Composting (is supposed to) produce carbon dioxide (CO2) and water (H20) instead of Methane. Of course it's not perfect and some methane is produced. Unless you do a controlled experiment like Michael Graham you won't know. Maybe someone can look it up. read more
Rotting stuff in a landfill undergoes anaerobic decomposition and produces methane. A compost pile undergoes aerobic decomposition and requires oxygen (O2) for the process to work. Because it is exposed to oxygen it produces CO2 (carbon dioxide) instead of methane. read more
However, compost does release some amount of methane during decomposition, which can sometimes lead to accidental pollution. By understanding the natural processes that occur during composting, and promoting good management practices, you can diminish the chance of your compost releasing too much methane gas. read more