Kinetic models based in biomass components for the combustion and pyrolysis of sewage sludge and its compost

In the present work, pyrolysis and combustion of the sewage sludge (fresh and composted) have been simulated using five fractions: low stability organic compounds, hemicellulose, cellulose, lignin-plastic, and inorganic compounds. Thermal behavior and kinetic parameters (pre-exponential factor and apparent activation energy) of the main components of the sludge are similar to those reported for hemicellulose, cellulose, and lignin present in lignocellulosic biomass. Comparing non-isothermal thermogravimetric analysis data obtained from fresh and composted sewage sludge, it is possible to measure the efficiency of the composting process. Most of the biodegradable matter is volatized in a temperature range from 150 degrees C to 400 degrees C. Non-biodegradable organic matter volatilizes between 400 degrees C and 550 degrees C. In both, fresh and composted sludges, oxygen presence increases the mass loss rate at any temperature, but differences between pyrolysis and combustion are focused in two clearly defined ranges. At low temperature (200-350 degrees C), mass loss is related with a volatilization process. At higher temperature (350-550 degrees C), mass loss is due to slow char oxidation (oxidative pyrolysis). (C) 2009 Elsevier B.V. All rights reserved.