Growth, biomass estimates, and charcoal production of Acacia drepanolobium in Laikipia, Kenya

Charcoal is a major source for cooking energy in most African countries, for which demand from a burgeoning human population has sometimes outstripped the supply of wood from forests and woodland. Therefore. there is need to explore the potential of indigenous trees and shrubs for sustainable charcoal production. Acacia drepanolobium is an ideal candidate for sustained charcoal production because (a) it occurs in almost mono-specific stands in high densities over vast areas, (b) it coppices readily when harvested or top killed by fire. (c) it's hard wood makes good quality charcoal, (d) income from its charcoal is an attractive source of supplemental revenue. Information on its biomass, charcoal yield, and regrowth rates are needed for informed management and its conservation for sustainable charcoal production. but this information is currently lacking. Suitability of A. drepanolobium for sustained charcoal yield in Laikipia, Kenya, was evaluated by developing predictive equations for standing biomass and charcoal production, and by undertaking a chrono-sequence analysis of its regrowth. Woody biomass was strongly related to stem diameter (Y=3.77 x + 1.17, R-2=0.96, P<0.001). Mean charcoal production from earthen kilns was 2.83 Mg ha(-1). Height and stem diameter in coppicing stands increased at a mean rate of 28.6 cm year(-1) and 0.7 cm year(-1) respectively. Biomass in coppicing stands accumulated at a mean rate of 1.3 Mg ha(-1) year(-1) in a 14-year period, yielding dry biomass of 18.26 Mg ha(-1) useable wood that can produce a minimum of 3.0 ME ha(-1) of charcoal. We propose that A. drepanolobium can be harvested for sustainable charcoal yield over a 14-year cycle. Production should be commercialized using modern kilns to improve efficiency and maximize yields. (C) 2001 Elsevier Science B.V. All rights reserved.