The pyrolysis and combustion of solid residues from olive oil processing was studied. The objective of the study was to identify the possible hazardous compounds present in incomplete combustion of this material. The study comprises the identification and quantification of the combustion pollutants produced in a laboratory horizontal furnace. The thermal treatment was found to produce low amounts of pollutants, and in fact a small quantity of oxygen was enough to diminish the yields to extremely low levels, showing this way that the combustion efficiency was high. The ashes contained a significant quantity of potassium. No toxic or dangerous inorganic compounds were detected. (C) 2004 Elsevier B.V. All rights reserved.