The bioenergetic potential of four oak species from northeastern Mexico

Abstract

Lack of knowledge regarding the fuel quality of diverse tree species prevents their use. Furthermore, the potential use of wood with the bark of different tree species for pellet production is still relatively unexplored in the scientific literature. In Mexico, the sawdust of Quercus genus (oak) is underutilized, despite it being an important forest resource, due to some anatomical and technological characteristics. The sawdust of Quercus with bark is also considered to have a low economic value. The objective of this study was to analyze the energy characteristics of barked and debarked Quercus sideroxyla, Q. rugosa, Q. laeta, and Q. conzattii in order to evaluate their potential for pellet production. Granulometric distribution, bulk density, proximal analysis, and calorific value tests were carried out. The sawdust of the four tree species studied was in accordance with the limits established by the standard EN 14961-2. Sawdust with a particle size of 0.425 mm had the highest percentage of retained mass (30.33%) (p < 0.05) in the granulometry test. There were no statistical differences in granulometry (p > 0.05) between barked and debarked sawdust for all Quercus species. Barked sawdust presented higher bulk density (p < 0.05) than debarked sawdust (246 and 224 kg/m3, respectively). The moisture content did not show statistical differences (p > 0.05) between barked and debarked sawdust. The volatile material was higher (p < 0.05) in debarked sawdust (88.7%) than in barked sawdust (85.0%). The ash content was below 0.5%. The fixed carbon was higher (p < 0.05) in barked sawdust (14.6%). The calorific value was higher (p < 0.05) in barked sawdust and for the Q. rugosa species (19.5 MJ/kg). The results suggest that the oak species analyzed, both barked and debarked, showed good potential for pellet production. Future studies should quantify fuel quality for a variety of diameter distributions, and analyze pellet mechanical properties and ash slagging risk.