Physical and Thermochemical Properties of Selected Wood Species in Nigeria: A Fuel Suitability and Pelleting Potential Assessment

Abstract

Scientific studies on the impact of wood species on solid fuel production, performance, and sustainability are grossly inadequate. The knowledge of this is imperative as users of solid fuels are increasing rapidly, especially in Africa. On this note, it becomes necessary to explore measures that will improve its efficiency and sustainability as an energy source. This study investigates some properties of selected wood species used as an energy source in Nigeria and their pelleting potential. Nine samples were characterized and assessed for suitability of pelleting following four wood pellet quality standards. The properties investigated are physical (moisture content and density) and thermochemical (calorific value, ash content, volatile matter, fixed carbon, and ultimate properties (carbon, nitrogen, hydrogen, oxygen, sulfur, arsenic, cadmium, and lead)). These were selected because they are among the most important pellet parameters contained in the quality standards. The findings revealed a net calorific value between 10.61 MJ.kg−1 for Tectona grandis and 18.44 MJ.kg−1 for Eucalyptus cam. The ash content, volatile matter, and fixed carbon contents of the samples range between 2.1 and 24.4%, 65.94 and 87.77%, and 3.51 and 18.63%, respectively. Anogeissus leiocarpus was found to be the species with the best rating score in terms of fuel properties, while Vitellaria paradoxa was the lowest. However, in terms of conformity with the four wood pellet standards, Khaya senegalensis, Parkia biglobosa, and Eucalyptus cam., having presented density, calorific value, sulfur, arsenic, cadmium, and lead within the limits of the wood pellet quality standards, were considered the best wood species in terms of fuel suitability and pelleting potential. The findings therefore suggest that not all wood species are suitable as fuel. Thus, for species that do not meet the standard wood pellet requirements, alternatives such as the use of biomass blends, additives, or process adjustments can be employed to adapt the quality to the standards or by using the fuels in improved cookstoves.