After the successful publishing of The Introduction to Biogas, a friend of mine who is into Agricultural Engineering wrote me an email commenting on the article. He emphasized that I had left out the digestion process that takes place anaerobically in the digester, we discussed it over and how I felt it was too technical and all but at the end of the day I compromised and hence I just thought of giving you the basics of the digestion process and I realized that it wasn’t that hard writing about it.





 The biological conversion of organic material under anaerobic conditions can be described by the following four stages:

1 Hydrolysis

The first step involves the extra cellular enzyme-mediated transformation of higher molecular -mass organic polymers and lipids into basic structural building blocks such as fatty acids, monosaccharide, amino acids, and related compounds which are suitable for use as a source of energy and cell tissue.

2 Acidification


The fermentative bacteria degrade the soluble organic monomers of sugars and amino acids, producing volatile fatty acids (propionic, butyric and valeric acids), acetate, H2 and CO2. Ammonia is also produced by the degradation of amino acids.

3 Acidogenesis

Both long chain fatty acids and volatile fatty acids (VFA) are degraded generating acetate, carbon dioxide and hydrogen.

 4 Methanogenesis


The fourth and last step involves the bacterial conversion of hydrogen and acetic acid formed by the acid formers to methane gas and carbon dioxide. The bacteria responsi­ble for this conversion are strict anaerobes, called methanogenic. Due to their very slow growth rates, their metabolism is usually considered rate-limiting in the anaerobic treatment of organic waste (Mata-Alvarez, 2003).

The article on the challenges of this technology are still on their way, the manager of the blog is yet reviewing and therefore expect it soon.

For your view and comments about these and any other energy related issues, the author can be contacted on 



One thought on “

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s