Biodigestor FAQ

Filed Under: EARTH News
Date: January 31st, 2014

What is a biodigester?

A biodigester is an anaerobic space in which bacteria break down or “digest” organic material fed into the system. This process naturally produces biogas, which is then captured and used for many different purposes, and a liquid effluent, which can be used to fertilize crops or further treated and returned to the environment.

What kind of material goes into a biodigester?

Technically, all organic materials will decompose anaerobically and eventually produce biogas, but some work better than others for producing methane. For example, animal and human excrement break down quickly and produce a lot of energy in a biodigester system. Plant matter takes longer to digest, and tends to produce less gas.

Are there different kinds of biodigesters?

There are many different sizes and models available, ranging from small inexpensive biodigesters made from re-purposed or recycled materials to enormous industrial models that process thousands of liters of waste at a time. Biodigesters can be found in backyards, farms, hotels, restaurants, and just about anywhere where there is waste and a need for energy.

What is biogas?

Biogas is the natural product of anaerobic digestion. Depending on the kind of materials used, it can range from 40-75% methane gas and 25-55% carbon dioxide, followed by small amounts of water vapor, nitrogen, oxygen, hydrogen and amino acids.

What can biogas be used for?

The most common use for biogas in rural communities is for cooking (no really!). It produces an odorless flame that can be used instead of propane. It is also used by dairy farmers to heat and safely pasteurize large quantities of milk, or to keep new pig litters warm. If enough biogas is available, it can be used to power an electric generator.

What are the benefits of biodigesters?

Where do we begin?! Biodigesters are not only an elegant solution for waste but they also transform discarded materials into sustainable energy. The biogas acts as a substitute for fossil fuels and firewood, reducing deforestation or dependence on unsustainable energy. Finally, even the effluent that is leftover at the end of the digestion process can be used as fertilizer, increasing soil health and crop production.

Where can I get more information about biodigesters?

To see how real people are working to improve lives through biodigester technology, take a look at two stories of EARTH graduates Susana Fallas and Carolina Chantos:

Susana Fallas installs biodigesters in rural communities all over Mexico: https://www.earth.ac.cr/support-earth/meet-susana/?lang=en

Carolina Chantos works with biodigesters both big and small in Costa Rica: https://www.earth.ac.cr/feature/closing-the-energy-gap-in-costa-rica/?lang=en