NOVELTY - System has anaerobic digester with acid fermenter and methanol fermentation tank, culture tank which cultures microalgae, accumulation tank which induces the accumulation of useful substances in the microalgae, dehumidifying/desulfurizing equipment which dehumidifies and desulfurizes biogas discharged from the anaerobic digestion tank, gas holder which stores the biogas discharged through the dehumidifying/desulfurizing equipment, combined heat and power generator which generates electricity and heat energy from the biogas, and upgrading device.    USE - The system is useful for culturing microalgae (claimed).    ADVANTAGE - The culture system reduces cultivation cost of microalgae, as the system enables to culture microalgae using carbon dioxide and electricity.    DETAILED DESCRIPTION - System has an anaerobic digester (100) with an acid fermenter (110) and a methanol fermentation tank (120) which decomposes drain water discharged from the acid fermenter by microorganism, a culture tank (500) which cultures microalgae using anaerobic digestion effluent discharged from the anaerobic digester, an accumulation tank (600) which induces the accumulation of useful substances in the microalgae by changing one or more conditions among medium nutrients, light, temperature, and injection of certain ingredients, a dehumidifying/desulfurizing equipment (200) which dehumidifies and desulfurizes biogas discharged from the anaerobic digestion tank, a gas holder (210) which stores the biogas discharged through the dehumidifying/desulfurizing equipment, a combined heat and power generator (300) which generates electricity and heat energy from the biogas, and an upgrading device (310) which methane upgrades the biogas. An INDEPENDENT CLAIM is included for method for culturing microalgae.    DESCRIPTION OF DRAWING(S) - The drawing shows block diagram of microalgae culturing system. (Drawing includes non-English language text)    Anaerobic digester (100)    Acid fermenter (110)    Methanol fermentation tank (120)    Dehumidifying/desulfurizing equipment (200)    Gas holder (210)    Combined heat and power generator (300)    Upgrading device (310)    Culture tank (500)    Accumulation tank (600)