This two-part study firstly investigated Tetraselmis suecica grown in different CO2 (0.04-15% v/v) concentration through indoor and outdoor cultivation systems. A high CO2 concentration led to a high lipid content, and low nitrogen and oxygen content, which are desirable for transport fuel production. Pyrolysis characteristics were investigated by TG-IR and synchrotron IR microscopy. The results show Tetraselmis suecica grown in 10% CO2 had the highest decomposition rate corresponding to more volatile products produced during the main thermal cracking stage and derived from protein-and lipid-corresponding functional groups. Moreover, a high reaction temperature and CO2 concentration resulted in a low retention of surface functional groups. The nitrogen functional groups initially decomposed at a temperature range of 250-300 degrees C and still remained at 550 degrees C, while the lipid-corresponding functional groups completely disappeared at a temperature range of 400-500 degrees C. Besides, the decomposition of chemical components followed the order of carbohydrate, protein and lipid. (C) 2017 Elsevier Ltd. All rights reserved.