Characterization of Pyrolysis Products of Forest Residues and Refuse-Derived Fuel and Evaluation of Their Suitability as Bioenergy Sources

Abstract

The products generated from a fixed bed pyrolysis unit of solid waste materials were quantitatively characterized, and their energy potential was determined, in order to evaluate their suitability as energy sources. An elemental analyzer, a bomb calorimeter, an X-ray fluorescence spectrometer, a Couette viscometer and a TG-MS (thermogravimetric-mass spectrometry) analyzer were employed for the measurements. Biochars obtained at 450 °C were enriched in carbon; their calorific value was high (20–39 MJ/kg) and exceeded that of raw materials. These biochars can be utilized for energy production, preferably at temperatures below 1000 °C, to avoid slagging/fouling phenomena. The bio-oils of pinecones and forest residue obtained at 450 °C, with a density of 0.93–0.94 kg/m3, a pH of 2.1–3, a dynamic viscosity of 1.5–7 cP and a calorific value of 22–27 MJ/kg, were superior to typical flash pyrolysis oil and could be used in static applications for heat or electricity generation after a de-oxygenation process. The quality of RDF bio-oil was lower. The higher heating value of gases from pinecones and RDF fuels at 450 °C was satisfactory for the energy requirements of the process (13.6–13.8 MJ/m3); however, that of forest residue gas was moderately low.