Biogas Upgrading and Phytoremediation of Palm Oil Mill Effluent after Biogas Digester by Immobilized Oleaginous Microalgae

摘要

In order to purify biogas by removal of CO_2, the oleaginous microalga Scenedesmus sp. was immobilized in alginate gel beads and cultivated in the effluent from biogas digester and fed with biogas. The immobilized microalgae could efficiently purify biogas and effluent. The immobilized cells could be easily harvested by a simple sieving method without involving huge amounts of energy input. More than 88% of CO_2 was removed from biogas and the methane content was increased up to >95%. The CO_2 removal rate was as high as 4.63 g-CU_2 day~(-1) per 1 L-microalgal culture. The final biomass obtained was 2.98 g L~(-1) with a lipid content of 35.9%. The pigments including chlorophylls and carotenoids were also produced at 45.9 and 26.1 mg g~(-1) biomass, respectively. The immobilized microalgae was also effective for pollutant removal, i.e., COD removal (>71%), nitrogen removal (100%) and phosphorus removal (100%). Fatty acid compositions of produced lipids showed high C16-C18 (>98%) and their fuel properties were in accordance with the international standards. This strategy could be a promising biorefinery concept which is effective not only in biogas upgrading and removal of pollutants but also low-cost production of renewable energy.