Slow pyrolysis of relevant biomasses in the Mediterranean basin. Part 1. Effect of temperature on process performance on a pilot scale

The present study focused on assessing the effect of the temperature (350, 450 and 550 degrees C) on the pyrolysis performance of several biomasses: olive stone, almond shell, pine wood and olive-tree pruning. First, they were subjected to thermogravimetric and Differential Scanning Calorimetric analyses to determine their thermal decomposition and heat flux. Afterwards, several tests were performed in a pilot plant reactor for char production. Moreover, a characterisation of the pyrolysis products and an assessment of both energy requirements and potentially energy self-sufficient process were performed. Our results show that the process was feasible with low grade pretreated biomass and it would become self-sufficient with the energy from gas and liquid fractions at 350 degrees C. The analyses of the char samples (proximate, elemental and organic carbon (C-org) analyses) show that almost all of them had features indicating that they were "biochar", suggesting high stability at higher formation temperatures based on their molar ratios (H/C-org; O/C-org). However, a more detailed characterisation is necessary to assess the quality of char as a soil amendment. (C) 2014 Elsevier Ltd. All rights reserved.