Which gas is typically present in anaerobic digester gas in the lowest concentration?

In anaerobic digester gas, hydrogen sulfide is typically present in the lowest concentration compared to other gases such as carbon dioxide and methane. Anaerobic digestion is a process where organic material is broken down by microorganisms in the absence of oxygen, producing methane as a primary product. While methane can be present in concentrations of up to 60-70% in digester gas, and carbon dioxide is also found in significant amounts (around 30-40%), hydrogen sulfide is generally produced in much smaller quantities.

The presence of oxygen is negligible in an anaerobic digester since the process is designed to operate without it. Thus, the production of hydrogen sulfide, which can occur due to the breakdown of sulfur-containing compounds, is much lower than the levels of methane and carbon dioxide, making it the gas found in the lowest concentration in anaerobic digester gas.