About this Course

Biogas is produced by fermenting bacteria and metha­nogens under anaerobic conditions and at optimal tem­perature, pH and environmental conditions. This process works best when fermenting bacteria and methanogens are balanced and working together. When conditions inside the digester change and fermenting bacteria and metha­nogens are no longer in balance, the digester is at risk of going “sour” and eventually ceases to produce biogas.

Fermenting bacteria and methanogens work in tandem to produce biogas. Methanogens are microorganisms that live in an anaerobic environment and convert organic acids produced by the fermenting bacteria into methane.

Complex organics include proteins and polysaccharides. These are reduced to higher organic acids by hydrolytic and acidogenic bacteria. Higher organic acids are converted into acetic acid by acetogenic, homoacetogenic and syntrophic bacteria. Methanogens convert acetic acid into methane. It should be noted that the primary conversion route is from complex organics to acetic acid to methane, although hydrogen is also a significant component of methane generation.

This course provides information on factors that need to be managed in order to maintain biogas production. These factors – microbial population, feedstocks, loading rate, mixing, and environmental issues – determine the effectiveness of digester operation.

Learning Outcomes & Objectives:

• Describe the role each factor plays in biogas production.
• Identify possible feedstocks for a digester.
• Suggest possible loading rates.
• Identify tools that estimate biogas yield.
• Understand why fermenting bacteria and methanogens work together
• What “sour” digesters are, and how they can be pre­vented.