Which of the following is least important when reducing sewage to gases?

When considering the reduction of sewage to gases, anaerobic bacteria plays a critical role, as they thrive in environments without oxygen and effectively break down organic matter, leading to gas production such as methane. Similarly, aerobic bacteria are crucial because they require oxygen to decompose waste, although this process primarily produces carbon dioxide rather than methane.

Protozoa also contribute to sewage treatment by feeding on bacteria and organic matter, enhancing the breakdown process.

In contrast, earthworms, while beneficial for soil health and aeration, do not play a direct role in the biochemical processes that convert sewage into gases. Their primary function involves consuming organic materials and enriching the soil with nutrients rather than engaging in the anaerobic or aerobic breakdown of sewage. Thus, their contribution is less significant compared to that of the microbial organisms in the context of gas generation from sewage treatment.