Does compost increase long-term soil carbon as humus?

1) What kind of claim is this?

This is a cause-and-effect claim about long-term carbon storage.

2) What context is assumed or missing?

Rates of decomposition and soil conditions are not specified.

3) What has to be true for this to work?

A meaningful share of compost carbon would need to become stable over time.

4) When would this not hold?

The claim weakens if most added carbon breaks down quickly.

5) What follows if we accept it?

Compost use may be seen as a long-term carbon storage strategy.