Tennessee Wastewater Operator Practice Exam

What percentage of methane is typically found in biogas produced by anaerobic digestion?

1. 50

2. 60

3. 65

4. 70

The correct answer is: 65

The typical composition of biogas produced by anaerobic digestion generally consists of a mixture of gases, primarily methane and carbon dioxide, along with small amounts of other gases such as hydrogen sulfide and ammonia. In many cases, methane content in biogas can range from about 50% to 70%. When examining the average composition, methane generally constitutes about 60% to 65% of biogas, making the option representing 65% a common figure seen in many sources discussing biogas production. The variations in methane percentages can occur due to factors such as feedstock, digestion conditions, and the specific anaerobic digestion process used. This means that while other options also provide a reasonable range, 65% is a strong representative figure of methane content typically expected in biogas resulting from anaerobic digestion, aligning with many industry standards and empirical observations. This understanding is crucial for wastewater operators as it informs them about the energy potential of biogas, necessary for effective management and optimization of anaerobic digestion systems.