Oxy-fuel or O-2/CO2 combustion technology was used to investigate the combustion of Chlorella vulgaris by thermogravimetric analysis (TGA). Oxy-fuel combustion occurs in an O-2/CO2 atmosphere instead of an O-2/N-2 atmosphere and offers an alternative method of C vulgaris preparation for biofuels processing. Our results show that three stages were observed during C vulgaris combustion and the main combustion process occurred at the second stage. Compared with a 20%O-2/80%N-2 atmosphere, the mass loss rate at the DTG peaks (R-p) and the average reaction rate (R-v) in a 20%O-2/80%CO2 atmosphere was lower, while the ignition temperature (T-l) was higher. As oxygen concentration increases in an O-2/CO2 atmosphere, R-p, R-v and the apparent activation energy (E) increases, while T-l, the final temperature detected as mass stabilization (T-f) and the residue mass (M-r) decreases; As the heating rate (beta) increases, T-l, T-f, and R-p increase, while M-r decreases. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.