used for lighting for at least a century, and possibly millennia. But it was mostly abandoned in the United States after cheap and abundant fossil fuel was harnessed in the early 20th century. Home-scale biodigesters have remained on the sidelines in the developed world, but are poised for a comeback as interest in a replacement fuel increases.



There are good reasons to consider building biodigesters for a community, small farm, or even home. Biodigesters yield two products that are extremely useful for the home and garden—high-nitrogen compost and flammable gas.

Biodigesters anaerobically (without air) break down organic matter in a slurry held in a tank. The nitrogen remains in the composted slurry as ammonia, a vital plant nutrient. The flammable gas produced by biodigesters is about twothirds methane and one-third carbon dioxide—very similar to natural gas—making it a good cooking fuel. Cooking requires intense direct application of heat on demand, and renewable options for accomplishing this are limited. Solar energy is dispersed and not consistently available, making solar cooking challenging, and burning wood contributes to particulate pollution and further depletes diminishing resources in the developing world. Cooking is not a huge consumer of energy in the industrialized world, but doing it more sustainably is challenging. Unlike cooking with solar electricity, biodigesters can be assembled with readily available materials by a handy homeowner. Any type of propane or natural gas stove will run on biogas. For maximum efficiency, propane stoves will require a larger air inlet.

jon
10/15/2017 1:34:47 PM

Your Natural Gas details are incorrect. I was in the industry for 42 years and I can tell you a cubic foot of natural gas is 88 to 96% methane depending on the source and various other flammable gases with a small amount of nitrogen. There is no 1/3 volume of CO2. This mix will burn in neither stove without modifications. The orifice would have to be larger for the bio gas as the BTU is likely to be about 700 btu/cf not 1000 BTU/cf and propane has a BTU of 2516 btu/cf and therefore would require a much larger orifice for the bio gas to burn. It would also require a resetting of the air mix. Though this work can be done by trial and error, this is work best done by a professional. It would also void any warrantee you have on the appliance and could be very dangerous to the DIYer.


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