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

The role of earthworms in reducing sewage to gases is significantly less critical compared to the other factors listed. While earthworms can contribute to the breakdown of organic matter in composting processes by aerating the soil and enriching it as they process waste, the primary mechanisms that drive the reduction of sewage to gases rely heavily on microorganisms, aerobic processes, and temperature control.

Microorganisms, particularly bacteria and archaea, are essential for the degradation of organic matter, converting solids into gases like methane and carbon dioxide through anaerobic and aerobic digestion. This biological activity is foundational in sewage treatment processes.

Aerobic processes are vital because they utilize oxygen to decompose organic materials efficiently, leading to higher rates of gas production. In many modern sewage treatment plants, aerobic digestion is preferred for its efficiency and ability to significantly reduce pathogens and organic materials.

Temperature control is also crucial, as it influences the metabolic rates of microorganisms. Optimal temperatures can enhance microbial activity and gas production during digestion processes.

In contrast, while earthworms have a role in soil health and organic matter breakdown in composting environments, they do not play a central role in the gaseous byproduct formation from sewage treatment, making them the least important factor in this context.