Which is not a component of marsh gas?

Ammonia is not a component of marsh gas. Ammonia is a compound of nitrogen and hydrogen with the formula NH3. It is a common nitrogenous waste, particularly among aquatic organisms, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to 45 percent of the world's food and fertilizers.

Marsh gas, swamp gas, and bog gas is a mixture of methane, hydrogen sulfide, and carbon dioxide, produced naturally within some geographical marshes, swamps, and bogs.

The surface of marshes, swamps, and bogs is initially porous vegetation that rots to form a crust that prevents oxygen from reaching the organic material trapped below. This is the condition that allows anaerobic digestion and fermentation of any plant or animal matter, which incidentally also produces methane.