Pyrolysis of four agricultural residues (maize, sunflower, grape and tobacco) has been carried out in order to quantify their energy content. The main characteristics of the charcoals formed and the nature and quantity of gases produced have been determined. The process was studied batchwise by varying the reaction time (15-60 min) and temperature (400-700 degrees C). Reaction times higher than 30 min do not exert any influence while increasing temperature yields high tired carbon solids, low volatile content and slight increases in ash. The increase in temperature is specially important to increase the production of gas, mainly hydrogen. From gas composition and proximate analysis, the heating power of gas and solid phases have been determined. A kinetic model of pyrolysis based on gas generation has been accomplished. From this model, rate constants of gas formation at different temperatures and activation energies have also been determined.