Sodium bicarbonate was replaced with ammonium bicarbonate, recovered from effluent of the pigment industry, for cultivation of CSMCRI's Chlorella variabilis (ATCC PTA 12198) with enhanced biomass and lipid productivity. Compared to Zarrouk's medium, utilizing ammonium bicarbonate in the medium instead of sodium bicarbonate yielded better biomass and lipid productivity in a shorter production time of 9d in a 5-L flask. The modified medium containing ammonium bicarbonate also yielded a higher total content of reducing sugar, which can be used for bioethanol production or as carbon source for further mixotrophic growth of C. variabilis.