When 1 tonne of olivine weathers, the chemical reaction removes 1.25 tonnes of free CO2 from the environment in terms of stoichiometry. However, in the process of mining, milling, and transporting that olivine to that beach, we emit approximately .05 tonnes of CO2 ourselves. That .05 of a tonne is 4% of the 1.25 tonnes of CO2 that was removed in the weathering process. So, in a CO2 life cycle assesment of net emissions, that considered the "loss."