Which one of the following gases is released mostly from landfills in urban areas?

Landfills in urban areas are a significant source of methane (CH4) emissions. Landfill gas is primarily produced through the anaerobic decomposition of organic waste, such as food and garden waste, by bacteria in the absence of oxygen [2]. This process typically generates a gas mixture consisting of approximately 50% to 60% methane and 40% to 50% carbon dioxide [3]. While trace amounts of nitrogen, oxygen, and hydrogen are present in landfill gas, they are not the primary constituents released [3]. Municipal solid waste landfills are recognized as the third-largest source of human-related methane emissions globally [2]. Because methane is a potent greenhouse gas with high global warming potential, urban landfills are often monitored to capture this gas for energy production or to mitigate its environmental impact.

Sources

1. [2] https://www.atsdr.cdc.gov/hac/landfill/html/ch2.html
2. [3] https://pmc.ncbi.nlm.nih.gov/articles/PMC9529986/