Does composting release CO2?

Carbon dioxide (CO2) emissions from the composting mass are classified as biogenic. This means the same amount of gas is emitted during decomposition whether the organic material is composted or degrades in a natural setting.  Therefore, these emissions are considered carbon-neutral.

Compared to waste management alternatives, it’s the best of the bunch.

Other emissions sources, however, like those from equipment operation,  do add to the size of a composting facility’s environmental footprint.  These are nonbiogenic, a.k.a. anthropogenic, emissions.

This factsheet provides a good topic overview that includes values for helping composting operations with emissions calculations.