Evaluation of Pyrolysis Products of Industrial Wastes as Potential Feedstocks for Bioenergy and Biofuels

Abstract

This work aimed at evaluating all products from the low-temperature pyrolysis (350°C) of some industrial wastes, cotton stems and seeds (CSS), grape husks and curls (GRH), undigested sewage sludge (USS) and their blends in a fixed bed system and suggesting their possible applications. Solid and liquid products, biochars, and bio-oils were analyzed using various techniques by physicochemical, mineralogical, and chemical analyses. Gases were qualitatively and quantitatively analyzed using a thermogravimetric-mass spectrometry system. All biochar samples could be used for soil amendment. Co-application with composts or other by-products to soils could be more advantageous. USS and its blends with CSS or GRH at percentages 20% and 30% presented an increased potential for carbon sequestration and release of nutrient nitrogen to plants. Biochars of CSS and GRH and their blends with 10% USS, having a significant calorific value (21-24 MJ/kg), could be considered satisfactory for energy valorization purposes. The bio-oils produced from current wastes having density 0.95-1.22 kg/m<sup>3</sup>, pH 3.3-6.6, viscosity 118-381 cP, and heating value 20.4-28.1 MJ/kg, could substitute heavy fuel oil in static applications after a de-oxygenation process. The higher heating value of pyrolytic gas corresponding to CSS was low. In contrast, that corresponding to GRH and USS (9-10 MJ/m<sup>3</sup>) is considered satisfactory for the energy requirements of the pyrolysis process at low temperatures.