Which of the following is a by-product of aerobic decomposition?

Aerobic decomposition primarily occurs in the presence of oxygen, leading to the breakdown of organic materials by microorganisms. During this process, one of the main by-products produced is carbon dioxide gas. This occurs as the microorganisms metabolize the organic matter, utilizing oxygen for their respiration and releasing carbon dioxide as a by-product.

In contrast, biogas is typically associated with anaerobic decomposition, which occurs in the absence of oxygen and produces methane and carbon dioxide. Ozone is not produced as a by-product of decomposition processes under normal conditions. Hydrogen gas can be produced in some specialized conditions but is not a typical product of aerobic decomposition. Therefore, the identified by-product of aerobic decomposition that stands out is carbon dioxide gas, confirming its role in the natural recycling of organic materials through aerobic processes.