Tennessee Wastewater Operator Practice Exam

Which gas is a byproduct of both aerobic and anaerobic digestion processes?

1. Carbon dioxide

2. Hydrogen

3. Methane

4. Nitrogen

The correct answer is: Carbon dioxide

The byproduct of both aerobic and anaerobic digestion processes is carbon dioxide. During aerobic digestion, organic matter is broken down in the presence of oxygen, leading to the formation of carbon dioxide along with other byproducts such as water and biomass. In anaerobic digestion, organic materials are decomposed by microorganisms in the absence of oxygen, and while methane is a significant product of this process, carbon dioxide is also generated as a result of the metabolic processes of certain bacteria. This highlights the versatility of carbon dioxide as a common end product stemming from the breakdown of organic materials in both digesting environments. While other gases like hydrogen and methane are produced under specific conditions, they do not universally occur in both digestion processes. Nitrogen, on the other hand, is generally not regarded as a byproduct of either aerobic or anaerobic digestion in the context of organic matter processing.