Gases produced in greatest volume are methane, carbon dioxide, ammonia and hydrogen sulfide. There is also a complicated group of volatile organic substances that contribute to the odor. These substances include amines, mercaptans, alcohols, carbonyls and sulfides in trace amounts. Methane, the gas produced in greatest volume during the decomposition process, results from organic acids being degraded. This gas usually escapes to the atmosphere and is a potential air pollutant.
Carbon dioxide is the second most abundant gas produced as organic acids are degraded.
Because it is odorless, the pollution potential of this gas is often overlooked. Ammonia is released as amino acids in protein are broken down by bacteria. This gas is easily recognized because of its pungent odor. Hydrogen sulfide is also a part of the odor. Anaerobic reduction of sulfur-containing compounds such as certain amino acids result in formation of hydrogen sulfide.