BIOMASS AND ENERGY YIELD OF LEGUMINOUS TREES CULTIVATED IN AMAZONAS

Energy forests emerge as an alternative to fossil fuels for energy production. The good performance of these forests should consider the selection of fast-growing species, high biomass productivity and energy yield. The aim was to investigate growth and energy yield of Acacia auriculiformis and Acacia mangium in a short-rotation plantation in the Amazonas. The energy yield was determined on 12 trees per species, from the results of biomass, calorific value and basic density. When 9 years-old, A. mangium had the highest growth rates in height (1.9 m yr -1 ) and DBH (2.5 cm yr -1 ). The greatest biomass productivity was observed in A. mangium (33.4 Mg ha -1 yr -1 ), which was 84% higher than A. auriculiformis (18.1 Mg ha -1 yr -1 ). Basic density (0.54 g cm -3 ) and calorific value (4,400 kcal kg -1 ) showed no significant differences between species. The energy yield of A. mangium (1,317 Gcal ha -1 ) was twice as of A. auriculiformis (684 Gcal ha -1 ). A. mangium has better energy performance, compared to the A. auriculiformis , and therefore could the most recommended for the formation of energy forests in disturbed areas in the state of Amazonas.