Pyrolysis, combustion and gasification characteristics of Nannochloropsis gaditana microalgae (NG microalgae) were investigated by thermogravimetric analysis (TGA). NG microalgae pyrolysis and combustion could be divided into three main stages: dehydration, proteins and polysaccharides degradation and char decomposition. The effects of the initial sample mass, particle size and gas flow on the pyrolysis and combustion processes were studied. In addition, gasification operation conditions such as temperature, initial sample mass, particle size, sweep gas flow and steam concentration, were experimentally evaluated. The evolved gases were analyzed online using mass spectroscopy (MS). In pyrolysis and combustion processes, most of the gas products were generated at the second degradation step. N-compounds evolution was associated with the degradation of proteins. Furthermore, SO2 release from combustion could be related to sulphated polysaccharides decomposition. The main products detected during gasification were CO2, CO, H-2, indicating that oxidation reactions, water gas and water gas shift reactions, were predominant. (C) 2012 Elsevier Ltd. All rights reserved.