ABSTRACT
The suitability of integrating biological and thermal transformation of microalgal biomass to design a biorefinery was studied. The mixed cultivation of Chlorella sp. and Bracteacoccus sp. in city wastewater produced 12â¯gâ¯L-1 of biomass (0.77â¯gâ¯L-1â¯day-1) and removed nitrates and phosphates by 68% and 75%, respectively. Microalgae outcompeted the contaminating microbes by raising the pH of wastewater to 9.93. The lipid-free residual biomass was pyrolyzed at four heating rates (10, 20, 30, 40⯰Câ¯min-1) which showed a three-stage pyrolysis. The activation energies (182-256â¯kJâ¯mol-1) and their corresponding lower enthalpies at the conversional fractions from 0.2 to 0.6 indicated that product formation was being favored. The values of pre-exponential factors (1015-17â¯s-1), Gibbs free energy (159-190â¯kJâ¯mol-1) and entropy (43-81â¯Jâ¯mol-1) showed efficient pyrolysis. The data may lead to establish a robust microalgal biorefinery to produce biomass and energy along with primary treatment of city wastewater.