Until people/animals eat it, or it decomposes. Not saying this like we should ignore the co2 impact from data centers, but biomass is a pretty poor co2 absorber unless its cyano and falls to the ocean floor before decomposing

> Until people/animals eat it, or it decomposes.

Well, if you want to think about it that way (perfectly reasonable), you'd also want to consider the production of new alfalfa. Figure that at any given time, the world contains X amount of alfalfa, and that amount determines how much carbon is absorbed by the alfalfa industry.