ABSTRACT
The purpose of this work was to study the production of energy in an area of sensu stricto cerrado located on the Água Limpa Farm, University of Brasilia - Brazil. Aerial biomass and the characteristics of the wood and bark of the species found in the total area of 63.56 ha were determined. In ten 20 m x 50 m plots, the total height and diameter, of all the trees whose diameters were either equal to or greater than 5 cm, at 30 cm from the ground, were measured. Seven diameter classes were pre-determined. Then, three trees of each species were cut down at random and classified according to its diameter class. The green biomass of the stem and branches of each species was measured in the field. In laboratory, humidity, the wood/bark ratio, specific gravity, heat combustion, the content of fixed carbon, volatile material and ash of the wood and bark were obtained from cross-sections. It was also possible to estimate the dry mass of the wood and branches per tree, species and hectare as well as the amount of heat generated by this cerrado community. Forty-seven species were identified. The dry biomass of the community comprised 71% of wood and 29% of bark and trees had an average 53% of branches and 47% of stem. The mean production of total dry biomass in the area was 12.38 t/ha. Mean tree production was 18.39 kg. The specific gravity of the wood ranged from 0.2 g/cm3 to 0.78 g/cm3, and the bark from 0.17 g/cm3 to 0.67 g/cm3. The heat combustion of the woods varied from 4,516 kcal/kg to 4,989 kcal/kg, whereas that of the bark ranged from 17,526 kJ/kg to 24,019 kJ/kg. The mean heat combustion of the wood was 19,937 kJ/kg. The mean fixed carbon content was 20.73% in the wood and 25.19% in the bark. Vochysia thyrsoidea presented a great energy production (1,643 MJ/tree, 20 trees/ha e 32,859.00 MJ/ha) due to a great biomass production, but with specific gravity low (0.49 g/cm3) and heat combustion low (19,728 kJ/kg). Acosmium dasycarpum showing wood with good characteristics (heat combustion - 20,883 kJ/kg, specific gravity - 0,74 g/cm3) did not outstand in the community due to their energy production (318.26 MJ/tree, 1 tree/ha e 318.26 MJ/ha) because their biomass production was low. Nonetheless, there were species that presented wood with good characteristics and high dry biomass production: Sclerolobium paniculatum (1,279 MJ/trees, 46 trees/ha, 58,834 MJ/ha, 0,72 g/cm3 e 20,298 kJ/kg), Dalbergia miscolobium (336 MJ/tree, 84 trees/ha, 28,224 MJ/ha, 0,77 g/cm3 e 20,495 kJ/kg) e Pterodon pubescens (1,983 MJ/tree, 14 trees/ha, 27,760 MJ/ha, 0,73 g/cm3 e 20,733 kJ/kg).
Keywords:
energy production; biomass; “cerrado”