Generating Biogas at Home

You can be generating biogas at home to use for space and water heating, lighting, and cooking. Paul Scheckel guides you through the basics here.

| May 24, 2013

Looking for creative ways to generate more of your own power, lower your energy costs, and become more self-reliant? In The Homeowner’s Energy Handbook (Storey Publishing, 2013), Paul Scheckel offers practical solutions for adapting solar, wind, wood gasification, biogas, and micro hydro power systems for home use. In this excerpt from Chapter 13, Scheckel describes the basics of generating biogas at home, including how it works and how much biogas you can produce.

You can purchase this book from the MOTHER EARTH NEWS store: The Homeowner’s Energy Handbook.

Biogas is a mixture of gases formed anywhere organic material decomposes in the absence of oxygen, such as underwater, deep in a landfill, bubbling out of municipal solid waste, or in the guts of animals (including you). Sometimes called swamp gas, biogas is produced through the biological and chemical process of anaerobic digestion (AD). This is a natural process that happens without any assistance from you or me.

Simply put, anaerobic digestion is the microbial decomposition (digestion) of carbohydrates in an oxygen-free (anaerobic) environment. It begins with a process similar to the fermentation of alcohol, but AD occurs in the absence of oxygen and continues past fermentation. In fact, oxygen is toxic to the process, in that it inhibits the growth of methane-producing microbes, also known as methanogens, which are ultimately what we want to encourage for the production of biogas.

Biogas Basics

The main ingredient of biogas made in a controlled environment is methane. Methane (chemically known as CH4) is a hydrocarbon made up of one molecule of carbon and four molecules of hydrogen, and is lighter than air. Methane is also the primary component of natural gas, commonly used for cooking and heating, although biogas is not as energy-dense as natural gas. The methane content of the biogas you make will probably range from 50 to 80 percent, compared to about 70 to 90 percent with utility-supplied natural gas. Natural gas also contains up to 20 percent other combustible gases, such as propane, butane, and ethane, while biogas does not.

The exact makeup of biogas depends in part on the source of the gas, which is based on what is fed to the digester, and in turn what was fed to the producers of those ingredients. Noncombustible components of biogas can be considered impurities. These will be primarily carbon dioxide (CO2), along with small amounts of water vapor, nitrogen (N2), and possibly trace amounts of hydrogen sulphide (H2S). If air contaminates the process, nitrogen can dilute the biogas. Other trace impurities may be formed as well when generating biogas. You can remove these impurities if desired, but depending on how you intend to use the biogas, you may not need to.

8/17/2014 6:03:41 AM

Thanks for sharing this very useful yet easy to understand article. Will go on my blogroll soon. :-)

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