What is Biogas? And, What’s it Good For?

biogas and methane energy

Deep green energy, or biogas, is a valuable renewable energy source.

When organic matter breaks down or rots, it produces a mixture of carbon dioxide and methane. These gases, called biogases, can then be used in various applications.

Biogas is sometimes called deep green energy because it is such a valuable source of energy in rural areas. It provides a clean, easily-controlled source of renewable energy and requires very little labor, replacing firewood or fossil fuels.

What Is Biogas Made Of?

Biogas is made from organic matter. It’s produced by the natural fermentation process using materials such as:

  • farm waste (manure),
  • plant matter,
  • sewage,
  • biomass

How Is Biogas Made?

biogas is made in large containers called digesters. There are several types of digesters, but one thing they have in common is that they are anaerobic, or without oxygen. It is the action of anaerobic bacteria that produces the biogas. The three main types of digesters are:

Fixed dome – These biogas digesters begin underground. The organic matter (also called slurry) is displaced into a “compensation tank” as the biogas forms. The gas is collected in a brick structure that sits above ground, right over the rotting matter.

Floating drum – This type of digester also begins underground. A metal drum floats above the slurry, either in a water jacket or directly on the slurry. The drum floats higher and higher as it is filled with biogas.

Balloon – This kind of biogas digester is basically a big bag. The bottom of the bag contains the material, and the top of the bag contains the gas. It expands as the biogas is produced.

All biogas digesters need a regular supply of water to function properly.

The technology itself is divided into two types:

Batch digesters, which are used in large-scale production. They can accommodate a large amount of organic matter at one time.

Continuous flow digesters are better for smaller-scale production, such as for individual households and small businesses. These digesters are designed to add and remove organic matter as often as every day.

What are the Common Uses for Biogas?

Biogas can be used to:

  • Light homes and buildings
  • Cook (as with propane)
  • Run generators and make electricity
  • Power combustion engines

Biogas production is a very good use of waste matter, and can improve sanitation and make energy available in underdeveloped countries. Here in the United States, farmers are looking into biogas as a way to make use of the copious plant and animal waste that is generated on a farm. A farm in Vermont is run entirely on biogas generated by cow manure, and there is such a significant surplus that the farmers sell the extra electricity to their neighbors.


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