In climate footprint calculations, there are no practical reasons to include the carbon sequestration in biomass in the LCI (Life Cycle Inventory), as the sequestration post and the emission post are identical.
Plants sequester carbon dioxide from the air when they grow, as carbon (C) is the main building block in nature. The carbon is stored in all parts of the plants, below ground as well as above ground. The same amount of carbon is later released back into the atmosphere after the plant dies and its biomass is decomposed, burned, or digested.
In most cases, the release is in the shape of carbon dioxide, but in anoxic conditions, it may be in the shape of methane (CH4). This release happens every time, even if the carbon in some cases is stored in the biomass for a couple of years or decades after the plant is harvested.
Therefore, for climate footprint calculations, there are no practical reasons to include the carbon sequestration in biomass in the LCI (Life Cycle Inventory), as the sequestration post and the emission post are identical. However, if the process emits CH4 this release needs to be accounted for.