Which gas is generated from the decomposition of organic material in sewage?

The correct answer is hydrogen sulfide, which is a gas produced through the anaerobic decomposition of organic materials found in sewage. This process occurs mainly when organic matter breaks down in environments devoid of oxygen, such as in sewage treatment plants or sewage systems.

Hydrogen sulfide is a byproduct of the action of specific bacteria that digest the organic matter in such low-oxygen environments. It is notable for its characteristic odor of rotten eggs, and in addition to being a nuisance, at high concentrations, it can be hazardous to human health.

In contrast, while other gases like ammonia can also be generated during the decomposition process, it is primarily the presence of sulfur-containing compounds in the organic matter that leads to the production of hydrogen sulfide. Carbon monoxide is typically associated with incomplete combustion of carbon-containing materials, and nitrogen is a major component of the atmosphere but is not specifically generated from sewage decomposition. Hence, hydrogen sulfide is the primary gas of concern generated during the breakdown of organic materials in sewage.