Properties of charcoal produced from some endemic and exotic acacia species grown in Riyadh, Saudi Arabia

Production and properties of charcoal from four years old Acacia assak, A. negrii, A. seyal, A. karroo, A. ampliceps, A. stenophylla and A. salicina grown in the Experiments and Research Station, College of Agriculture, King Saud University, Riyadh, Saudi Arabia were studied. The first three species are indigenous while the others are exotic. 21 trees were felled and disks of 20 cm each from their stem were cut and shipped to the Wood Testing Laboratory at the Faculty of Agriculture, Alexandria University, Egypt. Specific gravity, charcoal yield and gross heat of combustion of the wood of these species were determined. Wood samples were charcoaled then the physical (apparent density, gross heat of combustion) and chemical properties (moisture, volatile, ash and fixed carbon content) of the produced charcoal produced were determined. A. amplecips, A. negrii and A. asak showed quality charcoal in terms of high gross heat of combustion and fixed carbon content with low moisture and ash content comparing with the other acacia species under investigation. Introduction Consumption of firewood and charcoal is very large in Saudi Arabia. People traditionally use wood and charcoal for heating in winter and cooking on special occasions. This is still the custom in spite of the availability of electricity, butane gas and other petroleum derivatives at token prices. Felling living trees for the above purposes has caused shrinkage of acreage covered by natural trees and shrubs. To regulate or restrict this process, Ministry of Agriculture introduced a licensing system for utilization of dry (dead) plants for obtaining firewood, for producing charcoal, or for transporting either. The impact of these new regulations is evident, as a result of public awareness campaigns on the importance of maintaining trees and shrubs, as well as applying penalties for violators. There are still unlicensed operations of felling and transporting trees and shrubs. However, the production figures of firewood and charcoal in Saudi Arabia still far from filling even a part of the large consumption. Therefore, maintaining the existed trees may not enough to fill the gab between supply and real need but adding new tree plantations through afforestation and reforestation enterprises is more realistic providing suitability of planted species to firewood and charcoal production. Acacia trees seem to be the best candidate species for this task. In Saudi Arabia the acacia communities represent the climax stage of xerophytic vegetation and generally have high species cover and low species diversity (Shaltout and Mady, 1996). Because Saudi Arabia is a large country with high diversity in topography and ecosystems it consequently has different plant species including acacias for different regions. Due to the accumulative experience of the locals, only few of acacia species are used for firewood and charcoal production while others are important sources of browse, pole timber, gum, tannins and other purposes. The present study was designated to compare the potential of charcoal production and its properties from Acacia karroo, A. ampliceps, A. stenophylla and A. salicina as exotic species in addition to Acacia assak, A. negrii and A. seyal as endemic species. Material and Methods In order to produce charcoal from acacia and evaluate its properties, woody samples were taken in February 2001 from four years-old trees planted in the field in the Riyadh, Saudi Arabia. Planting method and silvicultural practices were presented in details by Aref et al. (2003). The acacia species used were Acacia assak (Forssk.), A. negrii Pichi-Sermoli, A. seyal Del. A. karroo Hayne, A. ampliceps Maslin, A. stenophylla and A. salicina Lindley. The first three species are indigenous while the others are exotic. Seeds of both A. assak and A. negrii were brought from the south west region of Saudi Arabia, while those of A. seyal were collected from Riyadh. The seeds of the exotic species were imported from Alexandria, Egypt.