Impact of heavy metals from flue gas integration with microalgae production

Abstract

Integration of microalgae cultivation with coal-based flue gas is a widely proposed approach to supply carbon dioxide (CO2). The utilization of coal derived CO2 in microalgae growth systems will introduce heavy metals (toxic metals and metalloids), originally present in coal, into the cultivation system. This study evaluates the effect of 10 heavy metals (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Se and Zn) at four different concentrations on the growth and lipid yield of microalgae, Scenedesmus obliquus. Results show at the baseline heavy metal concentration of 1×, corresponding to the concentrations expected from a coal fired power plant, a 12% higher biomass and 61% higher lipid yield when compared to a control containing no heavy metals. Higher concentrations of heavy metals, twofold (2×), fivefold (5×) and tenfold (10×), are shown to inhibit both growth and lipid production. Analysis shows that most heavy metals added to the culture were sorbed to the biomass with Hg mostly lost to the environment. Discussion focuses on how flue gas-derived heavy metals could result in both positive and negative outcomes for biomass and biodiesel production and the environmental implications of a commercial microalgae growth system that utilizes coal based flue gas as a CO2 source.