In this work, a thermodynamic analysis of a stand alone gasifier is carried out. The analysis uses the nonstoichiometric approach based on the minimization of the Gibbs free energy. The gasification temperature, amount of oxygen required, composition of syngas, and cold gas efficiency are predicted at the carbon boundary point (CBP) using Aspen Plus. The influence of nitrogen when air is used as the gasifying agent is studied. It is found that the presence of nitrogen results in a lower gasification temperature, higher oxygen requirement, lower concentration of CO and H-2, higher concentration of CO2 and CH4, and lower cold gas efficiency. The influence of pressure when air is used as the gasifying agent is also studied. It is found that increasing the pressure results in higher gasification temperatures, higher oxygen requirement, lower concentration of CO and H-2, higher concentration of CO2 and CH4, and lower cold gas efficiency. Performance charts in the form of contour plots are presented to predict the performance of a high pressure gasifier using air as gasifying agent.