Is Zakat obligatory on the income from leasing a portion of food refrigeration warehouses, or on the full value of the warehouses, or on the surplus of the revenue that has completed a hawl (lunar year)?

Zakat is obligatory on the rents of warehouses if a year has passed over them and they have reached the Nisab, either by themselves or by what is added to them from their own kind. There is no Zakat on the warehouse itself.