Enhancement of Marine Phytoplankton Growth by Steel-making Slag as a Promising Component for the Development of Algal Biofuels

Abstract

Growing phytoplankton for the production of biofuels is one of the expected alternatives to the usage of safer and renewable type of energy. Steel-making slag, a by-product of the steel manufacturing process, is known to contain nutrients such as iron, phosphate and silicate, which are essential for the growth of marine phytoplankton. A batch experiment was carried out to examine the dissolution of phosphate and silicate from steel-making slag and their effects on the growth of a common neritic marine diatom Skeletonema costatum. The dephosphorized slag used in this study released iron moderately, maintaining a constant concentration of dissolved iron, which highly differed from the results of iron sulfate (FeSO₄) and iron powder used as references. FeSO₄ showed a rapid increase in iron ion for several days but the concentration rapidly decreased due to hydrolysis. The growth of S. costatum was significantly enhanced by the addition of slag because the released ratio of silicate, phosphate and iron was close to the required ratio for the growth of phytoplankton. Therefore, steel-making slag is a promising component for the enhancement of phytoplankton growth in the production of algal biofuels.