COMPARATIVE STUDY OF BURNING EFFICIENCIES OF WOOD OF DIFFERENT MOISTURE CONTENTS

Abstract

In Ethiopia the rural community relies almost entirely on biomass fuels both for subsistence and for productive purposes. With increasing population and dwindling forest resources, the consumption of wood fuel has far exceeded its supply since wood fuel is being consumed at an unsustainable rate. Besides, people are not aware of the effects of moisture in wood on its efficiency. This study was conducted to test the burning efficiencies of woods of different moisture contents. One type of wood (eucalyptus) of five different moisture contents was used in five identical wood burning stoves purposefully fabricated for this purpose. Tests were conducted over five days there by giving five replications. During the tests, food temperature, stove body temperature and stove outlet temperature measurements were conducted along with ambient air temperatures. The data obtained were temperature corrected and time synchronized by employing appropriate mathematical methods. From the tests the following results were obtained. Woods with both high and low moisture contents did not do well in the combustion process compared to the wood with moderate moisture content (around 10%). High moisture content delayed the onset of cooking and low moisture content decreased the overall duration of effective cooking. Wood of moisture content of 50% or greater with respect to oven-dried wood failed to cook (reach cooking temperature). Increased moisture content in wood (around 30%) delayed the time to reach cooking temperature by about two times and hence elongated the cooking time. There is also extended smoke time as observed from smoke outlet temperature. As far as maximum cooking temperature is concerned statistically, there was no significant difference between woods with moisture contents 0 to 34%. Excess loss of moisture has a counter effect on the burning efficiency of wood. Extra time must be given if it is inevitable to cook with wood with moisture content of this range.