Fast pyrolysis of biomass of different type and origin: Effect on bio-oil and char

Pyrolysis is considered the most promising approach to convert biomass and to generate valuable bio-oils and biochars. This study aimed to investigate fast pyrolysis of different types of wastes from Mediterranean biomasses (Opuntia Ficus Indica, Pomegranate, Aleppo Pine Cones, and Pinus Pinea Cones) and compare the quality of bio-oils and chars. Biomasses were characterized by proximate and ultimate analyses, FTIR spectroscopy, X-ray diffraction, thermogravimetric and calorimetric analysis. Fast pyrolysis experiments were carried out in a heated strip reactor with a heating rate of 103 K/s and holding time of 3 s at 1000 K. Tar products were readily quenched and collected on a cold pyrex bridge, positioned above the sample holder at near ambient temperature, so as to minimize secondary reactions. Tar samples were characterized by GC-MS analysis and the quality in terms of chemical families was discussed. Char samples were recovered from the strip and analysed by SEM, elemental analysis, and XRD. The results show that the bio-oils and char composition vary sensibly: - Aleppo pine cones and pinus pinea cones, the hardest of the examined biomasses, upon fast pyrolysis produce a bio-oil that is made of oxygenated aromatic compounds and a bio-char with high carbon content (>60 %), which could be envisaged for soil amendment and carbon sequestration. - Pyrolysis of Opuntia Ficus Indica wastes (peels and cladodes) generates chars with comparably lower carbon content, but particularly rich in potassium (K) and calcium (Ca). The bio-oil from the peels is still rich in aromatic compounds, similar to APC and PPC, while the bio-oil from the cladodes is almost exclusively made of anhydrosugars. - Pyrolysis of pomegranate peels generates a carbon-rich char, as APC and PPC, but the biooil is rich in anhydrosugars and also furfural. From the morphological point of view, all bio-chars seem to be made up of agglomerates of irregular elongated or semi-spherical shaped particles with large macropores.