The digester may not have produced a sufficient amount of gas, a leak may exist in the gas collection system, or the digester may have acidified and not be producing methane. Acidification Acid-forming bacteria break complex organic wastes down into volatile fatty acids. Proteins are broken down into amino acids and further into volatile fatty acids. Carbohydrates are broken down into simple sugars and then into volatile fatty acids. Fats and oils are broken down to long chain fatty acids and then to volatile fatty acids.
Acetogenic bacteria use the volatile fatty acids and form acetic, propionic, and lactic acids.
In addition, hydrogen and carbon dioxide gas can be released by the acetogenic bacteria. Other bacteria use hydrogen and carbon dioxide produced in stage 1 to form methane. The anaerobic digestion process is carried out by a delicately balanced population of various bacteria. These bacteria can be very sensitive to changes in their environment. Temperature is a prime example.