Fertilization of the ocean with nutrients such as nitrate and phosphate is one of the countermeasures against the global warming problem. In the present paper, we evaluated the effective ratio of the nutrients sprinkling into the ocean to the nutrients assimilation by phytoplankton. When the nutrients equivalent to the 1/500 of the annual accumulated amount of CO2 in the atmosphere were sprinkled within the circle of 7.1 - 100 km radius by a ship, less than 0.01 % of the nutrient was found to be transferred to the deep ocean without assimilation. The rest remained in surface ocean, most of which was found to be incorporated in the phytoplankton within one year. We also evaluated the energy balance of transportation of the fertilizers by ship to that taken up by the fertilization in ocean, The energy evaluation indicated that the amount of CO2 produced from the transportation process was about 0.23 % of the amount that is expected to be taken up into the ocean from the atmosphere. Furthermore, we estimated the energy balance of fertilization with activated sludge instead of fertilizer. It was found that fertilization by activated sludge containing a great deal of water needed a large amount of energy for the transportation by ship.