An Investigation of Ambient Drying of Eucalyptus Grandis Wood

Abstract

Eucalyptus has a high growth rate and material density which makes it an attractive biomass source for alternative fuel in Hawai’i. A challenge to implementing biomass-based energy systems is managing the moisture content using low cost methods. Ambient air drying may be an ideal option. This thesis reports results of natural-environment wood drying experiments and the development of both empirical and finite element models to describe moisture content over time as a function of solar insolation, ambient temperature, precipitation, and relative humidity. Hawai’i has at least 10 climate zones, making it an ideal location to conduct drying experiments under varied environmental conditions. For this project, logs were placed in two locations on the island of Hawai’i; Lalamilo to represent dry climates, and Waiakea to represent wet climates. The change in mass as water evaporated from the logs was monitored on an hourly basis for a period of nine months and the results were compared with model prediction. The drying curves and constant parameters derived from the empirical model were then used in a scenario analysis. The scenario analysis determined 1) the best time of year to harvest logs, 2) the length of time needed to dry logs at different locations, and 3) whether the extra cost to transport logs to a dry site was justified.